Severe Storm Outlook Narrative (AC)
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000
ACUS11 KWNS 230352
SWOMCD
SPC MCD 230351
ALZ000-TNZ000-MSZ000-ARZ000-230745-

MESOSCALE DISCUSSION 0091
NWS STORM PREDICTION CENTER NORMAN OK
0951 PM CST SUN FEB 22 2015

AREAS AFFECTED...PORTIONS OF SERN AR...NRN MS...SWRN TN...AND NWRN
AL

CONCERNING...WINTER MIXED PRECIPITATION

VALID 230351Z - 230745Z

SUMMARY...A MIXTURE OF FREEZING RAIN AND SLEET WILL CONTINUE TO
PROGRESS EAST FROM PARTS OF THE LOWER MS VALLEY TOWARDS THE TN
VALLEY LATE THIS EVENING INTO EARLY TONIGHT. FREEZING RAIN RATES OF
A FEW HUNDREDTHS OF AN INCH PER HOUR ARE POSSIBLE.

DISCUSSION...THE 03Z REGIONAL WSR-88D MOSAIC DEPICTS A RELATIVELY
LARGE AREA OF PCPN STRETCHING EWD FROM THE ARKLATEX TOWARDS THE TN
VALLEY THIS EVENING. THIS PCPN SHIELD IS PROGRESSING EWD IN RESPONSE
TO FORCING FOR ASCENT FROM A WEAK SRN STREAM IMPULSE /EVIDENT IN
EVENING WV IMAGERY/...AS WELL AS ADIABATIC ASCENT ACTING IN CONCERT
WITH THIS IMPULSE.

CURRENT KNQA DATA AND THE UPSTREAM 00Z LZK SOUNDING INDICATE A WARM
NOSE CENTERED AROUND 1.5-2 KM AGL IS ENSURING MELTING OF ICE
HYDROMETEORS ALOFT ACROSS THE MCD AREA...WITH ONLY A THIN CORRIDOR
OF SNOW TO THE NORTH. DUAL-POL CC DATA ALSO SUGGEST WAA ALOFT IS OF
SUFFICIENT STRENGTH TO OFFSET ANY DIABATIC COOLING EFFECTS FROM
MELTING OF HYDROMETEORS...AS RECENT KNQA DATA INDICATE LESS OF A
DOWNWARD PERTURBATION OF THE NRN EXTENT OF THE MELTING LAYER OVER
THE LAST HOUR. THEREFORE...WHILE POCKETS OF SLEET ARE STILL
EXPECTED...FZRA IS FORECAST TO BECOME THE MORE DOMINANT P-TYPE OVER
THE NEXT FEW HOURS. IN LOCATIONS FARTHER EAST WHERE SFC TEMPS ARE
STILL ABOVE FREEZING...N/NELY FLOW WILL SUPPORT CONTINUED COOL/DRY
AIR ADVECTION. AS SUCH...LOWERING WET-BULB TEMPS WILL COMBINE WITH
INCREASING SATURATION TO SUPPORT A CHANGEOVER FROM RAIN TO FREEZING
RAIN THIS EVENING...WITH RATES OF A FEW HUNDREDTHS OF AN INCH PER
HOUR POSSIBLE.

..PICCA/EDWARDS.. 02/23/2015

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

ATTN...WFO...OHX...BMX...HUN...MEG...JAN...LZK...

LAT...LON   33599072 33479165 33739189 34499139 35109028 35188835
            35108737 34818703 34308703 34058725 33728904 33599072




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