DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 290601
SWODY1
SPC AC 290559

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1159 PM CST MON JAN 28 2008

VALID 291200Z - 301200Z

..THERE IS A SLGT RISK OF SVR TSTMS FROM THE MID MS VALLEY REGION
NEWD ACROSS THE TN/OH VALLEYS...

..SYNOPSIS...
STRONG/SHARP MID-LEVEL SHORT-WAVE TROUGH IS FORECAST TO MOVE RAPIDLY
EWD ACROSS THE PLAINS THROUGH THE FIRST HALF OF THE PERIOD. THE
TROUGH IS THEN EXPECTED TO TAKE ON AN INCREASINGLY-NEGATIVE TILT AS
IT CONTINUES QUICKLY ACROSS THE OH/TN VALLEYS AND GREAT LAKES REGION
THROUGH 30/12Z. THIS TROUGH WILL BE ACCOMPANIED BY INTENSE
DEEP-LAYER WIND FIELD...INCLUDING 850 WINDS IN EXCESS OF 55-60 KT
AND 500 MB SWLY JET STREAK IN EXCESS OF 100 KT JUST AHEAD OF THE
TROUGH.

AT THE SURFACE...A COLD FRONT INITIALLY FORECAST TO EXTEND SWWD FROM
LK SUPERIOR SWWD ACROSS MO AND THEN INTO W TX WILL MOVE RAPIDLY
EWD/SEWD AHEAD OF THE APPROACHING UPPER SYSTEM. THIS FRONT SHOULD
LIE ROUGHLY ALONG THE MS RIVER VALLEY IN ROUGHLY THE 29/21Z TO
30/00Z TIME FRAME...AND THEN WILL CONTINUE MOVING RAPIDLY EWD --
EVENTUALLY CROSSING THE APPALACHIANS AND NEARING THE ATLANTIC COAST
BY THE END OF THE PERIOD.

ELSEWHERE...ANOTHER TROUGH -- INITIALLY OFF THE PAC NW/WRN CANADA
COAST WILL MOVE ACROSS THE PAC NW AND INTO THE GREAT BASIN THROUGH
THE END OF THE PERIOD.

..MID MS/TN/OH VALLEYS...
STRONG SLY FLOW IS FORECAST ACROSS THE ERN HALF OF THE CONUS AT THE
START OF THE PERIOD...WITHIN BROADENING WARM SECTOR AHEAD OF THE
APPROACHING COLD FRONT. BY AFTERNOON...50S DEWPOINTS SHOULD SPREAD
AS FAR N AS THE OH VALLEY REGION...WITH 60S DEWPOINTS REACHING
AR/SRN TN. THIS WILL SUPPORT MARGINAL WARM-SECTOR
DESTABILIZATION...WITH 250 TO 500 J/KG MIXED-LAYER CAPE FORECAST TO
SPREAD ACROSS SERN MO/AR/LA THROUGH THE AFTERNOON AND INTO WRN
KY/WRN TN/MS THROUGH EARLY EVENING.

THUNDERSTORMS MAY BE ONGOING AT THE START OF THE PERIOD ACROSS PARTS
OF THE OZARKS/MID MS VALLEY REGION...AND SHOULD INCREASE THROUGH
MIDDAY/EARLY AFTERNOON AS THE FRONT APPROACHES. WHILE LACK OF
INSTABILITY WILL ACT AS A LIMITING FACTOR...VERY STRONG LARGE-SCALE
UVV -- INDICATED BY NAM FORECASTS OF 12-HOUR H5 HEIGHT FALLS IN
EXCESS OF 27 DAM -- AND STRONG UVV INVOF THE SHARPENING FRONT WILL
SUPPORT STORM REDEVELOPMENT ACROSS IL/ERN MO/ERN AR. STORMS SHOULD
RAPIDLY EVOLVE INTO A SQUALL LINE...WHICH WILL LIKELY EXPAND BOTH
NWD AND SWD WHILE MOVING RAPIDLY EWD ACROSS THE MID MS/OH/TN
VALLEYS.

WITH VERY STRONG DEEP-LAYER WIND FIELD...EXPECT DAMAGING WINDS WITH
THIS LINE OF STORMS -- PARTICULARLY INVOF SMALL-SCALE LEWPS AND
BOWS. MARGINAL HAIL WILL ALSO BE POSSIBLE...ALONG WITH THE
POTENTIAL FOR A COUPLE OF TORNADOES.

A DECREASE IN LIGHTNING IS EXPECTED INTO THE EVENING/OVERNIGHT...AS
CONVECTIVE LINE MOVES INTO EVEN WEAKER INSTABILITY ACROSS THE UPPER
OH VALLEY/CENTRAL APPALACHIANS. HOWEVER...INTENSITY OF THE SYSTEM
ALOFT AND STRENGTH OF THE DEEP-LAYER FLOW WILL LIKELY SUPPORT A
PERSISTENT/LOW-TOPPED LINE OF RAPIDLY-MOVING SHOWERS WITH EMBEDDED
LIGHTNING AS FAR NE AS OH/PA/WV/WRN NY. LOCALLY-DAMAGING WINDS WILL
BE POSSIBLE WITH THIS LINE -- EVEN IN THE ABSENCE OF LIGHTNING.

.GOSS.. 01/29/2008

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