DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 170534
SWODY1
SPC AC 170531

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1231 AM CDT SUN AUG 17 2008

VALID 171200Z - 181200Z

...NO SVR TSTM AREAS FORECAST...

...SRN HIGH PLAINS/SRN AND CNTRL ROCKIES...
A SLOW MOVING UPPER-LEVEL LOW OVER THE CNTRL ROCKIES WILL ACCELERATE
SEWD TODAY. SCATTERED THUNDERSTORMS WILL LIKELY BE ONGOING AHEAD OF
THE UPPER-LEVEL LOW THIS MORNING WITH CONVECTIVE COVERAGE EXPANDING
THIS AFTERNOON AS SFC TEMPS WARM. THE WIDESPREAD NATURE OF
CONVECTION THIS MORNING MAY HAMPER DESTABILIZATION AND LIMIT THE
RESULTANT SEVERE WEATHER THREAT. HOWEVER...FORECAST SOUNDINGS ACROSS
THE REGION AT 21Z TODAY SUGGEST 30 TO 35 KT OF VERTICAL SHEAR WILL
BE PRESENT ALONG THE INSTABILITY AXIS IN ERN NM AND SE CO. THIS MAY
BE ENOUGH FOR MULTICELLS CAPABLE OF PRODUCING MARGINALLY SEVERE WIND
DAMAGE. COLD AIR ALOFT ASSOCIATED WITH THE UPPER-LEVEL TROUGH MAY
ALSO BE FAVORABLE FOR HAIL WITH THE MORE INTENSE CELLS NEAR PEAK
HEATING.

...WRN ORE/NRN CA...
AN UPPER-LEVEL RIDGE AXIS ORIENTED FROM SRN CA NWD ACROSS WRN NV
INTO ERN ORE IS FORECAST TO DRIFT EWD TODAY ALLOWING HEIGHTS TO FALL
ALONG THE COASTS OF NRN CA...ORE AND WA. AT THE SFC...DEWPOINTS IN
THE LOWER TO MID 60S F SHOULD BE IN PLACE ACROSS PARTS OF WRN ORE
AND NRN CA WHERE POCKETS OF MODERATE INSTABILITY ARE FORECAST BY
THIS AFTERNOON. AS LARGE-SCALE ASCENT INCREASES AND SFC TEMPS
WARM...ISOLATED TO SCATTERED THUNDERSTORMS SHOULD DEVELOP ALONG THE
INSTABILITY AXIS. FORECAST SOUNDINGS IN WRN ORE AT 21Z SHOW ABOUT 35
KT OF VERTICAL SHEAR WITH STEEP MID-LEVEL LAPSE RATES WHICH WOULD BE
SUPPORTIVE OF A FEW ROTATING STORMS WITH HAIL POTENTIAL. MARGINALLY
SEVERE WIND DAMAGE COULD ALSO OCCUR AS LOW-LEVEL LAPSE RATES BECOME
STEEP IN THE AFTERNOON. HOWEVER...THE EXTENT OF THE SEVERE THREAT
REMAINS QUESTIONABLE DUE TO UNCERTAINTIES CONCERNING CONVECTIVE
COVERAGE.

...GREAT LAKES...
WEST TO NORTHWEST FLOW WILL BE IN PLACE TODAY ACROSS THE GREAT LAKES
REGION AS A SUBTLE SHORTWAVE TROUGH APPROACHES THE REGION THIS
AFTERNOON. AHEAD OF THE TROUGH...MODEL FORECASTS SHOW POCKETS OF
MODERATE INSTABILITY BY THIS AFTERNOON AND DEVELOP ISOLATED TO
SCATTERED THUNDERSTORMS FROM NERN MN SEWD INTO NRN LOWER MI.
FORECAST SOUNDING ALONG THIS CORRIDOR SUGGEST ENOUGH VERTICAL SHEAR
WILL EXIST FOR MARGINALLY SEVERE MULTICELLS. UNIDIRECTIONAL WINDS
WITH ABOUT 20 KT OF FLOW AT 850 MB AND STEEP LOW-LEVEL LAPSE RATES
SHOULD BE ENOUGH FOR STRONG WIND GUSTS. A PLUME OF STEEP MID-LEVEL
LAPSE RATES IS FORECAST JUST AHEAD OF THE SHORTWAVE TROUGH AND THIS
COMBINED WITH RELATIVELY COLD TEMPS ALOFT SHOULD ALSO PROMOTE A HAIL
THREAT.

..BROYLES/LEVIT.. 08/17/2008

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