Oklahoma Severe Weather Discussion - May 2011

[venture]

This thread will be used to discussion upcoming/ongoing severe weather events through the month of May. This initial post will contain information, images, and links that can be used at any time. Images posted later through the thread may or may not be accurate on the day you are viewing them (check the post comments). Information contained in this thread should not be used as an alternative to weather radios, media, or other means of getting weather warnings/advisories.

_________Norman Warning Area Map __________________ Tulsa County Warning Area Map____

Tornado Warning | Tornado Watch | Severe Thunderstorm Warning | Severe Thunderstorm Watch | Blizzard Warning | Red Flag Warning | Fire Warning | Winter Storm Warning | Winter Storm Watch | Freezing Rain Advisory | Heavy Snow Warning | Winter Weather Advisory | Severe Weather Statement | Special Weather Statement | Hazardous Weather Outlook | Fire Weather Watch
Other Color Meanings: http://www.weather.gov/wwamap-prd/faq.php

SPC Convection (Severe Weather) Outlooks

________ Day 1 ________________ Day 2 _________________ Day 3 ___________ Days 4 through 8 ___


*Click any above graphic to view discussion.*

SPC Fire Weather Outlooks

________ Day 1 ________________ Day 2 ______________ Days 3 to 8 _____


*Click any above graphic to view discussion.*

CoD NEXRAD Radar Mosaic


CoD Visible Satellite Image (will appear blank overnight)


Oklahoma Mesonet Current Conditions


SPC Severe Weather Reports (Today and Yesterday)
________ Today _____________ Yesterday _____


Useful Links
COD Weather Analysis Page: http://weather.cod.edu/analysis/
NWS Norman Enhanced Page: http://www.srh.noaa.gov/oun/enhanced.php
Storm Prediction Center: http://www.spc.noaa.gov/
Oklahoma Mesonet: http://www.mesonet.org/
West Texas Mesonet: http://www.mesonet.ttu.edu/
Oklahoma Fire Weather: http://www.srh.noaa.gov/oun/?n=fireweather
Oklahoma Road Conditions: http://www.dps.state.ok.us/cgi-bin/weathermap.cgi
Severe Weather Values Reference Guide: http://weatherspotter.net/index11.php -or- http://www.theweatherprediction.com/severe/indices/
TwisterData Model Page: http://www.twisterdata.com/
Earl Barker's Central US Model Page: http://128.121.193.153/central_models.htm
NSSL WRF Model: http://www.nssl.noaa.gov/wrf/
NSSL 4KM WRF Model Forecast Soundings: http://www.nssl.noaa.gov/wrf/sdg/

[venture]

Going to jump right into the May outlook as April 30th doesn't look to have any severe weather except in extreme far SE OK.

Sunday May 1
Showers and storms develop in Southern OK mainly south of I-40. This will increase through the evening and bring some heavy rain across SC and eastern OK.

Monday May 2
Light rain remains around the state building into Central and Southern OK through the day. Some areas could see over a half inch of rain, but these will mainly be to the southeast areas of the state.

May 3rd and 4th look mostly quiet some some northerly winds turning to the south late in the period.

Thursday May 5th
Strong southerly winds will start to bring moisture back to the state. A cold front will be moving into the state and approaching Central OK by mid afternoon. Some showers and storms ahead of the front. Most instability will be kept south of I-40 during this. Severe risk looks marginal at this time.

Friday May 6th
Quiet across the area.

It appears we will be entering an extended period for severe weather risk after May 6th.

Saturday May 7th
Strong high pressure system moves to the east providing very strong southerly and southeasterly winds before day break. Moisture return could very well be in question with the front that passes a couple days earlier, but right now the models are thinking moisture return will happen. By early evening, dewpoints in the mid 60s are widespread along and east of I-44. A a frontal boundary looks poised to move into NW OK by later in the afternoon/evening. A dryline will also setup somewhere along the OK/TX border and move east. Forecast instability by evening will be highest across most of Central Oklahoma from Lawton to Tulsa. CAPE could approach or exceed 4000 j/kg. LI values will be around -10 across the area. Forecast sounding is definitely concerning when looking at the prime indicators for severe weather. The atmosphere should be at a very comfortable level with moisture content and the cap will be very breakable, but not too easy. 00Z May 8 OKC sounding is pretty loaded - bunch of techie figures coming. Lapse Rates (L57) are around 7.0, LCLs will be decently low at 875 make surface based storms probably, LI at -8.4, SI at -7.4, Total Totals Index at 60, K-Index at 40, SWEAT index at 610, EI at -4.2, CAPE at 2571, CAP at 1.7, HEL at 290, SRDS 10.3, EHI at 3.8, BRN at 16.4, and BSHR at 157. These numbers and their ideal values for severe weather can vary based on how they are exactly calculated and who is doing it.

So what do we tend to need for severe storms...here is a quick break from the outlook for some mind numbing info. CAPE we normally want north of 2500, Total Totals over 55, LI will below -5 (approaching -8 or less). BRN anywhere from 10-50...but ideally in the teens for supercells. SWEAT over 500 is significant. EHI higher than 1.5 is pretty siginificant. HEL near 200 is a good indicator that if a tornado occurs, the energy present could aid in the formation of a moderate or stronger tornado.

So looking at Saturday, there is definitely an elevated risk of severe weather. If the models were forecasting this 24 hours out, we would probably look at a moderate risk. Since we are 7 days out, not happening yet. :-) These things can change down to the final few hours, so would just advise to make note of this date and follow along. One last piece is that forecast storm motions are going to be 307 at 22 kts. So storms will be moving roughly NE at 25 mph. Models do initiate precip starting in North central OK and back build through Central OK.

Sunday May 8th
This was our previous day to watch...nothing is changing. Fairly strong surface low is coming out and while precip forecasts are pretty sparse here, the amount of instability is extremely high. There will be a much stronger cap forecast for this day, so that can really keep a high instability day in check. We’ve seen plenty of moderate risk days with tornado watches around and not a cloud in the sky. This very well could be one of those. Dryline will punch into SW OK but lag back through the Northern TX panhandle. Dewpoints could reach well into the 70s in Central and SE OK, but the models may be a bit crazy with that. Winds strong out of the SE for most of the state. Instability again will be very high over central and Southeast OK. Bullseye of enhanced values over South central OK with LI values less than -12 and CAPE values approaching 6000 j/kg. Forecast sounding is much more mixed and not as unified as the Saturday sounding. Some indices are on target for an elevated severe day, others aren’t buy anything at all and keep it very quiet. At this point we just need to wait and see, but it could be significant if a storm is able to pop.

Monday May 9th
Another day, another elevated risk for severe. That last two days are pretty wordy but I’ll make this quick. Take Sunday, copy it, raise the instability a bit, and move it from I-35 to the east. Dryline should be about 50 miles west of I-35 by evening. Forecast sounding looks week, but we just have to keep this one in mind.

Tuesday May 10th
Okay, broken record. Same as Monday …and Sunday. Move it back to the west a bit more except for extreme SW OK. CAP looks rough still. Instability extremely high again though. CAPE values over 4000 for most of Central and Eastern OK. LI values -10 or lower over the same areas. Forecast sounding looks good, not exceptional.

Wednesday May 11th
Better chance of precip this day. CAP looks to be a bit weaker and precip is forecast somewhere around the I-44 corridor. Highest instability roughly along and east of I-35 with CAPE values mainly 2000 or more. LI values generally -6 or lower across the same areas.

Thursday May 12th
Are you sick of severe weather yet? Tired of going through your 3rd fence you installed for the week? Stop reading now. LOL I think I’m just going to copy and paste going forward. I can only type the same thing so much. Sounding looks good to great. LI’s are crazy -11 or lower. LCLs look good. CAP looks good. CAPE over 5000 over Central OK along the I-35 corridor (east and west of it by like 50 miles)…with values over 4000 for most of the state except far western OK. Storms look like they’ll form in Northern OK and build south over the eastern 2/3rds of the state. Not a lot of rain, but chance is there.

Friday May 13th
Hey guess what? You know when we were all complaining about snow and blizzards and cold. Yeah Spring time in Oklahoma. Same deal…but areas Central and Southern OK. Blah blah blah. Not as intense as Thursday, but yeah.

Saturday May 14th
Not an extreme day again, but risk is there. But hey…more rain right? Best severe risk looks like central and south central OK.

Sunday May 15th
Wait What? Low instability?? Rain chances??? North winds???? Could it actually be a cold front coming through calming things down? Maybe, but this day always changes so don't read much into it.

Okay so that’s the outlook. It looks rough starting next weekend, but just keep in mind. This is a LONG way out. Forecasts change. Severe weather is impacted by many factors and any preceding activity each day can change how the following day is. Boundaries, left over clouds, nothing taking place, etc. So take it will a grain of salt. I honestly expect most of the forecast to dramatically change before we get into the period. The best guess right now is that we will likely see some severe weather during this period and it can occur on one of those days. Getting more specific this far out is just play darts with the weather map.

[Thunder]

Hi, just making a post to subscribe. Will be back later to read this. Thanks.

[Thunder]

Here is a map provided by KOCO for May 3rd, 1999.

http://kocoweatherblog.files.wordpre...igoutbreak.png

12 years anniversary coming up

[venture]

Here is a map provided by KOCO for May 3rd, 1999.

http://kocoweatherblog.files.wordpre...igoutbreak.png

12 years anniversary coming up

That's actually by NWS Norman, not KOCO. More info is from here: http://www.srh.noaa.gov/oun/?n=events-19990503

[Thunder]

Kool. I only remember that one tornado on that day. I had no clue about all the other tornadoes. I know people said how many tornadoes was in that state on that day, but I don't remember seeing them. All I remember was that one monster and all the stations was so focused on that. I wonder how it was for the many others affected by the other tornadoes. Interesting tracks on the map.

[venture]

No major update to the forecast tonight. I won't do another complete run down until Sunday or Monday evening. Long range models change too much and the work going into to reviewing each day would make it a waste of time at this point.

General change for tonight's run is a more easterly setup for the main storms and an extremely strong cap overhead when our chances are the highest. It is way to early to really weigh the chances or specifics of the setup again. So with a pretty broad brush we can say...

- Between May 6th and 10th there will be a risk for severe weather in roughly the eastern 2/3rds of the state on at least one of those days. Models have continued to indicate such a setup, so it seems likely...just that location, frequency, and every other specific are pretty much up in the air.
- Cap strength will be a very big player and forecast precip amounts are extremely low or non-existent.
- May 12th or 13th may provide another chance for storms over the area or at the very least a widespread area of rainfall (really the only major chance after this weekend). Front comes in around the same time which will dry things out and quiet them down considerably...again.

[Thunder]

Nice rain today. Probably for all day. Should be quite enjoyable for many. Enjoy it while the rain lasts.

Also look at the very first post. There is a NEXRAD radar showing all the rain.

[venture]

Some nice rain around, few storms rolling in...but nothing major.

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE NORMAN OK
1109 AM CDT SUN MAY 1 2011

OKZ024-025-027>029-039>041-045-046-011630-
CANADIAN OK-OKLAHOMA OK-CLEVELAND OK-GRADY OK-MCCLAIN OK-
JEFFERSON OK-MURRAY OK-GARVIN OK-CARTER OK-STEPHENS OK-
1109 AM CDT SUN MAY 1 2011

...SIGNIFICANT WEATHER ADVISORY...

THIS SIGNIFICANT WEATHER ADVISORY IS FOR CANADIAN...CARTER...
CLEVELAND...GARVIN...GRADY...JEFFERSON...MCCLAIN.. .MURRAY...OKLAHOMA
AND STEPHENS COUNTIES.

SCATTERED THUNDERSTORMS...EXTENDING FROM WESTERN SIDES OF THE
OKLAHOMA CITY METRO...TO MARLOW...TO JUST WEST OF ARDMORE...WILL
MOVE QUICKLY NORTHEAST THROUGH NOON. MOST STORMS WILL PRODUCE A
BRIEF PERIOD OF SMALL HAIL AND HEAVY RAIN.

SEVERE WEATHER IS NOT EXPECTED AND NO WARNINGS ARE ANTICIPATED AT
THIS TIME.

[Thunder]

It was major! I was at the store and was leaving early (pain too extreme) and there was a whole bunch of hail outside! Out on streets felt like winter wonderland. :-O Then drive a bit, no hail, then get home, lots of hail. Nice hailstorm all around.

[venture]

Holding off on any other major updates still. Generally models still indicate the chance for two periods of unsettled weather coming up.

The first starts on Friday, May 6th and runs until Tuesday May 10th. Instability will be high to very high in certain portions of the state during this time period. However, cap strength will also be pretty stout so that could keep thunderstorm coverage to a min. Best area it appears at this time would be Northern OK on the 9th and transitioning to mostly the eastern one-half of Oklahoma there after. By the end of this period, most of the activity should push into SE OK before leaving the state.

Looks like a 3 day break and another period of unsettled weather from Saturday May 14th until Tuesday May 17th or so (model coverage ends here). Coverage areas bounce around a lot here, but this looks to be mostly Central and southern OK.

Everything bounces around a lot though from run to run, so as we get closer we should be able to nail things down a bit better. By tomorrow the early portion of the first period will be covered by more models, so we can use those to compare.

[venture]

Going to do a more thorough look at the upcoming storm chances since some local people are already talking up next week. ECMWF is indicating a pretty deep trough digging in out west early next week that should help change the weather pattern we've been stuck in. Since a lot of data from that model is limited, will be sticking mostly with GFS for this here. Please remember things change almost every 6 hours when a new model run is started, so what is said here is never set in stone until you see it out the window.

Friday - May 6

Looks like it will be a quiet day with both NAM and GFS keeping instability low to moderate with a strong cap. No major features in the state to really get activity going as dryline doesn't look like it will be established yet.

Saturday - May 7

Instability increases along with more low level moisture. Dewpoints should easily make it in to the 60s by Saturday and a dryline will be established along the OK/TX border out west. Wide swath of high to extreme instability will be present over much of Western, Central, and Northeast Oklahoma...the highest values from Central into NE OK. Forecast sounding indicates an environment that would be favorable for severe storms, except for one little factor. The Cap. The cap looks to be pretty stout on Saturday, but not unbreakable with enough forcing. Should a storm go up, it will likely be severe with large hail and if allowed to mature, the environment would be favorable for a tornado. However, if nothing can break through - it'll be a sunny and quiet day.

Sunday - May 8

Another day with high to extreme instability in the state. Another day with an intense cap present. Much like Saturday, most of the ingredients are present for higher end severe weather, but a very strong cap will be in place to stop a lot from happening. By all accounts if a storm would happen to go up this day, the energy and dynamics in the atmosphere would definitely offer up some very large hail and tornadoes. However...its dry upstairs and we may be lucky to see a cloud form. We'll need to watch this because the potential is there.

Monday - May 9

Another day with strong instability mainly along and east of I-35. Dryline appears to surge east quite a bit this day and taking the chance of storms, potentially, east of OKC proper...but other areas of the metro area could still be in the thick of it. Storm chances look low still due to a decently strong cap.

Tuesday - May 10

First realm shot of storms according to the models as they do break out precip finally in the state. This is a bit more uncertain because GFS isn't having much run to run consistency on this time period. It has bounced around from East of I-44, to all but western 1/4th of OK, to SE 1/3rd of OK. So it is really going to depend on where things setup on Tuesday. If the cold front doesn't come through as fast as forecast, severe weather chances will be further west and north. If it comes in faster, further south. We'll just have to wait and see on this one.

Wednesday - May 11

This one started to get hyped a bit by a local met, but it really depends what you look at. If you focus on last nights 06Z GFS, yeah severe chances are there. If you look at yesterdays 00Z run and today's 12Z run, everything is south of OK. So if we average it out, everything is south of OK as it looks now.

Friday - May 13

Forecast doesn't show much in the way of severe weather, but it does appear we could have some decent rain towards evening into Saturday morning.

Saturday - May 14 to Wednesday May 18th

General risk of storms pretty much every day somewhere in Oklahoma. Models are pretty erratic at this point so won't really get into much detail with them. We'll just have to wait and see.

[ou48A]

On her noon weather show today KFOR’s Emily Sutton discussed her thoughts about a significant severe WX event 8 days from now.

[jn1780]

On her noon weather show today KFOR’s Emily Sutton discussed her thoughts about a significant severe WX event 8 days from now.

Morgan was highlighting Tuesday. It seems way to early to be showing a special graphic when the dryline and cold front can set up anywhere at this point in time, but you know its May 3, so they want to talk about the next possible severe weather event.

[venture]

Okay here we go. Pretty thorough review again with pictures. YAY! Anyway... LOL here is how things look via the evening model runs.

Friday - May 6th



Instability will increase on friday as moisture starts to return from the Gulf. We aren't looking at things being too crazy however. A strong cap will be in place but models are hinting on a SLIGHT weakness in SW OK. If I storm would happen to go up (right now it looks like less than 10% of a chance), it will likely go severe if it can get established and break the cap. Dynamics would be favorable for rotating storms with some moderately large hail. Not going to outlook any type of risk since the chance for a storm is so low, but it may be a slight risk day if the cap weakens enough or we get some upper air support that isn't showing up.

Saturday - May 7th



Pretty simply setup. Dryline is chillin' out in western Oklahoma enjoying the scenery, moisture flowing up from the Gulf, and instability continues to rise as we warm up. Surface features are a little challenging to pinpoint here. Models show a push of very dry air coming into SW OK by late afternoon but keeps the wind shift (normally associated with the dryline) well west of the OK/TX border. So we'll just have to see how that plays out. Instability like I mentioned will be increase in the area shaded green. There is some hint that the CAP could weaken a bit along I-44 as well which could help a storm or two break through. So far forecast precip amounts remain zero for the period, so will hold off on any risk outlooks. Forecast sounding is really quite volatile for the day, so if anything does form it has the chance to go severe very quickly with large hail and maybe a risk for tornadoes.

Sunday - May 8th



Instability continues to build and starts to get into what some would call the "extreme" category. Dryline shifts further into the state towards the afternoon as well. This is another day where forecast soundings are very impressive and anything will go severe should a storm be able to form. However, the cap is forecast to be extremely stout this day so activity could be kept to maybe a storm if anything at all.

Monday - May 9th



Pretty similar to Sunday, except the dryline is a bit further east. Cap is still pretty rough and instability continue to be very high to extreme.

Tuesday - May 10th



So we come to the hyped Tuesday forecast. Dryline will have retreated Monday evening to the west and begins to push east again...with some help. Storm system will be moving through the Midwest and another piece of energy closer to home. Cap is forecast to weaken ahead of the dryline over an area that will be extremely unstable. Looking at the forecast soundings, some of the values are pretty incredible...which others highlight how hard it is to forecast something like this a week out. Let me be clear, not every parameter is in place that screams major tornado outbreak. Most of the values are there though that would say that if things stay on course, a higher end severe weather day for the southern plains could be on tap. The other interesting part of this, is this is the first day out of all of these reviewed that models actually initiate precip in the state (ahead of the dryline). If the trend continues the next couple of days I'll probably bump things up to a slight risk and tweak as we get closer. I also won't be shocked if SPC started following this on their 4-8 Day Outlook. We will just need to watch it, but it is a week out so if things keep going the way they do...everyone should at least be prepared to monitor conditions on Tuesday. Storm motion forecasts have storms moving Northeast @ 25-30 mph...so typical severe weather day if this verifies when it comes to tracks of the storms.

Wednesday - May 11th & Thursday - May 12th



The cold front arrives and will bring to an end most of the severe weather, at least in Northwest OK. Dryline will still be in the state in far SW OK, but quickly overtaken by the front. Storms will fire ahead off the front and dryline and march east. Forecast precip amounts show very heavy rainful in the green area. The purple area is where the highest instability is located and where the risk of additional severe weather would be.

Moving into Thursday...



Potentially heavy rain will move east some and bring a good soaking for central OK and Northeast OK. Models forecast activity will move out of the state later in the day, but we'll just need to see if this continues. Models have jumped around a bit here so we'll see to see how it goes.

After Thursday things appear to dry out quit a bit. Next round of storm chances increase on May 17th, but won't touch those for now due to time constraints.

[venture]

Here is the Day 4-8 Outlook from SPC...

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0259 AM CDT WED MAY 04 2011

VALID 071200Z - 121200Z

...DISCUSSION...
MODELS DEPICT A WNWLY FLOW REGIME FROM THE PACIFIC NW INTO THE MID
ATLANTIC ON SAT/D4 WITH PERHAPS AN EMBEDDED DISTURBANCE MOVING
QUICKLY EWD SOMEWHERE BETWEEN THE NRN PLAINS INTO THE OH VALLEY. BY
THIS TIME...LOW LEVEL MOISTURE WILL HAVE BEGUN TO RETURN NWD FROM
THE SRN PLAINS INTO THE LOWER MO VALLEY. ELEVATED THUNDERSTORMS MAY
BE ONGOING SAT MORNING OVER PORTIONS OF IA/MO/IL/IND...SHIFTING EWD
AS A LOW LEVEL JET VEERS. SEVERITY OF THIS CONVECTION WILL DEPEND ON
THE STRENGTH OF ANY UPPER SUPPORT...BUT AS PREVIOUSLY ALLUDED
TO...PREDICTABILITY IS NOT HIGH AT THIS TIME.

BY SUN/D5...THERE IS STRONG EVIDENCE THAT A LARGE UPPER TROUGH WILL
BEGIN TO TAKE SHAPE ACROSS THE WRN STATES WITH AN 80+ KT MID LEVEL
JET DIGGING SWD ALONG THE W COAST. THE BOUQUET OF MREF SOLUTIONS AS
WELL AS DETERMINISTIC MODELS SHOW LITTLE AGREEMENT ON D5 WITH HOW
QUICKLY AND HOW FAR S THIS TROUGH WILL DEVELOP. THIS WILL HAVE AN
IMPACT ON THE PROBABILITY OF SEVERE CONVECTION OVER THE SRN/CNTRL
HIGH PLAINS NEAR THE DRYLINE WHERE CAPPING WILL BE A CONCERN...AND
ALSO WITH POSSIBLE NOCTURNAL CONVECTION FOCUSED OVER NEB/IA/MO/IL
OVERNIGHT WITH A SWLY LOW LEVEL JET. BOTH THESE AREAS HAVE
POTENTIAL...BUT NOT ENOUGH TO INTRODUCE ANY SEVERE AREAS WITH SUCH
UNCERTAINTY.

FOR THE REMAINDER OF THE PERIOD MON/D6 TO WED/D8...THERE WILL LIKELY
BE A SEVERE THREAT EACH DAY ALONG THE DRYLINE ACROSS THE CNTRL/SRN
PLAINS...AND PERHAPS EXTENDING EWD FROM A SURFACE LOW/WARM FRONT
ACROSS THE MIDWESTERN REGION AS THE UPPER TROUGH...AND/OR PIECES OF
THE TROUGH EMERGE OVER THE REGION.

SEVERE AREAS BEGINNING SUN/MAY 8TH AND LASTING THROUGH ABOUT MAY
10TH ARE LIKELY FORTHCOMING FOR MUCH OF THE CNTRL U.S. AS THE EVENT
NEARS AND PREDICTABILITY INCREASES.

[venture]

No real changes to the forecast for now. Chance might be a bit better Friday and Sunday for an isolated storm or two. We'll have to see. Conditions continue to appear favorable for severe weather through Thursday should storms forms. Tues/Wed still look to be the most favorable for any significant severe weather to take place.

[venture]

SPC has started to add areas to their outlook for Sunday, Monday and Tuesday. All 3 days have a risk associated with them now mainly along and WEST of I-35 - how's that for something new.

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0400 AM CDT THU MAY 05 2011

VALID 081200Z - 131200Z

...DISCUSSION...
FORECAST MODELS AND VARIOUS ENSEMBLE MEMBERS ARE IN RELATIVELY GOOD
AGREEMENT THROUGH SUN/D4 IN DIGGING A STRONG UPPER TROUGH ACROSS THE
WRN STATES...AND MOVING AN UPPER LEVEL RIDGE AXIS FROM THE CNTRL
PLAINS EWD TO THE MS RIVER BY 00Z MON. AS THIS OCCURS...LOW PRESSURE
WILL DEEPEN OVER THE CNTRL HIGH PLAINS...AND SLY SURFACE FLOW WILL
BRING MID TO UPPER 60S F BOUNDARY LAYER DEWPOINTS INTO OK AND SRN KS
E OF A DRYLINE. STRONG HEATING AND MIXING W OF THE DRYLINE BENEATH
WSWLY MID LEVEL FLOW OF 30-40 KTS AND A VERY STEEP LAPSE RATE
PROFILE SHOULD BE FAVORABLE FOR SUPERCELLS CAPABLE OF VERY LARGE
HAIL...GUSTY OUTFLOW WINDS AND PERHAPS A FEW TORNADOES...ALTHOUGH
T/TD SPREADS MAY BE TOO HIGH FOR A SIGNIFICANT TORNADO THREAT.
ALTHOUGH LOW LEVEL MOISTURE QUALITY WILL BE GREATER WITH EWD
EXTENT...CAPPING WILL BE A PROBLEM. STORM MOTIONS SHOULD BE
SLOW...SO EXPECT STORMS TO AFFECT A RELATIVELY CONCENTRATED AREA
BEFORE DYING BY LATE EVENING.

ON MON/D5...MODELS REMAIN IN GOOD AGREEMENT WITH THE UPPER AIR
PATTERN AS THE TROUGH SINKS SWD ACROSS THE GREAT BASIN. LOW PRESSURE
WILL AGAIN DEEPEN OVER THE CNTRL HIGH PLAINS WITH SLY SURFACE FLOW
PERSISTING. WITH MOISTURE IN PLACE...IT APPEARS MORE DRYLINE STORMS
WILL OCCUR...SIMILAR TO THE PREVIOUS DAY.

BY TUE/D6 INTO WED/D7...FLOW OVER THE PLAINS WILL BECOME
INCREASINGLY MERIDIONAL AS THE UPPER TROUGH BOTTOMS AND BEGINS
MOVING EWD. ALSO AT THIS TIME...A SUBTROPICAL JET IS EXPECTED TO
MOVE NWD AND PHASE WITH THE MAIN TROUGH...INCREASING UPPER LEVEL
WIND PROFILES. ALL THE WHILE...A DRYLINE WILL REMAIN ACROSS THE
CNTRL/SRN PLAINS WITH STRONG INSTABILITY AND AMPLE VEERING SHEAR
PROFILES FOR SUPERCELLS EACH DAY. TUE AND WED APPEAR TO HAVE A
GREATER TORNADO THREAT THAN ON SUN/MON WITH HIGHER THETA-E AIR AND
BETTER HODOGRAPHS. AN ISOLATED STRONG TORNADO MAY OCCUR...ESPECIALLY
ON TUE WHEN A STRONG NOCTURNAL LOW LEVEL JET RESPONSE IS FORECAST TO
OCCUR DURING THE EVENING.

GIVEN SOME SUBSTANTIAL DIFFERENCES WITH THE TROUGH ON D7...WILL
DEFER ON ADDING ANY ADDITIONAL AREAS.

[venture]

We'll probably see some tweaks to a Sunday outlook, but this is what it is looking like so far.



Dryline will be established in Western OK. Behind it, extremely dry with temps well into the 90s if not low 100s. Fire danger will likely be very high to extreme in those areas. Ahead of the dryline moisture will be flowing in on decent SE winds at the surface. Instability will be pretty high anywhere ahead of the dryline but the highest levels will be from Central into Northern OK. Depending on the position of the dryline will really depend on where things setup. Positioning right now is for early evening, which it'll likely start to retreat afterwards.



Forecast sounding is pretty mixed on the ability for severe weather to occur. The two figures to really look at are CINH and CAP about mid way down. A CAP strength of 5.1 is going to be pretty tough to break. Instability looks very favorable for high end severe weather, but it does no good if a cloud can't even form. Should any storms get established, storm motion will be ENE at 25 mph.

I'll get more details on Monday, Tuesday, and Wednesday as we get closer. Right now it still looks like Tuesday/Wednesday could be significant severe days for the southern plains.

[venture]

Updated outlook graphics. These are my forecasts, the SPC forecasts are from Thursday and the Friday update isn't available yet. Have 4 days of focused outlooks.



Not going to put out an outlook for Sunday, but the SPC area isn't too bad. If I were to put out an area it would be a bit more to the east of the SPC are and north of a Lawton to Norman line. There will be a batch of energy that will eject out as displayed on the 500MB images covering the late afternoon/early evening time frame. The cap is forecast to be very strong (See: http://www.chatokc.com/svroutlook/05-08-11-sounding.GIF) but we might see some weakening of it. Any upper air support that will bring lift will help in any storm formation, but coverage should be very low and therefore won't put an outlook up now. If things look like the cap will break for one or two storms, I'll put one in.



Monday looks a bit better. I did put in a slight risk area over the eastern half of the SPC area. This will be in an area ahead of the dryline, in mostly high instability, and where there are indications of the cap being weakest. Doesn't appear to be the same batch of energy passing over to help with convection development, but with a weaker cap a few storms seem more likely. Forecast sounding: http://www.chatokc.com/svroutlook/05-09-11-sounding.GIF



Tuesday looks like a severe weather day over a large area. Instability will be high, the cap will be weakening, and a batch of energy will eject out over SW OK by late afternoon. Storms will likely start forming in SW OK around 5-7PM and increase in coverage through the evening. Conditions will be favorable for severe storms with large hail, damaging winds, and a growing tornado threat. SPC has outlined Western & Central OK and already mentioned the risk of strong tornadoes. This could be one of those typical "Day before the Day" events that weather geeks tend to refer to. I went ahead and did a pretty broad slight risk for most of Oklahoma. Forecast Sounding: http://www.chatokc.com/svroutlook/05-10-11-sounding.GIF



Flat out severe weather day. Outbreak potential will be there. The main batch of energy will be ejecting out through the afternoon. Cold front will be dropping into NW OK and a dryline extending through SW OK. Instability will be very high ahead of these boundaries along and west of I-35. The cap will also be weakest in these areas. Did another pretty broad slight risk area for this day as the models have been extremely consistent in this day and it seems like this is going to happen. Forecast Sounding: http://www.chatokc.com/svroutlook/05-11-11-sounding.GIF

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New SPC Day 3 Outlook is out and they have included a slight risk for most of Western OK.



...SRN HIGH PLAINS...
DRYLINE WILL LIKELY MIX EWD INTO SCNTRL KS...WRN OK AND CENTRAL
EDWARDS PLATEAU REGION BY 21Z SUNDAY. STRONG EML WILL BE
PROBLEMATIC AS CAPPING CONCERNS PREVAIL. HOWEVER...WEAK HEIGHT
FALLS ASSOCIATED WITH AN EJECTING IMPULSE IN COMBINATION WITH VERY
HOT BOUNDARY LAYER TEMPERATURES WILL BE IMPETUS FOR WIDELY SCATTERED
TSTMS FROM SCNTRL KS SWD INTO WRN N TX LATE SUNDAY AFTERNOON.
BUOYANCY WILL BE ROBUST OWING TO AMPLE BOUNDARY LAYER MOISTURE AND
8.5 DEG C PER KM H7-H5 LAPSE RATES AND SUPERCELLS WILL BE LIKELY
SHOULD STORMS FORM WITH VERY LARGE HAIL AND POSSIBLY A TORNADO.
ACTIVITY SHOULD DIMINISH BY MID-EVENING AS STORMS MOVE INTO
INCREASINGLY CAPPED NOCTURNAL BOUNDARY LAYER ENVIRONMENT.

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New Day 4-8 Outlook is up highlighting Tuesday & Wednesday

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0353 AM CDT FRI MAY 06 2011

VALID 091200Z - 141200Z

...DISCUSSION...
UPPER FLOW WILL BECOME MORE MERIDIONAL ACROSS THE COUNTRY IN THE
MEDIUM RANGE AS THE WEST COAST TROUGH DEEPENS AND THEN BEGINS TO
EJECT ENE INTO THE PLAINS BY TUE AND WED. AS THE TROUGH DIGS INTO
THE GREAT BASIN...SWLY LOW/MID-LEVEL FLOW WILL TRANSPORT A VERY
STRONG EML ACROSS THE PLAINS FROM THE MEXICAN PLATEAU. AT THE SAME
TIME...THERE WILL BE IMPROVING LOW-LEVEL GULF MOISTURE ACROSS THE
PLAINS...PARTICULARLY TUESDAY AND WEDNESDAY.

DRYLINE TSTM INITIATION IS COMPARATIVELY MORE UNCERTAIN ON MONDAY
AFTN THAN ON SUNDAY AS MID-LEVELS FURTHER WARM IN ADVANCE OF THE
DIGGING IMPULSE INTO THE DESERT SW. MORE ROBUST SEVERE EVENTS
APPEAR LIKELY ON TUESDAY AND...PARTICULARILY...ON WEDNESDAY /DAY 5
AND 6/ AS THE UPPER STORM SYSTEM BODILY MOVES ONTO THE PLAINS.
THESE STORMS WILL DEVELOP IN INCREASINGLY LARGE HODOGRAPHS AND
BUOYANCY...YIELDING THREATS FOR VERY LARGE HAIL...TORNADOES AND
DAMAGING WIND GUSTS.

BEYOND DAY 6...MEDIUM RANGE GUIDANCE INTRODUCES A INCREASING SPREAD
ON THE HANDLING OF THE TROUGH AS IT TRANSLATES EWD ACROSS THE
MIDWEST AND NERN STATES. THIS RENDERS THE REMAINDER OF THE MEDIUM
RANGE PREDICTABILITY TOO LOW TO DELINEATE SVR WEATHER AREAS.

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Nothing new from the afternoon OUN AFD...but just reaffirming the severity of next week.

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORMAN OK
244 PM CDT FRI MAY 6 2011

.DISCUSSION...WARMING TREND WILL CONTINUE THE NEXT FEW DAYS ACROSS
THE FA WITH FIRE WEATHER ISSUES BECOMING A CONCERN IN THE WEST.
WEAK SURFACE BOUNDARY WILL DRIFT INTO NRN PARTS OF THE FA LATE
TONIGHT AS S/W TROUGH MOVES THROUGH THE NRN PLAINS. MODELS
CONTINUE TO DEVELOP PRECIP TO THE NE OF THE FA OVERNIGHT AS LLJ
INTERACTS WITH DEVELOPING WARM FRONT NEAR KS BORDER. ALTHOUGH IT
LOOKS LIKE MOST OF THE ACTIVITY SHOULD REMAIN NORTH OF THE FA WILL
INCLUDE SOME LOW POPS FOR FAR NE PARTS OF THE FA TONIGHT. WEAK
BOUNDARY IS EXPECTED TO DRIFT SWD INTO NRN PARTS OF THE AREA
SATURDAY BEFORE WEAKENING AND LIFTING BACK NORTH. ALTHOUGH W4RM
MID LEVEL TEMPS WILL INHIBIT STORM INITIATION ALONG THE DRYLINE
THROUGH MONDAY...VERY HOT TEMPS AND CONVERGENCE ALONG THE DRYLINE
MIGHT BE SUFFICIENT TO INITIATE A STORM OR TWO. THUS WILL CONTINUE
THE TREND OF PREVIOUS FORECAST AND LEAVE MENTION OF ISOLATED
THUNDERSTORMS IN FOR THOSE AREAS. IF STORMS CAN INITIATE...THEY
WILL LIKELY BE SEVERE GIVEN THE STRONG INSTABILITY. THUNDERSTORM CHANCES
WILL BEGIN TO IMPROVE TUESDAY...AND ESPECIALLY WEDNESDAY...AS THE
MAIN UPPER TROUGH BEGINS TO LIFT NEWD FROM THE ROCKIES INTO THE
PLAINS AND THE COLD FRONT/DRYLINE PUSH FARTHER INTO THE AREA.
CONDITIONS WILL BE FAVORABLE FOR MORE WIDESPREAD SEVERE WEATHER
DURING THAT TIME FRAME. COOLER AND DRIER WEATHER WILL THEN RETURN
THURSDAY AS THE FRONT PUSHES WELL SOUTH OF THE AREA.

[venture]

No major update for tonight. 00Z GFS has sped up a bit with the system, a tend it has shown all day today with each run. It is crashing the cold front through much faster on Wednesday. Initially last nights run had it just west of Highway US 281 near Weatherford. Tonights run has it almost 30 miles to US 177 east of the Metro area. Comparing ECMWF and GFS there is a pretty wide gab between the two. The EC is definitely slower than GFS and has been more stable in predicting this storm. The GFS has tended to get closer aligned to it through time, but they still aren't lining up for Wednesday. So we can't really take GFS too literal as there isn't a lot of agreement out there right now. Also we've seen GFS be very consistent on the placement, for the most part, for the last several days and now it is accelerating more and more. We are also just now seeing the first part of this storm system come on shore out west, so I'm not ready to make any wild changes.

Below is the visible satellite image from early Saturday morning just after midnight local time. You can see the system moving out of the Northern Plains that brought a weak boundary through the state yesterday that gave NE OK some light rain and a rumble of thunder. Our main system we are watching is still off the coast of BC with the first batch of energy from it now moving through the Pac Northwest. Once the system is fully on shore we'll be able to get more accurate measurements for the models to correctly pick up on.

[venture]

Day 2 Outlook has continued with a slight risk by the SPC over Central and SW Oklahoma. It is also a hatched area which is in respect to the instability and dynamics in place that large hail will be likely with any storm that can form and get going. Tornado threat is not zero and will be possible should any storm get established. The graphic below I have the SPC outlook area and some other information show the region with a very strong cap, the dryline out west, and a quick look at the surface vs. 500 mb winds. As storms move east into the capped area, they will like start to decrease rapidly unless it is intense enough to work through it. Day 2 outlook below but took out most of the text that doesn't apply to us.



DAY 2 CONVECTIVE OUTLOOK CORR 1
NWS STORM PREDICTION CENTER NORMAN OK
1246 AM CDT SAT MAY 07 2011

VALID 081200Z - 091200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE CNTRL/NRN PLAINS...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE SRN HIGH PLAINS...

CORRECTED FOR PROBABILITY LINES

...SYNOPSIS...
UPPER FLOW REGIME WILL BECOME INCREASINGLY MERIDIONAL ON SUNDAY AND
FEATURE A DEEP TROUGH OVER THE N ATLANTIC AND A DIGGING IMPULSE OVER
THE WRN STATES. A WEAK MID-LEVEL SHORTWAVE TROUGH WILL EJECT ENE
AHEAD OF THE LATTER SYSTEM INTO THE CNTRL/SRN PLAINS BY SUNDAY
AFTERNOON. AT THE SFC...A COLD FRONT TIED TO THE ATLANTIC TROUGH
WILL SETTLE INTO THE CAROLINAS. TAIL END OF SAME FRONT WILL
REDEVELOP NWD AS A WARM FRONT FROM THE MIDWEST INTO THE DAKOTAS AS A
DRYLINE/LEE TROUGH STRENGTHENS ACROSS THE CNTRL/SRN HIGH PLAINS.

...SRN PLAINS...
CONDITIONAL THREAT FOR ISOLD SUPERCELL STORMS WILL EXIST MID-AFTN
SUNDAY INTO THE MID-EVENING HOURS. MODELS CONTINUE TO INDICATE THAT
A WEAK TROUGH/HEIGHT FALLS WILL GRAZE THE REGION DURING PEAK
HEATING. FCST TEMPERATURES WILL BE IN EXCESS OF 100 DEG F WEST OF
THE DRYLINE AND THERE MAY BE A SUFFICIENTLY DEEP CIRCULATION ALONG
THE BOUNDARY FOR WEAKENING CINH/ISOLD TSTM INITIATION ACROSS WRN
OK/NW TX. ROUGHLY 50 KTS OF CROSS-BOUNDARY DEEP-LAYER SHEAR AND
VERY STEEP MID-LEVEL LAPSE RATES WILL BE FAVORABLE FOR VERY LARGE
HAIL WITH ANY STORM THAT CAN FORM. A TORNADO CANNOT BE RULED OUT
EARLY IN THE EVENING...BUT LCL/S WILL BE SOMEWHAT HIGH. THE ZONE OF
SVR THREAT WILL BE NARROW SINCE ANY SUSTAINED STORM WILL MOVE INTO
AN INCREASINGLY CAPPED ENVIRONMENT OVER NCNTRL TX/CNTRL OK DURING
THE LATE EVENING.

MORE UNCERTAINTY EXISTS FOR CONVECTIVE INITIATION ELSEWHERE ALONG
THE DRYLINE FROM CNTRL KS TO THE E PARTS OF THE EDWARDS PLATEAU
WHERE CAP WILL REMAIN VERY STRONG.


..RACY.. 05/07/2011