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Area forecast discussion 
National Weather Service Austin/San Antonio Texas
642 am CDT Sat may 30 2015

rain showers/isolated thunderstorms and rain currently along a boundary from kdrt to kerv to
kbmq to Kile will slowly weaken as it moves to the southeast across south
central Texas this morning. Boundaries and a cold frontal passage
will lead to rain showers/thunderstorms and rain midday into tonight. Have gone with
rain showers/thunderstorms and rain at the taf sites for 12z to 14z and tempos for thunderstorms and rain for
this afternoon into evening with vcsh otherwise. IFR/MVFR ceilings
become VFR with the passage of the boundary and will generally
remain VFR for the rest of today through Sunday morning...except
for MVFR ceilings in rain showers/thunderstorms and rain and possibly a period tonight. S to southeast
winds 5 to 10 kts will turn to north to NE with the surface boundaries
and frontal passage. Some gusts to 50 kts and gr are possible in
and near thunderstorms and rain.


Previous discussion... /issued 253 am CDT Sat may 30 2015/

Short term (today through sunday)...

The main highlight this period will focus on the currently
ongoing thunderstorm complex north/northwest of the region and its evolution
through the day today that could result in locally heavy rainfall
and flash flooding. Will bump up the timing of the Flash Flood
Watch to start at 4am this morning given current trends and
continue it through 7am Sunday.

Current radar imagery across the state of Texas reveals a southward
traveling thunderstorm complex. Radar trends indicate a gust
front/outflow boundary had developed out well ahead of the complex
as it pushes south and this will likely undercut the updrafts and
keep them in a weakened state. The question becomes how will this
outflow boundary or another possible boundary from the storms
currently in New Mexico and how they may interact with a sea-breeze
will shape today's rain and thunderstorm potential. Today's
resultant storm activity will be highly mesoscale driven with some
aid on the synoptic scale as a weak shortwave trough will be over
the region.

Overall, feel hrrr/rap have decent handle on current situation and
overall signals from Storm Prediction Center sseo suggest that southward progressing
boundary and weakening storms will enter Hill Country around 4-5am.
General band of light to moderate rain may make it to the I-35
corridor near 8-10am with southern areas remaining dry through noon.
The question will be how much momentum will this boundary have and
how much cloud cover could result. If momentum slows and sets up a
convergence boundary with the sea-breeze in an unstable environment
then the conditions will be set for localized showers and storms
with localized heavy rainfall during the afternoon. A second
scenario is that the outflow continues through much of the region
through late morning and a second boundary (from current New Mexico
storms) in combo with weak front in association with the shortwave
trough and also acts to help trigger localized heavy showers and
storms. A third scenario would be the first boundary hangs up over
the region but with slightly stronger convection initially this
morning and creates more cloud cover/stratiform rain. This would
deplete some of the available buoyant energy later this afternoon by
keeping temperatures down and keep the atmosphere slightly more stable. At
this stage...feel the first two scenarios are more likely and have a
concern for localized heavy rainfall of 1-2 inches with localized 3
inches over already saturated ground. These conditions could lead to
rapid run-off and localized flash flooding. Will maintain the Flood
Watch as is area wise given precipitable waters 1.6" and the numerous triggers
possible. Overall heavy rain threat will diminish through Sunday

For Sunday...lingering showers and some isolated thunderstorms will
remain possible as the base of the trough pivots across the region.
While rain will be possible...heavy rain does not appear likely at
this point.

Long term (sunday night through friday)...

A much needed break from the active wet pattern finally looks to
develop in the long term period with no major impact weather

By models are in agreement that the trough from
Sunday will linger and possibly close off in the northern Gulf or
lower Mississippi River valley. Shortwave ridging and deeper middle to
upper level northerly flow Monday through Wednesday should keep most
of the area dry. The only small caveat would be limited moisture
return in the low-levels from southeast surface winds. There may be some sea-
breeze activity that could make into far southeast coastal prairie zones but
coverage is not expected to be high. Global models diverge middle-week
on strength of the ridge over Texas with GFS being weaker with
impulses riding the north edge across the Panhandle while European model (ecmwf) is
much stronger with little evidence of disturbances. Will have to
monitor how this evolves and watch for any northwest flow tstorm complex
developing on the dryline in far west/northwest Texas and possibly shifting
this direction. Confidence in this possibility is not high at this
point however. GFS ensembles support the European model (ecmwf) and it appears a weak
to moderate Omega block could take form middle to late week with Texas
under the drier ridge. This will allow for swollen and elevated
river levels to recede. Temperatures should be near normal with
readings in the upper 80s/low 90s and lows in the upper 60s/near 70.


Preliminary point temps/pops...
Austin Camp Mabry 86 67 81 65 85 / 70 50 30 10 10
Austin Bergstrom international Airport 85 66 81 62 85 / 70 60 30 10 10
New Braunfels Muni Airport 86 67 82 65 86 / 70 60 30 10 10
Burnet Muni Airport 82 65 79 63 84 / 70 50 20 10 10
del Rio International Airport 86 67 85 68 89 / 60 40 30 10 10
Georgetown Muni Airport 83 65 80 62 84 / 70 50 20 10 10
Hondo Muni Airport 86 67 83 66 86 / 70 50 30 10 10
San Marcos Muni Airport 85 66 81 64 84 / 70 60 30 10 10
La Grange - Fayette regional 86 68 81 65 85 / 70 60 30 10 20
San Antonio International Airport 86 68 83 67 86 / 70 50 30 10 10
Stinson Muni Airport 86 69 83 67 86 / 70 50 30 10 10


Ewx watches/warnings/advisories...
Flash Flood Watch through Sunday morning for the following
Caldwell...Comal...De Witt...Dimmit...Edwards...Fayette...frio...
Uvalde...Val Verde...Williamson...Wilson...Zavala.




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