Wednesday, April 01, 2009

A few severe weather forecast excerpts....

From 9 p.m. NWS Birmingham AFD:
THE SCENARIO THAT WE THINK WILL HAPPEN IS THAT CONVECTION WILL
BEGIN TO GET GOING AHEAD OF THE FRONT AFFECTING AT LEAST AREAS WEST
OF INTERSTATE 65 AS EARLY AS 3 PM. THE THREAT WOULD EXTEND INTO
THE LATE EVENING HOURS AS THE FRONT PUSHES THE LINE TO THE EAST.
THE THREAT WILL COME IN THE FORM OF A SQUALL LINE. THIS LINE COULD
PRODUCE STRONG STRAIGHT LINE WINDS...LARGE HAIL AND POSSIBLY
ISOLATED TORNADOES. IN ADDITION TO THIS LINE...ISOLATED SUPERCELLS
COULD DEVELOP AHEAD OF THIS LINE. THESE STORMS COULD POSE THE
GREATEST THREAT OF TORNADIC ACTIVITY. THE LINE OF STORMS COULD
HANG AROUND THE EXTREME EASTER PORTION OF THE AREA EVEN A FEW HOURS
AFTER MIDNIGHT. UPDATES HAVE BEEN SENT.
From 9 p.m. NWS Birmingham HWO:
SEVERE THUNDERSTORMS ARE LIKELY ON THURSDAY BEGINNING IN THE
AFTERNOON AND LASTING THROUGH THE EVENING HOURS. THE THREATS ARE
DAMAGING WINDS...LARGE HAIL AND ISOLATED TORNADOES. FOR AREAS
WEST OF I-65...THE SEVERE THREAT WILL BE HIGHEST BETWEEN 3 PM AND 9
PM CDT. FOR AREAS EAST OF I-65...THE SEVERE THREAT WILL BE HIGHEST
FROM 6 PM UNTIL MIDNIGHT.
From 6:45 p.m. NWS Huntsville AFD:
DURING THE AFTN... STORM SYSTEM BECOMES BETTER ORGANIZED OVER ARK/MO...AS
A COLD FRONT PUSHES TOWARD THE MS RIVER. BY EARLY AFTERNOON...
SUFFICIENT LOW LVL SHEAR AND INSTABILITY WILL SUPPORT SUPERCELLS
ALONG/JUST AHEAD OF THE COLD FRONT WHICH IS EXPECTED TO ENTER NW
AL BTWN 21Z-00Z... AND EXIT THE AREA BY 06Z/FRI. BEST UPR LVL
DYNAMICS AND LOW LVL MESOSCALE FEATURES COME TOGETHER BETWEEN 21Z-
03Z ACROSS THE AREA. MODELS CONTINUE TO SHOW 0-1KM HELICITY OF
300-400 M2/S2 ACROSS THE AREA AHEAD OF THE FRONT...WITH 500-1000
J/KG MLCAPE. STEEP LOW/MID LVL LAPSE RATES WILL SUPPORT ROTATING
SUPERCELLS CAPABLE OF PRODUCING LARGE HAIL...DAMAGING WINDS AND
ISOLD TORNADOES. THESE THREATS ARE HIGHLIGHTED IN BOTH SPC/S DAY 2
OUTLOOK AND A SPECIAL WEATHER STATEMENT PRODUCT /HUNSPSHUN/. IN
ADDITION TO THE SEVERE THREAT...WINDY CONDITIONS WILL DEVELOP
THURSDAY. NON-CONVECTIVE WIND GUSTS COULD EXCEED 40
MPH...ESPECIALLY ACROSS THE HIGHER TERRAIN.

From 4:08 p.m. NWS Huntsville HWO:
A STRONG STORM SYSTEM WILL AFFECT THE AREA THURSDAY.
THUNDERSTORMS ARE EXPECTED TO DEVELOP IN THE MORNING AND BECOME
MORE NUMEROUS DURING THE AFTERNOON AND EVENING. CONDITIONS ARE
LOOKING FAVORABLE FOR SEVERE THUNDERSTORMS...WITH TORNADOES...
DAMAGING WINDS...AND LARGE HAIL ACROSS THE AREA. AT THIS TIME...IT
APPEARS THE MOST ACTIVE PERIOD FOR SEVERE WEATHER WILL BE BETWEEN 4
PM AND 10 PM ACROSS THE CENTRAL TENNESSEE VALLEY.


From 10:00 p.m. NWS Jackson, MS AFD:

AS AN INTENSE MID LEVEL JET MAX MOVES ABOVE THE SURGING WARM
SECTOR...THE COMBINATION OF STRONG PRESSURE FALLS...VERY STRONG
SHEAR (0-6KM 60-70KTS, 0-1KM 20-30KTS) AND INSTABILITY (MLCAPE >1500
J/KG, 700-500MB LAPSE RATES ~8 C/KM) WILL SET UP A FAVORABLE
ENVIRONMENT FOR SCATTERED TO NUMEROUS SEVERE THUNDERSTORMS...WITH
SUPERCELLS LIKELY AND ALL SEVERE WEATHER MODES POSSIBLE. THE
GREATEST RISK FOR ANY STRONG/LONG-TRACK TORNADOES APPEARS TO BE
SHAPING UP FOR AREAS SOUTHEAST OF THE NATCHEZ TRACE PARKWAY OVER
SC/EC MS. THIS IS THE MOST FAVORABLE AREA IN RELATION TO THE UPPER
LOW AND WHERE THE GREATEST INSOLATION SHOULD EXIST GIVEN BETTER
PRESENCE OF A CAPPING INVERSION...AND TIMING OF THE FRONTAL PASSAGE
LATER IN THE DAY. IN ADDITION...THE RICHEST GULF MOISTURE MAY BE
CONFINED TO THIS AREA AS WELL. MEANWHILE...THE GREATEST COVERAGE OF
SEVERE WEATHER SHOULD END UP BEING OVER NRN PORTIONS OF THE
ARKLAMISS GIVEN BETTER FORCING AND LESS CAPPING. A QLCS MAY DEVELOP
AND SHIFT QUICKLY EWD ACROSS NORTH CENTRAL MS DURING THE AFTN WITH
THE POTENTIAL TO PRODUCE VERY INTENSE STRAIGHT-LINE WINDS AND LARGE
HAIL/TORNADOES.

From 3:05 p.m. NWS Jackson, MS HWO:

A SEVERE WEATHER OUTBREAK WILL BE POSSIBLE DURING THE MIDDAY HOURS
ON THURSDAY AS A POWERFUL UPPER LOW MOVES ACROSS THE MID SOUTH AND
CLASHES WITH AN UNSTABLE AIRMASS. VERY STRONG WINDS ALOFT WILL SPREAD
ACROSS THE WARM SECTOR...AND DEVELOP SCATTERED SUPERCELL THUNDERSTORMS
ALONG WITH CLUSTERS OF STORMS ALONG A COLD FRONT. LARGE HAIL...BETWEEN
QUARTER AND GOLF BALL SIZE...DAMAGING WINDS GREATER THAN 65 MPH...AND
TORNADOES WILL ALL BE POSSIBLE. THE MAIN TIME FRAME FOR THIS ACTIVITY
WILL BE FROM 10 AM TO 2 PM.

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