SPC AC 251248
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0748 AM CDT MON AUG 25 2008
VALID 251300Z - 261200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF AL...FL AND GA...
...SYNOPSIS...
AMPLIFIED BAND OF WLYS WILL EXTEND FROM THE NE PACIFIC ACROSS SRN
CANADA INTO NEW ENG THIS PERIOD...AS WEAK FLOW PERSISTS OVER THE
CNTRL AND SRN STATES. STRONG...PROGRESSIVE E PACIFIC TROUGH WILL
MOVE INTO WA/ORE LATER TODAY BEFORE CONTINUING E INTO ID/WRN MT
EARLY TUESDAY. ASSOCIATED DOWNSTREAM HEIGHT RISES IN ONTARIO WILL
SUPPORT FURTHER AMPLIFICATION OF TROUGH OVER QUEBEC/NEW ENG. IN THE
SOUTH...HYBRID CIRCULATION NOW OVER SRN MS...MARKING T.D. FAY/S
MERGER WITH A MID LATITUDE VORT...EXPECTED TO EDGE SLOWLY NNE INTO
NRN AL BY THE END OF THE PERIOD.
...AL/FL/GA...
SLOW MOVEMENT OF DEEP...HYBRID CIRCULATION OVER MS WILL MAINTAIN
INFLOW OF VERY RICH MOISTURE /PW AOA 2 IN/ ACROSS MUCH OF AL...NW
FL...GA... AND SC. ONLY A VERY GRADUAL WEAKENING OF THE SYSTEM/S
WIND FIELD IS EXPECTED THROUGH TUESDAY. AREA OF CONCENTRATED
CONVECTIVE RAIN/EMBEDDED TSTMS NOW IN ERN QUADRANT OF CIRCULATION
SHOULD SHIFT SLOWLY NNE WITH THE UPR SYSTEM THROUGH THE PERIOD.
SATURATED THERMODYNAMIC PROFILES WILL KEEP ASSOCIATED SFC COLD POOL
WEAK. COUPLED WITH DEEP...LARGELY UNIDIRECTIONAL SSW FLOW...EXPECT
REGENERATIVE/BACK-BUILDING ACTIVITY TO PERSIST INTO TUESDAY. WHILE
THIS CONVECTION OCCASIONALLY WILL ORIENT INTO BROKEN BANDS PARALLEL
TO THE DEEP FLOW...WEAK COLD POOL LIKELY WILL CONTINUE TO FAVOR
BREAKDOWN OF THE BANDS INTO SEMI-DISCRETE STRUCTURES. GIVEN
FRICTIONALLY AND ISALLOBARICALLY-BACKED NEAR-SFC FLOW AHEAD OF THE
CIRCULATION CENTER...SETUP WILL CONTINUE TO SUPPORT A LIMITED
POTENTIAL FOR ISOLD TORNADOES AND SHORT-LIVED BOWING SEGMENTS WITH
HIGH WIND. THIS THREAT SHOULD BE GREATEST DURING THE AFTN AND MAY
EXTEND E ALONG WEAK STNRY FRONT/WIND SHIFT LINE FROM SRN AL E INTO
PARTS OF GA AND PERHAPS SC INTO EARLY TUESDAY. IN ADDITION...
ISOLD...DIURNALLY-ENHANCED CONVECTIVE CELLS MAY PERIODICALLY FORM IN
CONVERGENT...MOIST SLY FLOW E OF THE ABOVE-MENTIONED ACTIVITY.
THESE ALSO MAY POSE A THREAT FOR TORNADOES...ESPECIALLY AS THEY
CROSS WEAK W/E FRONT.
...CNTRL HI PLNS...
PATTERN WILL ONCE AGAIN FAVOR DEVELOPMENT OF ISOLD TO SCTD AFTN
TSTMS INVOF LEE TROUGH AND HIGHER TERRAIN OF ERN CO AND WY...GIVEN
MOIST SSELY LOW LVL FLOW BENEATH MODEST /15-25 KT/ NNW MID LVL JET.
LARGE SCALE FORCING FOR ASCENT APPEARS WEAKER THAN ON SUNDAY...WITH
NO SHORTWAVE DISTURBANCE OF NOTE APPARENT IN WV IMAGERY.
NEVERTHELESS...THE STORMS SHOULD GRADUALLY MOVE/DEVELOP SEWD INTO
UNSTABLE AIR /SBCAPE TO 2000 J PER KG/ OVER THE CNTRL HI PLNS
THROUGH EARLY EVE. DESPITE MODEST MID TROPOSPHERIC FLOW...LARGE
DIRECTIONAL COMPONENT IN THE WIND PROFILES /120-150 DEGREES IN THE
LOWEST 6 KM/ AND 30 KT DEEP NNWLY SHEAR SHOULD ONCE AGAIN SUPPORT
ORGANIZED MULTICELLS/BRIEF SUPERCELLS WITH LARGE HAIL...LOCALLY DMGG
WIND...AND POSSIBLY A BRIEF TORNADO.
...NEW ENG/LONG ISLAND...
COLD FRONT ASSOCIATED WITH AMPLIFYING UPR TROUGH WILL MOVE SE ACROSS
ERN AND SRN NEW ENG TODAY. ONGOING SHOWERS/TSTMS ALONG FRONT SHOULD
BE REPLACED BY ADDITIONAL DEVELOPMENT INVOF FRONT AND SEA BREEZE
BOUNDARIES OVER SRN NEW ENG AND LONG ISLAND EARLY THIS AFTN. ISOLD
SVR WIND/HAIL MAY OCCUR WITH SOME STORMS BEFORE THEY MOVE OFFSHORE
LATER IN THE DAY. ASIDE FROM THE EARLY TIMING OF COLD FRONTAL
PASSAGE AND MODEST PREFRONTAL INSTABILITY...ANOTHER FACTOR
OFFSETTING A MORE SUBSTANTIAL SVR THREAT WILL BE THE INITIALLY WEAK
DEEP SHEAR.
..CORFIDI/JEWELL.. 08/25/2008
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
|
