Area Forecast Discussion
Issued by NWS San Angelo, TX

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FXUS64 KSJT 172047
AFDSJT

Area Forecast Discussion
National Weather Service San Angelo TX
247 PM CST Sun Dec 17 2017

.SHORT TERM...
(Tonight and Monday)

Skies are partly to mostly sunny over west central Texas this
afternoon, with some high cloudiness streaming over the area. Mostly
clear skies for much of tonight and radiational cooling will allow
temperatures to drop to near dewpoint values overnight. With
moistening of the boundary layer, patchy fog development is expected
across much of our area late tonight and early Monday morning. Will
be monitoring for the possibility of localized dense fog at a few
locations, mainly in the southern part of our area. Low cloud
development is also expected over the area mainly south of a Mertzon
to Mason line. Overnight lows will be mostly in the lower 40s, with
a few upper 30s in the northwestern part of our area.

An upper low, currently over the Arizona/Mexico border, will move
slowly east into extreme southwestern New Mexico by late Monday
afternoon. Patchy fog and low cloud cover will break up Monday
morning, but with increasing low-level moisture, additional cloud
cover is expected to develop over the eastern third of our area
during the afternoon. Should also have some high cloudiness
overspreading our area with the approaching system and southwest
flow aloft. This should have a limiting effect on temperatures, and
going with highs under the GFS MOS. Also carring low PoPs for the
possibility of a few showers developing over the southeastern part
of our area, mainly in the afternoon.

.LONG TERM...
(Monday Night through Sunday)

Forecasts in the long term continues to undergo major changes, as
the models continue to shift to a drier forecast for the Christmas
weekend.

First, the mid week system will bring decent rainfall chances to
areas mainly east of an Abilene to San Angelo line for Monday
Night and Tuesday, as a potent shortwave rolls across the area.
Increased rain chances even more for this time period.

Now for Christmas Weekend, which continues to be a low confidence
forecast. The models have gone from a closed low across the
Southwest US to rapidly moving shortwave to a weak shortwave at
best on the 12Z run. Not only does this produce a drier forecast,
it provides virtually no push on the arctic front and slows its
progress. The GFS and ECMWF push a cold front across the area on
Friday, but keep the brunt of the cold air farther north across
Oklahoma and the Panhandle. The ECMWF doesn`t bring the true
arctic front into the area until Sunday, with the GFS waiting til
Monday. In fact, GFS now has highs on Saturday and Sunday near 70
across West Central Texas. Models usually struggle with the push
of the arctic fronts, underestimating its southward push. Thus,
while I will raise temperatures a few dgerees for the weekend, I
wont go anywhere near model guidance and await a better feel for
the arctic front movement.


&&

.PRELIMINARY POINT TEMPS/POPS...
Abilene  65  41  61  46 /   0   0   5  20
San Angelo  69  41  65  46 /   0   0  10  30
Junction  67  43  63  49 /   0  10  20  50
Brownwood  64  44  59  49 /   5   0  10  30
Sweetwater  65  41  61  45 /   0   0   5  10
Ozona       64  42  63  45 /   0   5   5  30

&&

.SJT WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

19/07



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