Sunday, May 27, 2007

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 272001
SWODY1
SPC AC 271959

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0259 PM CDT SUN MAY 27 2007

VALID 272000Z - 281200Z

..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE UPPER OH
VALLEY...NY AND PA...

..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF MT...

..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF WRN NEB AND FAR
NE CO...

..UPPER OH VALLEY/NY/PA...
A WELL-DEFINED UPPER-LEVEL TROUGH OVER ONTARIO AND THE GREAT LAKES
WILL MOVE EWD AND APPROACH THE REGION THIS AFTERNOON. AT THE SFC...A
COLD FRONT IS MOVING SEWD ACROSS LOWER MICHIGAN...IND AND IL WITH A
STATIONARY FRONT EXTENDING EWD ACROSS NY. SOUTH AND EAST ACROSS THE
WARM SECTOR...SFC HEATING...LOW-LEVEL CONVERGENCE AND LARGE-SCALE
ASCENT ASSOCIATED WITH THE APPROACHING TROUGH WILL PROVIDE SUPPORT
FOR THE CONTINUED DEVELOPMENT OF NUMEROUS THUNDERSTORMS THIS
AFTERNOON AND EVENING.

CONCERNING THE SHEAR ENVIRONMENT...A 65 KT MID-LEVEL JET IS ANALYZED
BY THE RUC OVER THE GREAT LAKES REGION. THIS FEATURE IS CREATING
MODERATE VERTICAL SHEAR ACROSS THE NWRN PART OF THE SLIGHT RISK
AREA. AS A RESULT...A FEW SUPERCELLS MAY DEVELOP IN NY...NW PA AND
NRN OH. CONSIDERING THE LARGE NUMBER OF STORMS...MULTICELLS WILL
ALSO BE COMMON. AS THE JET OVER THE GREAT LAKES CONTINUES
EWD...VERTICAL SHEAR PROFILES ACROSS THE SERN PART OF THE SLIGHT
RISK AREA MAY BECOME STRONGER SUGGESTING THE SUPERCELL THREAT MAY
INCREASE LATE THIS AFTERNOON. IN ADDITION...THE STRONG LOW-LEVEL
FLOW AND VEERED LOW-LEVEL WIND PROFILES SUGGEST WIND DAMAGE WILL BE
POSSIBLE WITH THE STRONGER CELLS. ALTHOUGH MID-LEVEL LAPSE RATES ARE
NOT THAT STEEP...500 MB TEMPS AROUND -12 C SHOULD BE COLD ENOUGH FOR
A MARGINAL HAIL THREAT ESPECIALLY WITH SUPERCELLS THAT DEVELOP.

..NRN ROCKIES/NRN HIGH PLAINS...
AN UPPER-LEVEL TROUGH NEAR THE WEST COAST WILL MOVE EWD INTO THE
PACIFIC NORTHWEST TODAY. AS A RESULT...LARGE-SCALE ASCENT WILL
INCREASE ACROSS THE NRN ROCKIES AND THIS COMBINED WITH SFC HEATING
SHOULD RESULT IN SCATTERED THUNDERSTORM DEVELOPMENT BY LATE
AFTERNOON. AS THE TROUGH APPROACHES FROM THE WEST...VERTICAL SHEAR
PROFILES WILL BECOME STRONG OVER WRN AND CNTRL MT DUE TO A 50 KT
MID-LEVEL JET CURRENTLY ANALYZED OVER ERN ORE BY THE RUC. ALTHOUGH
INSTABILITY IS WEAK ATTM...CLEARING IS EVIDENT ON VISIBLE SATELLITE
IMAGERY ACROSS WCNTRL MT SUGGESTING DESTABILIZATION WILL CONTINUE
THIS AFTERNOON. THIS COMBINED WITH VERY STEEP MID-LEVEL LAPSE RATES
ON FORECAST SOUNDINGS SHOULD RESULT IN A THREAT FOR LARGE HAIL WITH
THUNDERSTORMS THAT DEVELOP IN AREAS WITH MAXIMIZED INSTABILITY. DUE
TO THE RELATIVELY WEAK INSTABILITY...ANY SEVERE THREAT THAT DEVELOPS
SHOULD BE CONCENTRATED NEAR PEAK HEATING.

..CNTRL HIGH PLAINS...
LATEST WATER VAPOR IMAGERY SHOWS A WLY FLOW PATTERN IN PLACE ACROSS
THE HIGH PLAINS WITH A SUBTLE UPPER-LEVEL RIDGE OVER THE NRN HIGH
PLAINS. CURRENT RUC ANALYZES SEVERAL SMALL VORTICITY MAXIMUMS MOVING
EWD ACROSS NRN CO AND WRN NEB ATTM SUGGESTING A SUBTLE SHORTWAVE IS
PRESENT IN THE WLY FLOW. AT THE SFC...DEWPOINTS ACROSS MOST OF WRN
NEB AND FAR NERN CO ARE IN THE 50S F AND AN AXIS OF MODERATE
INSTABILITY IS LOCATED ACROSS THIS AREA. ALTHOUGH VERTICAL SHEAR
PROFILES ON REGIONAL WSR-88 VWPS APPEAR MARGINAL FOR
SUPERCELLS...THE LATEST PROFILER DATA FROM MCCOOK NEB SHOWS STRONG
VEERING WITH HEIGHT IN THE LOW TO MID-LEVELS. AS A RESULT...STORM
ORGANIZATION ACROSS THE INSTABILITY AXIS APPEARS LIKELY AND AN
ISOLATED SUPERCELL THREAT MAY DEVELOP LATE THIS AFTERNOON. STEEP
MID-LEVEL LAPSE RATES AND THE INSTABILITY SUGGEST LARGE HAIL WILL BE
THE PRIMARY THREAT WITH THE ACTIVITY.

.BROYLES.. 05/27/2007

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