Area Forecast Discussion
Issued by NWS Midland/Odessa, TX

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722
FXUS64 KMAF 202331
AFDMAF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MIDLAND/ODESSA TX
531 PM CST Tue Jan 20 2015

.DISCUSSION...

&&

.AVIATION...
Have post frontal conditions with a brisk N wind that should
decrease overnight and veer around to the east by tomorrow. VFR
conditions will give way to MVFR cigs at most TAF sites by
morning.

&&

.PREV DISCUSSION... /ISSUED 404 PM CST Tue Jan 20 2015/

DISCUSSION...

Despite a cold front moving through the area this afternoon,
temperatures have once again warmed to well above normal, in the
middle 60s across southeast New Mexico to a balmy 80 degrees in
Terrell county Texas. Much colder air will filter into the area
behind the front tonight, with clouds and precipitation chances
increasing as a potent storm system takes aim on the region.
A southern stream trough is expected to continue to deepen and
develop a closed circulation as it drops from the Four Corners
Region toward West Texas over the next 24 hours. The GFS, NAM, and
Canadian display this trend, and maintain a slower passage of this
feature than the ECMWF, which remains the outlier in a much
quicker progression and maintains an open wave. Thus, have trended
the forecast away from the ECMWF toward more agreeable guidance.
A weaker shortwave will eject across the area ahead of this
feature on Wednesday, which will result in fairly widespread rain
chances. Steepening lapse rates across the Big Bend Area and Lower
Trans Pecos could result in some isolated thunderstorm development
Wednesday afternoon, though no severe weather is currently
anticipated.

Precipitation chances will continue to increase by Wednesday night
as the larger southern stream trough nears the area, and as
temperatures drop, expect to see the rain begin to change over to
snow first across the higher terrain of the Guadalupe, Davis, and
Glass Mountains, as well as across southeastern New Mexico and the
far northwestern Permian Basin. Rain, and perhaps a rain snow mix
are possible Thursday morning as temperatures warm above freezing
for a short time, though by Thursday afternoon and especially
Thursday night, temperatures will drop below freezing as the low
continues to dig south, and a transition from rain to all snow is
expected across the entire area except for the Presidio Valley,
Marfa Plateau, Big Bend Area, and Terrell County, where
temperatures look to remain just above freezing. Upon continued
review of local climatology, this still looks to be a stellar set-
up for a heavy snow event across southeast New Mexico and west
Texas. Precipitable water values with this system are well above
normal for this time of year, ranging from 0.50" to 0.75" across
the area for the duration of the event, from Wednesday through
Thursday night. Also, strong lift will be supported by the closed
low passing over the area, as well as an accompanying 300mb jet
axis entrance region that remains over the region through Friday
morning, and a potent 500mb vort max rounding the base of the
trough Thursday night. Rapid cooling of 700mb temperatures on
Thursday evening and Thursday night also reinforce not only the
occurrence of heavy snow, but that the best opportunity for
accumulations will be overnight Thursday night and early Friday
morning.

While accumulations will likely be adjusted in later forecast
packages, it looks like widespread accumulations of 2 to 4 inches
of snow are possible, with 5 to 6 inches possible across northern
Lea county, New Mexico as well as in the Guadalupe, Davis, and
Glass mountains, particularly above 4000ft. A Winter Storm Watch
has been issued for the entire area except for the Presidio
Valley, Marfa Plateau, Big Bend Area, and Terrell County. Please
see the watch product for details.

Not many changes were made to the extended this forecast package,
and did not deviate much from the blended forecast. Dry conditions
are expected to prevail beyond Friday, and temperatures will
slowly rebound over the weekend, climbing back into the 60s area-
wide by next Tuesday.

&&

.MAF WATCHES/WARNINGS/ADVISORIES...
NM...WINTER STORM WATCH from Wednesday evening through late Thursday
     night FOR THE FOLLOWING ZONES... Central Lea County...Eddy
     County Plains...Guadalupe Mountains of Eddy County...
     Northern Lea County...Southern Lea County.

TX...WINTER STORM WATCH from late Wednesday night through late
     Thursday night FOR THE FOLLOWING ZONES... Andrews...
     Borden...Crane...Davis/Apache Mountains Area...Dawson...
     Ector...Gaines...Glasscock...Guadalupe Mountains...Howard...
     Loving...Martin...Midland...Mitchell...Pecos...Reagan...
     Reeves County and Upper Trans Pecos...Scurry...Upton...Van
     Horn and Highway 54 Corridor...Ward...Winkler.


&&

$$

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