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

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792
FXUS64 KEWX 211054
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
454 AM CST Wed Feb 21 2018

.SHORT TERM (Today through Thursday)...
As of 430AM, temperatures were dropping dramatically across the
northernmost areas of the CWA, with upper 30s in northern Burnet and
Llano counties. The CAA associated with this front has been very
poorly handled in the models, with only the short term models coming
close to reality. This has made forecasting the hourly Ts a challenge
as the cold front progresses, as well as pinpointing the Max Ts for
today.

Thus far, the majority of the precip has moved off much faster than
originally thought as well, with the bulk of the heavier rains now in
the eastern portions of HGXs area and showers being undercut by the
cold front to the north diminishing quickly. Some additional
development has occurred back out west towards Del Rio and according
to the latest suite of hi-res models, this will be the last round of
possible heavy rains through the rest of the day actually. Trended
down considerably on PoPs with this forecast beyond 18Z as the NAM
projects this development out west to push eastward across the CWA
rather quickly. But would not be surprised if PoPs need to be
tempered down even further by later this morning.

Due to the aforementioned challenges with temps due to the strength
of the cold front, leaned heavily towards the direction of the NAM
for lows overnight tonight, which were 5-7 degrees cooler than
previously forecast. As another weak impulse comes across the Rio
Grande and eventually the Hill Country overnight and temperatures
continue to fall to near freezing, a slight possibility for light
freezing rain may occur across northern Edwards, Kerr, Gillespie, and
much of Llano and Burnet counties. Do not believe there will be much
in the way of impacts however as temperatures will struggle to fall
much below freezing due to extensive cloud cover, but some exposed
surface may have a sheen of light ice where precip does indeed occur
overnight.

Models do little to add confidence to the temperature forecast for
Thursday, as guidance differs considerably. MAV projections for KAUS
are in the upper 50s for highs Thursday while MET shows mid 40s.
Trended more towards the cooler NAM as this has been a much better
performer for this shallow cold front situations. Beyond that, precip
will be mostly due to overrunning Thursday, as a 30 kt LLJ is draped
across the region, resulting in another cloudy, off and on light
showery, and chilly day with rather high PoPs but low QPF.

&&

.LONG TERM (Thursday Night through Tuesday)...
Winds will shift back to the south and southeast Friday morning as a
warm front retrogrades back north. The continued southwest flow
regime will continue to bring weak impulses across the region while a
stubborn LLJ continues to bring in low level moisture from the south.
The next front looks to be Saturday as the GFS brings this feature in
from the northwest Saturday morning and through the CWA by Saturday
night. This should clear out PoP chances for the overnight period
Saturday.

Another shortwave passage progged for Sunday night may result in some
low end PoPs for the eastern CWA (east of I-35) overnight Sunday and
Monday and yet another shortwave trough is advertised for Wednesday
morning, which even presents a negative tilt as it approaches the
northern tier of Texas. Thus, many periods in the extended include
PoPs and thunder chances through the next 7 days.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              54  36  50  46  69 /  90  30  70  60  60
Austin Bergstrom Intl Airport  55  38  51  46  70 /  90  30  70  60  60
New Braunfels Muni Airport     57  37  53  48  71 /  80  40  60  50  50
Burnet Muni Airport            43  32  46  42  65 /  90  30  70  60  60
Del Rio Intl Airport           59  40  58  51  70 /  60  30  40  40  40
Georgetown Muni Airport        48  32  48  44  66 /  90  30  70  60  60
Hondo Muni Airport             63  40  55  50  70 /  80  30  60  50  50
San Marcos Muni Airport        57  37  52  47  71 /  80  40  70  60  50
La Grange - Fayette Regional   60  40  55  50  74 /  80  50  60  50  50
San Antonio Intl Airport       61  39  53  49  70 /  80  30  60  50  50
Stinson Muni Airport           62  41  55  50  72 /  80  40  60  40  50

&&

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

$$

Mesoscale/Aviation...04
Synoptic/Grids...TB3



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