SWODY1
SPC AC 260528
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1228 AM CDT SUN SEP 26 2010
VALID 261200Z - 271200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
A SIGNIFICANT CLOSED LOW IS IN THE PROCESS OF DEVELOPING OVER THE
MIDDLE MISSISSIPPI VALLEY. MODELS ARE NOW FAIRLY SIMILAR...
INDICATING THAT THIS FEATURE WILL CONTINUE TO DIG SOUTH
SOUTHEASTWARD...DEEPEN...AND BECOME CUT OFF FROM THE STRONGER
WESTERLIES...WHICH WILL REMAIN GENERALLY NEAR OR NORTH OF THE
CANADIAN/U.S. BORDER THROUGH THE PERIOD. BY 12Z MONDAY...THE
CYCLONIC CIRCULATION CENTER APPEARS LIKELY TO REACH THE NORTH
CENTRAL GULF STATES...WITH ONE SHORT WAVE IMPULSE LIFTING NORTHWARD
NEAR AND TO THE LEE OF THE SOUTHERN AND CENTRAL APPALACHIANS...AND
ANOTHER MORE SIGNIFICANT IMPULSE PIVOTING AROUND ITS SOUTHWESTERN
PERIPHERY...ACROSS THE LOWER MISSISSIPPI VALLEY.
MEANWHILE...SUBTROPICAL RIDGING WILL PERSIST ACROSS MUCH OF THE
WESTERN STATES. AFTER TEMPORARILY FLATTENING...THE RIDGE IS
EXPECTED TO BUILD BACK NORTHWARD NEAR AND TO THE LEE OF THE CANADIAN
ROCKIES...AHEAD OF A VIGOROUS IMPULSE LIFTING TOWARD THE BRITISH
COLUMBIA COAST. AS THIS OCCURS...A DOWNSTREAM SHORT WAVE TROUGH IS
EXPECTED TO BEGIN TO DIG ACROSS THE CENTRAL CANADIAN PROVINCES AND
ADJACENT INTERNATIONAL BORDER AREA.
...SOUTHEAST...
LARGE-SCALE FORCING FOR UPWARD VERTICAL MOTION ASSOCIATED WITH THE
APPROACHING UPPER TROUGH IS EXPECTED TO SUPPORT CONSIDERABLE
CONVECTION TODAY WITHIN A SEASONABLY MOIST AIR MASS CHARACTERIZED BY
SURFACE DEW POINTS NEAR 70F AND PRECIPITABLE WATER AROUND 2
INCHES...ALONG AND SOUTHEAST OF A SURFACE FRONT ACROSS THE GULF AND
SOUTH ATLANTIC COAST STATES. STRONGER MID/UPPER WIND FIELDS APPEAR
LIKELY TO GENERALLY REMAIN ON THE COOL SIDE OF THE FRONT...HOWEVER.
AND...COUPLED WITH INCREASINGLY SATURATED THERMODYNAMIC PROFILES
WITH WEAK LAPSE RATES...THE ENVIRONMENT DOES NOT APPEAR PARTICULARLY
CONDUCIVE TO THE DEVELOPMENT OF SEVERE STORMS THROUGH MUCH OF THE
DAY.
LATE THIS AFTERNOON THROUGH TONIGHT...MODELS DO SUGGEST WEAK SURFACE
CYCLOGENESIS MAY COMMENCE ALONG THE SURFACE FRONT...FROM NEAR THE
CENTRAL GULF COAST NORTHEASTWARD TOWARD THE SOUTHERN APPALACHIANS.
AS THIS OCCURS...SOUTHERLY 850 MB FLOW ACROSS THE WARM SECTOR IS
PROGGED TO STRENGTHEN ACROSS EASTERN GEORGIA INTO THE PIEDMONT OF
THE CAROLINAS...PERHAPS UP TO 40+ KT BY LATE THIS
EVENING...CONTRIBUTING TO SIZABLE CLOCKWISE CURVED LOW-LEVEL
HODOGRAPHS IN THE PRESENCE OF A MOIST BOUNDARY LAYER. WHILE THIS
MAY GENERALLY COINCIDE WITH FURTHER STABILIZING TRENDS WITH THE LOSS
OF DAYTIME HEATING...IT IS NOT CLEAR THAT THE RISK FOR SEVERE
STORMS...CAPABLE OF PRODUCING TORNADOES/DAMAGING WIND GUSTS...IS
COMPLETELY NEGLIGIBLE.
..KERR/HURLBUT.. 09/26/2010
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