USA Weather — Severe Weather Division
This outlook is expired and is no longer valid.
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE CENTRAL PLAINS...AND OVER THE NORTHEASTERN GULF COAST AND PARTS OF FLORIDA...
...SUMMARY...
SCATTERED SEVERE THUNDERSTORMS PRODUCING A THREAT FOR DAMAGING WINDS, LARGE HAIL, AND PERHAPS A COUPLE TORNADOES ARE FORECAST THIS AFTERNOON AND EVENING ACROSS THE CENTRAL PLAINS INTO PARTS OF THE MIDWEST. DAMAGING WINDS WILL ALSO BE POSSIBLE ACROSS THE NORTHEAST GULF COAST AND PARTS OF FLORIDA TODAY.
...CENTRAL/NORTHERN PLAINS AND MIDWEST...
A WELL-DEFINED SHORTWAVE TROUGH OVER THE CENTRAL PLAINS THIS MORNING IS EVIDENT ON WATER VAPOR IMAGERY. ANOTHER SHORTWAVE TROUGH IS ALSO NOTED EXTENDING ACROSS CENTRAL MONTANA THIS MORNING. THESE TWO FEATURES WILL SLOWLY SLIDE EASTWARD ON THE NORTHERN EXTENT OF AN INTENSE RIDGE CENTERED OVER TEXAS, AND SHOULD ALSO PHASE DURING THE AFTERNOON AND OVERNIGHT TIMEFRAME. VERY LIMITED SURFACE REFLECTION IS NOTED THIS MORNING, WITH A WEAK WARM FRONT EXTENDING ACROSS SOUTHERN KANSAS FROM AN ELONGATED LOW/TROUGH CENTERED OVER THE CENTRAL HIGH PLAINS. A STRONGER COLD FRONT EXTENDING INTO THE PACIFIC NORTHWEST WILL MORE QUICKLY SPREAD EAST TODAY, EVENTUALLY RESULTING IN A BROADLY CONSOLIDATING LOW PRESSURE BY TONIGHT ACROSS THE DAKOTAS OR NEBRASKA FROM THESE TWO FEATURES.
VIGOROUS THUNDERSTORM ACTIVITY PERSISTS THIS MORNING ASSOCIATED WITH A MODEST SURFACE WARM AIR ADVECTION REGIME. WHILE THIS ACTIVITY IS SLOWLY SPREADING EAST-NORTHEAST, SIGNIFICANT CLOUD COVER AND CLOUD DEBRIS EXTENDS ACROSS MUCH OF THE CENTRAL PLAINS INTO THE MIDWEST. THIS ACTIVITY SHOULD EVENTUALLY MOVE OUT OF THE REGION OR DISSIPATE BY EARLY AFTERNOON, ALLOWING SUFFICIENT TIME FOR AT LEAST SOME SURFACE HEATING TO OCCUR WITHIN A VERY MOIST AIRMASS, CHARACTERIZED BY LOW TO MID 70S DEWPOINTS. GIVEN THE PRESENCE OF STEEP LAPSE RATES >8.0-8.5 C/KM, THIS SHOULD BE ENOUGH TO YIELD MODERATE TO LOCALLY STRONG MLCAPE OF 2000-3000 J/KG BY MID AFTERNOON. MODEL SOUNDINGS SUGGEST, HOWEVER, THAT WEAK LOW-LEVEL CINH MAY REMAIN EVEN THROUGHOUT THE AFTERNOON; THE DEGREE OF WHICH WILL MOSTLY DEPEND ON THE EXIT TIMING OF THE ONGOING CONVECTION AND THE EXTENT OF SURFACE HEATING. HOWEVER, IT IS EXPECTED THAT SCATTERED CONVECTIVE DEVELOPMENT OCCURS LATE THIS AFTERNOON AS MODEST INCREASES IN FORCING ARE NOTED, AIDED BY LOW-LEVEL CONVERGENCE AND ORTHOGRAPHIC LIFTING FURTHER WEST. DEEP-LAYER SHEAR IN THE 35-45KT RANGE WITH LENGTHY HODOGRAPHS AND MODERATELY CURVED LOW-LEVELS SHOULD SUPPORT A MIXED CONVECTIVE MODE THIS AFTERNOON AND EVENING FROM THE COLORADO FRONT RANGE NORTHWARD THROUGH THE CENTRAL DAKOTAS. DAMAGING WINDS ALONG WITH SOME HAIL THREAT SHOULD EVOLVE WITHIN THESE STORMS AS THEY SPREAD EAST, WITH A FEW SIGNIFICANT GUSTS >75MPH POSSIBLE FROM ANY BOWING SEGMENTS THAT DEVELOP. A BRIEF TORNADO OR TWO MAY ALSO OCCUR WHERE LOCALIZED SRH IS HIGHER.
NOTABLY, SOME GUIDANCE HAS SUGGESTED INCREASING COVERAGE/ORGANIZATION THIS EVENING OVER WESTERN TO CENTRAL NEBRASKA, RESULTING IN A MORE ORGANIZED CLUSTER OR MCS EVENTUALLY DEVELOPING AND PROPAGATING EAST-SOUTHEAST. SUCH A SCENARIO WOULD RESULT IN A CONCENTRATED CORRIDOR FOR ENHANCED DAMAGING WIND POTENTIAL. THIS CURRENTLY REMAINS QUESTIONABLE, HOWEVER, GIVEN THE UNCERTAINTIES WITH THE DEGREE OF DESTABILIZATION. HAVE THEREFORE DEFERRED CONSIDERATION OF HIGHER WIND PROBABILITIES TO A LATER UPDATE IF CONFIDENCE INCREASES. REGARDLESS, SPORADIC WIND DAMAGE POTENTIAL SHOULD PERSIST WITH ANY STRONGER STORM CLUSTERS THAT SPREAD EASTWARD TONIGHT.
...GULF COAST...
A WEAK STATIONARY FRONT EXTENDS ACROSS SOUTHERN GEORGIA, ALABAMA, AND MISSISSIPPI THIS MORNING. LIMITED MOVEMENT OF THIS BOUNDARY OUTSIDE OF CONVECTIVE INFLUENCES IS ANTICIPATED TODAY. EXTENSIVE MOISTURE WITH MID 70S TO LOW 80S DEWPOINTS ARE NOTED TO THE SOUTH OF THE BOUNDARY. AS A RESULT, INTENSE DESTABILIZATION IS EXPECTED TODAY AS HEATING OCCURS, WITH MLCAPE LIKELY TO EXCEED 3500-4000 J/KG BY THIS AFTERNOON. SCATTERED THUNDERSTORMS ARE ALREADY NOTED OVER THE FAR NORTHEAST GULF INTO PARTS OF THE FLORIDA BIG BEND, AND SHOULD PRODUCE OUTFLOW BOUNDARIES GIVEN THE CURRENT PULSE TYPE NATURE. THESE BOUNDARIES, ALONG WITH A DEVELOPING SEABREEZE AND THE STATIONARY FRONT ITSELF SHOULD ALL PROVIDE FOCUS FOR SCATTERED TO NUMEROUS THUNDERSTORM DEVELOPMENT THIS AFTERNOON. THE PRESENCE OF 20-30KT NORTHERLY SHEAR ACROSS THE NORTHEASTERN GULF COAST AND NORTHERN FLORIDA SHOULD ALLOW FOR SOME LOOSE ORGANIZATION INTO MULTICELL CLUSTERS/LINE SEGMENTS. DAMAGING WINDS, BOTH FROM ISOLATED WET MICROBURSTS AND THE MULTICELL CLUSTERS SHOULD BE THE PRIMARY HAZARD TODAY, WITH GREATEST COVERAGE MAINLY OVER THE NORTH FLORIDA AND FAR SOUTHERN AL/GA.