SWODY1
SPC AC 190531
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1231 AM CDT THU APR 19 2007
VALID 191200Z - 201200Z
..NO SVR TSTM AREAS FORECAST...
..SYNOPSIS...
HIGH-AMPLITUDE SYNOPTIC PATTERN WILL CONTINUE OVER CONUS THROUGH
PERIOD. SOME EWD SHIFT OF WRN TROUGH/CENTRAL RIDGE/ERN TROUGH
PATTERN IS FCST BY 20/12Z...AS HEIGHTS RISE IN WAKE OF STRONG
SHORTWAVE TROUGH AND ACCOMPANYING UPPER LOW NOW OVER INDIANA. THIS
PERTURBATION SHOULD DIG SEWD ACROSS SRN APPALACHIANS DURING
DAY...THEN ACCELERATE ESEWD ACROSS CAROLINAS AND DEAMPLIFY AFTER
20/00Z. ASSOCIATED SFC CYCLONE -- ANALYZED ATTM OVER CENTRAL
APPALACHIANS -- ALSO WILL MOVE SEWD ACROSS SAV RIVER REGION OR SRN
SC.
FARTHER NW...STRONG MID/UPPER LEVEL LOW -- NOW EVIDENT IN MOISTURE
CHANNEL IMAGERY OVER SRN ID -- IS EXPECTED TO LIFT NEWD ACROSS
WRN/NRN WY AND ERN MT...BECOMING MORE CLOSELY STACKED IN VERTICAL
WITH SFC CYCLONE. ASSOCIATED LOW LEVEL FRONT WILL CONTINUE TO SWEEP
EWD OVER CENTRAL ROCKIES AND NRN HIGH PLAINS...REACHING WRN PORTIONS
SD/NEB/KS BY 20/00Z AND OCCLUDING WITH WARM FRONT OVER SWRN SD OR
N-CENTRAL/NWRN NEB. WARM FRONT SHOULD LIFT NWD SLOWLY ACROSS ERN
PORTIONS NEB/KS AND CENTRAL SD...AS STRONG ISALLOBARIC FORCING
MAINTAINS STRONG ELY FLOW COMPONENT TO ITS NE. COLD FRONT ALSO WILL
ACT AS EFFECTIVE DRYLINE...FOLLOWED BY DRY/WLY DOWNSLOPE FLOW ACROSS
CENTRAL HIGH PLAINS.
..SERN CONUS...
WIDELY SCATTERED TO SCATTERED TSTMS SHOULD MOVE/DEVELOP SEWD ACROSS
NARROW SWATH AHEAD OF SFC LOW...MOST VIGOROUS OF WHICH MAY PRODUCE
HAIL. GUSTS SHOULD REMAIN GENERALLY BELOW 50 KT SVR CRITERIA BUT
STILL MAY HARM SOME TREES AND PRODUCE MINOR DAMAGE TO CONSTRUCTION.
MAIN LIMITING FACTOR WILL BE LACK OF MORE ROBUST MOISTURE...WITH DEW
POINTS REMAINING BELOW 60 F MOST AREAS. NONETHELESS...COLD MIDLEVEL
TEMPS...SFC DIURNAL HEATING...AND WEAK CINH SHOULD CONTRIBUTE TO
NARROW PLUME OF MRGL SFC-BASED BUOYANCY -- BELOW 500 J/KG -- IN
ADVANCE OF SFC LOW TRACK. THIS SHOULD BE SUFFICIENT TO SUPPORT
CLUSTER OF TSTMS MOVING SEWD FROM HIGHER TERRAIN THROUGH AFTERNOON
HOURS...ACROSS PIEDMONT AND PERHAPS ONTO COASTAL PLAIN BY EARLY
EVENING. ALTHOUGH LOW LEVEL FLOW IS NOT FCST TO BE PARTICULARLY STG
INVOF SFC LOW...BACKED FLOW TO ITS E WILL ENHANCE BOTH
STORM-RELATIVE INFLOW AND DEEP-LAYER BULK SHEAR. NEARLY STRAIGHT
LINE HODOGRAPHS ALSO MAY SUPPORT SOME STORM SPLITTING AND BRIEF
SUPERCELL STRUCTURES.
..CENTRAL/NRN PLAINS...
TSTMS MAY BE ONGOING AT BEGINNING OF PERIOD OVER PORTIONS
CENTRAL/NRN HIGH PLAINS -- CARRYING OVER FROM ONGOING ACTIVITY NOW
OVER PORTIONS WY/MT. ADDITIONAL DEVELOPMENT WITH STG GUSTS AND/OR
HAIL IS POSSIBLE BY MID/LATE AFTERNOON OVER WRN/CENTRAL
DAKOTAS...AND BEHIND RESIDUAL CLOUD/PRECIP DEBRIS...BUT WITH VERY
LIMITED LOW LEVEL THERMODYNAMIC SUPPORT. LACK OF RICHER MOISTURE
WILL KEEP MLCAPES BELOW 500 J/KG IN MOST AREAS...DESPITE STEEP
MIDLEVEL LAPSE RATES. ALTHOUGH SFC DEW POINTS AND DIURNAL HEATING
EACH WILL BE STRONGER WITH SWD EXTENT ALONG/AHEAD OF
FRONT/DRYLINE...STRONGEST MID/UPPER ASCENT WILL PASS N OF NEB/KS BY
LATE AFTERNOON AND THIS AREA WILL LIE BEHIND AXIS OF TROUGH ALOFT.
SFC HEATING AND FRONTAL ASCENT MAY BE VIGOROUS ENOUGH TO INITIATE
BKN LINE OF CONVECTION DURING LATE AFTERNOON FROM S-CENTRAL/SERN NEB
TO N-CENTRAL/W-CENTRAL KS. STRONGEST STORMS MAY PRODUCE GUSTS AND
HAIL NEAR SVR LEVELS. CONVECTION SHOULD DIMINISH MARKEDLY AFTER
DARK.
.EDWARDS/GRAMS.. 04/19/2007
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