SWODY2
SPC AC 171725
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1125 AM CST FRI FEB 17 2012
VALID 181200Z - 191200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE TX COAST...LOWER MS
VALLEY AND CNTRL TO ERN GULF COAST STATES...
...LOWER MS VALLEY/CNTRL AND ERN GULF STATES...
AN UPPER-LEVEL TROUGH IS FORECAST TO MOVE ACROSS SRN AND ERN TX ON
SATURDAY AS A SHARPLY DEFINED COLD FRONT ADVANCES INTO THE LOWER MS
VALLEY. NUMEROUS THUNDERSTORMS WILL LIKELY BE ONGOING ALONG AND
AHEAD OF THE COLD FRONT ON THE TX COAST AT THE BEGINNING OF THE
PERIOD. A LARGE MASS OF CONVECTION OR A LINEAR MCS SHOULD BE IN
PROGRESS AT 12Z MOVING EWD INTO THE LOWER MS VALLEY BY EARLY
SATURDAY AFTERNOON AND INTO THE CNTRL GULF COAST STATES SATURDAY
EVENING. A SEVERE THREAT WILL LIKELY EXIST AS THE MCS MOVES ENEWD
ACROSS THE SLIGHT RISK AREA SATURDAY AND SATURDAY NIGHT.
AS THE UPPER-LEVEL SYSTEM MOVES ACROSS SOUTH TX SATURDAY...A
WELL-DEVELOPED 65 TO 80 KT MID-LEVEL JET WILL MOVE OUT OF THE SRN
PLAINS AND OVERSPREAD THE LOWER MS VALLEY. THIS JET PATTERN SHOULD
SUPPORT THE DEVELOPMENT OF A SQUALL-LINE JUST TO THE RIGHT OF THE
MID-LEVEL JET MAX. FORECAST SOUNDINGS AT 21Z SATURDAY IN THE
VICINITY OF THE SQUALL-LINE IN SE LA SHOW AN IMPRESSIVE SHEAR
ENVIRONMENT WITH 0-6 KM SHEAR IN THE 50 TO 65 KT RANGE AND 0-3 KM
STORM RELATIVE HELICITY OF 300 TO 400 M2/S2. THIS SHOULD BE
FAVORABLE FOR ROTATING STORMS EMBEDDED IN THE SQUALL-LINE OR WITH
DISCRETE STORMS THAT DEVELOP OUT AHEAD OF THE LINE WITH A THREAT FOR
TORNADOES. THE GREATEST THREAT FOR TORNADOES SHOULD EXIST TOMORROW
AFTERNOON NEAR NEW ORLEANS AND IN THE MS DELTA WHERE MODEL FORECASTS
SHOW MODERATE INSTABILITY AND STRONG LOW-LEVEL SHEAR JUST TO THE
WEST OF THE LOW-LEVEL JET MAX. THIS SETUP MAY BE ENOUGH FOR AN
ISOLATED STRONG TORNADO OR TWO. THE TORNADO THREAT SHOULD CONTINUE
INTO THE EVENING ACROSS THE CNTRL GULF COAST AS A 50 TO 65 KT
LOW-LEVEL JET MOVES ENEWD ACROSS THE SLIGHT RISK AREA. THE
SQUALL-LINE WILL ALSO LIKELY HAVE A PERSISTENT WIND DAMAGE THREAT
FROM SRN LA LATE SATURDAY MORNING EXTENDING ENEWD TO CNTRL GA DURING
THE OVERNIGHT PERIOD.
THE MODELS ARE IN GOOD AGREEMENT CONCERNING THE SPEED OF THE SYSTEM
SO CONFIDENCE IS FAIRLY HIGH THAT A NARROW CORRIDOR FOR NUMEROUS
SEVERE WEATHER EVENTS WILL EXIST ACROSS THE LOWER MS VALLEY. THE
MAIN UNCERTAINTY CONCERNS INSTABILITY. IF MORE INSTABILITY IS
REALIZED AHEAD OF THE SQUALL-LINE THAN IS CURRENTLY FORECAST...THEN
A MORE SUBSTANTIAL THREAT FOR WIND DAMAGE WILL BE POSSIBLE. THIS
POSSIBILITY JUSTIFIES A 30 PERCENT SEVERE PROBABILITY ALONG THE
PROJECTED TRACK OF THE LINEAR MCS.
..BROYLES.. 02/17/2012
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
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