DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 281956
SWODY1
SPC AC 281954

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0254 PM CDT WED AUG 28 2013

VALID 282000Z - 291200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF MT AND ND...

...DISCUSSION...
CURRENT FORECAST APPEARS IN LINE WITH ONGOING CONVECTIVE EVOLUTION
ACROSS THE CONUS...WITH SHOWERS AND SCATTERED STORMS ONGOING ACROSS
NEW ENGLAND AND INTO THE UPPER OH VALLEY AND MID-ATLANTIC REGION AND
ACROSS PORTIONS OF THE GREAT BASIN AND INTO ID/MT. WITH CAPE/SHEAR
COMBINATION ON THE MARGINAL END IN BOTH REGIONS...LOW-PROBABILITY
SEVERE WEATHER FORECAST STILL APPEARS APPROPRIATE.

SOMEWHAT GREATER SEVERE RISK REMAINS EVIDENT FROM THE ERN HALF OF MT
INTO ND IN WEAK UPSLOPE FLOW REGIME...WITH THE INITIATION OF THIS
EVENT POSSIBLY EVOLVING FROM WITHIN FESTERING ONGOING CONVECTION
OVER ERN MT AS REVEALED BY VISIBLE IMAGERY AND LIGHTNING DATA INVOF
GARFIELD AND PETROLEUM COUNTIES. WITH ADDITIONAL
HEATING/DESTABILIZATION ACROSS THE AREA AND INCREASING LARGE-SCALE
ASCENT AHEAD OF AN ADVANCING MID-LEVEL VORT MAX NOW AFFECTING WRN
MT...STORMS SHOULD EVENTUALLY INTENSIFY/GROW UPSCALE AND POSE
DAMAGING WIND AND HAIL RISK THROUGH THIS EVENING AND INTO THE
OVERNIGHT HOURS.

..GOSS.. 08/28/2013

.PREV DISCUSSION... /ISSUED 1124 AM CDT WED AUG 28 2013/

...SYNOPSIS...
A MID-UPPER HIGH WILL PERSIST OVER MO/AR...AS A SERIES OF
LOW-AMPLITUDE SPEED MAXIMA ROTATE AROUND THE PERIPHERY OF THE
HIGH...FROM THE NRN GREAT BASIN TO THE NRN PLAINS AND GREAT
LAKES/CENTRAL APPALACHIANS. SEPARATE SUBTROPICAL LOWS WILL MOVE
NWD/NEWD OVER KS...AND WWD OVER THE FL STRAITS. FARTHER W...A
MIDLEVEL TROUGH WILL MAKE SLOW EWD PROGRESS TOWARD THE PAC NW. THE
PRIMARY THREAT AREAS FOR ISOLATED SEVERE STORMS TODAY AND TONIGHT
WILL BE ACROSS THE NRN PLAINS AND NEAR/W OF THE CENTRAL
APPALACHIANS.

...SE OH/WV THIS AFTERNOON...
A SERIES OF WEAK/CONVECTIVELY-ENHANCED SPEED MAXIMA WILL PROGRESS
SEWD/SSEWD FROM THE UPPER OH VALLEY TO THE CENTRAL APPALACHIANS AND
MID ATLANTIC COAST THROUGH TONIGHT. SATELLITE LOOPS SHOW WIDESPREAD
CLOUD DEBRIS OVER PA/VA/WV FROM OVERNIGHT CONVECTION...AND THESE
CLOUDS WILL TEND TO LIMIT DAYTIME HEATING/DESTABILIZATION TODAY.
ANY SIGNIFICANT CLOUD BREAKS WILL LIKELY BE CONFINED TO THE WRN
FRINGE OF THE THICKER CLOUD SHIELD FROM SE OH INTO WV THIS
AFTERNOON...WHERE SURFACE-BASED THUNDERSTORM DEVELOPMENT IS MORE
PROBABLE. A FEED OF MODERATE INSTABILITY FROM THE W...ALONG WITH
25-40 KT WLY/NWLY LOW-MIDLEVEL FLOW...WILL SUPPORT A RISK FOR
ISOLATED DAMAGING GUSTS THIS AFTERNOON.

...NE UT/SE ID/SW MT THIS AFTERNOON...
CONVECTION WILL LIKELY INCREASE WITHIN A BROKEN BAND FROM EXTREME NW
UT NWD INTO SW MT...ALONG THE PATH OF THE EMBEDDED SPEED MAX THAT
WILL REACH MT THIS AFTERNOON/EVENING. TYPICAL INVERTED-V PROFILES
AND SOME ENHANCEMENT TO THE MIDLEVEL FLOW COULD SUPPORT ISOLATED
STRONG/DAMAGING GUSTS THIS AFTERNOON.

...ERN MT THIS EVENING INTO WRN/CENTRAL ND TONIGHT...
AN EMBEDDED SPEED MAX OVER ID THIS MORNING WILL MOVE NEWD OVER MT BY
THIS EVENING...REACHING ND OVERNIGHT. OUTFLOW FROM OVERNIGHT
CONVECTION HAS REINFORCED A BAROCLINIC ZONE ACROSS SD...AND WEAK LEE
CYCLOGENESIS IS EXPECTED THIS AFTERNOON ACROSS THE NRN HIGH PLAINS
FROM N CENTRAL MT INTO NE WY. THIS WILL HELP MAINTAIN A WEAK ELY
FLOW REGIME WITHIN THE MOIST POST-FRONTAL AIR MASS ACROSS THE
DAKOTAS. MODIFIED 12Z OBSERVED AND MODEL FORECAST SOUNDINGS SHOW
THE POTENTIAL FOR MLCAPE OF 1500-2000 J/KG THIS AFTERNOON INTO ERN
MT...WHERE STRONGER SURFACE HEATING SHOULD WEAKEN CONVECTIVE
INHIBITION.

SCATTERED THUNDERSTORM DEVELOPMENT IS EXPECTED BY ABOUT 00Z ACROSS
ERN MT IN THE ZONE OF MODERATE INSTABILITY AND WEAKENING CONVECTIVE
INHIBITION...IN ADVANCE OF THE EJECTING SPEED MAX. THERE WILL BE
SOME POTENTIAL FOR SUPERCELLS WITH LARGE HAIL/DAMAGING WINDS THIS
EVENING GIVEN THE DEGREE OF BUOYANCY AND STRAIGHT HODOGRAPHS WITH
EFFECTIVE BULK SHEAR OF 35-40 KT. THEREAFTER...STORMS MAY
MERGE/GROW INTO A SMALL MCS THAT WILL MOVE INTO WRN ND
TONIGHT...WITH AN ACCOMPANYING RISK FOR A FEW DAMAGING GUSTS AND
ISOLATED LARGE HAIL. THE OVERNIGHT CONVECTION WILL BE MAINTAINED BY
WAA ON THE NOSE OF A 25-30 KT LLJ.

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