SWODY2
SPC AC 180547
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1247 AM CDT FRI APR 18 2008
VALID 191200Z - 201200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
UPPER TROUGH WILL CLOSE OFF AS IT EJECTS ENEWD INTO THE TN AND OH
VALLEYS SATURDAY. ATTENDANT SURFACE LOW WILL OCCLUDE WITH TRAILING
FRONT EXTENDING FROM THE LOW OVER IL SWD INTO THE ERN GULF COAST
EARLY SATURDAY. THE FRONT WILL ADVANCE EAST AND LIKELY EXTEND FROM
NRN FL...THE COASTAL CAROLINAS NWWD INTO THE MID ATLANTIC BY THE END
OF THE PERIOD.
FARTHER WEST...A LARGE UPPER TROUGH WILL CONTINUE TO AMPLIFY SWD
THROUGH THE PACIFIC NW AND INTO THE GREAT BASIN. SEVERAL IMPULSES
WILL LIKELY EJECT NEWD THROUGH THE ROCKY MOUNTAINS IN ADVANCE OF
THIS FEATURE. AS THE UPPER TROUGH AMPLIFIES...A BAROCLINIC ZONE WILL
DEVELOP SEWD AND EXTEND FROM THE NRN ROCKIES SWWD THROUGH SRN CA BY
THE END OF THE PERIOD.
...SERN STATES THROUGH OH VALLEY...
MID TO UPPER 50S BOUNDARY LAYER DEWPOINTS WILL ADVECT NEWD INTO
PRE-FRONTAL WARM SECTOR THROUGH PARTS OF GA AND THE CAROLINAS. OWING
TO THE OCCLUSION...MOISTURE FARTHER NW ACROSS THE OH VALLEY WILL BE
MORE LIMITED WITH DEWPOINTS IN THE 40S. AXIS OF MARGINAL INSTABILITY
WILL DEVELOP IN WARM SECTOR OVER THE SERN STATES AND FARTHER NW INTO
THE OH VALLEY WHERE STEEPER MID LEVEL LAPSE RATES WILL EXIST. STORMS
SHOULD REDEVELOP WITHIN ZONE OF LOW LEVEL CONVERGENCE AND ASCENT
FROM PARTS OF THE SERN U.S. NWD INTO THE OH VALLEY AS DIABATIC
HEATING COMMENCES. A FEW STORMS MIGHT BECOME CAPABLE OF PRODUCING
HAIL...PARTICULARLY IN VICINITY OF THE UPPER LOW WHERE 500 MB
TEMPERATURES AOB -20C AND STEEP MID LEVEL LAPSE RATES WILL EXIST.
ACTIVITY WILL WEAKEN WITH THE LOSS OF HEATING. THE STRONGER
MID-UPPER FLOW ATTENDING THE UPPER JET ROTATING THROUGH BASE OF
UPPER TROUGH WILL LIKELY REMAIN NW OF MOIST AXIS OVER THE SERN
STATES. HOWEVER...BULK SHEAR FROM 30-40 KT WILL CHARACTERIZE A
PORTION OF THE WARM SECTOR. AT THIS TIME IT APPEARS THE
THERMODYNAMIC ENVIRONMENT WILL REMAIN TOO MARGINAL FOR SEVERE STORMS
IN THIS REGION.
...PACIFIC NW AND NRN ROCKY MOUNTAIN REGIONS....
STEEP LAPSE RATES ASSOCIATED WITH VERY COLD AIR ALOFT (500 MB
TEMPERATURES AOB -35C) AND ASCENT WILL PROMOTE MARGINAL INSTABILITY
AND SCATTERED LOW TOPPED THUNDERSTORMS OVER WRN WA AND OREGON WITHIN
CYCLONICALLY CURVED UPPER JET ROTATING THROUGH BASE OF AMPLIFYING
UPPER TROUGH. FORECAST SOUNDINGS SUGGEST SOME OF THIS ACTIVITY COULD
PRODUCE SMALL HAIL.
FARTHER EAST...STEEP LAPSE RATES AND COOL MID LEVEL TEMPERATURES
WILL CONTRIBUTE TO MARGINAL INSTABILITY AS DIABATIC HEATING
COMMENCES OVER THE NRN ROCKY MOUNTAIN REGION. POTENTIAL WILL EXIST
FOR IMPULSES TO EJECT NEWD AHEAD OF THE UPPER TROUGH. SCATTERED
SHOWERS AND A FEW THUNDERSTORMS WILL BE POSSIBLE OVER THE HIGHER
TERRAIN DURING THE AFTERNOON AND EVENING.
..DIAL.. 04/18/2008
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