SWODY1
SPC AC 040548
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1248 AM CDT WED MAY 04 2011
VALID 041200Z - 051200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
A DEEP LONGWAVE TROUGH EXTENDING FROM THE GREAT LAKES TO SRN
APPALACHIANS AT THE START OF THE FORECAST PERIOD WILL TRACK NEWD
TODAY...WITH THIS SYSTEM EVOLVING INTO A CLOSED LOW ACROSS THE MID
ATLANTIC AND NERN STATES. AT 12Z THURSDAY...THE CLOSED LOW SHOULD
BE CENTERED OVER NY. A COLD FRONT ATTENDANT TO THE ERN TROUGH WILL
MOVE OFF THE NC COAST THIS MORNING...WHILE THE SRN EXTENT MOVES SWD
ACROSS THE FL PENINSULA. THE SURFACE LOW WILL TRACK FROM NH THROUGH
MAINE.
MEANWHILE...AN UPSTREAM TROUGH WILL AMPLIFY SEWD ACROSS THE NRN AND
CENTRAL PLAINS WITH THE STRONGEST HEIGHT FALLS EXPECTED AFTER
05/00Z. A COLD FRONT ATTENDANT TO THIS SYSTEM WILL ADVANCE E/SEWD
ACROSS THE NRN AND CENTRAL PLAINS...AND SHOULD EXTEND FROM THE UPPER
MS VALLEY SWWD THROUGH ERN KS...NWRN-WRN OK INTO THE TX SOUTH PLAINS
BY 12Z THURSDAY.
...CENTRAL AND NRN PLAINS...
OFFSHORE LOW LEVEL FLOW IN THE WAKE OF A COLD FRONT THAT MOVED INTO
THE GULF OF MEXICO TUESDAY NIGHT AND A SURFACE RIDGE EXTENDING SWWD
INTO DEEP S TX TODAY WILL INHIBIT THE RETURN OF MOISTURE NWD INTO
THE CENTRAL PLAINS THIS FORECAST PERIOD. A COUPLE OF IMPULSES
EMBEDDED WITHIN THE TROUGH MOVING INTO THIS REGION COMBINED WITH
MIDLEVEL COLD ADVECTION ATOP STRONG SURFACE HEATING SHOULD SUPPORT
CONVECTIVE SHOWERS/FEW TSTMS ACROSS THE NRN/CENTRAL HIGH PLAINS THIS
AFTERNOON. VERY WEAK INSTABILITY SHOULD PRECLUDE A SEVERE WEATHER
THREAT.
MEANWHILE...A SURFACE LOW FORMING ALONG THE COLD FRONT IN NRN KS/
SRN NEB LATE THIS AFTERNOON WILL TRACK NEWD ALONG THIS BOUNDARY
REACHING IA/SRN MN BY 12Z THURSDAY. THE TIMING OF GREATER HEIGHT
FALLS AND FORCING FOR ASCENT IS NOT EXPECTED OVER ERN NEB UNTIL
AFTER 05/00Z. THIS FACTOR COMBINED WITH THE LACK OF GREATER
MOISTURE AVAILABILITY /PW VALUES AT OR BELOW 0.75 INCH AND SURFACE
DEWPOINTS MID-UPPER 40S/ AND AN EML ARE EXPECTED TO LIMIT SURFACE
BASED DEVELOPMENT IN THE MID-LATE AFTERNOON. TSTMS SHOULD DEVELOP
ACROSS ERN NEB/WRN IA DURING THE EVENING AS STRONGER MIDLEVEL
FORCING REACHES THIS REGION ATOP LOW LEVEL WAA. HOWEVER...WEAK
INSTABILITY IS EXPECTED TO LIMIT THE SEVERE WEATHER POTENTIAL...AND
THUS SEVERE PROBABILITIES ARE NOT WARRANTED AT THIS TIME.
...FAR ERN NC...
FORECAST SOUNDINGS SUGGEST THE CAP OVER FAR ERN NC SHOULD WEAKEN
JUST AFTER 12Z TODAY AS THE COLD FRONT MOVES THROUGH THIS REGION.
ALTHOUGH DEEP LAYER SHEAR WILL BE STRONG...WEAK INSTABILITY
PRECEDING THE FRONT AND LOW LEVEL WINDS VEERING WITH THE FRONTAL
PASSAGE SUGGEST A LIMITED SEVERE WEATHER THREAT. A STRONGER WIND
GUST OR TWO WILL BE POSSIBLE THROUGH 15Z...BUT OVERALL COVERAGE DOES
NOT WARRANT THE INCLUSION OF SEVERE PROBABILITIES.
...CENTRAL AND S FL...
THE AIR MASS S OF THE COLD FRONT IS EXPECTED TO BECOME MODERATELY
UNSTABLE TO SUPPORT TSTM DEVELOPMENT ALONG THIS BOUNDARY AND INVOF
OF SEA BREEZE/FRONT INTERACTIONS/COLLISIONS. GENERALLY WEAK FORCING
ALOFT AND WEAK MIDLEVEL LAPSE RATES SHOULD PRECLUDE A GREATER SEVERE
WEATHER THREAT AND THE NEED FOR THE INTRODUCTION OF SEVERE
PROBABILITIES. HOWEVER...A STRONG WIND GUST OR TWO WILL BE POSSIBLE
WITH STRONGER ACTIVITY.
..PETERS.. 05/04/2011
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