SWOMCD
SPC MCD 210622
ILZ000-KYZ000-TNZ000-MOZ000-ARZ000-MSZ000-OKZ000-KSZ000-211215-
MESOSCALE DISCUSSION 0273
NWS STORM PREDICTION CENTER NORMAN OK
1222 AM CST THU FEB 21 2008
AREAS AFFECTED...WRN...NRN/CENTRAL OK...SERN KS...SRN MO/NRN
AR...FAR SRN IL...FAR WRN KY/TN
CONCERNING...WINTER MIXED PRECIPITATION
VALID 210622Z - 211215Z
A MIX OF FREEZING RAIN/SLEET WILL DEVELOP THROUGH 12Z. HRLY
ACCUMULATION RATES UP TO 0.25 INCH WILL BE POSSIBLE WITH CONVECTIVE
SHOWERS.
LATEST IR SAT/VWP AND PROFILER DATA ALL CONFIRM THE EXISTENCE OF
INCREASING LOW LEVEL WAA OVER NRN AR/SRN MO IN ASSOCIATION WITH
STRENGTHENING LOW LEVEL JET /25-30 KTS/. RECENT RADAR IMAGERY SHOWS
PRECIP DEVELOPING IN RESPONSE. A SECONDARY BRANCH OF THE LOW LEVEL
JET EXISTS OVER WRN TX CLOSER TO THE MAIN UPPER TROUGH CENTERED OVER
AZ. REGIONAL SOUNDINGS THIS EVENING SHOWED THE PRESENCE OF AN
ELEVATED WARM LAYER ABOVE A SHALLOW SUB-FREEZING AIRMASS. AN
INVERSION CENTERED AROUND 750 MB /NOTED ON THE OUN...AMA AND DDC
SOUNDINGS/ WAS LIMITING PRECIPITATION SO FAR OVER MUCH OF OK GIVEN
THE SHALLOW MOIST LAYER /BENEATH 850 MB/. HOWEVER...FURTHER EAST
THIS INVERSION WAS NON-EXISTENT PER THE 00Z SGF/LZK SOUNDINGS.
STRENGTHENING MOISTURE ADVECTION SUPPORTED BY THE LOW LEVEL JET
LOCATED OVER THE ARKLATEX REGION INTO THE ELEVATED WARM LAYER WILL
SUPPORT THE POTENTIAL FOR CONVECTIVE INSTABILITY TO BE RELEASED OVER
ERN PORTIONS OF THE MD AREA /SRN MO...NRN AR AND FAR WRN TN/KY AND
SRN IL/ THROUGH 12Z. THIS WILL LIKELY RESULT IN SCT SHOWERS/TSTMS
OVER THIS REGION DEVELOPING THROUGH 12Z...WITH HRLY PRECIPITATION
RATES OVER 0.25 INCH IN ISOLATED LOCATIONS. DESPITE INITIAL PTYPE OF
SLEET...FREEZING RAIN WILL LIKELY BE THE PRIMARY PTYPE OVER NRN
AR/SRN MO WHERE THE DEPTH OF THE ELEVATED WARM LAYER WILL BE
SUFFICIENTLY LARGE. FURTHER NE OVER FAR WRN TN/KY AND SRN IL...THE
MORE LIMITED DEPTH OF THIS ELEVATED WARM LAYER THROUGH 12Z SHOULD
KEEP A P-TYPE OF SLEET.
FURTHER WEST...THE PROFILER FROM JAYTON INDICATES A STRENGTHENING
LOW LEVEL JET /AROUND 30 KTS/...WITH BACKING FLOW NOTED AT 1 KM OVER
WRN OK /PER THE VICI PROFILER/. RECENT RUC DATA INDICATES THAT THIS
LOW LEVEL JET WILL DEVELOP EWD INTO WRN OK THROUGH 09Z AND INTO
CENTRAL OK BY 12Z. INCREASING LARGE SCALE ASCENT ASSOCIATED WITH
APPROACHING UPPER TROUGH SHOULD SUPPORT A WEAKENING OF THE
AFOREMENTIONED INVERSION CENTERED AROUND 750 MB. THE PRESENT SFC
FREEZING LINE EXTENDING FROM TUL TO OKC TO LTS SHOULD REMAIN NEARLY
STATIONARY OR ONLY MOVE SLOWLY SWD GIVEN EXTENT OF CLOUD COVER AND
WEAKENING LOW LEVEL CAA. NORTH OF THIS AXIS...FREEZING DRIZZLE/LIGHT
FREEZING RAIN SHOWERS ARE EXPECTED TO INCREASE AS MOISTURE ADVECTION
STRENGTHENS AFTER 09Z. ISOLATED TSTMS ARE POSSIBLE TOWARDS 12Z OVER
CENTRAL/NERN OK AND SERN KS IF THE WEAKENING OF THE INVERSION IS
SUFFICIENT TO RELEASE CONVECTIVE INSTABILITY. HOWEVER...MOST
LOCATIONS WILL SEE HRLY FREEZING RAIN RATES LESS THAN 0.02 IN/HR.
.CROSBIE.. 02/21/2008
..PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
..NOTICE...
SPC WINTER WEATHER MESOSCALE DISCUSSIONS WILL BE ISSUED ON A
SCHEDULED BASIS FROM DECEMBER 1 THROUGH FEBRUARY 28...FOUR
TIMES A DAY...AROUND 00 UTC...06 UTC...12 UTC...AND 18 UTC
FOR SIGNIFICANT SHORT RANGE WINTER WEATHER EVENTS.
ATTN...WFO...PAH...MEG...LSX...LZK...SGF...EAX...TSA...TOP...ICT...OUN...DDC...
38389490 37419832 36129955 34739942 34539863 34949719
35659619 35949473 35579388 34689248 34879085 35208933
37808859 38138980 38389202
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