Many questions arise about the exact criteria used for watches, warnings and advisories commonly referred to as "headlines" by the National Weather Service. This article will cover those items and be a reference to refer back to for the information. Any general or specific event discussion should remain in the discussion threads.

This article is a work in progress, so please excuse the dust. :)

All headlines are going to be presented with 3 areas of criteria. The first column would be those that apply to the NWS Norman County Warning Area ("CWA"), the second will be in respect to the Tulsa CWA, with the first showing the generic or base criteria give by the NWS. Each NWS forecast office has the ability to modify the advisories to meet expectations of local impacts. In some areas snowfall that will only accumulate 6" over an entire 24-hour period won't justify a warning, but in another location it will. This should bring some clarity on how things can vary.

Winter Season Headlines

Watch variations for Blizzard and Winter Storm are issued when conditions are expected to develop, typically, in the next 12 to 36 hours but sometimes can be extended out to 48 hours prior to the start of the event.

Headline NWS Norman Criteria NWS Tulsa Criteria NWS Base Criteria
Blizzard Warning Sustain Winds/Gust over 35 mph with falling/blowing snow with visibility under 1/4 mile for 3 hours or more. Sustain Winds/Gust over 35 mph with falling/blowing snow with visibility under 1/4 mile for 3 hours or more. Sustain Winds/Gust over 35 mph with falling/blowing snow with visibility under 1/4 mile for 3 hours or more.
Ice Storm Warning Ice accumulation over 1/4 inch or when significant disruption to utilities and/or traffic expected. Ice accumulation exceeding 1/4 inch.
Winter Storm Warning Snow, Ice, Sleet over 12 and/or 24 hours with one or more exceeding warning criteria by local office.
Freezing Rain Advisory Issued for ice from rain/drizzle that won't exceed 1/4 inch. Light ice from rain or drizzle meeting/exceeding local criteria.
Winter Weather Advisory Issued with more than one (snow, sleet, ice) expected but values remain below warning criteria for all. 1-3 inches of snow or icing expected. Less than 1 inch if outside normal season. Snow, Ice, Sleet over 12 and/or 24 hours with one or more exceeding advisory criteria by local office.
Wind Chill Warning Wind chills below -20F. Wind chill values reaching or falling below -18F
Wind Chill Advisory Wind chills between -19F to -5F. Wind chill values reaching or falling below local criteria.
NOTE: The Snow Advisory, Heavy Snow Warning, Blowing Snow Advisory, and Freezing Drizzle Advisory were consolidated into the above advisories and are no longer in use since 2009. Also, some local OKC media tends to use "Travelers Advisory" in place of the official Winter Weather Advisory criteria. No reasoning is given for this since the Winter Weather Advisory isn't specifically focused on only travel conditions.

Severe Weather Headlines

These are the basic severe weather headlines that don't include any flood advisories. SPC watch durations are typically around 6 hours in length and are issues one hour in advance, on average, of the initiation of severe weather.

Headline Storm Prediction Center or NWS Norman Criteria
Tornado Warning Radar indicated or spotter reported tornado that is imminent or occurring.
Tornado Watch Issued when conditions are favorable for multiple or strong tornadoes.
PDS Tornado Watch Issued when conditions favor significant tornadoes and/or an outbreak of tornadoes.
Severe Thunderstorm Warning Issued with radar evidence or spotter report that a storm is producing wind gusts of 58 mph, structural wind damage, and/or hail over 1 inch in diameter.
Severe Thunderstorm Watch Issued when conditions are favorable for severe weather include damaging winds, hail, and tornadoes.
PDS Severe Thunderstorm Watch Issued for extremely destruction and widespread thunderstorm wind events, derecho.
Significant Weather Advisory Issued for strong thunderstorms under severe limits, usually with winds of 40-58 mph and hail up to 1 inch. The advisory is issued under the Special Weather Statement product.
NOTE: The local media of OKC typically reports Significant Weather Advisories as "Heavy T-Storm" through their on air First Warning Alert System's county maps.

Flood Advisories and Non-Precip Advisories Coming Soon