MESO: Mesoscale Discussion 1956

ACUS11 KWNS 180744
SWOMCD
SPC MCD 180744
GAZ000-FLZ000-ALZ000-180945-

MESOSCALE DISCUSSION 1956
NWS STORM PREDICTION CENTER NORMAN OK
0244 AM CDT TUE SEP 18 2012

AREAS AFFECTED...FL PANHANDLE/SOUTHEAST AL/SOUTHWEST GA

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 180744Z - 180945Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...SCATTERED TSTMS WILL CONTINUE TO INCREASE THROUGH THE
EARLY MORNING HOURS...INCLUDING THE POSSIBILITY OF SOME LOW-TOPPED
SUPERCELLS ACROSS THE FL PANHANDLE/SOUTHEAST AL/SOUTHWEST GA.
ISOLATED WIND DAMAGE AND/OR A BRIEF TORNADO MAY BE POSSIBLE. A WATCH
IS NOT CURRENTLY EXPECTED GIVEN THE PERCEIVED LIMITED/ISOLATED
NATURE OF THE THREAT...BUT CONVECTIVE TRENDS WILL CONTINUE TO BE
MONITORED THROUGH THE EARLY MORNING HOURS.

DISCUSSION...SATELLITE/VOLUMETRIC RADAR/LIGHTNING DATA REFLECT A BIT
OF AN INCREASE IN SCATTERED RELATIVELY LOW-TOPPED TSTMS ACROSS THE
FL PANHANDLE AND FAR SOUTHEAST AL SINCE 06Z. A SURFACE LOW IS
LOCATED ACROSS SOUTHWEST/CENTRAL AL AS OF 07Z...WITH AN
EASTWARD-MOVING COLD FRONT EXTENDING SOUTHWARD INTO THE GULF OF
MEXICO. AHEAD OF THE COLD FRONT AND EAST-SOUTHEAST OF THE SURFACE
LOW...SURFACE TEMPERATURES HAVE ACTUALLY WARMED OVER THE PAST FEW
HOURS /1-4 DEG F OVER 2 HR/ ACROSS THE FL PANHANDLE/SOUTHEAST AL AS
A STEADY LOW-LEVEL MOIST INFLUX OTHERWISE CONTINUES FROM THE GULF
/GENERAL 1-2 DEG F RISE OF SFC DEWPOINTS BUT EVEN HIGHER NEAR
PAM-AAF AREAS/.

LARGELY IN RESPONSE TO THE AMPLIFICATION/INCREASINGLY NEUTRAL TILT
OF THE UPPER SYSTEM CENTERED ACROSS SOUTHERN MS/EASTERN LA
OVERNIGHT...LOW/MID LEVEL SOUTHWESTERLY WINDS CONTINUE TO STRENGTHEN
ACROSS THE REGION PER WSR-88D VWP DATA. WHILE SOME VEERING WILL
CONTINUE TO OCCUR JUST ABOVE THE SURFACE AHEAD OF THE COLD
FRONT...INCREASING SPEEDS/MODEST TURNING WILL ACCOUNT FOR A MODERATE
LOW-LEVEL SRH ENVIRONMENT. THE WSR-88D VWP FROM ELGIN AFB IS
SUGGESTIVE OF AS MUCH AS 150 M2/S2 OF 0-1 SRH. GIVEN THIS...AND A
SUFFICIENTLY WARM/INCREASING MOIST BOUNDARY LAYER...STORMS MAY
ACQUIRE LOW-LEVEL ROTATION/BECOME LOW-TOPPED SUPERCELLS THROUGH THE
EARLY MORNING HOURS...WITH SOME POTENTIAL FOR A TORNADO AND/OR WIND
DAMAGE. WHILE A WATCH IS NOT CURRENTLY ANTICIPATED...CONVECTIVE
TRENDS WILL CONTINUE TO BE MONITORED/REEVALUATED THROUGH THE EARLY
MORNING HOURS.

..GUYER/HART.. 09/18/2012

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...FFC...TAE...BMX...MOB...

LAT...LON 30258701 31298690 32348607 32298442 31498412 30488450
29988551 30258701

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