Aug 27, 2013 1730 UTC Day 2 Convective Outlook
Updated: Tue Aug 27 17:30:55 UTC 2013 (20130827 1730Z Day 2 shapefile | 20130827 1730Z Day 2 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20130827 1730 UTC Day 2 Outlook Graphic
Probabilistic Graphic
20130827 1730 UTC Day Probabilitic Graphic
Probability of severe weather within 25 miles of a point.
Hatched Area: 10% or greater probability of significant severe within 25 miles of a point.
Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
   SPC AC 271728

   DAY 2 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1228 PM CDT TUE AUG 27 2013

   VALID 281200Z - 291200Z

   ...NO SVR TSTM AREAS FORECAST...

   ...SYNOPSIS...
   AN EXPANSIVE MID-LEVEL ANTICYCLONE WILL PERSIST ACROSS MUCH OF THE
   CONUS INTO WED. MEANWHILE...A DISORGANIZED IMPULSE ON THE E SIDE OF
   THE ANTICYCLONE WILL MOVE SEWD FROM THE GREAT LAKES REGION TO THE
   MID ATLANTIC AND OFF THE COAST...SERVING TO MAINTAIN A
   HIGHER-AMPLITUDE TROUGH OVER THE WRN ATLANTIC WATERS. A WEAK COLD
   FRONT ACCOMPANYING THIS IMPULSE WILL SHIFT SWD ACROSS PARTS OF THE
   GREAT LAKES...OHIO VALLEY...AND NORTHEAST STATES...WHILE THE SAME
   BOUNDARY TRAILS NWWD INTO THE NRN PLAINS. OTHER PERTURBATIONS
   EMBEDDED WITHIN A MERIDIONALLY- EXTENSIVE...WRN-CONUS MONSOONAL
   MOISTURE PLUME WILL TRACK AROUND THE NRN FLANK OF THE ANTICYCLONE
   FROM THE NRN ROCKIES TO THE ADJACENT PLAINS.

   ...NRN ROCKIES AND NRN PLAINS TO IA...
   CONVECTION MAY BE ONGOING AT THE BEGINNING OF THE PERIOD OVER PARTS
   OF THE DAKOTAS IN A WEAK WARM ADVECTION REGIME...BUT SHOULD WEAKEN
   THROUGH THE MORNING. MEANWHILE...THE AFOREMENTIONED FRONT WILL
   GRADUALLY EDGE NWD OR REMAIN QUASI-STATIONARY THROUGH THE DAY.
   LOW-LEVEL ASCENT INVOF THIS FEATURE MAY BE BOLSTERED BY DIFFERENTIAL
   HEATING ACCOMPANYING REMNANTS OF PREVIOUS CONVECTION AND ITS
   ASSOCIATED OUTFLOW BOUNDARIES TO SUPPORT CONVECTIVE DEVELOPMENT
   DURING THE AFTERNOON FROM PARTS OF ERN MT ACROSS THE DAKOTAS INTO
   IA. THE COMBINATION OF MODERATE TO STRONG DESTABILIZATION WITHIN THE
   MOIST BOUNDARY LAYER N OF THE FRONT...AND MODEST DEEP SHEAR OWING TO
   20-25-KT WLY/S OVERLYING GENERALLY WEAK ESELY LOW-LEVEL FLOW...MAY
   SUPPORT A FEW ORGANIZED CONVECTIVE STRUCTURES. SPORADIC/MARGINAL
   SVR/WIND HAIL POSSIBLE WILL BE POSSIBLE INTO THE EVENING HOURS.

   ADDITIONAL CONVECTION IS EXPECTED TO DEVELOP WITHIN THE MONSOONAL
   MOISTURE PLUME FROM THE MOUNTAINS OF CNTRL ID TO SWRN MT DURING THE
   AFTERNOON...AND GRADUALLY MOVE OVER THE LOWER PLAINS OF MT IN THE
   EVENING. SOME INTENSIFICATION TO MID-LEVEL FLOW MAY YIELD SUFFICIENT
   DEEP SHEAR FOR A FEW MULTICELLS...WITH THE POTENTIAL FOR MICROBURSTS
   TO PRODUCE AN ISOLATED SVR GUST AIDED BY STEEP LOW/MID-LEVEL LAPSE
   RATES. THIS ACTIVITY COULD SPREAD ACROSS PARTS OF THE DAKOTAS
   OVERNIGHT WED NIGHT.

   LARGE-SCALE/DEEP FORCING FOR ASCENT WILL BE GENERALLY LIMITED/SUBTLE
   WITHIN BOTH REGIMES...WHICH BREEDS LOW CONFIDENCE IN THE
   IDENTIFICATION OF ANY CORRIDORS OF GREATER SVR POTENTIAL.

   ISOLATED CONVECTION MAY ALSO DEVELOP INVOF THE BOUNDARY INTO IA
   DURING THE AFTERNOON...AND A CONDITIONAL/ISOLATED SVR-WIND THREAT
   CANNOT BE RULED OUT WITH THIS ACTIVITY. WARM MID-LEVEL CONDITIONS
   MAY PROVE HOSTILE TO THE MAINTENANCE OF ANY INTENSE CONVECTION IN
   IA...PRECLUDING THE INTRODUCTION OF SVR PROBABILITIES.

   ...UPPER OH VALLEY TO THE MID ATLANTIC AND NE STATES...
   WEAK FRONTAL CONVERGENCE ALONG WITH OROGRAPHIC EFFECTS AROUND THE
   CNTRL APPALACHIANS WILL FOCUS THUNDERSTORM DEVELOPMENT THROUGH THE
   DAY...AIDED BY ASCENT PRECEDING THE AFOREMENTIONED SHORTWAVE TROUGH.
   THE ACTIVITY WILL HAVE A TENDENCY TO MOVE SEWD TOWARD THE COAST INTO
   THE EVENING. MODESTLY ENHANCED MID-LEVEL FLOW WILL CONTRIBUTE TO
   EFFECTIVE BULK WIND DIFFERENCES AROUND 25 KT TO SUPPORT MULTICELL
   CLUSTERS AND ISOLATED DMGG WIND FROM THE UPPER OH VALLEY TO THE MID
   ATLANTIC. WITH FAIRLY RICH TROPOSPHERIC MOISTURE SUPPORTING PW
   GENERALLY AOA 1.8 INCHES...ABUNDANT WATER-LOADING COULD ENHANCED THE
   POTENTIAL FOR STRONG DOWNBURSTS. THE LACK OF STRONGER DEEP SHEAR AND
   WEAK MID-LEVEL LAPSE RATES ARE CURRENTLY EXPECTED TO PREVENT A MORE
   SUBSTANTIAL SVR THREAT FROM EVOLVING. FARTHER N INTO THE NE
   STATES...THUNDERSTORMS SHOULD LACK ORGANIZATION OWING TO WEAK DEEP
   SHEAR ASSOCIATED WITH WEAKER MID-LEVEL FLOW.

   ...PORTIONS OF AZ AND SERN CA...
   MONSOONAL MOISTURE/PW WILL INCREASE THROUGH THE DAY...WITH
   OROGRAPHIC ASCENT EXPECTED TO ENCOURAGE THUNDERSTORM DEVELOPMENT
   OVER THE MOUNTAINS. STORMS COULD ADVANCE OVER THE LOWER ELEVATIONS
   DURING THE AFTERNOON AND EVENING WITH STRONG WIND GUSTS POSSIBLE.
   WEAK MID-LEVEL LAPSE RATES AND WEAK TROPOSPHERIC FLOW SHOULD LARGELY
   MITIGATE THE SVR POTENTIAL.

   ..COHEN/GOSS.. 08/27/2013

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