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

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FXUS64 KEWX 072337

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
637 PM CDT Fri May 7 2021

Not much change in the 00z TAFs from the 18z TAF forecast. The main
chance is to rise the expected IFR cigs at SAT/SSF to low end MVFR
for Saturday morning. The forecast is now for cigs to build into the
I-35 corridor and drop to MVFR between 06z and 08z and remain MVFR
until 16z to 17z on Saturday morning. While winds overnight will
generally decrease to 10-12 knots, by sunrise gusty southerly winds
will be resuming preventing any fog development. As VFR cigs return
for Saturday afternoon gusty winds will continue through the rest of
the TAF period. At DRT the expected window for MVFR is shorter,
between 12z and 16z. Winds at DRT will be slightly more southeasterly
compared to the almost due south winds along the I-35 corridor.


.PREV DISCUSSION... /ISSUED 320 PM CDT Fri May 7 2021/

SHORT TERM (Tonight through Saturday Night)...
A small amount of low level moisture returned this morning only to
see surface dew points quickly mix out with the drier air above the
boundary layer this afternoon. The moisture will return quickly for
this evening, and low cloudiness areas should pick up by around
midnight tonight. The upper ridge over TX will deflate quickly
tonight as a progressive subtropical pattern returns with a broad
upper trough that is part of a broader upper low digging into the Nrn
Rockies. This will increase surface winds and gusts, so little or no
fog is expected from the moisture return. A few pockets of drizzle or
light streamer showers may develop over parts of the Coastal Prairies
toward daybreak Saturday. More warm, breezy and humid conditions are
expected Saturday night.

LONG TERM (Sunday through Friday)...
The relatively low amplitude wave moving through the SWrn CONUS into
TX will push a dry-line east into Central TX while a weakening cold
front stalls over Central TX just north of the CWA late Sunday. There
is a chance that no precipitation makes it this far south but if an
outflow boundary reaches the area, the SPC has us in a Marginal Risk
area. Even the more bullish NAN model with regard to the front keeps
the stronger convection to the NE, so we`ll downplay the severe
threats that might threaten our CWA borders over the weekend. By
Monday, moisture really ramps up over the area and there could be a
tropical connection with a weak but developing tropical Pacific
disturbance. Pwat values approach 2 inches by 00Z Tuesday, leading to
a breakable cap across the CWA but probably mostly likely over the
weak frontal zone along our northern CWA border and over the Burro
Mountains in Mexico.

This destabilization out west may end up drawing the front south
across half the area Monday evening with a complex taking shape to
cover 2/3rds of the area Monday evening. Again a few severe storms
could be possible, but will leave the specifics vague for another
forecast package due to frontal location uncertainties. Certainly
there could be a region for locally heavy downpours up to 3 inches,
but will not speculate on where at this time. The front is by midday
Tuesday, forecast by the deterministic consensus to be stuck over
the area to bring a likely PoP category for Tuesday evening into
early Wednesday morning. By this time, a heavy rain event should have
happened, but the destabilizing trends for Monday may shade the
potential for the heaviest rains forward in time, should the front
maintain enough momentum from outflows to continue south.

By early Saturday morning, with the arrival of some more finer res
and regional models, we might be able to pinpoint timing and threat
regions for the period Monday evening through early Wednesday morning
for better messaging. Most models depict some weak stability behind
the front, so the forecast for late Wednesday into Thursday could
become more dry in terms of rain chances. The more confident aspect
of the extended forecast is that there is enough meridional flow in
the mid levels to keep a continental NE low level wind over the area
into Thursday which should bring another welcome period of mild
weather throughout the extended forecast, and slightly cooler than
usual for mid-May.


Austin Camp Mabry              87  65  88  71  91 /   0   0  10  -   20
Austin Bergstrom Intl Airport  86  63  88  71  91 /   0   0  20  -   20
New Braunfels Muni Airport     88  66  90  72  93 /   0  -   10  -   10
Burnet Muni Airport            85  64  87  69  88 /   0   0  10  10  20
Del Rio Intl Airport           92  69  95  72 101 /   0  -   20  -    0
Georgetown Muni Airport        86  64  88  70  90 /   0   0  10  10  20
Hondo Muni Airport             89  65  92  69  96 /   0  -   10  -   -
San Marcos Muni Airport        87  64  89  71  91 /   0  -   20  -   10
La Grange - Fayette Regional   88  65  87  73  88 /   0   0  20  -   20
San Antonio Intl Airport       87  66  89  71  93 /   0  -   10  -   10
Stinson Muni Airport           89  67  92  72  95 /   0  -   10  -   -




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