SWODY1
SPC AC 110557
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1257 AM CDT WED APR 11 2007
VALID 111200Z - 121200Z
..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE
SOUTHEAST...
..THERE IS A SLGT RISK OF SVR TSTMS OVER THE LOWER AND MIDDLE OH
VALLEY REGION...
..SYNOPSIS...
WHILE AN UPPER TROUGH IS FORECAST TO MOVE INLAND/EXPAND SEWD ACROSS
THE WRN U.S. THIS PERIOD...THE MAIN FEATURE ALOFT WITH RESPECT TO
THE SEVERE CONVECTIVE FORECAST WILL BE A DEVELOPING LOW MOVING INTO
THE MIDWEST REGION.
AS THIS FEATURE AND ASSOCIATED 100 KT MID-LEVEL JET STREAK SHIFT
EWD...A COLD FRONT -- ASSOCIATED WITH A SURFACE LOW MOVING FROM MO
INTO LOWER MI THROUGH THE PERIOD -- WILL SHIFT RAPIDLY EWD ACROSS
THE OH/TN VALLEYS AND SERN U.S. THROUGH THE PERIOD. WIDESPREAD
CONVECTION -- AND AT LEAST SOME SEVERE POTENTIAL -- WILL ACCOMPANY
THIS STORM SYSTEM THROUGH THE PERIOD.
..THE SOUTHEAST...
A LINEAR BAND OF SHOWERS AND THUNDERSTORMS SHOULD BE ONGOING AT THE
START OF THE PERIOD ALONG AND AHEAD OF COLD FRONT FROM WRN KY/WRN TN
SWWD ACROSS NRN MS INTO SERN AR/NRN LA. WHILE MARGINAL
BOUNDARY-LAYER MOISTURE AND WIDESPREAD PRECIPITATION SHOULD LIMIT
DESTABILIZATION ACROSS THE TN VALLEY...GREATER DESTABILIZATION
SHOULD OCCUR WITH SWD EXTENT TOWARD THE GULF COAST...AS LIMITED
HEATING AND GREATER LOW-LEVEL MOISTURE YIELDS MEAN-LAYER CAPE IN THE
500 TO 1000 J/KG RANGE. HOWEVER...WHILE GREATER INSTABILITY WILL
EXIST NEARER THE GULF COAST...STRONGER LARGE-SCALE UVV -- AND MORE
VIGOROUS CONVECTION -- SHOULD REMAIN FURTHER N AS CYCLONIC MID-LEVEL
JET AXIS SHIFTS ACROSS NRN MS/NRN AL THROUGH THE AFTERNOON.
STORMS SHOULD INTENSIFY THROUGH EARLY AFTERNOON AS STORMS SPREAD
INTO/ACROSS AL...AND REMAIN VIGOROUS INTO GA THROUGH LATE AFTERNOON.
NEWD EXTENT OF SEVERE THREAT SHOULD REMAIN LIMITED...AS NELY
LOW-LEVEL FLOW ASSOCIATED WITH COLD AIR DAMMING E OF THE
APPALACHIANS SHOULD RESULT IN A PERSISTENTLY-STABLE BOUNDARY LAYER.
ATTM...STORM MODE REMAINS A QUESTION -- BUT LIKELY WILL BE SOME
COMBINATION OF LINEAR AND SUPERCELLULAR. DAMAGING WINDS WILL BE
POSSIBLE WITH THESE STORMS...ALONG WITH HAIL AND THE POTENTIAL FOR A
COUPLE OF TORNADOES. ATTM...WILL INTRODUCE A SLIGHT RISK ACROSS
PARTS OF AL AND VICINITY...WITH SOME UPGRADE IN PROBABILITIES
POSSIBLE IN LATER FORECASTS AS EVOLUTION BECOMES CLEARER.
..OH VALLEY REGION...
WIDESPREAD SHOWERS AND THUNDERSTORMS ARE FORECAST TO MOVE ACROSS THE
TN/OH VALLEYS THROUGH EARLY AFTERNOON...WHICH SHOULD LIMIT
INSTABILITY AND OVERALL SEVERE POTENTIAL INITIALLY. IT APPEARS ATTM
THAT MAIN SEVERE THREAT OVER THIS REGION WILL BE ASSOCIATED WITH A
DRY SLOT WHICH SHOULD SPREAD ACROSS PARTS OF IN/KY/OH DURING THE
AFTERNOON -- AHEAD OF THE UPPER LOW/INVOF SURFACE FRONTAL OCCLUSION.
THOUGH BOUNDARY-LAYER MOISTURE SHOULD REMAIN LIMITED /LIKELY AROUND
50 F/...HEATING WITHIN THE DRY SLOT COMBINED WITH COLD AIR ALOFT
/-24 TO -26 C AT H5/ SPREADING ACROSS THE OH VALLEY SHOULD YIELD
SUFFICIENT INSTABILITY FOR THE DEVELOPMENT OF VIGOROUS LOW-TOPPED
STORMS. ATTM...IT APPEARS THAT SEVERAL ADDITIONAL BANDS OF STORMS
SHOULD MOVE ACROSS THIS REGION. WITH SOMEWHAT VEERED BOUNDARY-LAYER
FLOW ANTICIPATED...STRONG BUT SOMEWHAT UNIDIRECTIONAL DEEP-LAYER
FLOW WILL SUPPORT DAMAGING WINDS...WHILE COLD AIR ALOFT SUGGESTS A
HAIL POTENTIAL. IN ADDITION...A COUPLE OF TORNADOES WILL BE
POSSIBLE -- PARTICULARLY NEAR AND JUST N OF THE OCCLUDED FRONT WHERE
BOUNDARY-LAYER FLOW SHOULD REMAIN MORE SELY.
DEPENDING UPON ACTUAL EVOLUTION OF THIS SCENARIO AND ASSOCIATED
DEGREE OF DESTABILIZATION...FAIRLY WIDESPREAD WIND DAMAGE COULD
OCCUR IF STORMS CAN EVOLVE INTO ONE OR MORE FAST-MOVING LINES.
ATTM...HOWEVER...WILL TAKE A LESS AGGRESSIVE APPROACH AS IT WOULD
SEEM THAT WIDESPREAD CONVECTION SHOULD LIMIT OVERALL DEGREE OF
INSTABILITY -- AND THUS INTENSITY OF CONVECTIVE REDEVELOPMENT WITHIN
THE DRY SLOT. POSSIBLE INCREASE IN SEVERE PROBABILITIES MAY BE
REQUIRED ACROSS THIS AREA IN LATER FORECASTS.
.GOSS/CROSBIE.. 04/11/2007
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
To unsubscribe from WX-STORM send e-mail to LISTSERV@PO.UIUC.EDU with
"unsub wx-storm" in the body of your message. For more information write chris@lib.siu.edu.
No comments:
Post a Comment