SWODY2
SPC AC 030559
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1259 AM CDT FRI AUG 03 2007
VALID 041200Z - 051200Z
..THERE IS A SLGT RISK OF SVR TSTMS PORTIONS MN...ERN SD...NERN
NEB...NRN IA....
..SYNOPSIS...
PROGRESSIVE NRN STREAM PATTERN FCST TO CONTINUE ALOFT BETWEEN
PACIFIC NW...NRN PLAINS AND NEW ENGLAND...WITH BROAD ZONE OF RIDGING
FROM SRN GREAT BASIN ACROSS SRN PLAINS TO LOWER MS VALLEY. UPPER
LEVEL CYCLONE CURRENTLY OVER BC COAST SHOULD MOVE INLAND AND
DEAMPLIFY SOMEWHAT...CROSSING CANADIAN ROCKIES AROUND 04/12Z AND
MOVING EWD OVER SASK BY 05/12Z. MID/UPPER LEVEL SHORTWAVE TROUGH --
NOW EVIDENT IN MOISTURE CHANNEL IMAGERY OVER CENTRAL/NRN GREAT BASIN
AND SRN ID -- IS FCST TO MOVE FROM NRN PLAINS ESEWD ACROSS UPPER MS
VALLEY AND UPPER GREAT LAKES DAY-2. MEANWHILE...DEEP-LAYER
TROUGHING SHOULD PERSIST ACROSS ERN GULF COAST REGION...PERHAPS
EXTENDING AS FAR E AS GA/CAROLINAS COASTS...AND WITH SOME SFC
REFLECTION OVER SRN GA/SC REGION.
SFC CYCLONE...ASSOCIATED WITH MID/UPPER TROUGH EXITING NRN
PLAINS...SHOULD MOVE EWD-NEWD FROM SD ACROSS PORTIONS MN.
STRENGTH/TRACK OF THIS FEATURE SHOWS CONSIDERABLE VARIATION AMONGST
OPERATIONAL AND SREF PACKAGES...HOWEVER CONSENSUS SCENARIO ABOVE IS
REPRESENTED IN SOME FORM BY MAJORITY OF THESE PROGS. ACCOMPANYING
SFC COLD FRONT SHOULD MOVE SEWD ACROSS PORTIONS WRN NEB AND NERN
CO...STALLING ALONG MOST OF CENTRAL PLAINS SEGMENT BY END OF PERIOD.
WARM FRONT IS FCST TO LIFT NEWD ACROSS MID/UPPER MS VALLEY IL AND
INDIANA.
..UPPER MIDWEST...
CONDITIONAL/CATEGORICAL SLGT RISK EXISTS FOR THIS PERIOD WITH MAIN
UNCERTAINTIES ATTM BEING PLACEMENT AND STRENGTH OF LOW LEVEL
CONVECTIVE FOCI. REMAINS OF DAY-1 MCS MAY MOVE SEWD FROM SD ACROSS
PORTIONS MN/WI/IA THROUGH EARLY PERIOD...WITH INFLOW LAYER ELEVATED
WELL ABOVE RELATIVELY STABLE SFC LAYER N OF WARM FRONT...AND SVR
THREAT BEING MRGL HAIL. PROSPECTS FOR THIS ACTIVITY TO REJUVENATE
TO PRODUCE ORGANIZED SVR DURING AFTERNOON APPEAR VERY
LOW/CONDITIONAL ATTM BECAUSE OF TRACK UNCERTAINTIES AND PRESENCE OF
RELATIVELY LOW-THETAE AIR MASS N OF SFC WARM FRONT...OVER
IL/INDIANA/LOWER MI.
PRIMARY SVR THREAT SHOULD BE AFTERNOON INTO EVENING WITH SOME
SUPERCELLS POSSIBLE INVOF SFC LOW AND ADJACENT WARM FRONTAL
SEGMENT...AND MULTICELL/LINEAR MODES NEAR COLD FRONT. STRONGEST
VERTICAL SHEAR AND BUOYANCY SHOULD EXIST ACROSS PORTIONS MN...IA AND
PERHAPS ERN NEB/SD BY MID-LATE AFTERNOON. FAVORABLE DIURNAL HEATING
AND SFC MOISTURE ARE EXPECTED ALONG AND S OF WARM FRONT OR OUTFLOW
BOUNDARY FROM MORNING MCS. EVAPOTRANSPIRATIVELY AIDED SFC DEW
POINTS 70S F SHOULD CONTRIBUTE TO MLCAPES EXCEEDING 2000
J/KG...BENEATH 30-45 KT 500 MB FLOW. DEEP-LAYER VERTICAL SHEAR
PROFILES SHOULD BE FAVORABLE FOR SUPERCELLS AND BOWS IN THIS
AREA...ESPECIALLY INVOF SFC WARM FRONT WHERE BACKED LOW LEVEL WINDS
ALSO WILL ENHANCE LOW LEVEL HODOGRAPH SIZE. STRENGTH OF ISALLOBARIC
FORCING AND POSITIONING/STRENGTH OF OUTFLOW BOUNDARY...IF ANY...ARE
UNCERTAIN ATTM AND MAY MAKE CONSIDERABLE DIFFERENCE IN GEOMETRY AND
MAGNITUDE OF LARGEST LOW LEVEL SHEAR FIELDS.
40-50 KT SWLY LLJ OVERNIGHT MAY FAVOR UPSCALE GROWTH OF
AFTERNOON/EVENING CONVECTION ACROSS UPPER MS VALLEY...WITH DAMAGING
GUSTS BEING MAIN CONCERN. ASSOCIATED SVR PROBABILITIES SHOULD
DIMINISH WITH TIME AND EWD EXTENT TOWARD LM...AS NEAR-SFC AIR MASS
BECOMES MORE STABLE.
..SRN/CENTRAL ROCKIES TO CENTRAL PLAINS...
WIDELY SCATTERED TO SCATTERED TSTMS MAY DEVELOP INVOF SFC COLD FRONT
ACROSS CENTRAL PLAINS DURING AFTERNOON. FRONTAL LIFT AND STG
DIURNAL DESTABILIZATION WILL CONTRIBUTE TO WEAKENING CINH BY AROUND
04/21-05/00Z. CONVECTION ALSO IS LIKELY FARTHER SWWD ACROSS
CENTRAL/SRN ROCKIES AND ERN AZ IN REGIME OF RICH LOW-MIDLEVEL
MONSOONAL MOISTURE AND DIURNAL HEATING OF HIGHER TERRAIN. THESE TWO
REGIMES SHOULD BLEND TOGETHER ACROSS CENTRAL/ERN CO. DEEP-LAYER
KINEMATIC PROFILES SHOULD WEAKEN SWD AND WWD WITH CLOSER PROXIMITY
TO UPPER RIDGING...HOWEVER SUFFICIENT BUOYANCY AND DCAPE SHOULD BE
PRESENT TO SUPPORT ISOLATED/BRIEF THREAT OF GUSTS NEAR SVR LEVELS.
..NRN ROCKIES...
ISOLATED TO WIDELY SCATTERED TSTMS SHOULD DEVELOP DURING AFTERNOON
OVER PORTIONS ID/SWRN MT. THIS ACTIVITY SHOULD OCCUR IN ZONE OF
STEEP MIDLEVEL LAPSE RATES AND FAVORABLE VERTICAL SHEAR...AND
BENEATH 80-90 KT OF UPPER LEVEL WINDS. LACK OF MORE ROBUST SFC
MOISTURE SHOULD PRECLUDE ORGANIZED SVR THREAT...HOWEVER MOST INTENSE
TSTMS MAY PRODUCE STG-SVR GUSTS.
..SERN CONUS...
SCATTERED-NUMEROUS TSTMS ARE LIKELY AGAIN IN ASSOCIATION WITH
PERSISTENT AREA OF LOW PRESSURE NOW OVER EXTREME NERN GULF. LAPSE
RATES ALOFT ARE FCST TO BE WEAK...AND SO WILL BE DEEP-LAYER SHEAR.
HOWEVER...LARGE NUMBER OF TSTMS WILL BOOST PROBABILITIES FOR A FEW
STG/DAMAGING WET MICROBURSTS AMONG THEM.
.EDWARDS.. 08/03/2007
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