SWODY1
SPC AC 210058
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0758 PM CDT FRI APR 20 2007
VALID 210100Z - 211200Z
..THERE IS A SLGT RISK OF SVR TSTMS PORTIONS WRN/NRN
NEB...SD...SERN ND...
..THERE IS A SLGT RISK OF SVR TSTMS PORTIONS TX PANHANDLE...
..SYNOPSIS...
HIGH AMPLITUDE WILL CHARACTERIZE MID-UPPER TROPOSPHERIC PATTERN
ACROSS CONUS THROUGH REMAINDER PERIOD...FEATURING SYNOPTIC TROUGH
OVER WRN STATES AND RIDGING FROM WRN GULF OF MEXICO TO HUDSON BAY.
BROAD FETCH OF SW FLOW ALOFT EXISTS DOWNSTREAM FROM PRONOUNCED
MID-UPPER LEVEL LOW THAT MOISTURE CHANNEL IMAGERY INDICATED OVER SRN
CA. THIS LOW IS FCST TO PIVOT EWD OVERNIGHT TO THE LOWER CO RIVER
VALLEY AND SWRN AZ.
AT SFC...LOW WAS ANALYZED OVER SWRN SD...WITH WARM FRONTAL ZONE NEWD
ACROSS ERN ND AND SWWD OVER E-CENTRAL/SERN WY. DIFFUSE LEE CYCLONE
NOW OVER ERN CO IS FCST TO LIFT NWD AND BECOME MORE SHARPLY DEFINED
OVERNIGHT ACROSS NEB PANHANDLE. ISALLOBARIC/ISALLOHYPSIC FORCING
ASSOCIATED WITH LEE CYCLONE/TROUGHING WILL MAINTAIN SELY SFC WINDS
OVER MUCH OF CENTRAL/SRN HIGH PLAINS. THIS SHOULD RESULT IN
CONSOLIDATION AND SLGT WWD RETREAT OF DOUBLE DRYLINE STRUCTURE
ANALYZED AT 23Z FROM SWRN SD SWD ACROSS W TX.
MEANWHILE...DECOUPLING BOUNDARY LAYER WILL LEAD TO INTENSIFICATION
OF 40-50 KT SLY LLJ FROM NRN COAHUILA TO OK PANHANDLE...VEERING TO
SSWLY ACROSS WRN KS TO ERN SD.
..NRN/CENTRAL PLAINS...
COMPLEX OF STG-SVR TSTMS -- SOME OF WHICH HAVE PRODUCED HAIL UP TO
1.75 INCH DURING PAST 1-2 HOURS -- SHOULD CONTINUE AND SHIFT NEWD
ACROSS ERN DAKOTAS THROUGH REMAINDER EVENING. REF WW 152 AND
RELATED MESOSCALE DISCUSSIONS FOR NEAR-TERM SVR FCST. ADDITIONAL
DEVELOPMENT/REJUVENATION OF ACTIVITY OVER THIS REGION MAY OCCUR
AFTER APPROXIMATELY 3Z...ASSOCIATED WITH STRENGTHENING LLJ AND
ASSOCIATED MOISTURE TRANSPORT AND ISENTROPIC LIFT.
APPARENTLY SFC-BASED DEVELOPMENT OCCURRING ATTM ACROSS SERN NEB ALSO
MAY EVOLVE INTO SEPARATE COMPLEX OF TSTMS DURING EVENING/OVERNIGHT
HOURS...WITH DAMAGING WIND POSSIBLE DURING FIRST 2-3 HOURS AND LARGE
HAIL BEING MAIN THREAT THEREAFTER. MODIFIED RAOBS AND FCST
SOUNDINGS SHOW MIDLEVEL LAPSE RATES OF 7-8 DEG C/KM...COMBINING WITH
SFC DEW POINTS LOW-MID 50S F TO SUPPORT MLCAPES AROUND 1000 J/KG.
ONCE BOUNDARY LAYER DECOUPLES SUFFICIENTLY FOR EFFECTIVE INFLOW
PARCELS TO BECOME ELEVATED...EXPECT MUCAPES NEAR 2000 J/KG WITH
FAVORABLE EFFECTIVE SHEAR VALUES FOR SVR...WITH LARGE HAIL MOST
PROBABLE.
..SRN HIGH PLAINS...
ISOLATED CLUSTER OF TSTMS HAS DEVELOPED INVOF ERN DRYLINE
SEGMENT...BETWEEN PVW-AMA...AMIDST STRONGLY HEATED/MIXED BOUNDARY
LAYER. ADDITIONAL DEVELOPMENT MAY OCCUR FOR ANOTHER 1-2 HOURS ON
SEGMENT OF TCU EXTENDING SWD TO BETWEEN PVW-LBB. AMA RAOB AND RUC
SOUNDINGS...ALONG WITH LIMITED DEPTH OF AVAILABLE VAD
WINDS...INDICATE FAVORABLE VERTICAL SHEAR PROFILES FOR SUPERCELLULAR
ORGANIZATION TO ARISE FROM THIS ACTIVITY. ADDITIONAL/ISOLATED
DEVELOPMENT MAY OCCUR FROM THIS REGION NWD ACROSS WRN KS...THOUGH
SBCINH WILL INCREASE THROUGH REMAINDER EVENING AS SFC COOLING
GRADUALLY OFFSETS THETAE ADVECTION. LARGE HAIL AND ISOLATED STG-SVR
GUSTS WILL BE POSSIBLE BEFORE ACTIVITY WEAKENS LATE THIS EVENING.
.EDWARDS.. 04/21/2007
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