DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 210104
SWODY1
SPC AC 210100

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0800 PM CDT SUN JUL 20 2008

VALID 210100Z - 211200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE CENTRAL PLAINS/CORN
BELT...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE NORTHEAST
STATES/SOUTHERN NEW ENGLAND...

...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS OF THE OHIO VALLEY TO
CENTRAL APPALACHIANS...

...CENTRAL PLAINS/CORN BELT...
LATEST SURFACE ANALYSIS FEATURES A 1009 MB SURFACE LOW ACROSS THE
NEB PANHANDLE...WITH A QUASI-STATIONARY ROUGHLY WEST-EAST FRONTAL
BOUNDARY EXTENDING FROM NORTHERN NEB AND WESTERN/SOUTHERN IA INTO
CENTRAL IL. TSTMS HAVE INCREASED SINCE LATE AFTERNOON ACROSS THE
HIGH PLAINS...AND A FURTHER UPSWING IN DEEP CONVECTIVE
COVERAGE/INTENSITY IS EXPECTED THE REMAINDER OF THE EVENING. SOME
QUASI-DISCRETE SUPERCELLS /INCLUDING THE POSSIBILITY OF TORNADO OR
TWO/ WILL REMAIN POSSIBLE WITHIN A HIGHLY SHEARED/VERY UNSTABLE
AIRMASS IN THE SHORT TERM...BUT TSTMS SHOULD GRADUALLY
EXPAND/CONGEAL AND GROW UPSCALE THROUGH MID/LATE EVENING INTO ONE OR
MORE SEVERE MCS/S. THIS APPEARS TO ALREADY BE OCCURRING ACROSS
NORTHWEST NEB AS OF 01Z. AIDED BY A SHORTWAVE TROUGH CURRENTLY OVER
THE NORTH CENTRAL HIGH PLAINS...THIS SCENARIO WILL BE FOCUSED
ALONG/NORTH OF THE WEST-EAST QUASI-STATIONARY FRONT...WHERE A
MOIST/UNSTABLE BOUNDARY LAYER...DEEP EASTERLY LOW LEVEL FLOW...AND
AN INCREASING/VEERING SOUTHERLY LOW LEVEL JET WILL SUPPORT FORWARD
MCS PROPAGATION WITH THE CONTINUED RISK FOR SEVERE HAIL AND A
STEADILY INCREASING NOCTURNAL DAMAGING WIND THREAT...ESPECIALLY
ACROSS NORTHERN/EASTERN NEB INTO WESTERN/SOUTHERN IA. 00Z OBSERVED
RAOBS FROM NORTH PLATTE/OMAHA/DAVENPORT REFLECT THE STRONG
INSTABILITY IN PLACE COINCIDENT WITH THE FRONTAL ZONE...WITH
3000-4500 J/KG MLCAPE.

...NORTHEAST STATES...
LINEAR BANDS OF STRONG/SEVERE TSTMS WILL PERSIST OVER THE NEXT FEW
HOURS FROM NJ INTO SOUTHERN NEW ENGLAND IN VICINITY OF
EAST-ADVANCING SURFACE LOW/COLD FRONT AND PREFRONTAL TROUGH. SOME
THREAT FOR DAMAGING WINDS WILL CONTINUE WITHIN THIS CORRIDOR OVER
THE NEXT FEW HOURS...WITH A DIMINISHING TREND THEREAFTER.

...OHIO VALLEY TO CENTRAL APPALACHIANS...
MCS/BOW ECHO THAT PRODUCED SEVERE WINDS IN THE CINCINNATI VICINITY
WILL CONTINUE TO RACE SOUTHEASTWARD/GRADUALLY WEAKEN OVER NEXT FEW
HOURS...ALONG WITH OTHER SMALLER LINEAR CLUSTERS ONGOING ACROSS
WV/FAR EASTERN KY. ORGANIZATION OF THESE LINEAR CLUSTERS/SMALL BOWS
WILL CONTINUE TO SUPPORT A DAMAGING WIND THREAT IN THE SHORT
TERM...BUT COOLING/DECOUPLING BOUNDARY LAYER SUGGESTS A GRADUALLY
WEAKENING TREND OVER THE NEXT FEW HOURS.

...WESTERN GREAT LAKES VICINITY...
ISOLATED TO SCATTERED TSTMS WILL PERSIST WITH SOME SEVERE HAIL/GUSTY
WIND RISK OVER THE NEXT FEW HOURS ALONG LOW LEVEL FRONTAL ZONE
ARCING FROM NORTHERN MN TO CENTRAL WI...THEN EASTWARD FROM A LAKE MI
SURFACE LOW INTO NORTHERN LOWER MI. OVERALL SEVERE THREAT SHOULD
REMAIN RELATIVELY ISOLATED/MARGINAL IN NATURE THE REMAINDER OF THE
EVENING.

..GUYER.. 07/21/2008

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