SPC AC 060557
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1157 PM CST TUE FEB 05 2008
VALID 061200Z - 071200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER THE UPPER OH VALLEY AND
MIDDLE ATLANTIC STATES SWD TO THE ERN GULF COAST...
...SYNOPSIS...
DYNAMIC UPPER LOW AND ASSOCIATED 110-120 KT MIDLEVEL JET STREAK WILL
LIFT RAPIDLY NEWD FROM THE MID MS VALLEY INTO THE NERN STATES WITH
AN INTENSE HEIGHT FALL CENTER OF 150-200M/12 HR OVERSPREADING THE OH
VALLEY AND MIDDLE ATLANTIC STATES. IN THE LOW LEVELS...SURFACE LOW
INITIALLY OVER SERN IND IS FORECAST TO UNDERGO DEEPENING TODAY WHILE
DEVELOPING ENEWD ALONG WARM OR QUASI-STATIONARY BOUNDARY INTO CNTRL
PA...BEFORE EVENTUALLY MOVING EWD OFF THE MIDDLE ATLANTIC COAST LATE
TONIGHT. STRONG COLD FRONT INITIALLY FROM THE MIDDLE OH VALLEY
SSWWD TO THE CNTRL GULF COAST WILL SURGE EWD...EVENTUALLY REACHING
THE ATLANTIC COAST TONIGHT.
...UPPER OH VALLEY TO MIDDLE ATLANTIC COAST...
FORECAST IS QUITE COMPLEX OWING TO EXPECTED ONGOING AND WIDESPREAD
NATURE OF STORMS AT 06/12Z WHICH MAY BE WELL E OF CURRENT MODEL
GUIDANCE BASED ON EXTRAPOLATION OF CURRENT RADAR DATA.
50-60 KT SWLY LLJ CURRENTLY FROM THE CNTRL GULF COAST INTO THE UPPER
OH VALLEY WILL GRADUALLY SHIFT EWD TODAY SUPPORTING A CONTINUED
INCREASE IN BOUNDARY LAYER MOISTURE WITH DEWPOINTS REACHING THE
MID/UPPER 50S. ALTHOUGH AFTERNOON TEMPERATURES WILL REMAIN LARGELY
IN THE 60S...THIS MOISTURE COUPLED WITH SIGNIFICANT DYNAMIC COOLING
IN THE MIDLEVELS WILL RESULT IN THE DEVELOPMENT OF WEAK CONVECTIVE
INSTABILITY AHEAD OF SURFACE LOW AND COLD FRONT WITH MLCAPES
APPROACHING 500-700 J/KG.
EXPECT ONGOING STORMS TO GRADUALLY INTENSIFY THROUGH THE DAY AS AIR
MASS SLOWLY DESTABILIZES AND LARGE-SCALE FORCING FOR ASCENT
INCREASES AHEAD OF UPPER LOW. FORECAST SOUNDINGS INDICATE THAT
VERTICAL SHEAR WILL BE VERY STRONG WITH 80-90 KT OF EFFECTIVE BULK
SHEAR...EFFECTIVE SRH VALUES OF 250-350 M2/S2 AND 50+ KT STORM
MOTIONS. AS SUCH...THE POTENTIAL WILL EXIST FOR EMBEDDED SUPERCELL
AND BOWING STRUCTURES WITH A THREAT OF DAMAGING WINDS AND/OR
TORNADOES...BOTH OF WHICH COULD BE SIGNIFICANT. STORMS SHOULD TEND
TO WEAKEN SOME BY LATE EVENING AS BOUNDARY LAYER SLOWLY
STABILIZES...THOUGH DAMAGING WINDS WILL REMAIN POSSIBLE ALONG THE
MIDDLE ATLANTIC COAST.
...TN VALLEY AND CNTRL GULF STATES EWD TO THE E-CNTRL AND SERN
ATLANTIC COAST...
A BAND OF PRE-FRONTAL STORMS SHOULD BE PRESENT AT THE START OF THE
PERIOD OVER MIDDLE/ERN TN SWWD INTO ERN MS/AL...ROOTED WITHIN A
MOIST BOUNDARY LAYER WITH DEWPOINTS IN THE 60S. WHILE STRONGER
HEIGHT FALLS WILL BEGIN TO PULL NEWD AWAY FROM THE REGION...MODEST
INSTABILITY /MLCAPES OF 500-1000 J PER KG/ AND FORCING ALONG COLD
FRONT SHOULD MAINTAIN A LINE OR CLUSTERS OF STORMS THROUGH THE
PERIOD.
THE PRESENCE OF 50-60 KT OF DEEP LAYER SHEAR SHOULD SUPPORT A
CONTINUED THREAT OF SUPERCELLS AND BOWING STRUCTURES WITHIN LARGER
CONVECTIVE BAND. ISOLATED TORNADOES WILL BE POSSIBLE AS WILL THE
POTENTIAL FOR CORRIDORS OF DAMAGING WINDS. THE TORNADO THREAT
APPEARS HIGHEST THIS MORNING INTO EARLY AFTERNOON...AS LOW-LEVEL
SHEAR IS FORECAST TO WEAKEN WITH TIME AS STRONGER ISALLOBARIC
FORCING DEVELOP NEWD AWAY FROM THE REGION.
..MEAD.. 02/06/2008
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z
|
