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

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FXUS64 KEWX 220553

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
1253 AM CDT Sat Apr 22 2017

Recent Hi-res models are trending toward a slower fropa in the San
Antonio area but continue to suggest frontal wind shifts at AUS/DRT
at around 11Z. Some light shower activity is suggested at AUS but
impacts should be minimal. Ahead of the front, will expect a low
mvfr cig in the next hour or two along I-35 then lowering to ifr a
few hours later. Most of the ifr cigs should be near and behind the
front, but by late morning stronger wind mixing should lift the cigs
back to mvfr and hover there for several hours of the day. vfr skies
should develop by late afternoon as the northerly gusts to around 25
knots begin to lay down.


.PREV DISCUSSION... /ISSUED 929 PM CDT Fri Apr 21 2017/

The anticipated cold front to push across the area later tonight is
on track and expected to reach the Hill Country between 2 and 3 am.

As of this writing (and based on latest surface observations), the
frontal boundary extends from Midland to San Angelo to Forth Worth
area. Latest HRRR and Texas Tech HiRes models are in good agreement
on timing and precipitation coverage as the front continues to push
to the southeast overnight into Saturday.

Previous forecast package has a good handle on the timing and
progression of the front as it moves and pushes away from the area
Saturday afternoon. Therefore, no changes made to the short-term
forecast on this update. Once the front moves away, expect clearing
from northwest to southeast areas and a cool down is expected
Saturday evening as a cool airmass spreads across the area in the
wake of the front.

PREV DISCUSSION... /ISSUED 656 PM CDT Fri Apr 21 2017/

Please see the 00Z aviation forecast discussion below.

VFR conditions are in place at area TAF sites and this will continue
through the remainder of the evening. Low cloud should first develop
along the I-35 corridor around 06Z (around 11Z at DRT), with bases
initially low end MVFR. Cigs should lower into IFR between 10-12Z
along I-35, with DRT still low end MVFR. We could also see some fog
develop at the I-35 terminals, but suspect cigs will be the main
concern. As the front moves through early tomorrow morning, northerly
winds will increase and become gusty around 18Z. We could also see a
shower or two develop along the front, but with chances low, we will
not mention in the forecast at this time. Afternoon wind gusts could
approach 25 kt between 18-00Z tomorrow. We should see enough drying
in the low-levels to allow cigs to rise and clouds to gradually thin
late tomorrow afternoon or early in the evening. For now, will show
improvement to VFR at AUS around 21Z, with remaining terminals still
likely still in the upper end of MVFR.

PREV DISCUSSION... /ISSUED 243 PM CDT Fri Apr 21 2017/

SHORT TERM (Tonight through Saturday)...

Only weather focus remains centered on the frontal passage expected
overnight/early Saturday morning that will bring gusty north winds of
20-25 mph but with only a thin line of showers that will not amount
to much rainfall accumulation. Much cooler temperatures are expected
Saturday afternoon and through the initial part of next week.

A strong shortwave trough is shifting across the south-central
Plains this afternoon and supporting a large storm system across
Oklahoma and north Texas. This storm activity will remain well north
of the region with no activity expected across south-central Texas
due to lack of forcing and a very strong capping inversion in place.
Given the surface low development across north Texas in response to
this system, gusty south to southwest winds are ongoing this
afternoon. Gusts could reach as high as 20 to 25 mph at times but
should subside through the evening hours as vertical mixing
decreases and effective boundary layer contracts.

Weather conditions will continue to be mild and pleasant through the
evening hours tonight as the front is not expected to enter the Hill
Country and northern I-35 corridor until 3am or so. As mentioned
earlier, forcing will remain north of the region, and with weak
lapse rates with little instability with continued weak capping
still in place with the frontal passage, only am expected a thin
light of light showers to come through south-central Texas. Attempted
to time it in weather and rain chance wise in 3 hour blocks through
the overnight hours. Front should be through Austin and San Antonio
through 9am Saturday morning, if not earlier. Strong north winds of
20-25 mph will be likely following frontal passage. Winds will
slowly decrease through the afternoon hours with slowly clearing
skies from north to south by late in the day. However, a good portion
of Saturday appears cloudy per model soundings. If thicker clouds
remain in place, high temperatures may struggle to reach into the low
to mid 70s.

LONG TERM (Sunday through Friday)...

Well-below normal temperatures are expected Sunday and Monday morning
with readings in some locations approaching record lows within a few
degrees. Warming will return however by mid- and late-week with
south to southwest flow returning. While most of the next 7 days will
be dry, rain chances look to increase late next week.

Skies are expected to clear with weak winds Sunday and Monday as
surface high pressure develops over the southern plains. This will
allow for some of the coolest temperatures in the past several months
to occur. With dewpoints in the mid 30s and radiant cooling
conditions nearly optimized, low temperatures are expected to fall
into the low to mid 40s in the Hill Country and the upper 40s to near
50 elsewhere. Low temperatures were lowered 2-3F degrees from
guidance given the pattern set-up and the likely over achieving of
cooling a greater possibility. Despite the cold mornings, a nice
warm up each afternoon is expected given the dryness of the air.
Moisture will begin to return Wednesday with warmer lows and higher
highs. Early indications are that pattern will flip back to an above
normal temperature regime mid- to late-week as south to southwest
flow in the mid and upper levels occurs.

Mostly dry conditions are expected through at least Wednesday of next
week with the dry air in place. A stronger trough is being
advertised in both the GFS and ECMWF for late next week across the
four corners region that then ejects into the southern plains. Have
introduced low rain chances at this point (20%) given the potential
mid-level support and moisture in place but much of the stronger
activity (at this point) looks to remain north of the region.


Austin Camp Mabry              50  75  49  80  60 /   0   0   0   0   0
Austin Bergstrom Intl Airport  48  73  47  79  59 /   0   0   0   0   0
New Braunfels Muni Airport     49  75  46  79  58 /   0   0   0   0   0
Burnet Muni Airport            46  72  46  78  60 /   0   0   0   0   0
Del Rio Intl Airport           52  78  54  84  62 /   0   0   0  10   0
Georgetown Muni Airport        48  72  47  79  60 /   0   0   0   0   0
Hondo Muni Airport             50  78  48  81  59 /   0   0   0   0   0
San Marcos Muni Airport        49  75  46  79  58 /   0   0   0   0   0
La Grange - Fayette Regional   50  72  48  79  59 /   0   0   0   0   0
San Antonio Intl Airport       52  75  49  80  60 /   0   0   0   0   0
Stinson Muni Airport           52  75  49  81  59 /   0   0   0   0   0




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