Thursday, April 19, 2007

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 200049
SWODY1
SPC AC 200046

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0746 PM CDT THU APR 19 2007

VALID 200100Z - 201200Z

..NO SVR TSTM AREAS FORECAST...

..SYNOPSIS...
HIGH AMPLITUDE SYNOPTIC PATTERN WILL CONTINUE OVER CONUS...FEATURING
WRN TROUGH...RIDGING FROM WRN GULF ACROSS GREAT LAKES TO HUDSON
BAY...AND ATLANTIC TROUGHING. STRONG SHORTWAVE TROUGH -- NOW
EVIDENT IN MOISTURE CHANNEL IMAGERY OVER SRN APPALACHIANS...WILL
WEAKEN OVERNIGHT AS IT EJECTS OFFSHORE CAROLINAS. MEANWHILE...UPPER
LEVEL LOW NOW OVER MT/SD BORDER REGION WILL LIFT NWD TO SRN
SASK...AS ANOTHER LOW DIGS SEWD ALONG CA COAST AND TOWARD MEAN
TROUGH POSITION.

AT SFC...DEEP/OCCLUDED LOW INITIALLY ANALYZED OVER E-CENTRAL MT
LIKEWISE WILL LIFT NWD ACROSS CANADIAN BORDER. COLD FRONT TRAILING
SEWD THEN SWD ACROSS NRN/CENTRAL PLAINS WILL WEAKEN...WHILE LEE
TROUGHING CONTINUES TO ITS W AND BENEATH SW FLOW ALOFT. ASSOCIATED
PRESSURE/HEIGHT FALLS SHOULD LEAD TO FRONTAL ZONE AND ACCOMPANYING
MOISTURE GRADIENT BACKING WWD/NWWD OVER WRN KS FROM PRESENT
POSITION. SECONDARY SFC CYCLONE NOW EVIDENT INVOF RTN IS FCST TO
CONSOLIDATE ACROSS NERN NM OVERNIGHT...WITHIN THAT LEE TROUGH. SFC
LOW -- ASSOCIATED WITH SRN APPALACHIANS PERTURBATION ALOFT -- WAS
ANALYZED AT 00Z OVER CENTRAL SC...AND SHOULD MOVE SEWD TOWARD COAST
ALONG QUASISTATIONARY FRONTAL ZONE.

..SC...
SCATTERED TSTMS -- MANY OF THEM BECOMING ELEVATED JUST ABOVE
DIABATICALLY STABILIZING NEAR-SFC LAYER -- WILL CONTINUE TO MOVE
GENERALLY SEWD THROUGH REMAINDER EVENING. MOST INTENSE TSTMS MAY
PRODUCE HAIL. THOUGH NOT PARTICULARLY STG...PRESENCE OF RELATIVELY
BACKED LOW LEVEL WINDS E OF SFC LOW IS EXPECTED TO ENHANCE
STORM-RELATIVE INFLOW AND BULK SHEAR...WHICH APPEAR FAVORABLE FOR
MAINTAINING SOME SVR PROBABILITIES BASED ON RUC FCST
SOUNDINGS...PRE-STORM CAE VWP...AND MODIFIED CHS RAOB DATA. REF SPC
MESOSCALE DISCUSSING 517 FOR ADDITIONAL/NOWCAST DETAILS.

..CENTRAL PLAINS....
POTENTIAL REMAINS ATTM FOR ISOLATED TO WIDELY SCATTERED TSTM
DEVELOPMENT INVOF WEAKENING COLD FRONT OVER PORTIONS S-CENTRAL NEB
SWWD TOWARD W-CENTRAL/SWRN KS. HOWEVER...DIABATIC COOLING OF
NEAR-SFC LAYER DURING NEXT FEW HOURS WILL LEAD TO INCREASINGLY
ELEVATED EFFECTIVE INFLOW PARCELS AND REDUCTION IN SVR GUST
POTENTIAL WITH ANY SUCH ACTIVITY. CONDITIONAL HAIL POTENTIAL WILL
REMAIN GIVEN SUSTAINED STORM DEVELOPMENT...WITH DEEP-LAYER/EFFECTIVE
SHEAR BEING FAVORABLE AT 40-45 KT AND MUCAPES 500-1000 J/KG.

..NRN PLAINS...
HEIGHT RISES ARE FCST ACROSS MUCH OF THIS REGION FOR REMAINDER
PERIOD...IN WAKE OF EJECTING MID/UPPER CYCLONE. WITH PRESENCE OF
FRONTOLYSIS...LITTLE OR NO SUPPORT FROM MID/UPPER LEVEL
FORCING...AND DECREASING SFC HEATING...OVERALL POTENTIAL FOR
CONVECTION AND ESPECIALLY SVR POTENTIAL WILL WEAKEN THROUGH
REMAINDER EVENING/OVERNIGHT HOURS.

.EDWARDS.. 04/20/2007

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