Area Forecast Discussion
Issued by NWS Midland/Odessa, TX

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626
FXUS64 KMAF 250556
AFDMAF

Area Forecast Discussion
National Weather Service Midland/Odessa TX
1256 AM CDT SUN SEP 25 2016

.DISCUSSION...

Please see the 06Z aviation discussion below.

&&

.AVIATION...

Scattered thunderstorms are ongoing just east of area terminals at
issuance. Thunderstorms could affect INK, MAF, and FST early in
the period, with gusty wind and MVFR visibility in heavy rain
possible. Thunderstorms are expected to increase in coverage
Sunday morning across TX terminals, gradually developing westward
to affect HOB and CNM. A cold front will begin to move through the
area late Sunday morning, accompanied by a north/northeast wind
shift with gusts to 30-35kt possible. Prevailing MVFR conditions
in heavy rain are expected thereafter, with IFR conditions
possible, especially during the afternoon/evening.

&&

.PREV DISCUSSION... /issued 155 PM CDT SAT SEP 24 2016/

DISCUSSION...

Southeastern New Mexico and West Texas appear set for heavy rainfall
event starting tonight and lasting into Monday, in addition to much
cooler temperatures.  A potent shortwave trough is currently
ejecting northeastward into the northern U.S. Plains early this
afternoon.  Surface frontogenesis will occur in the wake of this
upper trough and send a cold front southward in the lee of the
Rockies.  The front looks to move into the forecast area Sunday
afternoon with much cooler temperatures behind it.  A shortwave
trough will drop south into the base of the longwave trough over the
western CONUS and form a cutoff low over northern New Mexico by
25/12Z.  This will set the stage for widespread rainfall over the
forecast area starting tonight, and lasting into Monday morning.

A surface trough bisected West Texas from north to south this
afternoon.  A few showers and thunderstorms have already developed
on it so far, but expect more to form through max heating as lift
increases ahead of a shortwave trough translating over New Mexico
ahead of the large upper trough to the west.  Mid level support will
be enhanced further by the entrance region of a 80kt h25 jet over
New Mexico, with thunderstorms flourishing along and east of the
surface trough tonight, especially as an h85 LLJ strengthens over
the Permian Basin, provides moist inflow and destabilizes the
atmosphere.  Instability will top out around 1200-1500 J/Kg this
afternoon/early evening, but mid level lapse rates will be near
moist adiabatic and 0 to 6Km Bulk Shear will be 25 to 30kt at best.
Therefore, some of these storms could be strong, with a couple of
severe storms not out of the question.  Strong winds, hail, heavy
rainfall and frequent lightning strikes will be the main threats.

Moisture will continue to increase over the area tonight as height
falls to the east of the cutoff low backs/increases low level winds.
PWATS will rise to around 1.50 west Sunday afternoon to 1.75 east,
the latter being 2 S.D. above normal, and a record amount of
moisture climatologically for 25 September.  Large scale lift will
also increase over the area tonight/Sunday as the flow aloft becomes
more difluent, a series of shortwave troughs translate northward
around the eastern periphery of the upper low, upper lift is
enhanced by the presence of the RRQ of the h25 jet still over New
Mexico, and isentropic upglide increases along and behind the cold
front Sunday afternoon.  Unidirectional flow aloft over the region
could result in thunderstorms training over the same areas.
Considering some locations could see 3-5 inches of rainfall, will
continue the current Flash Flood Watch.  However, some models
retrograde the upper low Sunday which shifts the emphasis for heavy
rainfall farther west.  Will hold off issuing a Flash Flood Watch
farther west though and wait to see whether trends hold on later
model runs.  The heavy rainfall could also result in river flooding
along the Colorado and Rio Grande starting tonight and lasting into
Monday, if not a little beyond.  The threat of heavy rainfall will
persist Monday morning, but will leave the ending time of the Flash
Flood Watch at 26/12Z Monday for now.  The only other threat during
the next couple of days will be strong winds through Guadalupe Pass
behind the front. Mos guidance numbers look absurd with 80kt
sustained Sunday night, but 35 to 50kt appears to be within the
realm of possibility. Therefore, will upgrade the High Wind Watch to
a High Wind Warning running from 300 pm MDT Sunday to Noon MDT
Monday.

The cutoff low is expected to retrograde to southern California by
Tuesday afternoon, and then translates northeastward ahead of
another forming upper trough off the western CONUS.  So good rain
chances will persist Monday, which appears to be the coolest day
upcoming, with a weak upper ridge over the region thereafter
decreasing rain chances.  Temperatures will remain below normal
Tuesday and Wednesday, then rise closer to normal Thursday through
Saturday.

&&

.PRELIMINARY POINT TEMPS/POPS...
Big Spring                     55  59  51  71 /  80  70  20  10
Carlsbad                       55  60  52  68 /  80  60  20  10
Dryden                         66  67  56  70 /  90  70  50  30
Fort Stockton                  60  60  52  66 /  90  70  40  30
Guadalupe Pass                 48  51  45  60 /  90  60  30  20
Hobbs                          51  58  49  69 /  70  50  20  10
Marfa                          52  60  45  63 /  70  60  40  40
Midland Intl Airport           56  60  51  71 /  90  70  20  10
Odessa                         55  59  51  70 /  90  70  20  10
Wink                           60  60  52  70 /  90  70  30  10

&&

.MAF Watches/Warnings/Advisories...
NM...None.
TX...Flash Flood Watch through Monday morning for Andrews-Big Bend
     Area-Borden-Crane-Dawson-Ector-Gaines-Glasscock-Howard-
     Martin-Midland-Mitchell-Pecos-Reagan-Scurry-Terrell-Upton-
     Ward-Winkler.

     High Wind Warning from 3 PM Sunday to noon MDT Monday for
     Guadalupe Mountains.

&&

$$

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