SWODY1
SPC AC 270105
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0805 PM CDT THU APR 26 2007
VALID 270100Z - 271200Z
..THERE IS A SLGT RISK OF SVR TSTMS FROM THE OH VALLEY SWD ALONG
THE WRN SLOPES OF THE APPALACHIANS TO WRN GA/NRN FL...
..MIDWEST/OH VALLEY SWD TO SRN APPALACHIANS...
VIGOROUS DEEP-LAYER CYCLONE WAS CENTERED NEAR SRN LAKE MICHIGAN THIS
EVENING WITH A BROAD BELT OF 60-70KT SWLY MID LEVEL FLOW ROTATING
THROUGH THE SERN QUADRANT OF THE LARGE SCALE TROUGH... FROM THE TN
VALLEY TO THE UPPER OH VALLEY. ISALLOBARIC FORCING AND OROGRAPHY
WEST OF THE APPALACHIANS HAVE CONTRIBUTED TO STRONG LOW LEVEL
MOISTURE FLUX FROM THE GULF OF MEXICO NWD TO THE ERN GREAT LAKES
WITH A NARROWING AXIS OF LOW TO MID 60S DEWPOINTS EXISTING BETWEEN
THE ADVANCING SYNOPTIC COLD FRONT/DRYLINE...AND THE SPINE OF THE
APPALACHIANS. LARGE SCALE ASCENT AHEAD OF THE FRONT AND ACROSS THE
NARROWING WARM SECTOR WAS BEING AIDED BY STRONGLY DIFFLUENT MID AND
UPPER LEVEL FLOW. THESE LARGE SCALE DYNAMICS... AND PRONOUNCED LOW
LEVEL AND DEEP-LAYER VERTICAL SHEAR...WERE COMPENSATING FOR
GENERALLY WANING INSTABILITY AND SUPPORTING NUMEROUS SUPERCELLS AND
A BOWING LINE SEGMENT OR TWO FROM OH SWD ACROSS ERN KY/TN. RECENT
DEVELOPMENT HAS ALSO BEEN INCREASING ALONG THE TRAILING SEGMENT OF
THE FRONT/WIND SHIFT...FROM NWRN GA INTO NERN AL.
WHILE SEVERAL STORMS REMAIN QUITE INTENSE AND MAY BE PRODUCING WIND
DAMAGE AND HAIL AT THIS TIME...MUCH OF THE SEVERE CONVECTION HAS
PROBABLY REACHED A PEAK. ENSUING AND CONTINUED WEAKENING THROUGH THE
EVENING HOURS IS EXPECTED AS FRONTAL AND LARGE SCALE FORCING DEVELOP
INTO/ACROSS AN INCREASINGLY STABLE REGIME ASSOCIATED WITH BOTH
HIGHER TERRAIN AND DRIER/RESIDUAL CONTINENTAL POLAR AIR MASS EAST OF
THE APPALACHIANS.
..NC/VA...
CHANCE FOR MORE WIDESPREAD SEVERE TSTM DEVELOPMENT APPEARS TO BE
DECREASING ALONG THE VA/NC BORDER AREA THIS EVENING. WELL DEFINED
FRONTAL ZONE REMAINS SITUATED ACROSS THE REGION AND A MESOSCALE
FINE-LINE...ON LEADING EDGE OF SOUTHEAST NC MOISTURE SURGE...HAS
RECENTLY INTERSECTED AND MERGED WITH THE FRONT NW OF RDU. ONLY A
COUPLE OF MEAGER ATTEMPTS AT UPDRAFT/SHOWER DEVELOPMENT HAVE
OCCURRED ON THE COOL SIDE OF THE FRONT...ACROSS SRN VA...AND THIS
CONVECTION WAS WELL REMOVED FROM STEEPER LOW LEVEL LAPSE RATE
ENVIRONMENT ACROSS THE WARM SECTOR IN NC.
LARGE SCALE ASCENT WILL INCREASE STEADILY EAST OF THE APPALACHIANS
THROUGH TONIGHT AS MODEST MID LEVEL HEIGHT FALLS SPREAD NEWD. LATEST
GUIDANCE SUGGESTS THAT ANY CONVECTIVE DEVELOPMENT OCCURRING AS A
RESULT OF THIS WILL LIKELY OCCUR ON THE COOL SIDE OF THE FRONTAL
ZONE IN A REGION OF SOMEWHAT MARGINAL LAPSE RATES. WHILE ISOLATED
HAIL/WIND EVENT CANNOT BE COMPLETELY RULED OUT...PROBABILITY APPEARS
TOO LOW TO MAINTAIN A SLGT RISK OVER THE AREA.
..HIGH PLAINS...
SHORT WAVE TROUGH NOW DIGGING TO THE LEE OF THE NORTH CENTRAL
ROCKIES IS CONTRIBUTING TO CONVECTIVE DEVELOPMENT ACROSS NERN CO.
SOME OF THIS ACTIVITY MAY SPREAD INTO NWRN KS SHORTLY. DESPITE
SPARSE MOISTURE...VERY STEEP LAPSE RATES AND DPVA AHEAD OF THE UPPER
IMPULSE WILL CONTINUE TO SUPPORT ISOLATED TSTMS FROM THE
MOUNTAINS/FRONT RANGE EWD INTO THE HIGH PLAINS FOR A FEW MORE HOURS.
ISOLATED DAMAGING DOWNBURSTS AND SOME HAIL APPEAR POSSIBLE FROM ONE
OR TWO OF THESE CELLS OVER THE NEXT 1-2 HOURS.
.CARBIN.. 04/27/2007
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