SWODY2
SPC AC 040600
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0100 AM CDT FRI JUL 04 2008
VALID 051200Z - 061200Z
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS DAKOTAS AND NWRN MN...
...SYNOPSIS...
UPPER AIR PATTERN FCST TO DEAMPLIFY ACROSS WRN CONUS...WHILE EASTERN
MEAN TROUGH GENERALLY WEAKENS IN PLACE. SHORTWAVE TROUGH -- NOW
EVIDENT IN MOISTURE CHANNEL IMAGERY OFFSHORE ORE AND NRN CA -- IS
FCST TO MOVE NEWD INLAND PACIFIC NW DAY-1...THEN NEWD FROM WRN MT
AND CANADIAN HIGH PLAINS TOWARD NERN MB THIS PERIOD...WHILE MERGING
INTO ZONALLY ELONGATED CYCLONE COVERING HUDSON BAY REGION.
VORTICITY LOBE -- SPLITTING OFF SRN PORTION OF THAT TROUGH -- IS
PROGGED TO MOVE ENEWD ACROSS CENTRAL ROCKIES TO CENTRAL HIGH PLAINS
AND SD LATE IN PERIOD. OPERATIONAL PROGS AND SREF GUIDANCE TRACK
FCSTS ARE SIMILAR...BUT WITH QUITE VARIABLE SPEEDS.
MEANWHILE...BROAD AND GENERALLY WEAK MIDLEVEL FLOW -- E.G. 10-25 KT
AT 500 MB -- WILL CROSS MUCH OF ERN CONUS AROUND POSITIVELY TILTED
TROUGH...WHICH SHOULD EXTEND ROUGHLY FROM LOWER GREAT LAKES SWWD
ACROSS LOWER OH VALLEY TO LOWER MS VALLEY BY 5/12Z. NARROW CORRIDOR
OF SOMEWHAT STRONGER UPPER FLOW -- 60-80 KT AT 250 MB -- MAY EXTEND
FROM KY NEWD ACROSS CENTRAL/SRN NEW ENGLAND DURING MUCH OF
PERIOD...PARTICULARLY IF GRADIENTS ALOFT ARE ENHANCED BY
CYCLOGENESIS. WEAK 500 MB LOW MAY DEVELOP ALONG THIS TROUGH OVER OH
EARLY IN PERIOD...BASED ON OPERATIONAL WRF AND SEVERAL SREF
MEMBERS...BUT CONSENSUS FOR THIS FEATURE AND ANY RELATED SFC
FRONTAL-WAVE LOW FORMATION AMONGST BULK OF GUIDANCE IS RATHER POOR.
AT SFC...FRONTAL ZONE -- NOW ANALYZED FROM CENTRAL NEW ENGLAND SWWD
ACROSS PA AND OH VALLEY TO CENTRAL OK AND SRN NM -- IS FCST TO
BECOME QUASISTATIONARY BETWEEN NEW ENGLAND AND AR DURING THIS
PERIOD...AND ALSO...TO BECOME MORE DIFFUSE AS
INTERVENING/NEAR-FRONTAL CONVECTIVE EVENTS PRODUCE OUTFLOW
BOUNDARIES. WRN LIMB OF BAROCLINIC GRADIENT SHOULD MOVE/REDEVELOP
NWD ACROSS CENTRAL LOW PLAINS AND MO VALLEY AS WARM FRONTAL ZONE.
SEPARATE COLD FRONT -- ASSOCIATED WITH NRN STREAM MID-UPPER LEVEL
SHORTWAVE TROUGH -- IS EXPECTED TO MOVE EWD ACROSS NRN PLAINS
THROUGH PERIOD...REACHING FROM NRN MN SWWD ACROSS PORTIONS NEB
PANHANDLE AND SERN WY BY 6/12Z. DURING LATE AFTERNOON/EARLY
EVENING...PREFRONTAL SFC TROUGH SHOULD INTERSECT COLD FRONT OVER
BADLANDS/WRN SANDHILLS REGION OF NEB/SD AND EXTEND SWWD OVER ERN CO.
...DAKOTAS AND NWRN MN TO CENTRAL HIGH PLAINS...
WIDELY SCATTERED TO SCATTERED TSTMS ARE EXPECTED TO DEVELOP DURING
AFTERNOON INVOF SFC COLD FRONT AND PREFRONTAL TROUGH...WITH
ASSISTANCE BOTH FROM CONVERGENCE INVOF THOSE BOUNDARIES AND EROSION
OF CAPPING BY STG SFC HEATING. ALTHOUGH LOW LEVEL WIND PROFILES AND
HODOGRAPHS ARE NOT PROGGED TO BE VERY STRONG...WITH FLOW GENERALLY
AOB 15 KT IN SFC-700 MB LAYER -- COMBINATION OF LARGE BUOYANCY AND
SOMEWHAT MORE FAVORABLE MID-UPPER LEVEL WIND SHOULD AID IN STORM
ORGANIZATION. SOMEWHAT HIGH BASED STORMS ARE EXPECTED ATOP RATHER
FRAGMENTED SFC MOISTURE FIELD THAT WILL BE STRONGLY TIED TO AREAS OF
EVAPOTRANSPIRATIVE ENHANCEMENT. DEW POINT RANGE SHOULD BE LARGE --
FROM 50S OVER WRN PARTS OF OUTLOOK AREA TO MID/UPPER 60S IN ERN
DAKOTAS AND CENTRAL/ERN NEB. DAMAGING GUSTS AND HAIL WILL BE
PRIMARY CONCERNS.
MID-UPPER WIND PROFILE AND DEEP-LAYER VERTICAL SHEAR EACH ARE FCST
TO BECOME WEAKER WITH SWWD EXTENT ALONG FRONTAL ZONE AND SFC TROUGH
OVER NEB/CO...LEADING TO MORE MULTICELLULAR/PULSE STORMS...OUTFLOW
DOMINANCE...AND GENERALLY DISORGANIZED SVR POTENTIAL. VERY STEEP
LOW-MIDLEVEL LAPSE RATES ARE LIKELY DURING AFTERNOON AND EARLY
EVENING...HOWEVER...INCLUDING DEEP/WELL-MIXED BOUNDARY LAYERS
CONDUCIVE BOTH TO MAINTAINING STG-SVR HAIL/GUSTS IN DOWNDRAFTS...AND
TO COLD POOL DEVELOPMENT.
...SERN CONUS TO MID ATLANTIC...
VERY LARGE AREA OF CONVECTIVE POTENTIAL EXISTS DURING AFTERNOON INTO
EARLY EVENING WITHIN AND S OF FRONTAL ZONE...MUCH OF WHICH ALSO WILL
BEAR AT LEAST MRGL RISK FOR SVR GUSTS OR HAIL FROM
PULSE/MULTICELLULAR ACTIVITY. SPECIFIC AREAS OF MORE CONCENTRATED
POTENTIAL WILL BE STRONGLY TIED TO MESOSCALE BOUNDARY
INTERACTIONS...HOWEVER GENERAL AREAS OF CONCERN MAY INCLUDE
1. INVOF FRONTAL ZONE...ESPECIALLY FROM OH VALLEY REGION NEWD
BENEATH THAT SOMEWHAT ENHANCED UPPER FLOW...AND
2. FL AND GULF COAST SEA BREEZE BOUNDARIES THAT SHOULD
CONCENTRATE/ENHANCE MULTICELL POTENTIAL.
...NRN/ERN WY...
NARROW ZONE OF RELATIVELY ENHANCED LOW LEVEL MOISTURE IS FCST TO
ADVECT UP HIGHER ELEVATIONS...JUST BEHIND SFC FROPA...AND TEMPORALLY
COINCIDE WITH STRONGEST DIURNAL HEATING OF THOSE AREAS. STG
DIRECTIONAL TURNING WITH HEIGHT IS FCST...ALTHOUGH MID/UPPER WINDS
MAY BE MRGL AT BEST FOR SUSTAINED SUPERCELL POTENTIAL. MID-LATE
AFTERNOON WINDOW OF OPPORTUNITY EXISTS FOR A FEW TSTMS TO PRODUCE
HAIL AND GUSTS NEAR SVR LEVELS BEFORE COMBINATION OF LOW LEVEL
COLD/DRY ADVECTION AND NOCTURNAL COOLING SHUT DOWN SFC-BASED
CONVECTIVE REGIME.
...CENTRAL LOW PLAINS...LOWER MO VALLEY REGION...
STG LOW LEVEL SHEAR IS PROGGED INVOF WARM FRONTAL ZONE OVER THIS
REGION...AS NWLY MID-UPPER WINDS JUXTAPOSE WITH SELY LOW LEVEL FLOW.
ALTHOUGH SPEEDS ARE NOT FCST TO BE VERY STG -- GENERALLY AOB 20 KT
BELOW ABOUT 400 MB -- ANY TSTMS THAT DO FORM MAY DEVELOP
TRANSIENT/HEAVY-PRECIP SUPERCELL STRUCTURES AMIDST INCREASING LOW
LEVEL MOISTURE. STG SFC HEATING MAY WEAKEN CINH AT BASE OF ELEVATED
MIXED LAYER ENOUGH TO ALLOW ISOLATED AFTERNOON DEVELOPMENT...BUT
WARM FRONTAL CONVERGENCE IS FCST TO BE WEAK.
SVR POTENTIAL APPEARS TOO CONDITIONAL ATTM FOR CATEGORICAL OUTLOOK.
..EDWARDS.. 07/04/2008
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