SWODY2
SPC AC 300541
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1241 AM CDT SUN SEP 30 2007
VALID 011200Z - 021200Z
..NO SVR TSTM AREAS FORECAST...
..SYNOPSIS...
MODELS INDICATE THAT AN AMPLIFYING UPPER TROUGH...NOW DIGGING TOWARD
SOUTHERN BRITISH COLUMBIA/NORTHERN PACIFIC COASTAL AREAS... WILL
REMAIN PROGRESSIVE...AS A STRONG ZONAL UPSTREAM JET STREAK MIGRATES
ACROSS THE NORTHERN PACIFIC. THE EXIT REGION OF THIS JET IS PROGGED
TO NOSE INTO THE PACIFIC NORTHWEST COAST STATES MONDAY/MONDAY
NIGHT...SUPPORTING THE EASTWARD ACCELERATION OF THE DOWNSTREAM
TROUGH OUT OF THE GREAT BASIN...ACROSS THE NORTHERN/ CENTRAL
ROCKIES...INTO THE HIGH PLAINS. THIS IS FORECAST TO BE ACCOMPANIED
BY SIGNIFICANT SURFACE CYCLOGENESIS TO THE LEE OF THE ROCKIES.
WHILE THE PRIMARY CYCLONE DURING THIS PERIOD MAY FORM ACROSS
SASKATCHEWAN/MANITOBA...MODELS HAVE BEEN CONSISTENT IN FORECASTING
SECONDARY WAVE DEVELOPMENT ALONG A TRAILING COLD FRONT...ACROSS THE
NORTH CENTRAL PLAINS LATE MONDAY NIGHT/EARLY TUESDAY.
FARTHER EAST...A WEAKENING MID/UPPER CLOSED LOW...IN A DISTINCT
SOUTHERN BRANCH OF THE POLAR WESTERLIES...IS FORECAST TO CONTINUE A
BIT MORE SLOWLY EASTWARD ACROSS THE GREAT LAKES REGION...TO THE
SOUTH OF A NORTHERN BRANCH RIDGE. MEANWHILE...A COOL/DRY SURFACE
RIDGE WILL BE SLOW TO LOSE INFLUENCE ACROSS MUCH OF THE EASTERN
STATES. BUT...A DEVELOPING LOW...TO THE SOUTHEAST OF A MID-LEVEL
SUBTROPICAL RIDGE ACROSS THE SOUTHEAST...MAY BEGIN TO IMPACT THE
FLORIDA PENINSULA.
..EASTERN GREAT BASIN INTO CENTRAL ROCKIES...
MOISTURE RETURN FROM THE LOWER LATITUDE EASTERN PACIFIC WILL BE WELL
UNDERWAY BY EARLY MONDAY AHEAD OF THE APPROACHING SHORT WAVE TROUGH.
THIS MAY BE MOST RAPID AT MID/HIGH-LEVELS...ACCOMPANIED BY
CONSIDERABLE CLOUDINESS...BEFORE LOWER LEVELS EVENTUALLY MOISTEN.
AND...POTENTIAL FOR SUFFICIENT DESTABILIZATION TO SUPPORT VIGOROUS
CONVECTIVE DEVELOPMENT IS IN DOUBT. HOWEVER...LARGE-SCALE FORCING
FOR UPWARD VERTICAL MOTION AND STRENGTHENING SHEAR PROFILES NEAR A
50+ KT SOUTHWESTERLY 500 MB JET STREAK WILL BE FAVORABLE FOR
STRONG/SEVERE STORMS ACROSS EASTERN UTAH INTO WESTERN COLORADO..IF
POCKETS OF WEAK TO MODERATE INSTABILITY CAN FORM.
..PLAINS...
WITH THE MID-LEVELS WARMING ACROSS MUCH OF THE CENTRAL STATES BY
EARLY MONDAY...AND LOW-LEVEL MOISTURE ONLY BEGINNING TO RETURN
NORTHWARD FROM THE SOUTHERN PLAINS...POTENTIAL FOR SIGNIFICANT
DESTABILIZATION AND THE DEVELOPMENT OF STRONG/SEVERE STORMS DURING
THIS PERIOD SEEMS LOW. AN EXCEPTION COULD BE ALONG DEVELOPING LEE
SURFACE TROUGH ACROSS THE SOUTH CENTRAL HIGH PLAINS...WHERE MODELS
SUGGEST THAT A WEAKNESS IN CAPPING WILL EXIST...AND SHEAR PROFILES
WILL BE FAVORABLE FOR SUPERCELLS BY LATE MONDAY AFTERNOON. ANOTHER
COULD BE NEAR THE NOSE OF AN INTENSIFYING SOUTHERLY LOW-LEVEL JET
CORE...IN EXCESS OF 50 KT AT 850 MB...SOUTHEAST OF SECONDARY SURFACE
LOW...LATE MONDAY NIGHT INTO EARLY TUESDAY.
.KERR.. 09/30/2007
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