[MCD] SWOMCD

Sat Feb 18 11:22:19 UTC 2006

ACUS11 KWNS 181121
SWOMCD
SPC MCD 181121 
TNZ000-GAZ000-KYZ000-ALZ000-MSZ000-MOZ000-ARZ000-181715-

MESOSCALE DISCUSSION 0158
NWS STORM PREDICTION CENTER NORMAN OK
0521 AM CST SAT FEB 18 2006

AREAS AFFECTED...PORTIONS CENTRAL/ERN AR...NRN MS...NRN AL...TN...MO
BOOT-HEEL...EXTREME NERN GA...EXTREME SRN KY.

CONCERNING...WINTER MIXED PRECIPITATION 

VALID 181121Z - 181715Z

MIX OF WINTER PRECIP WILL CONTINUE OVER PORTIONS AR...SERN MO...SRN
KY AND TN...WHILE SHIFTING/EXPANDING SWD INTO AREAS OF MS/AL/NWRN GA
WHERE SFC TEMPS STILL WERE ABOVE FREEZING AS OF 1030Z. FREEZING
RAIN WITH .05-.10 INCH/HR RATES SHOULD DEVELOP FROM N-CENTRAL MS EWD
ACROSS NRN AL...EXTREME NWRN GA AND PORTIONS SERN TN AS FREEZING
LINE SHIFTS SWD THROUGH THIS AREA...IN RESPONSE TO COMBINATION OF
BOUNDARY LAYER CAA AND WET BULB COOLING FROM PRECIP EVAPORATION NEAR
SFC.  

PRECIP PHASE WILL GRADATE TO FREEZING RAIN/SLEET MIX THEN TO SNOW
WITH NWD EXTENT...WHILE LOW LEVEL COOLING DEEPENS AND SHIFTS SWD. 
THIS WILL LEAD TO ONGOING PLUME OF FREEZING RAIN AND SLEET FROM
W-CENTRAL AR TO MID TN CHANGING TO SNOW WITH TIME.  SNOW
ACCUMULATIONS 1.5 INCH/HOUR SHOULD OCCUR IN MANY
AREAS...LOCALLY/BRIEFLY EXCEEDING 2 INCH/HOUR IN HEAVIER BURSTS. 
MORE SPOTTY/LIGHT/INTERMITTENT PRECIP MIX IS EXPECTED WSWWD FROM
THIS AREA ACROSS ARKLATEX INTO CENTRAL TX.

THIS ACTIVITY IS EXPECTED TO BE MAINTAINED WITHIN
ELONGATED...WSW-ENE ORIENTED CONVEYOR OF LOW LEVEL MOISTURE
TRANSPORT AND WAA -- ATOP COOLING/POST-FRONTAL BOUNDARY LAYER. 
MODIFIED RAOBS AND RUC SOUNDINGS SHOW 5-7 KFT DEEP SUPERFREEZING
LAYER IN LOW-MIDLEVELS ATOP FCST FREEZING RAIN ZONE.  THIS LAYER
WILL BECOME SHALLOWER AND MORE ELEVATED WITH NWD EXTENT WHERE SLEET
IS FCST...THEN VANISH OVER FCST SNOW SWATH.  ELEVATED MUCAPES UNDER
100 J/KG -- ROOTED NEAR 700 MB -- WILL BE POSSIBLE FROM SERN AR TO
NRN AL AND SWRN/MID TN.  THIS INDICATES OCCASIONAL CONVECTIVE BURSTS
WILL LOCALLY BOOST PRECIP RATES FOR SHORT PERIODS.  LIFT WILL BE
MAINTAINED IN ENVIRONMENT OF 700-750 MB FRONTOGENESIS...AXIS OF
WHICH WILL SHIFT ESEWD ACROSS NRN MS/AL WITH TIME BEFORE WEAKENING
AROUND MID-DAY.

..EDWARDS.. 02/18/2006

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

ATTN...WFO...MRX...JKL...FFC...LMK...OHX...BMX...HUN...PAH...MEG...JAN...LZK...

35699213 36089172 36488942 36668768 36838505 36018422
35798391 35038467 34548568 33788783 33339036 34189194
34769235 35239230 

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