SWODY2
SPC AC 211729
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1229 PM CDT TUE OCT 21 2008
VALID 221200Z - 231200Z
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS CENTRAL/ERN TX TO
ARKLATEX REGION...
...SYNOPSIS...
HIGH AMPLITUDE UPPER AIR PATTERN FCST TO DEVELOP ACROSS CONUS THIS
PERIOD...AS LOWER GREAT LAKES CYCLONE EJECTS OFFSHORE NEW ENGLAND
AND HIGH AMPLITUDE RIDGING TAKES SHAPE ACROSS UPPER GREAT
LAKES...AND FROM CA TO NRN ROCKIES. STG SHORTWAVE TROUGH -- NOW
EVIDENT IN MOISTURE CHANNEL IMAGERY FROM CENTRAL MT SWD ACROSS WY/ID
BORDER REGION -- IS BACKED ON W SIDE BY 130-150 KT 250 MB JET CORE.
THIS TROUGH SHOULD CONTINUE TO AMPLIFY THROUGH REMAINDER DAY-1 AND
EARLY DAY-2 PERIOD AS IT MOVES SEWD ACROSS CENTRAL ROCKIES AND
CENTRAL HIGH PLAINS...WITH CLOSED 500 MB CYCLONE EVOLVING OVER
S-CENTRAL PLAINS BY 23/00Z. MESOSCALE DISCREPANCIES EXIST AMONG
PROGS REGARDING SPECIFIC CENTER POSITION OF LOW BY THAT
TIME...WHETHER OVER SOME PORTION CENTRAL/SRN KS OR NRN/NWRN
OK...HOWEVER STG CONSENSUS APPEARS IN SREF AND OPERATIONAL MODELS
WITH THIS CYCLONE BECOMING DEEP AND QUASISTATIONARY OVER KS BY END
OF PERIOD.
ASSOCIATED SFC COLD FRONT -- NOW MOVING EWD AND SEWD ACROSS ERN WY
AND WRN DAKOTAS -- IS FCST TO PLUNGE SEWD OVER SRN HIGH
PLAINS...MOST OF OK AND PORTIONS NRN/CENTRAL TX BY 23/00Z. BY
24/12Z...FRONT SHOULD REACH NWRN GULF...LA AND ERN AR...OCCLUDING
NWWD ACROSS MO AND INTO INCREASINGLY STACKED CYCLONE OVER KS.
...CENTRAL/ERN TX TO ARKLATEX REGION...
AS CONTINUATION OF REGIME MENTIONED IN DAY-1 OUTLOOK...STG/ISOLATED
SVR CONVECTION MAY BE ONGOING AT BEGINNING OF PERIOD ALONG AND
PERHAPS BEHIND SFC COLD FRONT...ACROSS PORTIONS KS/OK AND N TX.
THIS ACTIVITY WILL OCCUR IN REGIME OF STG LOW LEVEL FRONTOGENETIC
FORCING AND STRENGTHENING LARGE SCALE ASCENT ALOFT...ALONG WITH
INCREASING INFLOW-LAYER MOISTURE. COUNTERBALANCING AFFECT IN
MORNING HOURS WILL BE RELATIVELY COOL/STABLE NEAR-SFC LAYER...WHICH
SHOULD MITIGATE STRENGTH OF DOWNDRAFTS AND LEADING-EDGE COLD POOL
FLOW.
AS PREFRONTAL BOUNDARY LAYER HEATS THROUGH AFTERNOON...EXPECT SVR
PROBABILITY TO INCREASE. COMBINATION OF INSOLATION AND MOIST
ADVECTION WILL BOOST INFLOW-LAYER BUOYANCY AND LOWER THAT LAYER TO
SFC-BASED...AMIDST FAVORABLE DEEP-LAYER SHEAR. SFC DEW POINTS 60S F
ARE FCST ACROSS MUCH OF CENTRAL AND E TX BY MID-LATE AFTERNOON...S
OF TRANSITION ZONE BETWEEN GULF AND CONTINENTAL TRAJECTORIES THAT
WILL ACT AS A DROSOTHERMAL WARM FRONT. THIS BOUNDARY SHOULD LIE
FROM AL COAST NWWD ACROSS NRN LA AND SWRN AR BY 22/21Z...BECOMING
MORE DIFFUSE WITH WWD EXTENT. S OF MOISTURE BOUNDARY...E OF COLD
FRONT AND N OF UPPER TX COAST...MODIFIED NAM-KF SOUNDINGS SUGGEST
MLCAPES 800-1200 J/KG ARE POSSIBLE...AMIDST STRONGLY CURVED
HODOGRAPHS THAT INCREASE IN SIZE WITH NWD EXTENT.
MOST FAVORABLE SHEAR PROFILES WILL BE FROM E-CENTRAL/NE TX NWD
ACROSS AR/OK BORDER AREA...BUT INSTABILITY SHOULD DIMINISH SHARPLY N
OF DEW POINT BOUNDARY. AREA OF MOST FAVORABLE SHEAR/BUOYANCY
JUXTAPOSITION -- DENOTED BY CATEGORICAL RISK -- SHOULD BE
CHARACTERIZED BY 40-50 KT EFFECTIVE SHEAR VALUES AND 0-1 KM SRH
150-200 J/KG ASSUMING DEVIANT SUPERCELL MOTIONS. STORM MODE MAY BE
PRIMARILY LINEAR...SUGGESTING PREDOMINANT THREAT OF DAMAGING WIND
WITH MRGL SVR HAIL. HOWEVER...ANY RELATIVELY DISCRETE/SUSTAINED
ACTIVITY MAY POSE TORNADO AND ENHANCED HAIL THREAT. ACTIVITY MAY
BACKBUILD ACROSS PORTIONS CENTRAL/SE TX WHERE SHEAR WILL WEAKEN WITH
SWD EXTENT. EXPECT NOCTURNAL COOLING/STABILIZATION OF BOUNDARY
LAYER TO DIMINISH CAPE AND BRING DOWN SVR PROBABILITIES...CONCURRENT
WITH OCCLUSION AND ONSET OF FILLING STAGE OF MID-UPPER CYCLONE.
..EDWARDS.. 10/21/2008
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
To unsubscribe from WX-STORM send e-mail to LISTSERV@LISTSERV.ILLINOIS.EDU with
"unsub wx-storm" in the body of your message. For more information write cnovy@cox.net.
No comments:
Post a Comment