Area Forecast Discussion
Issued by NWS Austin/San Antonio, TX

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FXUS64 KEWX 201146
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
546 AM CST Tue Feb 20 2018

.AVIATION... /12Z TAFS/
A few weak embedded thunderstorm cells formed briefly SW of SAT prior
to TAF issuance which prompted a tempo group for the late morning.
The heavier cells are in line to move across the I-35 terminals over
the next few hours, and would otherwise leave the prevailing shra
without thunder. Rapid refresh models continue to be agressive with
stronger convection developing this morning, but mainly over the
higher terrain. Thus will not expect to see a lot of convective
action in the afternoon as areas of lift already seem to be in line
to shift north of the area by then. A few pockets of ifr cigs could
form among these areas of convection, but gusty overnight winds have
kept cigs higher than projections thus far. Will expect to see some
improvement in the mid afternoon with some late afternoon/early
evening vfr cigs followed by lowering cigs during the evening. Best
thunderstorm chances look to be along I-35 just ahead of the
approaching frontal boundary that should pass through AUS just prior
to 12Z.

&&

.PREV DISCUSSION... /ISSUED 415 AM CST Tue Feb 20 2018/

SHORT TERM (Today through Wednesday)...
An upper level trough will remain over the Southwestern States. One
impulse generated a couple of strong storms across parts of Val Verde
into Edwards Counties just before midnight, then exited our area.
Another impulse is approaching with showers increasing in coverage.
This trend will continue as the impulse moves across our area with
some instability allowing for isolated thunderstorms. The greatest
coverage of rains for today will be across the eastern Hill Country
to along the I-35 corridor. Some locally heavy downpours are possible
and may cause ponding of water in low lying areas and some flowing
water in small streams. A stronger impulse approaches overnight while
a cold front begins to move into our Central Texas counties. Showers
and thunderstorms will blossom overnight into Wednesday morning due
to the lower level focusing of the front, right entrance region of
the upper level jet, and moderate low level jet into and over the
front. The main threat will be locally heavy rains due to PWS up to
1.7 inches and possibly training of storms. Some flash flooding is
possible due to 1 to 2 inches of rain with isolated amounts over 4
inches. However, for now, widespread flash flooding is not expected
as soils remain fairly dry and models are not in complete agreement
on the locations of the heaviest rains. As a result, will hold off on
any watches. Should heavier rains be more widespread than forecast
today, soils may become more susceptible for runoff on Wednesday.
With instability becoming more elevated with time late tonight into
Wednesday as the front moves across our area, mainly isolated strong
storms with small hail are possible. Another day with well above
normal temperatures is expected today with steady or falling
temperatures most areas on Wednesday. Should the NAM and some Hi-res
models verify, then temperatures will be colder on Wednesday.

LONG TERM (Wednesday Night through Monday)...
The front will have exited our area by Wednesday evening and then
slows down as moves through southern Texas and the coastal areas
where it will eventually stall by Thursday and then lift back north
Thursday night into Friday. A series of weak impulses will keep
periods of showers and isolated thunderstorms going. Another upper
level trough moving toward the west coast forces the southwestern
states trough to move across the Southern Plains dragging another
cold front across our area on Saturday. This ends rains chances for
our western areas Sunday into Monday, while impulses ahead of the
next trough maintain rain chances for eastern areas. The roller
coaster of temperatures continues in the long term.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              73  53  57  43  59 /  80 100 100  50  50
Austin Bergstrom Intl Airport  73  54  58  44  61 /  80 100 100  50  50
New Braunfels Muni Airport     74  58  62  45  63 /  80 100 100  50  50
Burnet Muni Airport            74  47  52  39  57 /  90  90  90  50  60
Del Rio Intl Airport           81  63  69  46  63 /  20  50  50  40  50
Georgetown Muni Airport        73  49  54  41  56 /  90 100 100  50  50
Hondo Muni Airport             81  64  69  46  65 /  60  70  90  40  60
San Marcos Muni Airport        74  57  61  45  62 /  80 100 100  50  50
La Grange - Fayette Regional   76  60  65  47  67 /  70  80  90  70  60
San Antonio Intl Airport       76  61  65  46  64 /  80 100 100  40  50
Stinson Muni Airport           77  64  69  48  65 /  70 100 100  40  60

&&

.EWX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

Mesoscale/Aviation...Oaks
Synoptic/Grids...04



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