SWODY2
SPC AC 230545
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1245 AM CDT TUE SEP 23 2008
VALID 241200Z - 251200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
NRN STREAM PATTERN FCST TO DEAMPLIFY THROUGH PERIOD AS STG SHORTWAVE
TROUGH -- NOW EVIDENT IN MOISTURE CHANNEL IMAGERY OVER NRN ROCKIES
-- EJECTS NEWD FROM MN ARROWHEAD REGION EARLY IN PERIOD.
LOW-AMPLITUDE SHORTWAVE RIDGING WILL CROSS NRN ROCKIES AND NRN HIGH
PLAINS IN ITS WAKE...FOLLOWED IN TURN BY ANOTHER STG SHORTWAVE
TROUGH NOW EVIDENT NEAR 145W IN NERN PACIFIC. LATTER TROUGH IS
EXPECTED TO MOVE ONSHORE WA AND VANCOUVER ISLAND NEAR END OF PERIOD.
AT SFC...COLD FRONT NOW ANALYZED FROM CENTRAL DAKOTAS SSWWD ACROSS
ERN CO IS EXPECTED TO BE REINFORCED DAY-1 THEN MOVE EWD FROM UPPER
MS VALLEY REGION ACROSS LS/LM/WI THIS PERIOD...WEAKENING WITH TIME
AFTER ABOUT 24/18Z AS UPPER SUPPORT EJECTS AWAY FROM AREA. TRAILING
SEGMENT OF FRONT WILL BECOME QUASISTATIONARY SWWD ACROSS MO AND
SRN/CENTRAL KS BEFORE KS PORTION BEGINS TO LIFT NWD AS WARM FRONT.
OLDER/QUASISTATIONARY BAROCLINIC ZONE -- NOW DRAWN AS STATIONARY
FROM S-CENTRAL FL WSWWD ACROSS CENTRAL GULF TO NERN MEX -- SHOULD
MOVE SWD AS RIDGING BUILDS TO ITS N...IN WAKE OF ATLANTIC
CYCLOGENESIS...THOUGH SOME THUNDER IS POSSIBLE IN ASSOCIATED
BAROCLINIC ZONE OVER DEEP S TX.
MEANWHILE...MID/UPPER TROUGH -- PRESENTLY MOVING SEWD ACROSS
CENTRAL/SRN APPALACHIANS AND ADJACENT PIEDMONT REGION -- IS FCST TO
EVOLVE INTO BROAD/CLOSED CYCLONE...BECOMING CUTOFF AND
QUASISTATIONARY OVER COASTAL CAROLINAS AND/OR NEARBY ATLANTIC
WATERS. ALTHOUGH MOST PROGS INDICATE SOME RETROGRESSION OF THIS
FEATURE DURING LATTER HALF OF PERIOD...CONSIDERABLE SPREAD EXISTS
AMONG OPERATIONAL MODELS AND SREF MEMBERS REGARDING PLACEMENT OF
MIDLEVEL VORTEX CENTER...AND EVEN MORE DISPERSION IN STRENGTH AND
LOCATION OF RELATED SFC CYCLONE.
...TIDEWATER AREA...
FCST SOUNDINGS FROM AFTERNOON THROUGH SUBSEQUENT OVERNIGHT HOURS
REASONABLY SHOW ENLARGED/CURVED HODOGRAPHS CHARACTERISTIC OF STG LOW
LEVEL WAA REGIME WRAPPING NE-NW OF CYCLONE CENTER...BOOSTED
NOCTURNALLY BY 850 MB WINDS IN 50-75 KT RANGE DEPENDING ON MODEL
USED. FCST SOUNDINGS SUGGEST SUFFICIENT BUOYANCY TO SUPPORT
THUNDER...WITH EFFECTIVE INFLOW PARCELS REMAINING ELEVATED MOST OF
PERIOD. MOST AGGRESSIVE RETROGRESSION SCENARIO REPRESENTED BY
OPERATIONAL WRF WOULD RESULT IN INLAND SPREAD OF SUFFICIENT
SFC-BASED BUOYANCY TO SUPPORT SUPERCELL POTENTIAL...ESPECIALLY AFTER
APPROXIMATELY 25/00Z. HOWEVER...SVR POTENTIAL STILL APPEARS TOO
CONDITIONAL/MRGL FOR OUTLOOK GIVEN GREAT SPREAD IN PROGS OF LOCATION
AND MASS FIELDS WITH THIS SYSTEM.
...CENTRAL CONUS....
WIDELY SCATTERED TSTMS ARE POSSIBLE INVOF SFC FRONT...PRIMARILY IN
DIURNALLY DRIVEN WINDOW OF MAXIMIZED BUOYANCY AND WEAK MLCINH FROM
MID-AFTERNOON INTO EARLY EVENING. SREF GUIDANCE REASONABLY FCSTS
PLUME OF 60S F SFC DEW POINTS ALONG/AHEAD OF FRONT FROM VICINITY LM
SWWD ACROSS SWRN KS/NWRN OK...COMBINING WITH DIABATIC HEATING AND
6-7 DEG C/KM LOW-MIDLEVEL LAPSE RATES TO SUPPORT MLCAPE 500-1500
J/KG. ALTHOUGH GUSTS APCHG SVR LIMITS CANNOT BE RULED OUT WITH MOST
INTENSE TSTMS...VERY WEAK LOW-MIDLEVEL WINDS AND LACK OF MORE ROBUST
BULK SHEAR SHOULD KEEP SVR POTENTIAL TOO MRGL/ISOLATED AND
CONDITIONAL TO ASSIGN PROBABILITIES AOA 5 PERCENT ATTM.
..EDWARDS.. 09/23/2008
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