Friday, May 20, 2011

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 201630
SWODY1
SPC AC 201628

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1128 AM CDT FRI MAY 20 2011

VALID 201630Z - 211200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM ERN OK/AR SWWD INTO CNTRL
TX...

...THERE IS A SLGT RISK OF SVR TSTMS FROM CNTRL/ERN NEB INTO WRN
OK...

...ERN PARTS OF OK/TX INTO AR/NRN LA...

SRN EXTENSION OF NOCTURNAL QLCS IS EXPECTED TO PERSIST
TODAY...GRADUALLY MOVING/DEVELOPING EWD WITH TIME. THE INFLUX OF A
SEASONABLY MOIST AIR MASS /CHARACTERIZED BY BOUNDARY LAYER DEWPOINTS
IN UPPER 60S TO LOWER 70S/ WILL BE MAINTAINED BY A 35-45 KT SLY LLJ
WHICH SHOULD SERVE TO ENHANCE UPDRAFT STRENGTH ALONG LEADING EDGE OF
SYSTEM COLD POOL. ADDITIONAL MORE DISCRETE STORM DEVELOPMENT WILL
REMAIN POSSIBLE IN ADVANCE OF QLCS AND S OF WARM FRONT LIFTING NWD
INTO SRN MO WHERE LOW-LEVEL SHEAR WILL BE ENHANCED BY THE PRESENCE
OF THE LLJ. WHILE MID AND HIGH-LEVEL WIND FIELD WILL NOT BE
PARTICULARLY STRONG...THE PRESENCE OF 0-1 KM SRH OF 200-250 M2/S2
AND THE MOIST BOUNDARY LAYER SUGGEST A RISK FOR A FEW TORNADOES WITH
ANY SUPERCELLS THAT CAN BECOME ESTABLISHED. OTHERWISE...EXPECT
LARGER-SCALE CONVECTIVE SYSTEM TO REMAIN CAPABLE OF DAMAGING WIND
GUSTS AND HAIL TODAY INTO THIS EVENING.

FOR ADDITIONAL NEAR TERM GUIDANCE...SEE MCD 825.

...CNTRL/ERN NEB INTO WRN OK...

LATEST MODEL GUIDANCE SUGGESTS THAT BREAKS IN THE CLOUDS COUPLED
WITH HEIGHT FALLS/DYNAMIC COOLING IN THE MIDLEVELS ASSOCIATED WITH
VORTICITY MAXIMUM PIVOTING NNEWD THROUGH THE HIGH PLAINS MAY SUPPORT
A NARROW AXIS OF MODERATE INSTABILITY BY AFTERNOON IMMEDIATELY AHEAD
OF PACIFIC FRONT. THE STRONGEST DEEP-LAYER VERTICAL SHEAR /40-50
KT/ WILL RESIDE ACROSS OK INTO SRN KS...DECREASING TO 30-35 KT IN
NEB. AS SUCH...ISOLATED TO WIDELY SCATTERED STORMS /INCLUDING
SUPERCELLS/ WILL BE POSSIBLE THIS AFTERNOON INTO EVENING WITH THE
PRIMARY HAZARD BEING LARGE HAIL.

...NRN PLAINS...

AS MIDLEVEL DRY SLOT CONTINUES TO DEVELOP NWD TODAY...SOME POTENTIAL
FOR CLEARING WILL EXIST ALONG IMMEDIATE FRONT ARCING NWWD FROM CNTRL
NEB TO WEAK LOW PRESSURE OVER WRN SD. GIVEN VERTICALLY VEERING
WINDS WITH HEIGHT...BOUNDARY LAYER DEWPOINTS IN THE 50S AND A
RELATIVELY COOL THERMODYNAMIC PROFILE PER 12Z RAP SOUNDING...A RISK
FOR ISOLATED SEVERE STORMS WILL EXIST SHOULD SUFFICIENT
HEATING/DESTABILIZATION OCCUR. DUE TO UNCERTAINTY IN THE DEGREE OF
INSTABILITY THAT WILL DEVELOP LATER TODAY...LOW SEVERE WEATHER
PROBABILITIES WILL BE MAINTAINED.

...ERN CAROLINAS...

VORTICITY MAXIMUM OVER WV/VA LATE THIS MORNING WILL CONTINUE SEWD
TODAY...GLANCING THE REGION WITH WEAK HEIGHT FALLS/FORCING FOR
ASCENT. THIS MIDLEVEL SYSTEM WILL BE ATTENDED BY A WEAK SURFACE
TROUGH/COLD FRONT WHICH MAY SERVE AS THE FOCUS FOR ISOLATED TO
WIDELY SCATTERED TSTM DEVELOPMENT THIS AFTERNOON. DAYTIME HEATING
COUPLED WITH MODEST BOUNDARY LAYER MOISTURE CONTENT MAY YIELD MLCAPE
VALUES APPROACHING 500-1000 J/KG AHEAD OF FRONT. GIVEN MODESTLY
STRONG MID AND HIGH-LEVEL WNWLY FLOW OBSERVED BY 12Z SOUNDINGS...
SOME RISK FOR LOCALLY STRONG WIND GUSTS AND PERHAPS HAIL WILL EXIST
WITH ANY STORMS THAT CAN DEVELOP.

..MEAD/GRAMS.. 05/20/2011

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