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

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000
FXUS64 KEWX 250559
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
1259 AM CDT MON JUL 25 2016

.AVIATION.../06Z TAFS/
Similar to the last few nights, VFR conditions at the I-35 TAF
sites will transition to scattered to broken MVFR ceilings around
10Z before recovering to VFR by 14Z. Model guidance generally is
not supporting MVFR ceilings to develop, but we should have one
more morning where low clouds form before a pattern change occurs
tomorrow. Based on a persistence forecast, inserted broken MVFR
ceilings at SAT/SSF between 10-14Z while keeping the sky cover
scattered at AUS instead of broken since they have generally had a
harder time prevailing MVFR ceilings there the last few mornings.

An ongoing line of storms between CLL and UTS should continue to
dissipate over the next few hours well to the east of our area.
However, the disturbance responsible for this convection and its
associated outflows will help provide a focus for scattered
showers and thunderstorms to form tomorrow afternoon east of
Highway 281 and move to the south-southwest. Although there is
considerable uncertainty in the timing, hi-res models generally
suggest thunderstorms should at least be in the vicinity of AUS
between 21-01Z and SAT/SSF between 23-03Z. These showers and
thunderstorms are not expected to make it to DRT at this time.




&&

.PREV DISCUSSION... /ISSUED 1203 AM CDT MON JUL 25 2016/

UPDATE...
Have added slight chance POPs for Lee and eastern Fayette counties
as line of storms passing through the Huntsville area is moving to
the west at 20 MPH. Expect they will slowly weaken, however, one
or two showers or storms may make into our far eastern counties.
The boundary associated with these storms may contribute to rain
chances on Monday.

PREV DISCUSSION... /ISSUED 720 PM CDT SUN JUL 24 2016/

AVIATION.../00Z TAF CYCLE/

VFR conditions are ongoing across the terminals this evening and
this trend is expected to continue through 9-10Z overnight before
sporadic MVFR cloud decks develop once again. There are a few
SHRA/TSRA areas in the Texas coastal plains this late afternoon
but this activity will diminish through the next hour with no
impacts expected near TAF sites.

VFR will again prevail tomorrow after 14-15Z but slightly greater
TSRA/SHRA coverage is expected Monday afternoon. Will need to
monitor trends for direct inclusion of weather wording if
confidence increases for a particular site. A majority of the
TSRA/SHRA activity will remain across the coast and coastal plains
with a few isolated storms farther inland. Localized pockets of
MVFR visibility could occur with the heavier showers. KAUS may
have the best chance of seeing an isolated storm but will monitor
further. Winds will be near 5 knots overnight with only 10-15
knots expected tomorrow from the south to southeast.

PREV DISCUSSION... /ISSUED 255 PM CDT SUN JUL 24 2016/

SHORT TERM (Today through Monday)...
The heat will hang around for one more afternoon before a major
change in the weather comes late Monday. Heat index values this
afternoon are already up to 104 - 106 in spots across the I-35
corridor and the Coastal Plains. Due to increasing moisture an
isolated shower or storm is possible late this evening along the
sea breeze, but high resolution models keep that activity to a
minimum.

On Monday the ridge of high pressure weakens and pushes eastward.
This will open the door for two westward moving upper level
disturbances. Both right now can be seen on water vapor, one over
the lower Mississippi Valley, and the other over south Florida.
Models show the first disturbance kicking off a complex of storms
over Northeast Texas late tomorrow. This will move southwestward.
The combination of increased moisture, the outflow boundary from
the complex of storms, and daytime heating will lead to isolated
showers and thunderstorms late tomorrow into the evening hours.
The best chances for storms will be along and west of the US
Highway 281 Corridor. Precipitable Water values in forecast
soundings from the GFS approach 2 inches by Monday morning so
there will be the possibility of locally heavy rainfall from the
activity tomorrow afternoon. With those same soundings showing
limited CAPE and fairly weak shear the main threat from these
storms will be gusty winds in addition to the heavy rainfall.
Afternoon highs will "cool" a bit for Monday due to the increased
cloud cover. Heat Index values will still reach up to around the
105 mark.

LONG TERM (Monday Night through Saturday)...
As the lower Mississippi Valley trough moves west across the state
Monday night rain chances will continue. The south Florida trough
will approach the state late in the day on Tuesday. The
combination of the lift caused by both of these disturbances,
daytime heating, residual boundaries, and daytime heating will
lead to increased coverage of showers and thunderstorms across
South Central Texas on Tuesday. Again with PW values around 2
inches brief locally heavy rainfall will be possible. Gusty
thunderstorm winds and lightning will remain the hazards from the
stronger thunderstorms. Highs Tuesday will be at or below normal
across the area, in the lower 90s, thanks to the cloud cover and
precipitation. The NAM and ECMWF show a focus for showers and
storms across our western counties Tuesday night into Wednesday as
the low moves across the Rio Grande Plains. Wednesday will bring
another decent shot of rain as the low slowly moves west and
moisture remains across South Central Texas.

From here the long term models diverge. The GFS has weak ridging
across the area Thursday and Friday, keeping the trough across the
Midwest farther north. The ECMWF has the south Florida trough
hanging around northern Mexico which maintains the weakness in the
ridge. This allows not only for sea breeze each day, but isolated
showers and storms across most areas Thursday, and east of I-35
Friday and Saturday. As the ECMWF has been consistent with the
weakness in the ridge, and moisture should remain pooled over
South Central Texas will side with it and continue slight chances
for precipitation through Saturday before finally drying us out.

Temperatures have not been at or below normal since early June,
and this chance of precipitation is our most solid chance since
early June as well.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              99  76  94  75  94 /  40  40  60  20  40
Austin Bergstrom Intl Airport  98  75  93  74  94 /  40  40  60  30  40
New Braunfels Muni Airport     99  76  93  74  94 /  30  40  60  30  40
Burnet Muni Airport            96  74  92  73  92 /  30  40  50  20  40
Del Rio Intl Airport          101  80  96  76  96 /  10  20  50  30  30
Georgetown Muni Airport        97  75  93  74  93 /  40  40  50  20  40
Hondo Muni Airport            100  76  93  74  95 /  10  30  60  30  40
San Marcos Muni Airport        98  74  92  74  94 /  40  40  60  30  40
La Grange - Fayette Regional   97  76  93  75  94 /  40  40  60  30  50
San Antonio Intl Airport       98  77  92  75  94 /  30  40  60  30  40
Stinson Muni Airport          100  78  95  76  96 /  30  30  60  30  40

&&

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

$$

Mesoscale/Aviation...LH
Synoptic/Grids...04



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