SWODY1
SPC AC 041252
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0752 AM CDT SUN MAY 04 2008
VALID 041300Z - 051200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
A SERIES OF MID LEVEL SHORTWAVE TROUGHS ARE DIGGING SWD OVER ORE AND
JUST OFF THE CA COAST...AND CLOSED LOW FORMATION IS EXPECTED BY
TONIGHT OFF THE SRN CA COAST. DOWNSTREAM FROM THIS DEVELOPING
CLOSED LOW...SHORTWAVE RIDGING IS EXPECTED OVER THE SRN
PLAINS...WHILE A WEAK EMBEDDED SPEED MAX OVER NRN AR/SRN MO WILL
MOVE ESEWD TOWARD THE SRN APPALACHIANS. A SEPARATE NRN STREAM WILL
PERSIST IN CONJUNCTION WITH A CLOSED LOW OVER ONTARIO...WHILE THE
MID LEVEL WAVE NEAR THE ATLANTIC COAST WILL LIFT NEWD OVER NEW
ENGLAND AND WEAKEN.
...SE ATLANTIC COAST TODAY INTO TONIGHT...
AN INITIAL MID LEVEL TROUGH IS MOVING OVER THE SE ATLANTIC COAST
THIS MORNING...AND AN ASSOCIATED SURFACE COLD FRONT IS EXPECTED TO
STALL NEAR THE COAST. WEAK CYCLOGENESIS IS EXPECTED ALONG THE FRONT
INVOF SRN SC LATER TODAY INTO TONIGHT...DOWNSTREAM FROM THE MID
LEVEL WAVE APPROACHING FROM THE MS VALLEY. THOUGH THE MORE
WIDESPREAD CONVECTION WILL LIKELY REMAIN OFFSHORE...RESIDUAL
MOISTURE/INSTABILITY ALONG THE FRONT SHOULD SUPPORT AT LEAST
ISOLATED THUNDERSTORM DEVELOPMENT LATER TODAY INTO TONIGHT.
INSTABILITY /AFTERNOON MLCAPE NEAR 1500 J/KG/ MAY BECOME SUFFICIENT
FOR HAIL AND GUSTY OUTFLOW WINDS...BUT THE OVERALL SEVERE STORM
THREAT APPEARS RATHER MARGINAL.
...LOWER-MIDDLE RIO GRANDE VALLEY TODAY...
A SURFACE FRONT HAS STALLED ACROSS DEEP S TX...AND LOW-LEVEL
MOISTURE RETURN WILL COMMENCE TODAY UP THE RIO GRANDE VALLEY. THE
PRESENCE OF 68-72 F DEWPOINTS IN THE LOW LEVELS AND DAYTIME
HEATING...ALONG WITH THE APPROACH OF A WEAK MID LEVEL TROUGH FROM
NRN MEXICO...SHOULD SUPPORT AT LEAST ISOLATED THUNDERSTORM
DEVELOPMENT LATER TODAY.
...NRN GREAT BASIN THIS AFTERNOON/EVENING...
STEEP LAPSE RATES AND A GRADUAL INCREASE IN MOISTURE DOWNSTREAM FROM
THE DEVELOPING LOW OFF THE CA COAST WILL COMBINE WITH DAYTIME
HEATING TO SUPPORT WEAK INSTABILITY OVER MUCH OF THE NRN GREAT BASIN
THIS AFTERNOON. ISOLATED LOW-TOPPED THUNDERSTORMS WILL BE
POSSIBLE...ESPECIALLY ACROSS NW NV AND NE CA IN PROXIMITY TO THE MID
LEVEL TROUGH DIGGING SWD FROM ORE TO NRN CA.
...MN ARROWHEAD/NRN WI/UPPER MI THIS AFTERNOON/EVENING...
AN EMBEDDED SHORTWAVE TROUGH...WITHIN THE WRN PERIPHERY OF THE
LARGER CLOSED LOW OVER WRN ONTARIO...WILL ROTATE SEWD FROM MANITOBA
THIS MORNING TO NRN MN THIS AFTERNOON AND UPPER MI OVERNIGHT.
DESPITE COLD TEMPERATURES AND LIMITED MOISTURE THIS
MORNING...DAYTIME HEATING WILL CONTRIBUTE TO STEEP LOW-MID LEVEL
LAPSE RATES NEAR THE WEAK SURFACE LOW/COLD FRONT ACCOMPANYING THE
MID LEVEL TROUGH. THIS SHOULD RESULT IN THE DEVELOPMENT OF WEAK
INSTABILITY /MUCAPE NEAR 200 J/KG/ IN A SUFFICIENTLY COLD PROFILE
FOR CHARGE SEPARATION AND A FEW LIGHTNING STRIKES WITH LOW-TOPPED
CONVECTION THIS AFTERNOON/EVENING.
...SRN/CENTRAL HIGH PLAINS TONIGHT...
A 30-35 KT SLY LLJ IS FORECAST TO DEVELOP TONIGHT FROM W TX INTO WRN
KS. THIS LLJ WILL TRANSPORT MOISTURE NWD FROM SW TX...BENEATH STEEP
MID LEVEL LAPSE RATES. HOWEVER...THERE IS SOME CONCERN THAT THE
ELEVATED MIXED LAYER WILL BE TOO WARM TO ALLOW PARCEL SATURATION AND
THE FORMATION OF DEEP CONVECTION IN THE WAA REGIME.
THUS...THUNDERSTORM COVERAGE SHOULD REMAIN RATHER SPARSE...AT BEST.
..THOMPSON/SMITH.. 05/04/2008
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