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000
FXUS64 KMAF 241735
AFDMAF

Area Forecast Discussion
National Weather Service Midland/Odessa TX
1235 PM CDT SAT SEP 24 2016

.DISCUSSION...

See 18z aviation discussion below.

&&

.AVIATION...

There is a slight chance of showers and thunderstorms this
afternoon. Chances of convection increase this evening into
tonight and then especially Sunday morning into the afternoon
hours. Low ceilings are expected to start developing around 12z
then become more widespread by 18z. Winds will mostly be light out
of the south except at MAF and FST where elevated winds are
possible this afternoon and evening.

&&

PREV DISCUSSION... /issued 426 AM CDT SAT SEP 24 2016/

DISCUSSION...

While thunderstorm chances will begin to increase across the area
this afternoon, the main focus will be the potential for
widespread heavy rain and flash flooding tonight through Monday
morning, and the arrival of much cooler, well below normal
temperatures by the end of the weekend into early next week.

Per water vapor imagery, the upper ridge that has dominated the
past several days has shifted eastward, with a plume of
subtropical moisture advecting over the region in increasing
southwesterly flow aloft ahead of a potent upper trough. As the
trough begins to transition into a closed low that will lift
northeastward into the Northern Plains today, and another low
progged to develop and settle just south of the US/Mexico border
in Chihuahua on Sunday, the region will be under the right
entrance region of a 300mb jet rounding the base of the elongated
trough. As height falls overspread the region, increasing moisture
and upper support will yield increasing storm chances today over
far southeast New Mexico and the northwest Permian Basin
southwestward to the Big Bend Area and points east. Some storms
this afternoon could become strong to marginally severe, with
gusty winds over 50 mph and locally heavy rainfall the primary
threats. Small hail, and frequent lightning could also accompany
storms that develop. Temperatures today will be a bit cooler than
yesterday due to increasing moisture and cloud cover, though still
above normal. However, it looks to be our last day of above normal
temperatures for awhile.

Moisture will continue to increase over the area tonight as the
low cuts off at the base of the elongated trough and enhances
moist upslope flow over the region. Precipitable water values will
increase to nearly 1.75 inches across the Permian Basin, Lower
Trans Pecos, and Big Bend Area by Sunday morning, roughly 2
standard deviations above normal, and could potentially be a new
record high precipitable water amount for September 25th. Showers
and thunderstorms will increase in coverage areawide overnight due
to continued upper support from the trough as well as the 300mb
jet, with the best chance for storms across the eastern half of
the forecast area. Given the anomalously high precipitable water
values, heavy rainfall is a significant concern with storms that
develop, as slow moving, training storms will be possible.
Widespread thunderstorms with heavy rain will continue on Sunday,
with additional support from a strong cold front that will move
south through the region during the day. Despite the strong front,
severe weather is not anticipated, as model soundings are largely
moist adiabatic and lapse rates drop with the passage of the
front. However, the heavy rain threat will continue, and persist
into Sunday night, as continued upslope flow and isentropic
upglide will act facilitate continued storm development. Rainfall
totals of 3 to 5 inches through Monday morning are not unlikely
across the Permian Basin, Lower Trans Pecos, and Big Bend Area.
Thus, a Flash Flood Watch has been issued from this evening
through Monday morning. This watch may need to be expanded
westward to include the Upper Trans Pecos and Southeast New
Mexico, as heavy rain chances look to develop westward on Sunday,
but will leave this to later shifts to decide.

Sunday will be significantly cooler due to the combination of cold
air advection behind the front, diabatic cooling, and cloud
cover, with highs potentially 15 degrees cooler than today, and
nearly 10 degrees below normal. In the wake of the front, winds
will become gusty out of the northeast, with the strongest winds
of 45 to 55 MPH sustained expected through Guadalupe Pass. A High
Wind Watch has been issued for that area from Sunday afternoon
through Monday morning, please see the Watch product for details.

Cold advection behind the front will continue into Monday, with
high temperatures expected to only range from the middle 50s to
middle 60s for all but the Rio Grande Valley, where middle 70s are
possible. While rain chances will continue into Monday, the heavy
rain threat will diminish, with precipitation chances further
decreasing from north to south on Tuesday. The well below normal
temperatures will stick around through midweek next week, with a
gradual warming trend expected to end the week, with temperatures
returning to near normal values by Thursday/Friday.

&&

.PRELIMINARY POINT TEMPS/POPS...
Big Spring                     88  68  72  54 /  60  80  90  80
Carlsbad                       85  62  70  55 /  10  20  60  50
Dryden                         89  71  77  66 /  30  70  90  70
Fort Stockton                  89  67  74  60 /  40  70  90  80
Guadalupe Pass                 78  60  64  48 /  10  20  60  60
Hobbs                          83  61  69  55 /  30  30  70  50
Marfa                          83  59  69  53 /  50  60  80  50
Midland Intl Airport           87  66  72  55 /  50  70  90  80
Odessa                         86  66  72  54 /  50  70  90  70
Wink                           90  67  73  60 /  30  50  80  70

&&

.MAF Watches/Warnings/Advisories...
NM...None.
TX...Flash Flood Watch from 7 PM CDT this evening 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 Watch from Sunday afternoon through Monday morning for
     Guadalupe Mountains.

&&

$$

99/99/