MESOSCALE DISCUSSION 0059
NWS STORM PREDICTION CENTER NORMAN OK
0904 PM CST MON JAN 31 2011
AREAS AFFECTED...PORTIONS SWRN...CENTRAL AND NERN OK...NW TX.
CONCERNING...WINTER MIXED PRECIPITATION
VALID 010304Z - 010900Z
BAND OF FREEZING RAIN AND SLEET...WITH MORE PURELY FREEZING RAIN ON
ITS SRN/ERN FRINGES AND SLEET ON WRN FRINGES...IS EXPECTED TO
MOVE/EXPAND NEWD FROM NW TX ACROSS CENTRAL OK THROUGH 06Z...POSSIBLY
REACHING PORTIONS NERN OK INVOF TUL AROUND 08-10Z. ACTIVITY ALSO
MAY BACKBUILD SWWD SOMEWHAT ACROSS NW TX INTO AREAS E OF LBB AND S
OF CDS. ALSO...CONVERSION FROM RAIN TO FREEZING RAIN AND SLEET WILL
OCCUR WITHIN PORTIONS PRECIP PLUME INITIALLY SE OF FREEZING LINE.
EMBEDDED TSTMS MAY PRODUCE LIQUID EQUIVALENT RATES BRIEFLY REACHING
0.5-0.75 INCH/HOUR RANGE...BUT WITH .10-.25 INCH/HOUR RATES MORE
COMMON.
DEEP SHORTWAVE TROUGH -- ANALYZED ON 00Z UPPER-AIR CHARTS OVER
CENTRAL/NRN NM...IS EXPECTED TO MOVE EWD TO W TX BY ABOUT
09Z...PRECEDED BY EXTENSIVE AREA OF MIDLEVEL DCVA AND LOW-LEVEL WAA
ABOVE COLD BOUNDARY LAYER. SFC ANALYSIS SHOWS COLD FRONT CONTINUING
TO MOVE SWWD ACROSS NRN HILL COUNTRY OF CENTRAL TX...AS WELL AS
CONCHO VALLEY AND PERMIAN BASIN. FREEZING AND WET-BULB 0 LINES
LIKEWISE WILL MOVE SWD BENEATH PROGRESSIVELY MORE OF PRECIP PLUMES
NOW SPREADING NEWD FROM NW TX AND FROM ABI AREA. TIME SERIES OF
FCST SOUNDINGS SUGGESTS COMBINATION OF ELEVATED MOISTURE
TRANSPORT...FRONTOGENETIC FORCING AND ISENTROPIC ASCENT WILL MOISTEN
COLUMN IN MOST OF 700-850 MB LAYER AND KEEP IT SUPERFREEZING...WHILE
RAPIDLY INCREASING LAYER RH AND REMOVING CINH IN SUPPORT OF
CONVECTIVE PRECIP. MUCAPE 300-500 J/KG IS POSSIBLE...EXTENDING WELL
INTO ICING LAYERS SUITABLE FOR THUNDER. DEPTH OF SUPERFREEZING
LAYER SUGGESTS AMPLE MELTING OPPORTUNITY FOR GRAUPEL AND SNOW
GENERATED ALOFT...WHICH THEN WOULD FREEZE WITHIN DEEP POST-FRONTAL
BOUNDARY LAYER. EXCEPTIONS WILL BE
1. ON WRN MARGINS OF EXPANDING PRECIP PLUME...ESPECIALLY AFTER
06Z...WHERE LARGE-SCALE ASCENT/COOLING AHEAD OF APCHG MID-UPPER
TROUGH COULD KEEP/COOL COLUMN BELOW FREEZING AND FAVOR INCREASING
PROBABILITY OF SNOW...AND
2. ON SRN/ERN FRINGES WHERE FRONTAL LAYER MAY REMAIN SHALLOW ENOUGH
FOR DROPS TO REMAIN LIQUID TO SFC.
..EDWARDS.. 02/01/2011
ATTN...WFO...TSA...FWD...OUN...SJT...LUB...
The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or STORM2K.
. A lot more where that came from.
