SWODY2
SPC AC 241657
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1057 AM CST THU FEB 24 2011
VALID 251200Z - 261200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
MODELS INDICATE THAT BLOCKING WILL REMAIN PROMINENT WITHIN THE UPPER
PATTERN OVER THE EASTERN PACIFIC...WITH DOWNSTREAM SPLIT FLOW
BROADLY CONFLUENT ACROSS MUCH OF NORTH AMERICA...AND RATHER STRONG
AND GENERALLY ZONAL ACROSS THE U.S. IN PARTICULAR. WITHIN THIS
REGIME A LARGE SHORT WAVE TROUGH AND EMBEDDED CLOSED LOW ARE PROGGED
TO CONTINUE DIGGING NEAR THE PACIFIC COAST FRIDAY...WHILE A
SIGNIFICANT DOWNSTREAM PERTURBATION RAPIDLY ACCELERATES EAST OF THE
OHIO VALLEY INTO THE WESTERN ATLANTIC.
...APPALACHIANS INTO ATLANTIC SEABOARD...
SUBSTANTIAL FURTHER DEEPENING OF THE CYCLONE ASSOCIATED WITH THE
LATTER FEATURE APPEARS PROBABLE AS IT MIGRATES NORTHEAST OF THE
UPPER OHIO VALLEY INTO AREAS OFF THE NORTH ATLANTIC COAST...AND
EVENTUALLY THE CANADIAN MARITIMES. THIS WILL BE ACCOMPANIED BY
FURTHER INTENSIFICATION OF LOW- AND MID-LEVEL WIND FIELDS THROUGH A
BROAD WARM SECTOR OVERSPREADING MUCH OF THE ATLANTIC SEABOARD...WITH
GUIDANCE SUGGESTING STRENGTHENING OF A SOUTHERLY 850 MB JET FROM 70
TO 90 KTS FROM THE LEE OF THE SOUTHERN AND CENTRAL APPALACHIANS INTO
AREAS EAST OF THE MID AND NORTHERN ATLANTIC COAST BY LATE FRIDAY
AFTERNOON.
STRONGEST DIVERGENCE ALOFT ASSOCIATED WITH A COUPLED MID/UPPER JET
STRUCTURE IS PROGGED TO RAPIDLY SHIFT NORTHEAST OF THE CENTRAL
APPALACHIANS/UPPER OHIO VALLEY AND LOWER GREAT LAKES REGION...ALONG
AND NORTH OF THE SURFACE WARM FRONT...EARLY IN THE DAY. AS THIS
OCCURS...A WEAKENING PRE-COLD FRONTAL CONVECTIVE BAND NEAR THE
APPALACHIANS AT THE OUTSET OF THE FORECAST PERIOD PROBABLY WILL
WEAKEN FURTHER AS IT ADVANCES TOWARD THE ATLANTIC COAST. THIS BAND
APPEARS LIKELY TO PROGRESS ACROSS MID ATLANTIC COASTAL AREAS FIRST
AROUND MIDDAY...THEN LATER IN THE AFTERNOON ACROSS SOUTHERN ATLANTIC
AND NORTHEASTERN GULF COASTAL AREAS.
CLEARING IN THE WAKE OF THIS INITIAL BAND MAY ALLOW A WINDOW OF
OPPORTUNITY FOR PRE-FRONTAL SURFACE HEATING AND RENEWED CONVECTIVE
DEVELOPMENT DURING THE AFTERNOON FROM THE LEE OF THE CENTRAL
APPALACHIANS INTO THE NORTHERN MID ATLANTIC COAST...AIDED BY A
SECONDARY ZONE OF FORCING ASSOCIATED WITH THE PASSAGE OF THE
MID-LEVEL TROUGH AXIS. HOWEVER...SOMEWHAT MODEST BOUNDARY LAYER
MOISTENING AND WEAK LAPSE RATES WITHIN/ABOVE THE WARM SECTOR MAY BE
PROBLEMATIC WITH RESPECT TO DESTABILIZATION. IT IS NOT EVEN CLEAR
THAT THERMODYNAMIC PROFILES WILL BECOME SUPPORTIVE OF CONVECTION
CAPABLE OF PRODUCING LIGHTNING...AND THUNDERSTORM PROBABILITIES
ALONG AND EAST OF THE APPALACHIANS IN GENERAL MAY NOT BE MUCH ABOVE
THE MINIMUM 10 PERCENT THRESHOLD FOR A THUNDER OUTLOOK.
REGARDLESS...GIVEN THE LARGE MAGNITUDE OF THE LOW-LEVEL AND DEEP
LAYER MEAN FLOW FIELDS...ANY WARM SECTOR CONVECTIVE DEVELOPMENT MAY
BE CAPABLE OF CONTRIBUTING TO THE DOWNWARD TRANSFER OF HIGHER
MOMENTUM AIR TO THE SURFACE. CONVECTIVE ENHANCEMENT OF SURFACE
GUSTS TO SIGNIFICANTLY DAMAGING SPEEDS SEEMS LIKELY TO REMAIN RATHER
SPARSE IN COVERAGE...SO SEVERE PROBABILITIES BELOW SLIGHT RISK
LEVELS HAVE BEEN MAINTAINED. BUT...THE THREAT AREA HAS BEEN
EXPANDED TO ENCOMPASS MUCH OF THE ATLANTIC SEABOARD.
..KERR.. 02/24/2011
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
To unsubscribe from WX-STORM send e-mail to LISTSERV@LISTSERV.ILLINOIS.EDU with
"unsub wx-storm" in the body of your message. For more information write cnovy@cox.net.
No comments:
Post a Comment