SPC AC 080559
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1259 AM CDT THU MAY 08 2008
VALID 081200Z - 091200Z
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS MS/WRN TN TO
CAROLINAS/SRN VA...
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS CENTRAL PLAINS...
...SYNOPSIS...
MID/UPPER LEVEL LOW -- ANALYZED FROM RAOB DATA...MOISTURE CHANNEL
TRENDS AND VWP/PROFILER WINDS OVER ERN OK -- IS FCST TO DEAMPLIFY
INTO OPEN-WAVE TROUGH AND MOVE EWD FROM LOWER/MID MS VALLEY TO
VICINITY CENTRAL APPALACHIANS THIS PERIOD. ASSOCIATED SFC LOW WILL
FOLLOW SIMILAR TRACK...WHILE TRAILING COLD FRONT MOVES SEWD ACROSS
MS DELTA REGION AND MUCH OF AL.
FARTHER W...SHORTWAVE TROUGH -- NOW EVIDENT FROM ERN ID SWWD ACROSS
GREAT BASIN -- IS FCST TO MOVE EWD AND DEAMPLIFY SLIGHTLY ACROSS
CENTRAL PLAINS...THOUGH ACCOMPANYING VORTICITY FIELD MAY BECOME
CONVECTIVELY ENHANCED ACROSS KS BY MCS DESCRIBED BELOW. BY END OF
PERIOD...THIS TROUGH SHOULD MOVE INTO WRN MO. ASSOCIATED SFC
CYCLONE -- ANALYZED ATTM ACROSS SERN WY -- SHOULD
PROPAGATE/REDEVELOP SSEWD TO NEAR OK PANHANDLE BY 9/00Z...THEN
GENERALLY EWD ACROSS OK THROUGH END OF PERIOD. INVERTED TROUGH
SHOULD SHIFT EWD ACROSS KS...IN STEP WITH ATTACHED SFC CYCLONE.
...SERN CONUS...
TWO PRIMARY SVR REGIMES ARE EVIDENT THROUGH DAYLIGHT HOURS --
MS/AL/TN AND CAROLINAS/SRN VA. RELATIVE MAXIMA IN SVR PROBABILITIES
ARE TIED STRONGLY TO TWO PLUMES OF RELATIVE MAXIMA IN FCST
INSTABILITY. IN BETWEEN -- FCST BOUNDARY LAYER TRAJECTORIES EMANATE
FROM AREAS NOW SHOWING PRONOUNCED RELATIVE MINIMA IN THETAE.
SHALLOW/EASILY MIXED MOIST LAYER WAS EVIDENT IN 00Z RAOBS FROM
TLH...TBW AND SPECIAL SONDE OVER SERN GULF INVOF 26N86W. THIS AIR
MASS ALSO WAS MANIFEST IN DRY CORRIDOR ANALYZED DURING AFTERNOON
ACROSS FL PENINSULA AS WELL. REGIME SHOULD INFLUENCE MUCH OF GA
DURING UPCOMING PERIOD...HOWEVER RICH LOW LEVEL MOISTURE IN DEEPER
BOUNDARY LAYER IS EXPECTED TO ITS E AND W...SUPPORTING POTENTIAL IN
THE FOLLOWING AREAS...
-- MS/AL
SEVERAL BANDS OR CLUSTERS OF SVR TSTMS ARE EXPECTED TO DEVELOP
ACROSS THIS AREA FROM LATE MORNING THROUGH MID-LATE AFTERNOON...AS
MOIST BOUNDARY LAYER DIABATICALLY DESTABILIZES UNDER POCKETS OF STG
INSOLATION. MIXED CONVECTIVE MODES ARE ANTICIPATED...WITH LINE
SEGMENTS...BOWS AND SUPERCELLS ALL POSSIBLE. EXPECT NARROW
PREFRONTAL CORRIDOR OF SFC DEW POINTS RANGING FROM LOW-MID 60S F
OVER NRN MS/AL/SRN TN...TO UPPER 60S/LOW 70S CLOSER TO GULF COAST.
HOWEVER...SBCINH WILL INCREASE WITH PROXIMITY TO COAST AND MAY LIMIT
CONVECTIVE COVERAGE. MOST FAVORABLE SHEAR/BUOYANCY/LIFT/MOISTURE
OVERLAPS SHOULD BE FROM CENTRAL MS EWD ACROSS PORTIONS AL...DURING
AFTERNOON...WHERE FCST SOUNDINGS SUGGEST MLCAPES 1000-2000
J/KG...40-50 KT EFFECTIVE SHEAR MAGNITUDE...AND CURVED LOW LEVEL
HODOGRAPHS WITH 0-1 KM SRH 200-400 J/KG. SVR POTENTIAL IS EXPECTED
TO DIMINISH WITH TIME AND EWD EXTENT OVERNIGHT INTO MORE STABLE AIR
MASS.
-- CAROLINAS/VA
AIR MASS MODIFICATION CONTINUES OVER NEARBY PORTIONS GULF
STREAM...WITH SLY TO SSELY FLOW EXPECTED FROM THAT AREA INTO
CAROLINAS THROUGH MUCH OF TODAY. EXPECT SFC DEW POINTS MID 60S
F...WEAKENING CINH AND INCREASING COVERAGE OF TSTMS BY EARLY-MID
AFTERNOON...BENEATH STRENGTHENING MID-UPPER LEVEL GRADIENT WINDS.
THIS WILL YIELD SHEAR BUOYANCY PROFILES SUITABLE FOR SUPERCELLS AND
BOWS. HAIL AND DAMAGING GUSTS ARE POSSIBLE...AND ONE OR TWO STORMS
MAY POSE TORNADO THREAT.
...CENTRAL PLAINS...
BENEATH AND JUST AHEAD OF SHORTWAVE HEIGHT TROUGH...MIDLEVEL
DPVA/ASCENT RESULTS IN -16 TO -21 DEG C 500 MB THERMAL TROUGH THAT
REASONABLY IS PROGGED TO SHIFT EWD ACROSS CENTRAL ROCKIES AND
CENTRAL PLAINS DURING THIS PERIOD. AS THIS REGIME CROSSES PORTIONS
CENTRAL HIGH PLAINS...IN CONJUNCTION WITH SFC DIABATIC
HEATING...PRIND SBCINH WILL WEAKEN CONSIDERABLY WITH SCATTERED TSTMS
DEVELOPING AND MOVING EWD. RECENT SPECTRAL/NAM/NAM-KF PROGS ARE
REMARKABLY CONSISTENT IN DEVELOPING STG CONVECTIVE PRECIP SIGNAL
WITH THIS FEATURE. POTENTIAL EXISTS FOR THESE TSTMS TO ORGANIZE
UPSCALE QUICKLY AND DEVELOP COLD POOL...THEN PROCEED EWD ACROSS KS
WITH DAMAGING WIND MAIN THREAT...AND ISOLATED HAIL ALSO POSSIBLE.
MODIFIED NAM-KF FCST SOUNDINGS SUGGEST MLCAPES 500-1000 J/KG ARE
POSSIBLE FOR A FEW HOURS IN MID-LATE AFTERNOON...OVER WRN KS...AS
STEEP LAPSE RATES ALOFT OVERSPREAD RESIDUAL BOUNDARY LAYER MOISTURE
WITH SFC DEW POINTS 40S TO LOW 50S F.
..EDWARDS/GRAMS.. 05/08/2008
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