SWODY2
SPC AC 090653
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1253 AM CST FRI JAN 09 2009
VALID 101200Z - 111200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
POSITIVELY TILTED LONG WAVE TROUGH EXTENDING FROM IA/WI SWWD THROUGH
CENTRAL PLAINS TO NM/AZ AT 12Z SATURDAY WILL REMAIN PROGRESSIVE
DURING THE DAY 2 PERIOD. HOWEVER...MODELS SUGGEST SHORT WAVE
TROUGHS EMBEDDED WITHIN THE MAIN UPPER TROUGH SHOULD BECOME LESS IN
PHASE ON SATURDAY...WITH THE NRN TROUGH TRACKING EWD MORE QUICKLY
TOWARD THE MID ATLANTIC REGION BY 12Z SUNDAY.
SURFACE LOW...ASSOCIATED WITH NRN SHORT WAVE TROUGH...IS EXPECTED TO
SLOWLY DEEPEN AS IT TRACKS EWD FROM WRN KY THROUGH THE CENTRAL
APPALACHIANS...WITH STRONGER DEEPENING OCCURRING AS THIS SYSTEM
MOVES OFF THE MID ATLANTIC COAST SATURDAY NIGHT. TRAILING COLD
FRONT WILL PROCEED EWD THROUGH THE TN/LOWER MS VALLEYS AND GULF
COAST STATES...REACHING THE MID ATLANTIC STATES TO SRN GA/NWRN FL BY
END OF FORECAST PERIOD.
...LOWER MS VALLEY/CENTRAL GULF COAST STATES...
FORECAST SOUNDINGS INDICATE A WARM LAYER BETWEEN 500-700 MB WILL
EXIST ATOP LOW LEVEL MOISTURE RETURN WITHIN WARM SECTOR. SURFACE
DEWPOINTS IN THE LOWER-MID 60S ARE EXPECTED TO SPREAD INTO SRN MS TO
CENTRAL/SRN AL. HOWEVER...THE POSITIVE TILT OF THE PROGRESSIVE LONG
WAVE TROUGH AND STRONGER FORCING FOR ASCENT LAGGING THE SURFACE COLD
FRONT ARE EXPECTED TO MAINTAIN POOR LAPSE RATES. THIS WILL RESULT
IN ONLY A MARGINALLY UNSTABLE WARM SECTOR /MUCAPE AOB 500 J PER KG/.
THE LACK OF STRONGER MID/UPPER LEVEL FORCING AND WEAK INSTABILITY
SUGGEST FORCING FOR ASCENT ALONG THE FRONT WILL BE NEEDED FOR
PARCELS TO BECOME DEEP ENOUGH FOR TSTM DEVELOPMENT. THE RATHER
STRONG VERTICAL SHEAR /40-50 KT/ SUGGESTS THE POTENTIAL FOR A FEW
INTENSE STORMS EMBEDDED IN BROADER CONVECTIVE BAND ALONG FRONT WITH
THE THREAT FOR LOCALLY STRONG WIND GUSTS AND/OR AN ISOLATED TORNADO.
THIS THREAT SHOULD BE CONFINED TO SERN MS/LA TO SRN AL/FL PANHANDLE
WHERE INSTABILITY /ALTHOUGH STILL WEAK/ WILL BE GREATEST FOR THIS
REGION.
FARTHER N...ELEVATED TSTMS MAY BE ONGOING AT 12Z SATURDAY FROM ERN
AR TO WRN KY WHERE WEAKER MID LEVEL CAPPING/INSTABILITY WILL SUPPORT
CONVECTION DEEP ENOUGH FOR CHARGE SEPARATION. STRONGER FORCING FOR
ASCENT ATTENDANT TO THE NRN STREAM SHORT WAVE TROUGH MAY PROVE
SUFFICIENT IN WEAKENING CAP WITH NWD EXTENT AND ALLOWING ELEVATED
BUOYANCY TO REACH ICING LAYERS SUITABLE FOR LIGHTNING PRODUCTION EWD
ACROSS KY/TN. THIS ELEVATED TSTM THREAT APPEARS POSSIBLE TO SPREAD
INTO THE CAROLINAS LATE SATURDAY AFTERNOON/EVENING.
..PETERS.. 01/09/2009
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