SWODY1
SPC AC 020600
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0100 AM CDT SAT AUG 02 2008
VALID 021200Z - 031200Z
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS NEW
ENGLAND...MID-ATLANTIC TO CAROLINAS...
...SYNOPSIS...
AMPLIFIED UPPER AIR PATTERN FCST TO CONTINUE ACROSS NRN/ERN CONUS.
LATEST MOISTURE CHANNEL IMAGERY INDICATES BROAD CYCLONIC GYRE NOW
OVER SERN CANADA AND GREAT LAKES REGION CONTAINS SEVERAL EMBEDDED
VORTICITY MAXIMA...SHORTWAVE PERTURBATIONS AMD MESOBETA SCALE
CIRCULATION CENTERS. VORTICITY LOBE NOW OVER UPPER MI AND LH IS
FCST TO MOVE GENERALLY ESEWD ACROSS UPSTATE NY...WITH MOST
SHORT-RANGE MODEL AND SREF MEMBERS EVOLVING THIS FEATURE INTO
PRIMARY UPPER LOW CENTER OVER NRN NY OR NWRN NEW ENGLAND BY 3/12Z.
SYNOPTIC SCALE TROUGH WILL BUILD SWWD ACROSS APPALACHIANS...AND MOVE
ESEWD TOWARD ATLANTIC COAST. THIS TROUGH WILL EXTEND THROUGH WEAK
MID-UPPER COL TO SECONDARY/WEAK UPPER LOW -- ANALYZED AT 500 MB AT
2/00Z INVOF AAF. SFC COLD FRONT SHOULD MOVE SEWD/EWD ACROSS MID
ATLANTIC REGION AND CENTRAL/SRN APPALACHIANS...PRECEDED BY LEE
TROUGHING FROM ERN NY SWWD ACROSS ERN PA AND ALONG PIEDMONT THROUGH
CAROLINAS.
MEANWHILE...UPPER LOW OVER NRN AB WILL CONTINUE TO EJECT ENEWD
ACROSS NRN SASK...WITH POSITIVELY TILTED TROUGH TRAILING SWWD ACROSS
NRN ROCKIES AND INTERIOR PACIFIC NW REGION. AT SFC...WEAK COLD
FRONT NOW MOVING EWD ACROSS MT WILL MOVE EWD OVER CENTRAL DAKOTAS BY
3/00Z...COLLOCATED WITH INVERTED TROUGH EXTENDING SWD INTO LOW OVER
NEB PANHANDLE/EXTREME SWRN SD AREA. SFC WARM FRONT WILL MOVE NEWD
ACROSS CENTRAL PLAINS AND CENTRAL/ERN SD.
...NERN CONUS...
SCATTERED-NUMEROUS TSTMS IN BANDS AND CLUSTERS ARE EXPECTED TO
DEVELOP PRIMARILY ALONG/AHEAD OF SFC TROUGH...FROM MORNING THROUGH
AFTERNOON. GREATEST OVERLAP OF FCST BUOYANCY AND SHEAR SHOULD BE
OVER MID-ATLANTIC REGION AND SRN NEW ENGLAND...WHERE RELATIVELY
BACKED SFC WINDS E OF TROUGH WILL CONTRIBUTE TO ENLARGED LOW LEVEL
HODOGRAPHS. STORM MODE WILL INFLUENCE TORNADO POTENTIAL
STRONGLY...HOWEVER SUFFICIENT SHEAR IS EXPECTED TO SUPPORT SOME
TORNADO POTENTIAL FROM EITHER SUPERCELLS...BOWS OR QLCS
CIRCULATIONS. PRIMARY THREAT WILL BE DAMAGING WIND...AND LARGE HAIL
ALSO IS POSSIBLE. LOCATION AND MAGNITUDE OF GREATEST
DESTABILIZATION REMAINS UNCERTAIN ATTM...WITH CLOUDS/PRECIP FROM
EARLY ACTIVITY STRONGLY INFLUENCING DURATION/STRENGTH OF INSOLATION
RELATED HEATING ACROSS THIS REGION LATE MORNING INTO AFTERNOON. SFC
TEMPS 80S F WITH DEW POINTS MID-60S/LOW-70S SUPPORT MLCAPES 2500
J/KG IN FCST SOUNDINGS.
...CAROLINAS...
SCATTERED-NUMEROUS TSTMS ALSO ARE EXPECTED TO DEVELOP IN THIS
REGION...PRIMARILY DURING AFTERNOON...AND ALONG/E OF SFC TROUGH.
DAMAGING WIND AND ISOLATED LARGE HAIL WILL BE POSSIBLE. WHILE
DEEP-LAYER WIND FIELDS AND LOW-MIDLEVEL SHEAR WILL NOT BE AS STG AS
FARTHER NE IN MID-ATLANTIC...POTENTIAL EXISTS FOR DENSE COVERAGE OF
ORGANIZED MULTICELLULAR TSTMS WITH ACCOMPANYING THREAT FOR HAIL AND
DAMAGING GUSTS.
...DAKOTAS/UPPER MIDWEST...
AT LEAST THREE SPATIALLY/TEMPORALLY SEPARATED REGIMES OF POTENTIAL
FOR STG-SVR TSTMS MAY AFFECT THIS REGION...CLOSE ENOUGH OR
OVERLAPPED SO THAT THE WHOLE-PERIOD PROBABILITIES COMBINED INTO ONE
AREA. SOME SUBSET OF THIS AREA MAY REQUIRE CATEGORICAL SLGT UPGRADE
SHOULD CONFIDENCE INCREASE IN CONCENTRATED/ORGANIZED SVR WITH ANY OF
THESE REGIMES...
1. EARLY PERIOD AND AFTERNOON -- ND TO NWRN MN.
EWD EXTENSION OF CONVECTIVE REGIME NOW MOVING ACROSS ERN MT MAY
PERSIST INTO EARLY THIS PERIOD...WITH POTENTIAL FOR ISOLATED HAIL OR
STG GUSTS FROM MOST INTENSE TSTMS ACROSS ND. THIS REGIME SHOULD
MOVE NEWD INTO CANADA THROUGH MIDDAY...THOUGH ADDITIONAL DEVELOPMENT
DURING AFTERNOON CANNOT BE RULED OUT INVOF INVERTED TROUGH/FRONTAL
ZONE. STG CAPPING MAKES ANY AFTERNOON THREAT VERY
CONDITIONAL...ALTHOUGH FAVORABLE MOISTURE -- SFC DEW POINTS 60S F --
AND STEEP MIDLEVEL LAPSE RATES WILL YIELD UP TO 2000-3000 J/KG
MLCAPE FOR ANY CONVECTION THAT CAN DEVELOP INVOF BOUNDARY.
2. AFTERNOON -- CENTRAL HIGH PLAINS TO WRN/SRN SD.
EXPECT STG HEATING OF HIGHER TERRAIN OVER ERN WY...COMBINED WITH
WEAK/NELY UPSLOPE FLOW ON W SIDE OF TROUGH/FRONT...TO SUPPORT
POTENTIAL FOR HIGH-BASED TSTMS W OF DRYLINE...WITH POTENTIAL FOR
ISOLATED GUSTS/HAIL NEAR SVR LEVELS. ACTIVITY MAY MOVE INTO MORE
ROBUST BOUNDARY LAYER MOISTURE OVER WRN NEB AND SWRN SD...CONTINUING
POTENTIAL FOR STG-SVR WIND AND OCCASIONAL HAIL AMIDST VERY STG
INSTABILITY -- WITH SFC TEMPS 90S TO NEAR 100 F AND DEW POINTS
50S/60S POSSIBLY YIELDING MLCAPES APCHG 3000 J/KG. DEEP-LAYER SHEAR
WILL BE AT LEAST MRGLLY FAVORABLE...BENEATH 25-35 KT 500 MB WINDS.
MAIN LIMITING FACTOR WILL BE CAPPING.
3. AFTER DARK -- ERN SD/SRN MN/NRN IA REGION.
SCATTERED TSTMS MAY DEVELOP AFTER DARK AS NOSE OF 30-35 KT LLJ
IMPINGES UPON LOW LEVEL WARM FRONTAL ZONE...WITH RELATIVELY
MAXIMIZED POTENTIAL FOR ISENTROPIC ASCENT TO LFC. SHOULD THIS
OCCUR...STG INSTABILITY IS LIKELY...WITH STEEP MIDLEVEL LAPSE RATES
CONTRIBUTING TO ELEVATED MUCAPES NEAR 3000 J/KG IN NAM-KF FCST
SOUNDINGS. SUFFICIENT TURNING OF WINDS WITH HEIGHT IS EXPECTED FROM
INFLOW REGION UPWARD TO SUPPORT 35-40 KT EFFECTIVE SHEAR. SEVERAL
SHORT-RANGE PROGS DEVELOP WELL-DEFINED CONVECTIVE QPF SIGNAL
ASSOCIATED WITH THIS REGIME...LENDING SOME CONFIDENCE TO AT LEAST
MRGL THREAT FOR SVR HAIL ACROSS THIS AREA.
...NRN HIGH PLAINS...
COLD FRONT NOW PASSING THROUGH PORTIONS OF THIS AREA WILL LEAVE
BEHIND RELATIVELY DRY SFC AIR MASS -- WITH DEW POINTS COMMONLY
30S-40S F. WHILE THIS MRGL MOISTURE WILL LIMIT BUOYANCY...STRENGTH
OF DIABATIC HEATING ON ELEVATED TERRAIN STILL SHOULD BE SUFFICIENT
TO SUPPORT ISOLATED TO WIDELY SCATTERED TSTM DEVELOPMENT. ENHANCED
SWLY GRADIENT FLOW ALOFT -- E.G. 40-50 KT AT 500 MB -- WILL
CONTRIBUTE TO ENHANCED DEEP-LAYER SHEAR ACROSS PARTS OF THIS REGION
DURING PERIOD OF STRONGEST AFTERNOON HEATING AND INTO EARLY EVENING.
GIVEN SUCH KINEMATIC FIELDS...AND PRESENCE OF DEEP/WELL-MIXED
BOUNDARY LAYER -- SOME TSTMS MAY PRODUCE STG-SVR GUSTS.
...AZ...
CONVECTIVE COVERAGE PREVIOUS DAY WAS SPARSE ENOUGH THAT AIR MASS
THERMODYNAMICS STILL SHOULD BE SUITABLE FOR ANOTHER...PERHAPS
BETTER-ORGANIZED ROUND OF TSTMS THIS AFTERNOON INTO EARLY EVENING.
STG SFC HEATING WILL SUPPORT DEEPLY WELL-MIXED BOUNDARY LAYER OVER
DESERTS...IN ADVANCE OF TSTMS DEVELOPING OVER HIGHER TERRAIN AND
MOVING WWD TO SWWD. KINEMATICALLY...SOMEWHAT DEEPER LAYER OF NELY
TO ELY WINDS ALOFT IS FCST -- E. G. FROM ABOUT 600 MB TO TROPOPAUSE
PER NAM-KF FCST SOUNDING. POTENTIAL EXISTS FOR SOME TSTMS TO
ORGANIZE COLLECTIVE COLD POOL FOR CONDITIONAL RISK OF STG-SVR GUSTS.
WARM TEMPS AND RELATED WEAK LAPSE RATES ALOFT WILL LIMIT
BUOYANCY...WITH MLCAPES GENERALLY UNDER 750 J/KG FCST IN MOST AREAS.
THREAT SHOULD DIMINISH CONSIDERABLY AFTER DARK AS COMBINATION OF
DIABATIC COOLING AND OUTFLOW EFFECTS CONTRIBUTE TO STATIC STABILITY.
..EDWARDS/GRAMS.. 08/02/2008
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