Area Forecast Discussion
Issued by NWS San Angelo, TX

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FXUS64 KSJT 291113 AAA
AFDSJT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SAN ANGELO TX
512 AM CST MON DEC 29 2014

.AVIATION...
/12Z TAFS/

VFR conditions will prevail at the TAF sites today and tonight,
with scattered high cloud coverage expected. Some low cloud
development should occur toward morning across the area north of
Interstate 20. Carrying a Tempo SCT025 group at KABI from 10Z to
12Z. Winds will be mostly from the southwest at 5-8 KT today. An
initial wind shift (to north winds) should occur at KABI around
23Z. An arctic front will advance south across west central Texas
tonight, with north winds following its passage.

&&

.PREV DISCUSSION... /ISSUED 353 AM CST Mon Dec 29 2014/

SHORT TERM...
(Today and Tonight)

Temperatures will warm up nicely across our area today, ahead of the
arctic surge which arrives tonight. With just some scattered high
cloud cover and west west-southwest low-level flow, temperatures
will climb into the 60s for highs this afternoon. Have boosted max
temperatures above MOS guidance, which typically under-forecasts our
highs with these scenarios. Would not be surprised to see a few
upper 60s in our southern counties.

Initial wind shift will arrive in our northern counties late this
afternoon, with the main arctic surge reaching the Red River by
early this evening. The arctic front will advance south across our
area tonight, with temperatures dropping into the mid/upper 20s to
lower 30s by daybreak Tuesday. Some low cloud development into our
northern counties is expected toward morning.

LONG TERM...
(Tuesday through Monday)

Threat of wintry precipitation continues!

With the arctic front having surged south through West Central
Texas, temperatures will struggle to climb very much during the
day on Tuesday. They may actually being to fall along and north of
I-20 by afternoon. Don`t see much in the way of precipitation until
late afternoon. Mid levels remain dry and will take isentropic
lift in the lowest levels to squeeze out what will likely be very
light rain and drizzle. As usual...NAM is a little more aggressive
with it than the GFS...but even the GFS shows the isentropic
lift...albeit weaker. The problem of course is that is occurring
behind the arctic front where temperatures will be below freezing.
Looks very much like a freezing drizzle event for much of the
area, starting very late Tuesday afternoon and continuing into
Wednesday Night. Bumped PoPs up to account for it, although would
not be surprised if only a hundredth or two was recorded. With
temps in the 20s though, even that hundredth or two may be enough
to create some real travel headaches for New Years Eve.

Main upper low dives into the southwest US Wednesday Night and
begins to be a player as well. Shortwave rounds the base and comes
out across the area late Wednesday Night and early Thursday.
Strong warm advection will take shape and temperatures will begin
to climb above the surface. How quickly readings can climb at the
surface remains a big question...and the main concern for early
Thursday. Often, the surface high wedges in and the colder air is
slow to be scoured out. Or at least, slower than the models show.
If that happens late Wednesday Night into Thursday, we could be
looking at a much more significant winter weather event for early
New Years Day. Increased PoP chances during Wednesday Night into
Thursday, and kept the mention of freezing rain in until at least
noon.

Finally, models have slowed the passage of the upper low itself
until Saturday, so have increased rain chances for Friday and
Friday Night to account. Temperatures should be above freezing at
that point area wide so looking at showers and perhaps even a
thunderstorm.

&&

.PRELIMINARY POINT TEMPS/POPS...
Abilene  62  28  35  24  30 /   0   0  20  40  30
San Angelo  65  29  38  27  31 /   0   0  20  40  30
Junction  65  31  48  31  34 /   0   0  10  20  30

&&

.SJT WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

Aviation and Short Term: 19
Long Term: 07










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