DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 171929
SWODY1
SPC AC 171927

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0227 PM CDT FRI MAY 17 2013

VALID 172000Z - 181200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF TX...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE NRN
PLAINS...

...THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF THE CNTRL GULF
STATES...

...TX...

HAVE OPTED TO INTRODUCE 10 PERCENT SIG HAIL THREAT TO PORTIONS OF TX
AND EXPAND THE CATEGORICAL SLGT NORTH AND EAST TOWARD THE WRN PARTS
OF NCNTRL TX.

LATEST HIGH RES MODEL GUIDANCE HAS TRENDED TOWARD SCATTERED TSTM
DEVELOPMENT ALONG THE DRYLINE FROM EAST OF SJT TO NW OF MWL OVER THE
NEXT FEW HOURS. LATEST VIS IMAGERY SUPPORTS THIS EVOLUTION WITH
DEEPENING CU FIELD OVER MCCULLOCH COUNTY AND NEW CU OVER SHACKELFORD
COUNTY NE OF ABI. WITH SFC TEMPERATURES AROUND 103F AT BOTH ABI AND
SJT...AND WITH DEW POINTS NEAR 70 EAST OF THE DRYLINE...IT APPEARS
TSTMS WILL DEVELOP SHORTLY. EXTREME SBCAPE...ON THE ORDER OF 4000
J/KG...AND MODEST DEEP LAYER SHEAR SUGGEST VERY LARGE HAIL MAY
ACCOMPANY THESE STORMS. ADDITIONALLY...STRONG DOWNBURSTS COULD BE
OBSERVED GIVEN THE TEMP/DEW POINT SPREADS.

...ELSEWHERE...

EARLIER THOUGHTS REGARDING CONVECTION NEAR THE BLACK HILLS AND OVER
THE CNTRL GULF STATES REMAIN.

..DARROW.. 05/17/2013

.PREV DISCUSSION... /ISSUED 1145 AM CDT FRI MAY 17 2013/

CORRECTED TORNADO POINTS PRODUCT

...NERN WY INTO WRN/CENTRAL SD...
FULL-LATITUDE UPPER TROUGH HAS MOVED ONSHORE ALONG THE PACIFIC COAST
AND IS FORECAST TO PROGRESS EWD THROUGH TONIGHT REACHING THE
INTERMOUNTAIN REGION BY THE END OF THE PERIOD. SOUTHERLY LOW LEVEL
FLOW OVER THE PLAINS IS EXPECTED TO INCREASE IN RESPONSE TO THE
APPROACHING UPPER TROUGH...WITH NWD MOISTURE TRANSPORT CONTINUING
INTO THE NRN PLAINS. AT THE SURFACE...A LOW CURRENTLY OVER SERN WY
WILL MOVE SLOWLY NEWD TOWARD SWRN SD AS A WARM FRONT EXTENDING EWD
ACROSS SRN SD EDGES NWD. DEW POINTS ARE FORECAST TO REMAIN IN THE
50S EAST OF A DRY LINE OVER THE HIGH PLAINS...WITH LOWER 60S
POSSIBLE INTO PARTS OF SD...AND STRONG DIABATIC HEATING WILL RESULT
IN DEVELOPMENT OF A DEEP WELL-MIXED BOUNDARY WITH CAPE REACHING
1000-1500 J/KG.

ALTHOUGH DYNAMIC FORCING FOR LARGE SCALE ASCENT WILL BE
MINIMAL...HEATING OVER ELEVATED TERRAIN COMBINED WITH OROGRAPHIC
LIFT AND LOW LEVEL CONVERGENCE NEAR THE SURFACE LOW/WARM FRONT IS
EXPECTED TO SUPPORT CONVECTION INITIATION FROM PARTS OF NERN WY INTO
WRN SD DURING THE MID/LATE AFTERNOON HOURS. DEEP LAYER SHEAR WILL
BE ENHANCED AS STRONGER SWLY WINDS ALOFT /40-45 KT AT 500 MB/
OVERSPREAD THE REGION. THIS WILL SUPPORT POTENTIAL FOR HIGH-BASED
SUPERCELLS TO DEVELOP AND SPREAD ENEWD DURING THE LATE AFTERNOON AND
EVENING HOURS. AS THE LOW LEVEL JET STRENGTHENS AFTER
SUNSET...ACTIVITY MAY GROW UPSCALE INTO SEVERAL CLUSTERS/SMALL MCS/S
AND CONTINUE EWD DURING THE OVERNIGHT HOURS. A THREAT FOR PRIMARILY
HAIL MAY ACCOMPANY THESE STORMS.

...MS/AL...
UPPER LOW OVER THE MID-SOUTH IS EXPECTED TO CONTINUE SLOWLY
WEAKENING AS IT MOVES EWD. EXTENSIVE CLOUD COVER IS ASSOCIATED WITH
THE LOW ACROSS MS AND NRN AL WHICH IS LIKELY TO INHIBIT HEATING THIS
AFTERNOON. FARTHER SOUTH...VISIBLE IMAGERY SUGGESTS PRESENCE OF
SEVERAL LOW LEVEL BOUNDARIES EXTENDING FROM WEST-CENTRAL AL WSWWD
ACROSS CENTRAL AND SRN MS WITH SOME BREAKS IN THE CLOUDS NOTED. 12Z
RAOBS AT JAN AND LIX SUGGEST THAT DIABATIC HEATING MAY BE SUFFICIENT
TO WEAKEN THE CAP AND PERMIT STORMS TO DEVELOP LATER THIS AFTERNOON
AND EVENING WITHIN THE SRN SEMICIRCLE OF THE UPPER LOW. ALTHOUGH
THERE ARE SOME DIFFERENCES IN MODEL PRECIPITATION/CONVECTIVE STORM
FORECASTS ACROSS THIS AREA...THERE IS POTENTIAL FOR STORMS TO
DEVELOP AND FAVORABLE CAPE/SHEAR ENVIRONMENT SUGGEST POSSIBILITY OF
A FEW SEVERE STORMS TO OCCUR.

...TX...
THE SURFACE DRYLINE IS FORECAST TO EXTEND ACROSS WEST-CENTRAL TX
LATER THIS AFTERNOON. CONSENSUS OF MODEL GUIDANCE CONTINUES TO
INDICATE ISOLATED CONVECTION INITIATION ALONG THE DRYLINE LATE THIS
AFTERNOON AND EARLY EVENING. FORECAST SOUNDINGS IN THIS AREA SHOW
MLCAPE VALUES OF 2500-3500 J/KG WITH SUFFICIENT CAPPING TO LIMIT THE
NUMBER OF STORMS THAT CAN FORM. NEVERTHELESS...THERE WILL LIKELY BE
A NARROW ZONE ALONG THE DRYLINE WHERE A COMBINATION OF STRONG
HEATING AND DEEP MIXING CAN ELIMINATE THE CAP AND ALLOW A STORM OR
TWO. SUPERCELLS CAPABLE OF LARGE HAIL AND DAMAGING WINDS ARE THE
MAIN THREATS.

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