DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 191250
SWODY1
SPC AC 191247

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0747 AM CDT FRI OCT 19 2007

VALID 191300Z - 201200Z

..THERE IS A SLGT RISK OF SVR TSTMS OVER MUCH OF THE EASTERN
U.S....

..SYNOPSIS...
OCCLUDING SURFACE LOW IS FORECAST TO LIFT NNEWD INTO ONTARIO AS
UPPER TROUGH EJECTS NEWD THROUGH THE ERN STATES. AT THE
SURFACE...ATTENDANT COLD FRONT WILL CONTINUE EWD AND MOVE OFF THE
ATLANTIC SEABOARD BY LATE TONIGHT. AHEAD OF THE FRONT...RESERVOIR
OF UNSEASONABLY WARM AND MOIST AIR IS ALREADY IN PLACE FROM THE SERN
ATLANTIC STATES INTO ERN NY. 12Z SOUNDINGS AHEAD OF THE SYSTEM
INDICATE DEEP MOIST LAYER/SATURATED PROFILES WITH WEAK LAPSE RATES
ACROSS THE REGION.

..MID ATLANTIC THROUGH NERN STATES...
DESPITE NWD ADVECTION OF MID TO UPPER 60S LOW LEVEL DEWPOINTS...THE
PRE-FRONTAL WARM SECTOR SHOULD REMAIN ONLY MARGINALLY UNSTABLE DUE
TO EXPECTED WIDESPREAD CLOUDS AND WEAK MID LEVEL LAPSE RATES.
DESPITE THESE THERMODYNAMIC WEAKNESSES...SHEAR REMAINS VERY STRONG.
RESULTANT SCENARIO WILL THEREFORE BE QUITE MESSY TODAY AS STORM
CLUSTERS EVOLVE ACROSS A LARGE PORTION OF THE WARM SECTOR WITHIN
ZONE OF INCREASING UPPER DIVERGENCE AND LOW LEVEL CONFLUENCE
ASSOCIATED WITH NEWD EJECTING SHORTWAVE TROUGH. VERTICAL SHEAR
PROFILES AND LOW LEVEL HODOGRAPHS WILL SUPPORT POTENTIAL FOR
SUPERCELLS/LINES...WITH POTENTIAL FOR ISOLATED TORNADOES. ACTIVITY
WILL SHIFT EWD TOWARD THE ATLANTIC SEABOARD AND WEAKEN FRIDAY
EVENING.

..NRN FL THROUGH SRN GA AND THE CAROLINAS...
RICH LOW LEVEL MOISTURE WITH DEWPOINTS NEAR 70 WILL REMAIN OVER THIS
REGION. HOWEVER...PLUME OF DEEP MOISTURE WITH PWS NEAR 2 INCHES WILL
PERSIST AND SPREAD NEWD THROUGH WARM SECTOR...CONTRIBUTING TO AREAS
OF WIDESPREAD CLOUDS AND PRECIPITATION. EXPECTED MOIST ADIABATIC
PROFILES AND WIDESPREAD CLOUDS WILL LIKELY LIMIT INSTABILITY DURING
THE DAY WITH MLCAPE AOB 1000 J/KG ALONG WITH WEAK LAPSE RATES.
MODELS CONTINUE TO SUGGEST A SECONDARY LOW LEVEL JET WILL STRENGTHEN
FROM PARTS OF SRN GA THROUGH THE ERN CAROLINAS AS SRN BRANCH OF
SHORTWAVE TROUGH ADVANCES EWD DURING THE DAY. DEEP LAYER SHEAR OF
35 TO 45 KT WILL SUPPORT POTENTIAL FOR ORGANIZED STORMS INCLUDING
SUPERCELLS AND LINE SEGMENTS WITH BOW ECHOES. THE MAIN THREATS WILL
BE ISOLATED DAMAGING WIND/TORNADOES. HOWEVER...OVERALL THREAT MAY BE
LIMITED BY THE EXPECTED MARGINAL THERMODYNAMIC ENVIRONMENT.

.EVANS/GUYER.. 10/19/2007

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