SPC AC 051254

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0754 AM CDT FRI JUL 05 2013

   VALID 051300Z - 061200Z

   ...NO SVR TSTM AREAS FORECAST...

   ...SYNOPSIS...
   A MIDLEVEL SHORTWAVE TROUGH OVER THE PAC NW WILL PROGRESS INLAND TO
   THE NRN ROCKIES AS THE RIDGE IS SHUNTED SLOWLY SWD ACROSS THE
   ROCKIES.  DOWNSTREAM...A PERSISTENT TROUGH OVER THE MS VALLEY WILL
   BEGIN TO DRIFT EWD...THOUGH ITS MOTION WILL BE SLOW GIVEN THE CLOSED
   HIGH JUST OFF THE MID ATLANTIC COAST.  THUNDERSTORMS WILL BE
   POSSIBLE IN A BROAD SWATH OF THE ERN STATES...WITHIN THE DEEP
   TROPICAL MOISTURE PLUME BETWEEN THE MS VALLEY TROUGH AND THE WRN
   ATLANTIC CLOSED HIGH.  OTHERWISE...CONVECTION WILL PERSIST WITHIN
   THE RESIDUAL MOISTURE PLUME ACROSS THE ROCKIES.

   ...NE STATES TODAY...
   THE TROPICAL MOISTURE PLUME...WITH PW VALUES OF 1.75-2 INCHES AND
   BOUNDARY LAYER DEWPOINTS OF 68-72 F...CONTINUES NEAR AND W OF THE
   APPALACHIANS THIS MORNING.  STRONGER SURFACE HEATING WILL OCCUR
   ALONG THE ERN EDGE OF THE DEEPEST MOISTURE/THICKEST CLOUD
   COVER...FROM WRN/CENTRAL PA INTO CENTRAL NY AND NEW ENGLAND. 
   MEANWHILE...AN EMBEDDED MID-UPPER SPEED MAX WILL TRAVERSE THE LOWER
   GREAT LAKES TODAY IN CONJUNCTION WITH THE DIURNAL HEATING
   CYCLE...WHICH WILL SUPPORT AT LEAST SCATTERED THUNDERSTORM
   DEVELOPMENT ALONG THE DIFFERENTIAL HEATING ZONE.  ISOLATED DAMAGING
   GUSTS WILL BE POSSIBLE WITH THE STRONGEST STORMS IN THE ENVIRONMENT
   WITH MLCAPE OF 1500-2000 J/KG AND 35-40 KT MIDLEVEL FLOW...WHICH
   WILL SUPPORT SOME MOMENTUM TRANSFER WITH HEAVY PRECIPITATION
   LOADING.  POOR MIDLEVEL LAPSE RATES WILL LIMIT ANY HAIL THREAT...AND
   THE OVERALL SEVERE RISK SHOULD STILL BE TEMPERED SOMEWHAT BY MODEST
   LOW-LEVEL FLOW/SHEAR.

   ...NRN ROCKIES/HIGH PLAINS THROUGH EARLY TONIGHT...
   SCATTERED THUNDERSTORMS ARE ONGOING THIS MORNING ACROSS CENTRAL/NE
   MT ON THE NE EDGE OF THE ROCKIES MOISTURE PLUME...AND IN ADVANCE OF
   A LEAD SHORTWAVE TROUGH MOVING OVER ID.  THOUGH CLOUDS WILL SLOW
   DAYTIME HEATING ACROSS ERN MT...SOME HEATING IN CLOUD BREAKS WILL
   BOOST MLCAPE VALUES TO 1000-1500 J/KG BY MID AFTERNOON. 
   THUS...ADDITIONAL THUNDERSTORM DEVELOPMENT IS EXPECTED ALONG A WEAK
   SURFACE FRONT/INVERTED TROUGH IN E CENTRAL/NE MT BY EARLY-MID
   AFTERNOON...IN AN ENVIRONMENT WITH SUFFICIENT DEEP-LAYER VERTICAL
   SHEAR FOR ORGANIZED MULTICELL CLUSTERS...AS WELL AS ISOLATED
   SUPERCELLS.  GIVEN THE EARLY CONVECTION AND RATHER MODEST
   BUOYANCY...WILL MAINTAIN LOW HAIL/WIND PROBABILITIES IN THIS UPDATE.

   ...CENTRAL/NE MN THIS AFTERNOON/EVENING...
   A WEAK SURFACE COLD FRONT WILL DRIFT SEWD INTO NRN/CENTRAL MN BY
   LATE THIS AFTERNOON...WHICH WILL PROVIDE A FOCUS FOR SCATTERED
   THUNDERSTORM DEVELOPMENT.  THOUGH LOW-LEVEL MOISTURE HAS INCREASED
   GRADUALLY ACROSS MN...MLCAPE WILL LIKELY BE LIMITED TO ABOUT
   1000-1500 J/KG WITH DAYTIME HEATING...AND VERTICAL SHEAR WILL NOT BE
   PARTICULARLY STRONG IN THE UNSTABLE WARM SECTOR. 
   STILL...TEMPERATURE PROFILES WILL BE SUFFICIENTLY COOL ALOFT TO
   SUPPORT SOME MARGINAL HAIL RISK...AS WELL AS THE POSSIBILITY OF
   ISOLATED STRONG/DAMAGING GUSTS FOR A FEW HOURS THIS
   AFTERNOON/EVENING.

   ...ERN NM THIS AFTERNOON/EVENING...
   THE BELT OF STRONGER NLY MID-UPPER FLOW HAS SHIFTED EWD FROM NM/CO
   TO THE HIGH PLAINS FARTHER E...IN RESPONSE TO GRADUAL HEIGHT RISES
   FROM THE W.  THE NET RESULT WILL BE WEAKER VERTICAL SHEAR INTO NM
   COMPARED TO THE PREVIOUS FEW DAYS.  ALSO...MODIFIED 12Z SOUNDINGS
   SUGGEST THAT AFTERNOON BUOYANCY WILL REMAIN RATHER MODEST...AND THAT
   THE RISK FOR ORGANIZED/PERSISTENT STORMS IS BECOMING QUITE MARGINAL.

   ..THOMPSON/LEITMAN.. 07/05/2013

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