General Weather Discussion - May 2015

[venture]

Slight Risk for today has been extended all the way to I-35 and is now entirely hatched for Oklahoma. Main threat will be very large hail over 2 inches. Damaging wind and tornadoes will also be possible.

Chat room day for Wednesday, so will hold off any big model updates until the morning so I can get the new Euro run involved.
...CENTRAL/SOUTHERN PLAINS...
WARM-CONVEYOR SCATTERED SHOWERS/TSTMS WILL BE ONGOING AT 12Z TODAY
FROM PARTS OF NORTHEAST TX AND EASTERN OK NWD INTO THE MID MO
VALLEY. RESIDUAL CLOUD COVER IS EXPECTED ACROSS MUCH OF THE
WARM/MOIST SECTOR INTO THIS AFTERNOON. MEANWHILE...SLY LOW-LEVEL
WINDS WILL MAINTAIN POLEWARD MOISTURE RETURN/THETA-E ADVECTION EAST
OF THE DRY LINE...WITH PW VALUES EXCEEDING 1.25 INCHES. THIS
COMBINED WITH SURFACE HEATING WEST OF THE EARLY DAY CLOUDINESS WILL
CONTRIBUTE TO A DESTABILIZING AIR MASS WITH MLCAPE OF 1500-2500 J/KG
FROM SOUTH-CENTRAL KS SWD THROUGH WRN OK AND WRN/CENTRAL TX...WHILE
VALUES OF 1000-1500 J/KG NWD THROUGH CENTRAL KS AND SRN/ERN NEB.
EFFECTIVE BULK SHEAR OF 35-40 KT IS EXPECTED ALONG THE FULL EXTENT
OF THE DRY LINE WITH THIS SHEAR VECTOR ORIENTED PERPENDICULAR TO
THIS BOUNDARY WHICH SUPPORTS SUPERCELLS WITH STORMS THAT DEVELOP
LATE THIS AFTERNOON INTO THE EVENING.

MODELS CONTINUE TO INDICATE MUCH OF THE LEAD SHORTWAVE
TROUGH-RELATED LARGE-SCALE FORCING FOR ASCENT WILL OVERSPREAD THE
CENTRAL PLAINS/MIDDLE MO VALLEY...WHILE NEUTRAL HEIGHT TENDENCIES OR
WEAK RISES...WITH SOME MIDLEVEL WARMING WILL OCCUR ACROSS THE
SOUTHERN PLAINS PORTION OF THE DRYLINE. GIVEN THIS FACTOR AND
GUIDANCE FROM THE HIGH-RES MODELS AND CAMS SUGGEST STORM COVERAGE
NEAR AND EAST OF THE DRY LINE WILL TEND TO BE ISOLATED...WHICH
CONTINUES TO SUPPORT A SLIGHT RISK FOR SEVERE STORMS...AND NO
INCLUSION OF AN ENHANCED RISK AREA AS THIS TIME. SEVERE HAIL AND
DAMAGING WINDS MAY BE THE MOST COMMON RISKS...WITH A PLUME OF
STEEPER MIDLEVEL LAPSE RATES SPREADING ACROSS TX/OK/KS PORTIONS OF
THE SLIGHT RISK AREA THIS EVENING SUGGESTING VERY LARGE HAIL WILL BE
POSSIBLE. VERTICALLY VEERING WIND PROFILES WILL SUPPORT A TORNADO
THREAT. FORECAST SOUNDINGS INDICATED SOME BACKING OF LOW-LEVEL
WINDS ACROSS WRN-NORTH TX THROUGH WRN OK INTO SOUTH CENTRAL KS THIS
EVENING AS THE DRY LINE RETREATS WITH A TORNADO IN THOSE AREAS AS
WELL WITH ANY STORMS THAT DEVELOP.

[jn1780]

Slight Risk Friday extended to cover most of Oklahoma. Saturday is now has a large 30 percent risk area ( The highest the 4-8 product day allows them to do this far out).

[Anonymous.]

If this cloud deck burns off, lookout this afternoon!

[Bobby821]

From SPC on there latest outlook from this morning.

SUFFICIENT LOW-LEVEL MOISTURE...EFFECTIVE BULK SHEAR OF 35-40
KT...AND STRENGTHENING LOW-LEVEL SHEAR BY THIS EVENING WILL SUPPORT
A RISK FOR SUPERCELLS WITH TORNADOES AND VERY LARGE HAIL. THE
DAMAGING WIND RISK SHOULD BE SMALLER GIVEN THE EXPECTATION FOR
MAINLY ISOLATED/DISCRETE CELLS. THE PARAMETER SPACE IS FORECAST TO
BECOME FAVORABLE FOR SIGNIFICANT TORNADOES FROM WRN OK INTO CENTRAL
KS THIS EVENING...BUT WILL NOT RAISE TORNADO PROBABILITIES BECAUSE
CONFIDENCE IN SUPERCELL INITIATION ACROSS THIS SAME CORRIDOR REMAINS
A BIT TOO LOW.

[s00nr1]

I will be out with a couple of co-workers in western OK this afternoon. Will post any pics that are worthwhile.

[bandnerd]

Grr...supposed to have my band and orchestra picnic on Friday evening :/

[venture]

So far for this morning not a lot really going on. A few isolated showers with one denser patch developing over Southern Caddo. No high level cirrus/cloud debris today to worry about like we normally do, so that is one positive sign towards storm development. The cloud cover over Western OK is eroding some, but very slowly so far. So outside of that let's look at the rest of the setup...

- Moisture: Mid to upper 60s as far as dewpoints right now, with a pretty solid fetch of moisture from the south. So we are good there.
- Instability: SPC Mesoanalysis has most of the area marginally to moderately unstable area with short term models getting us very unstable by afternoon.
- Boundaries: Dryline will sharpen some and get barely into West Central and Northwest OK late this afternoon before retreating. Any left over boundaries from last night's storms will also help provide trigger areas.

Right now my feeling is that this will not be a very widespread event. Storm coverage is really limited in the current model runs, but signs are there that we'll get a few to go. The limit of extensive coverage will allow them to remain isolated and not fight for energy from other storms. So the focus now will be watching on how the cloud deck burns off. I would pay attention to both the dryline in NW OK but also and area that might get sparked off over SW OK/NW TX around late afternoon. If I were going out, I would take the easy launch point of Clinton and see how things evolve. Even though it is only a slight risk, I had some of my best chase days with slight risks - so stay aware!

Chat room is up and going for today: Weather Spotlight - Live Chat Room for Weather Event Coverage

[FighttheGoodFight]

We got some serious rain in Norman. Rained hard all night and kept me up with the thunder. My puppy however didn't even notice...

[venture]

We got some serious rain in Norman. Rained hard all night and kept me up with the thunder. My puppy however didn't even notice...

Norman won the 24 hour rain total...3.94", with 2.76" since midnight alone. Definitely a lot of water.

[Hollywood]

Beginning to see slivers of sun through the clouds in the north metro.

[venture]

Rick Smith @ounwcm

Getting more concerned about potential for dangerous storms this afternoon/evening. Lots of ingredients will be in place. Not a guarantee!

Rick Smith @ounwcm

Pay very close attention to the #okwx and #texomawx. Watch for updated outlooks and don't leave work without checking the weather.

[venture]

Outlook upgraded to Enhanced.

[venture]

...northwest ok...
The area with the lowest confidence in robust convective initiation
along the dryline is over northwest ok. However...virtually all
models agree on a strong cape/shear environment by late afternoon
with little cap. Any storm that forms in this region would have a
high conditional risk of significant severe weather. However...
Will maintain only 5 percent tornado and 15 percent hail
probabilities at this time.

...southwest ok into tx...
Visible satellite imagery shows strong heating occurring over parts
of western north tx...where dewpoints are in the mid 60s. This area
may be far enough southwest to recover from the subsidence
associated with the shortwave over ks...with another area of higher
confidence in convective initiation. Supercells capable of very
large hail and isolated tornadoes are expected to occur in this
region during the mid afternoon through evening hours.

[venture]

Couple early storms trying to go up. Small hail main risk right now.

[venture]

Storm has gone severe already.

THE NATIONAL WEATHER SERVICE IN NORMAN HAS ISSUED A


* SEVERE THUNDERSTORM WARNING FOR...
SOUTHERN CADDO COUNTY IN SOUTHWESTERN OKLAHOMA...


* UNTIL 130 PM CDT


* AT 1246 PM CDT...A SEVERE THUNDERSTORM WAS LOCATED 5 MILES WEST OF
BOONE...MOVING NORTHEAST AT 30 MPH.


HAZARD...60 MPH WIND GUSTS AND HALF DOLLAR SIZE HAIL.


SOURCE...RADAR INDICATED.

[Anonymous.]

Nice clearing taking place, but these little storms popping up this early could keep revamping the cloud deck we have been burning off all day.

[venture]

AREAS AFFECTED...PORTIONS OF WEST TEXAS...NORTHWEST TEXAS AND
SOUTHWEST OKLAHOMA

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 061803Z - 062000Z

PROBABILITY OF WATCH ISSUANCE...95 PERCENT

SUMMARY...THUNDERSTORMS EXPECTED TO DEVELOP RAPIDLY BETWEEN 18 AND
19Z. SEVERE HAIL AND WIND GUSTS ARE THE PRIMARY THREATS
INITIALLY...BUT TURNING LOW-LEVEL HODOGRAPHS SUGGEST A TORNADO
THREAT FOR ANY SUSTAINED UPDRAFTS.

DISCUSSION...STRONG HEATING HAS CONTRIBUTED TO RAPID DESTABILIZATION
AHEAD OF A DIFFUSE DRYLINE WITH AN EASTERN EDGE STRETCHING FROM EAST
OF LBB TO NEAR SHAMROCK. ALTHOUGH THE MCD AREA IS UNDER NEUTRAL TO
SLIGHT MID-LEVEL HEIGHT RISES IN THE WAKE OF THE EXITING
WAVE...LITTLE TO NO CONVECTIVE INHIBITION IS PRESENT OVER THE AREA.
MIXED-LAYER CAPE VALUES HAVE RISEN ABOVE 2000 J/KG WITH LOW-LEVEL
LAPSE RATES ABOVE 8 C/KM. WITH EFFECTIVE SHEAR OF 30-40
KT...SUPERCELL STRUCTURES WILL BE THE FAVORED MODE FOR PERSISTENT
UPDRAFTS...BUT LONGEVITY OF THE SUPERCELLS COULD BE NEGATIVELY
IMPACTED BY STORM INTERACTIONS AS NUMEROUS STORMS ARE EXPECTED TO
DEVELOP UNDER LITTLE INHIBITION AND POSSIBLY ENHANCED BY LIFT FROM A
WEAK POTENTIAL VORTICITY ANOMALY PROGRESSING THROUGH THE BROAD
CYCLONIC FLOW IN UPPER-LEVELS. REGARDLESS OF STORM MODE...SEVERE
HAIL IS LIKELY WITH THE STRONGER STORMS...WITH SEVERE WIND GUSTS
POSSIBLE GIVEN THE STEEP LOW-LEVEL LAPSE RATES. ALTHOUGH LOW-LEVEL
WIND SPEEDS REMAIN SOMEWHAT MODEST...LOW-LEVEL HODOGRAPHS SHOW
CURVATURE...WITH EFFECTIVE HELICITY VALUES OF 100-150 M2/S2 FOR
STORMS THAT DEVIATE TO THE RIGHT OF THE MEAN FLOW AND SHEAR.

[venture]

AREAS AFFECTED...MUCH OF CNTRL KS...S CNTRL NEB

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 061809Z - 062045Z

PROBABILITY OF WATCH ISSUANCE...95 PERCENT

SUMMARY...STORMS WILL DEVELOP ACROSS NWRN INTO CNTRL KS WITH
TORNADOES...LARGE HAIL AND DAMAGING WIND POSSIBLE.

DISCUSSION...VISIBLE SATELLITE SHOWS CU INCREASING IN DEPTH ACROSS
MUCH OF CNTRL KS INTO SWRN NEB DUE TO HEATING AND A RAPID NWD
ADVECTION OF LOW-LEVEL MOISTURE WITH DEWPOINTS RISING INTO THE 60S
F. MEANWHILE...AN UPPER TROUGH AXIS EXTENDS FROM NERN CO INTO WRN
KS...WITH ENHANCED VORTICITY ON THE N SIDE OF THE MIDLEVEL JET.

NEARBY VWPS SHOW SUBSTANTIAL LOW-LEVEL TURNING OF THE WINDS WITH
HEIGHT...FAVORABLE FOR SUPERCELLS. THE LACK OF A CAPPING INVERSION
COMBINED WITH THE RELATIVELY HIGH-RH BOUNDARY LAYER AND AMPLE
LOW-LEVEL SRH SUGGEST TORNADOES MAY OCCUR. LARGE HAIL IS ALSO LIKELY
BUT MID TO UPPER LEVEL FLOW IS WEAK...SUGGESTING HP SUPERCELLS WITH
LARGE PROPAGATIONAL COMPONENT. SOME HIGH RESOLUTION MODELS SUGGEST A
LINEAR MODE AND DAMAGING WIND THREAT AS WELL...MAINLY OVER NRN KS
INTO SRN NEB.

[venture]

Nice clearing taking place, but these little storms popping up this early could keep revamping the cloud deck we have been burning off all day.

The short term models seemed to anticipate this, and the feeling I'm getting from SPC/NWS is that it won't matter.

No CIN out there and instability already very high.

[venture]

[venture]

Tornadoes

Probability of 2 or more tornadoes	Mod (50%)
Probability of 1 or more strong (F2-F5) tornadoes	Mod (30%)

Wind

Probability of 10 or more severe wind events	High (70%)
Probability of 1 or more wind events > 65 knots	Low (10%)

Hail

Probability of 10 or more severe hail events	High (90%)
Probability of 1 or more hailstones > 2 inches	Mod (40%)

Combined Severe Hail/Wind

Probability of 6 or more combined severe hail/wind events

High (>95%)

[Anonymous.]

Most "impressive" watch for OK this season, I think.

Once these little cells shove off, and the big boys come out to play on the dryline, we could be in business.

[adaniel]

Just a general question. With the probabilities so high (can't remember a tornado watch having 50% probabilities in some time), would this qualify as a PDS?

[venture]

Just a general question. With the probabilities so high (can't remember a tornado watch having 50% probabilities in some time), would this qualify as a PDS?

Nope. Need 50% EF2-EF5 typically...even that can be borderline.

[OKCisOK4me]

Where is the dryline positioned at right now? Oklahoma Texas border?