Area Forecast Discussion
Issued by NWS San Angelo, TX

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FXUS64 KSJT 222356

Area Forecast Discussion
National Weather Service San Angelo TX
656 PM CDT Thu Apr 22 2021

...New AVIATION...

(This evening through Friday)
Issued at 250 PM CDT Thu Apr 22 2021

Temperatures are well-below normal today with widespread low cloud
cover, and patchy drizzle/fog has occurred in our southern
counties. With moist southeast to south low-level flow tonight
and early Friday morning, low cloud cover will remain over the
area with some additional patchy drizzle/fog possible. After the
cool day today, little temperature change is expected tonight.
Lows are expected to be in the mid 50s to near 60 degrees.

An upper trough will move east across New Mexico on Friday, and into
West Texas by late afternoon. A dryline will mix east into our
western counties by early afternoon, and across the eastern half of
our area through the afternoon. With the approach of the trough and
increasing mid to upper level ascent, isolated to scattered showers
and thunderstorms will develop along or just east of the dryline.
East of the dryline, dewpoints will be 60-65 degrees. With moderate
instability and favorable deep layer shear, a few storms may be
strong to severe east of a Throckmorton to Albany to Junction line.
The main severe weather hazards will be large hail, damaging winds
and dangerous lightning. The convection will be east of our area by
(if not before) 00Z.

Our western counties will have elevated (possibly approaching
critical) fire weather conditions Friday afternoon behind the
dryline, where warm and very dry air will be combined with breezy
west or west-southwest winds.


(Friday night through next Thursday)
Issued at 231 PM CDT Thu Apr 22 2021

The upper level trough helping to initiate storms on Friday will
start moving out of our area Friday night. Behind it, the winds will
shift to the north which will help moderate our temperatures on
Saturday - mid 70s in the Big Country to the low 80s further south.
Sunday will see the winds turning back to the south and the heat
cranking back up. The 850 mb thermal ridge starts to set back up
over our area on Sunday and is likely to stick around through
Tuesday. Sunday through Tuesday will see high temperatures well
above average for this time of year in the upper 80s to low 90s. Dew
points will start to creep up during this period as well, pushing
into the upper 50s by Tuesday. The southerly low level flow can be
thanked for that, pulling gulf moisture back into the area. This
will help with the chance for storms on Tuesday.

Models are in good agreement about the progression of a large upper
level trough from the west coast on Monday, through the Four Corners
region, and into our area on Tuesday. In conjunction with this, lee
cyclogenesis is expected to occur in the south central rockies with
the surface low pushing eastward into the central Plains. A nice
warm sector will overspread much of Texas with ample instability.
Add to this a sharp dryline expected to mix east across our area,
along with the ascent from the upper level trough and the chance for
strong to severe thunderstorms on Tuesday is prevalent. Where the
dryline ends up will play a huge role in how much of our area sees
convective initiation. The GFS is much more progressive, pushing the
dryline nearly through our area by afternoon, which would be much
drier for us. The best chance for convection currently looks to be
in the evening and into the overnight hours but as we get closer,
details should become more clear. Definitely something to watch.

A weak cold front passes through Tuesday night, veering surface
flow back to the north. Temperatures will fall back into the upper
70s to mid 80s. Not a huge relief but more manageable for late


(00Z TAFS)
Issued at 648 PM CDT Thu Apr 22 2021

Deteriorating conditions expected this evening and overnight
as ceilings lower to IFR across the area, along with some
reduction to visibilities as patchy fog develops. Some light
drizzle may also develop across the terminals mainly after
midnight but will hold off for newer model data before adding
to the forecast. Ceilings will gradually lift/scatter out to
VFR from west to east tomorrow afternoon as a dryline advances
east across the area. Convection also possible ahead of the
dryline after 17Z, and will add vicinity thunder to KBBD and
KJCT this forecast cycle.


Abilene  56  83  52  77 /   5  30   0   0
San Angelo  57  84  52  82 /  10  20   0   0
Junction  58  84  52  84 /  10  30   0   0
Brownwood  57  80  52  78 /  10  60   0   0
Sweetwater  54  83  52  77 /   5  10   0   0
Ozona       58  83  53  82 /  10  10   0   0




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