Area Forecast Discussion
Issued by NWS San Angelo, TX

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FXUS64 KSJT 251103

Area Forecast Discussion
National Weather Service SAN ANGELO TX
503 AM CST WED NOV 25 2015

(Today and Tonight)

A little patchy drizzle along the I-10 Corridor is possible this
morning. Otherwise, expect cloudy, mild and breezy conditions today
with highs in the lower 70s, becoming partly cloudy briefly this
afternoon.  A surface low pressure system was located along the
front range of the Rockies, and has formed in response to increasing
upper southwesterly flow extending across much of the western U.S.
into West Central Texas.  The southwest flow aloft will continue
today and tonight in advance of an upper low diving south across

Meanwhile, the Surface low will continue to pump plenty of gulf
moisture into the region through tonight in the form of low clouds
and increasing surface dewpoint temperatures into the lower 60s.
Lowered Pops today and tonight as a strong CAP or elevated warm
layer (EML) should prevent convection from forming. However, can`t
rule out a little light drizzle developing tonight or a few showers
beneath the EML.

(Thanksgiving through Tuesday)

...Locally heavy rain possible this Holiday weekend...
... Freezing rain possible across the northwestern Big Country...

The second half of the week is looking quite active with numerous
forecast concerns, to say the least. All available guidance
continues to indicate a prolonged period of rainfall will affect the
forecast area this Holiday weekend. A deep upper-level trough will
remain anchored across the western CONUS, with a pair of closed mid-
level circulations rotating around each other (Fujiwhara effect),
with southwest flow aloft forecast over Texas. Embedded disturbances
will eject northeast in this flow through the weekend, bringing
periodic increases in ascent to our region, helping increase
rainfall coverage/intensity.

Meanwhile, the latest National Hurricane Center (NHC) forecast takes
Hurricane Sandy (currently a hurricane) into the southern Gulf Of
California as a tropical storm (Friday night), weakening to a tropical
depression a little south of the Texas Big Bend (Saturday night).
This is an almost ideal track for a prolonged feed of mid to upper-
level moisture from the system to be advected over West Central
Texas, enhancing our rainfall efficiency. Taking a closer look at
the precipitable water values for 12z Friday, the models show values
ranging from around 1.5 inches along Interstate 20, to 1.7 inches
across the Heartland and Northwest Hill Country. To put this in
perspective, the climatology for this time frame is around 1 inch at
Midland and 1.42 inches at Del Rio.

Another piece to this puzzle will be a strong surface cold front
blasting through the area Friday. This front looks to be a
shallow/Arctic front in nature.  This front will enter
Haskell/Throckmorton counties shortly after midnight Friday morning,
and will clear the Interstate 10 corridor by early afternoon.
However, the 850 front looks to bisect the forecast area Friday and
Saturday. Considerable moisture coupled with isentropic lift over
the 850mb front and ascent from the approaching upper
trough/remnants of Sandy will likely lead to a heavy rainfall
potential. This could be even more of a concern across the
northwestern Big Country, where forecast soundings show enough
cooling in the lowest 1000 feet of the atmosphere to make freezing
rain a concern. Our current thinking is the precipitation rates may
help mitigate the potential for any frozen accumulations, as most of
the NAM/GFS soundings show surface temperatures only a degree or two
below freezing.

The much talked about upper trough will be passing by to our
northeast by Monday. Subsidence behind the trough axis will bring
drier air to the region, ending our rain chances.


Abilene  72  62  71  44 /  10  20  60  80
San Angelo  73  64  74  55 /  10  20  50  60
Junction  72  65  72  62 /  10  20  50  60


.SJT Watches/Warnings/Advisories...


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