DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 182002
SWODY1
SPC AC 182000

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0300 PM CDT TUE JUN 18 2013

VALID 182000Z - 191200Z

...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON/EVENING ACROSS
CENTRAL/SRN IL AND INDIANA...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS MUCH OF THE HIGH PLAINS
THIS AFTERNOON/EVENING...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS NE ID/NW MT THIS
AFTERNOON/EVENING...

...ERN GA INTO THE CAROLINAS...
AN EXTENSIVE AREA OF SCTD STORMS HAS DEVELOPED OVER AL/GA EARLY THIS
AFTERNOON WITH THE AREA OVER THE CAROLINA COASTAL PLAIN LARGELY VOID
OF STORMS/CLOUD COVER PRIOR TO 20Z. ALTHOUGH MODERATE WSWLY MID
LEVEL FLOW HAS OVERSPREAD THE REGION AHEAD OF A WEAK DISTURBANCE
MOVING ACROSS THE CAROLINAS/VA THIS AFTERNOON/EVENING...MODEST MID
LEVEL LAPSE RATES OBSERVED ON THE MORNING AREA RAOBS HAVE LIMITED
THE MAGNITUDE OF DESTABILIZATION DESPITE TEMPS RISING TO NEAR 90 DEG
F. 9 KM CAPPI RADAR DATA INDICATES THE UPDRAFTS HAVE SO FAR
REMAINED TEMPERED...AND EXPECTING THIS TREND TO CONTINUE INTO THE
EARLY EVENING HOURS AS SCTD STORMS EVENTUALLY MOVE INTO THE CAROLINA
COASTAL PLAIN...PERHAPS YIELDING A FEW POCKETS OF WIND DAMAGE. AS A
RESULT...HAVE REMOVED 15 PERCENT WIND PROBABILITIES GIVEN THE
EXPECTED COVERAGE OF THE SEVERE WIND THREAT.

ELSEWHERE...ONLY MINOR MODIFICATIONS HAVE BEEN MADE TO THE OUTLOOK.
THE MOST NOTABLE CHANGE INCLUDES A SOUTHWARD SHIFT OF THE 10 PERCENT
THUNDERSTORM PROBABILITY LINE OVER THE SRN GREAT LAKES AND OVER THE
NERN U.S. TO REFLECT VISIBLE SATELLITE TRENDS AND A CONFINING OF
SEVERE HAIL/WIND PROBABILITIES OVER THE OH VALLEY WHERE AN AGITATED
CU FIELD/COLD FRONT ARE LOCATED AS OF MID-AFTERNOON.

..SMITH/KERR.. 06/18/2013

.PREV DISCUSSION... /ISSUED 1117 AM CDT TUE JUN 18 2013/

...CENTRAL AND SRN IL/INDIANA THIS AFTERNOON/EVENING...
WATER VAPOR IMAGERY SHOWS AN EMBEDDED SHORTWAVE TROUGH MOVING ESEWD
OVER IA...AND THIS WAVE WILL CROSS IL/INDIANA THIS
AFTERNOON/EVENING. THE MIDLEVEL WAVE COINCIDES WITH A FRONTAL ZONE
ACROSS CENTRAL IL/INDIANA...WHICH WILL PROVIDE A FOCUS FOR
THUNDERSTORM DEVELOPMENT THIS AFTERNOON. MODIFIED 12Z SOUNDINGS
FROM DVN/ILX SHOW THE POTENTIAL FOR MLCAPE OF 1500-2000 J/KG...WITH
STEEP LOW-MIDLEVEL LAPSE RATES AND STRONG DEEP-LAYER VERTICAL SHEAR
WHICH WILL SUPPORT A RISK FOR COUPLE OF SUPERCELLS CAPABLE OF
PRODUCING LARGE HAIL AND DAMAGING WINDS.

...HIGH PLAINS THIS AFTERNOON/EVENING...
FALLING PRESSURES ACROSS THE NRN ROCKIES...IN ADVANCE OF THE DEEP
TROUGH MOVING INLAND OVER THE PAC NW...WILL INDUCE SELY UPSLOPE FLOW
ACROSS THE CENTRAL HIGH PLAINS. DEEP-LAYER BULK SHEAR WILL BE
SUFFICIENT FOR SUPERCELLS WITH MODEST WLY FLOW ALOFT ABOVE SELY
LOW-LEVEL FLOW...IN A STEEP LAPSE RATE ENVIRONMENT WITH 1500-2000
J/KG MLCAPE. EXPECT THUNDERSTORM INITIATION BY EARLY-MID AFTERNOON
ALONG THE E SLOPES OF THE BIG HORN AND LARAMIE RANGES IN WY...AS
WELL AS THE FRONT RANGE OF CO/NE NM...POSSIBLY AIDED BY WEAK ASCENT
OVER NRN CO/WY IN ADVANCE OF A WEAK SHORTWAVE TROUGH EJECTING NEWD
FROM UT. STORMS WILL THEN SPREAD EWD THROUGH THE AFTERNOON/EVENING
ONTO THE HIGH PLAINS...WITH AN ACCOMPANYING RISK FOR LARGE HAIL AND
A FEW DAMAGING GUSTS. SOME OF THE CONVECTION COULD PERSIST INTO
TONIGHT ACROSS THE TX/OK PANHANDLES IN RESPONSE TO A DEVELOPING LLJ
AND INCREASING MOISTURE FLUX FROM THE SE.

ADDITIONAL STORMS COULD FORM THIS AFTERNOON ALONG A RESIDUAL OUTFLOW
BOUNDARY ACROSS NW/W CENTRAL KS. VERTICAL SHEAR WILL BE AT LEAST
MARGINALLY FAVORABLE FOR SUPERCELLS WITH THE POTENTIAL TO PRODUCE
ISOLATED HAIL/DAMAGING GUSTS.

...NW MT/NE ID THIS AFTERNOON/EVENING...
LARGE SCALE ASCENT DOWNSTREAM FROM THE DEEP PAC NW TROUGH...AND THE
NRN EXTENT OF A STEEP LAPSE RATE PLUME...WILL COMBINE WITH DAYTIME
HEATING AND BOUNDARY LAYER DEWPOINTS IN THE UPPER 40S TO LOWER 50S
TO SUPPORT MODERATE INSTABILITY AND THUNDERSTORM DEVELOPMENT BY MID
AFTERNOON ACROSS NE ID/WRN MT. STORMS WILL THEN SPREAD NNEWD OFF
THE HIGHER TERRAIN...AND WILL BE CAPABLE OF PRODUCING AT LEAST
ISOLATED DAMAGING WINDS AND LARGE HAIL. THE STRONGEST VERTICAL
SHEAR...AND GREATER POTENTIAL FOR SUPERCELLS...WILL BE NEAR THE
BAROCLINIC ZONE ACROSS NW/N CENTRAL MT.

...ERN GA INTO THE ERN CAROLINAS THIS AFTERNOON...
A MIDLEVEL SHORTWAVE TROUGH AND ASSOCIATED SURFACE LOW OVER THE SRN
APPALACHIANS WILL PROGRESS EWD TO THE ATLANTIC COAST BY TONIGHT. A
WIDE SWATH OF THICK CLOUDS/RAIN ACCOMPANIES THIS TROUGH FROM THE MID
ATLANTIC SWWD TO THE SRN APPALACHIANS AND PIEDMONT OF THE CAROLINAS.
REGIONAL 12Z SOUNDINGS AND RECENT VWP/S REVEAL SOMEWHAT ENHANCED
LOW-MIDLEVEL WSWLY FLOW OF 30-40 KT...THOUGH THE CLOUDS AND MOIST
PROFILES/POOR LAPSE RATES WILL TEND TO LIMIT DESTABILIZATION THIS
AFTERNOON...ASIDE FROM STRONGER SURFACE HEATING ACROSS THE COASTAL
PLAINS WHERE MIDLEVEL FLOW WEAKENS. THE NET RESULT IS A MARGINAL
SITUATION FOR MULTICELL CLUSTERS WITH DAMAGING WINDS.

...E/SE TX INTO LA/MS THIS AFTERNOON...
A WELL-DEVELOPED MCV FROM OVERNIGHT CONVECTION PERSISTS OVER N
CENTRAL TX AS OF MID-LATE MORNING. E-S OF THE MCV AND WEAK
ASSOCIATED SURFACE LOW IN NE TX...DAYTIME HEATING AND CONVERGENCE
ALONG WEAK SURFACE FRONTAL BOUNDARIES WILL SUPPORT THUNDERSTORM
DEVELOPMENT. DEEP-LAYER FLOW IS RELATIVELY WEAK WITHIN THE UNSTABLE
WARM SECTOR...AND LAPSE RATES ALOFT ARE NOT STEEP. ISOLATED WET
MICROBURSTS WILL BE POSSIBLE THIS AFTERNOON...BUT SEVERE STORM
COVERAGE SHOULD REMAIN RATHER SPARSE.

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