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May 5, 2014 1300 UTC Day 1 Convective Outlook

May 5, 2014

May 5, 2014 1300 UTC Day 1 Convective Outlook

day1otlk

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0731 AM CDT MON MAY 05 2014

VALID 051300Z – 061200Z

…NO SVR TSTM AREAS FORECAST…

…SUMMARY…
STRONG TO MARGINALLY SEVERE THUNDERSTORMS ARE POSSIBLE THIS AFTERNOON…FIRST OVER WESTERN AND SOUTHERN VIRGINIA AND NEARBY WEST VIRGINIA…THEN OVER THE BLACK HILLS REGION AND SURROUNDING HIGH PLAINS.

…SYNOPSIS…
UPPER-AIR PATTERN THIS PERIOD WILL BE CHARACTERIZED BY BROAD/LOW-AMPLITUDE ANTICYCLONIC FLOW OVER MUCH OF CONUS…DOWNWIND FROM SLOWLY PROGRESSIVE NWRN TROUGH. SERIES OF SHORTWAVE PERTURBATIONS WILL RESULT IN SRN PORTION OF THAT TROUGH EVOLVING INTO CLOSED 500-MB LOW OVER WRN NV BY 12Z…WITH TROUGH EXTENDING NNEWD OVER NRN ROCKIES AND SWD ACROSS SRN CA COAST. WEAK SHORTWAVE PERTURBATION — EVIDENT IN MOISTURE-CHANNEL IMAGERY OVER UPPER MS VALLEY ATTM — SHOULD MOVE ESEWD TODAY…REACHING CENTRAL APPALACHIANS IN 00-03Z TIME FRAME.

AT SFC…WAVY FRONTAL ZONE FROM NC TO CENTRAL KY…CENTRAL MO…SRN KS…NERN CO…AND NERN WY WILL MOVE LITTLE. HYBRID LEE-SIDE/FRONTAL-WAVE LOW SHOULD BECOME BETTER-DEFINED OVER ERN WY LATE AFTN INTO EVENING…MOVING OVER SWRN SD OVERNIGHT. TROUGH WILL EXTEND N OF THAT LOW…INITIALLY OVER SERN MT THEN OVER WRN SD.

…S-CENTRAL APPALACHIANS/PIEDMONT…
CONDITIONAL SVR RISK HAS BECOME APPARENT ENOUGH TO DRAW MRGL PROBABILITIES FOR THIS AFTN. MAIN LIMITING FACTOR IS LACK OF MORE ROBUST MOISTURE. AREAS OF SFC DEW POINTS IN MOST PROGS OF MID-50S F APPEAR TOO HIGH BASED ON DRIER UPSTREAM CONDITIONS…AND ON LIKELIHOOD THAT BOUNDARY-LAYER MIXING LARGELY WILL OFFSET MOIST ADVECTION AND EVAPOTRANSPIRATION FROM RECENT RAINS AND GREEN-UP. STILL…POCKETS OF UPPER-40S TO LOW-50S VALUES MAY DEVELOP AND…IN TANDEM WITH SUFFICIENT SFC HEATING AND FRONTAL LIFT…REMOVE CINH. FRONTAL BAROCLINICITY ALSO MAY BE REINFORCED BY DIFFERENTIAL HEATING AND/OR WEAK OUTFLOW FROM CONVECTION NOW UPSHEAR OVER WV. WEAK DCVA AHEAD OF LOW-AMPLITUDE PERTURBATION ALOFT ALSO MAY AID CONVECTIVE ENVIRONMENT LATE THIS AFTN VIS DESTABILIZATION ALOFT. AS SUCH…A FEW TSTMS MAY FORM THEN MOVE ESEWD NEAR FRONT…IN ENVIRONMENT CHARACTERIZED BY 500-1000 J/KG MLCAPE…WELL-MIXED SUBCLOUD LAYER AND 45-60 KT EFFECTIVE SHEAR MAGNITUDE. NOCTURNAL DIABATIC COOLING SHOULD REDUCE MLCAPE AND REMOVE ALREADY WEAK SVR THREAT THIS EVENING.

…NORTHERN HIGH PLAINS…BLACK HILLS REGION…
DIURNAL/SFC-BASED CONVECTIVE INITIATION APPEARS UNCERTAIN ATTM…HOWEVER IF THAT OCCURS…ANY SUSTAINED TSTMS MAY OFFER AT LEAST BRIEFLY SVR HAIL AND STG/DAMAGING GUSTS. MEAN RIDGE WILL PASS E OF THIS AREA AROUND MIDDAY…FOLLOWED BY SMALL BUT STEADY HEIGHT FALLS CONCURRENT WITH PERSISTENT AFTN HEATING. DEEP SHEAR WILL BE FAVORABLE BENEATH 50-70-KT 500-MB FLOW AND 70-90-KT 250-MB WINDS…ESPECIALLY NEAR AND E OF SFC LOW/TROUGH WHERE BOUNDARY-LAYER WINDS ARE BACKED. LACK OF MORE ROBUST MOISTURE SHOULD LIMIT MLCAPE TO AROUND 700 J/KG.

ISOLATED HAIL NEAR SVR LIMITS ALSO MAY OCCUR WITH SUBSEQUENT/ELEVATED CONVECTION THIS EVENING OVER WRN SD…HOWEVER POTENTIAL APPEARS VERY LOW AND DECREASES SHARPLY WITH NWD EXTENT.

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