Area Forecast Discussion
Issued by NWS Midland/Odessa, TX

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FXUS64 KMAF 261919
AFDMAF

Area Forecast Discussion
National Weather Service Midland/Odessa TX
219 PM CDT Tue Sep 26 2017

.DISCUSSION...

...The potential for heavy rainfall and flash flooding will continue
tonight, Wednesday and Wednesday night behind a cold front, and
ahead of a slow moving upper trough...

Scattered showers and thunderstorms continue to develop over
southeastern New Mexico and West Texas this afternoon as warm moist
air overrides a cold front, due to southwest flow aloft over the
region ahead of an upper trough extending from the Great Plains to
the desert southwest U.S.  Warm rain processes are yielding 2
inches per hour rainfall rates, and likely higher amounts, despite
a dearth of lightning.  Flash Flood Warnings are currently in
effect over the Permian Basin, with more expected.

Over southwest Texas ahead of the front, less cloud cover has
allowed heating and destabilization of the atmosphere.  0 to 6 km
bulk shear is 30-40kt in these areas, so a few organized stronger
storms could produce hail and strong winds, in addition to
locally heavy rainfall, as SBCape rises to at least 1500 J/Kg this
afternoon.  These storms will also be aided by the RRQ of an h25
jet which will translate northeastward over western portions of
the forecast area late this afternoon/tonight.

Expect elevated instability to increase this afternoon/evening over
the area due to the proximity of the upper jet, and the threat of
heavy rainfall increasing over the Permian Basin overnight as a
modest h85 low level jet noses into the region above the advancing
cold front.  Pwats around 1.5 inches, or 1-2 S.D. above normal, will
exist over the eastern half of the forecast area tonight and
Wednesday, in part due to remnant mid and upper level moisture from
former Tropical System Pilar.  Training of thunderstorms could occur
around the slow moving front, further enhancing rainfall totals,
with 1-3 inch totals possible over the Watch area, and perhaps
isolated amounts of 4-5 inches.  Considered adding southeastern
New Mexico, and Culberson and Jeff Davis counties to the Watch
since the highest rainfall rates may occur in these areas due to
them being closest to the RRQ of the h25 jet, and seeing the
strongest thunderstorms.  However, think the overall coverage
will not be as great as farther east, so will keep the Flash Flood
Watch (FFA) in it`s current configuration.

The front will press south through most of the area by Wednesday
morning.  Expect high gap winds to occur through Guadalupe Pass
overnight and Wednesday morning, so have issued a High wind Warning
there.  Heavy rainfall may be ongoing over the eastern third of the
forecast area Wednesday morning, but with the h25 jet progged to
weaken, and the cold front/cloud cover hindering atmospheric
destabilization during the day, there may be a break in the heavy
rainfall during the day.  The axis of heavier rainfall may shift
eastward Wednesday afternoon, but will leave the FFA intact since
progs are indicating another round of showers/thunderstorms capable
of heavy rainfall developing on an easterly h85 LLJ Wednesday night.
By Thursday, rainfall rates may be low enough to let the FFA go, but
later shifts will have to monitor.

Temperatures will be below normal through Saturday as cloud cover
and more rain aid a surface ridge residing over the region.
Temperatures will rebound to near normal levels, and rain chances
will decrease this weekend as the ua trough lifts northeastward and
westerly flow aloft returns.

&&

.PRELIMINARY POINT TEMPS/POPS...
Big Spring                     63  68  60  68 /  90  80  60  50
Carlsbad                       59  67  59  67 /  60  60  60  60
Dryden                         69  76  68  78 /  80  70  70  70
Fort Stockton                  62  72  61  70 /  80  70  70  70
Guadalupe Pass                 54  62  55  62 /  60  50  50  50
Hobbs                          56  64  55  63 /  80  70  60  60
Marfa                          54  71  55  70 /  60  60  60  60
Midland Intl Airport           62  68  60  69 /  90  80  60  60
Odessa                         61  67  60  68 /  90  80  60  60
Wink                           63  69  60  70 /  80  70  60  60

&&

.MAF WATCHES/WARNINGS/ADVISORIES...
NM...None.
TX...Flash Flood Watch through Thursday 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 7 PM this evening to 8 AM MDT Wednesday
     for Guadalupe Mountains.

&&

$$

80/67


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