SWOMCD
SPC MCD 041128
ALZ000-TNZ000-MSZ000-ARZ000-LAZ000-TXZ000-OKZ000-041700-
MESOSCALE DISCUSSION 0087
NWS STORM PREDICTION CENTER NORMAN OK
0528 AM CST FRI FEB 04 2011
AREAS AFFECTED...PORTIONS NE TX...SERN OK...CENTRAL/SRN
AR...CENTRAL/NRN LA...CENTRAL/NRN MS...EXTREME SWRN TN...EXTREME
NWRN AL.
CONCERNING...WINTER MIXED PRECIPITATION
VALID 041128Z - 041700Z
FREEZING RAIN WITH GEN .05-.10 INCH/HOUR RATES SHOULD CONTINUE OVER
BROAD SWATH FROM S-CENTRAL LA NEWD ACROSS W-CENTRAL
MS...MOVING/EXPANDING NEWD OVER MORE OF N-CENTRAL AND CENTRAL MS
THROUGH ABOUT 16Z. EMBEDDED CONVECTIVE BURSTS...SOME WITH
THUNDER...BRIEFLY WILL OFFER .10-.25 INCH/HOUR FREEZING RAIN RATES.
FREEZING RAIN WILL GRADE TO SNOW WWD ACROSS PORTIONS EXTREME
N-CENTRAL/NWRN LA AND S-CENTRAL/SERN AR. SNOW RATES MAY REACH 1
INCH/HOUR IN HEAVIEST EMBEDDED BANDS AND SWATHS WWD ACROSS RED RIVER
REGION OF NE TX AND SWRN OK...SWD TO NEAR I-20.
BROAD PLUME OF PRECIP RELATED TO ELEVATED WAA/ASCENT AND MOISTURE
TRANSPORT ALOFT IS EXPECTED TO EXPAND NEWD ACROSS ARKLATEX
RETION...AR...AND MS AT FASTER RATE THAN ITS GENESIS REGION SHIFTS
EWD ONLY VERY SLOWLY ACROSS LA AND E TX. LARGE-SCALE ASCENT RELATED
TO DCVA...IMMEDIATELY PRECEDING MID-UPPER CYCLONE THAT IS EJECTING
NEWD FROM W TX...ALSO WILL CONTRIBUTE TO ASCENT OVER WRN PORTIONS OF
DISCUSSION AREA. NET EFFECT SHOULD BE EXPANSION OF ONGOING PRECIP
PLUME...WHILE WET-BULB EFFECTS LEAD TO ADDITIONAL BOUNDARY-LAYER
COOLING OVER MUCH OF THIS AREA. MODIFIED RUC/ETA-KF FCST SOUNDINGS
INDICATE NEARLY 9 KFT DEEP SUPERFREEZING LAYER OVER PORTIONS SRN
MS...TRENDING TO AROUND 4-5 KFT OVER CENTRAL LA AND DISAPPEARING
OVER E TX AND NWRN LA...IN GOOD AGREEMENT WITH CURRENT TRANSITION
ZONE FROM FREEZING RAIN TO SNOW. THIS TRANSITION ZONE...WHICH ALSO
CORRESPONDS TO SATURATION/LIFT NEAR BASE OF DENDRITIC GROWTH LAYERS
ALOFT...SHOULD DRIFT EWD ACROSS NRN LA AND SRN AR. LTG DETECTION
EQUIPMENT ALSO HAS OBSERVED CG STROKES DURING PAST HOUR FROM MORE
DISCRETELY CELLULAR CONVECTION FORMING INVOF POE...AND MOVING
RAPIDLY NEWD BEFORE MERGING INTO BROADER PRECIP PLUME. MODIFIED
FCST SOUNDINGS SUGGEST THIS ACTIVITY IS ROOTED AROUND 650 MB --
ABOVE SUPERFREEZING LAYER BUT WELL WITHIN RANGE WHERE SUPERCOOLED
LIQUID DROPS ARE BEING PROCESSED THROUGH AN LFC...BENEATH MUCAPE
100-200 J/KG.
..EDWARDS.. 02/04/2011
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...BMX...HUN...MEG...JAN...LIX...LZK...LCH...SHV...
TSA...FWD...OUN...
LAT...LON 34579602 35029543 34829232 35198986 35028819 34568769
33688801 32348877 31139048 30559238 32039445 32519580
33629628 34579602
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