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Area forecast discussion
National Weather Service Austin/San Antonio Texas
422 am CDT Tue Apr 25 2017

Short term (today through wednesday)...

Big story today and tomorrow will center on the well-above normal
temperatures and the windy conditions. Readings will be 8-12f
degrees above normal as a dryline shifts through the region. This
dryline/front will shift through the entire area Wednesday, bringing
windy and critical fire weather conditions.

A broad longwave trough is currently deepening across the western
Continental U.S. Per water vapor satellite channels and rap analysis. This
trough is aiding surface cyclogenesis across North Texas supporting
strong surface to 700 mb south to southwest winds. The tightening
pressure gradient in this layer is already being reflected in
elevated 15 mph surface winds this morning with kewx radar VAD wind
profile indicating near 40 to 50 knots at 2 to 3 kft above the
ground. The question will be will these winds be able to translate
down through mixing late this morning/afternoon that result in
sustained winds greater than 25 mph? While wind gusts to 30 mph will
be likely, feel the sustained winds >25 mph could be difficult. Will
hold off on a Wind Advisory for now but if higher winds start
occurring by mid-morning, it is quite possible for a short duration
Wind Advisory to be issued.

A dryline situated across The Big Bend is expected to shift east
through the day today to at least the I-35 corridor. Much drier and
warmer 925-850mb air will move in behind this boundary and allow for
a rapid surface warm up. Much of the area will be above normal with
highs in the upper 80s east to mid to upper 90s west. No records are
expected. Thankfully, a strong enough cap, weak forcing, and limited
moisture along and east of the dryline will quell any shower or
storm potential today.

By Wednesday, the dryline retreats west initially overnight and then
shifts much farther eastward through the entire region by early
afternoon as the mid and upper trough sharpens over the south-
Central Plains. Strong west winds of 20 to 30 mph will be likely
Wednesday. This wind combined with the very dry air (dewpoints in
the 20s west to 40s east) will result in critical fire weather
concerns along and west of the US Highway 281 corridor with elevated fire
conditions for the remaining areas. A red flag warning and a Wind
Advisory will need to be monitored for on Wednesday. Temperatures
will cool slightly out west but central and eastern areas will remain
hot before the slight cool down Thursday morning with the drier air
in place.

&&

Long term (thursday through monday)...

Despite the cooler morning Thursday, the heat will be back on late
week with increasing rain chances (20-40%) over the weekend as
another trough pivots across the central Continental U.S.. models are in
moderate agreement but finer scale details (see below) remain
incongruent on just how enhanced the rain/storm signals will be late
Saturday into Sunday when a stronger front is advertised to move
southward.

Thursday will start cool and finish warm with near normal readings.
However, a Big Warm-up occurs again Friday as south/southwest flow
develops in advance of a strengthening trough over the western US.
Low-level moisture is advertised to return in earnest Friday and
with temperatures expected in the upper 80s to low 90s, cape values
along with lapse rates are progged to be quite high. While shear
appears to be low, will need to watch closely for the potential of
isolated thunderstorms Friday afternoon. A weak cap appears to be in
place at this time (and this should win out) but if a storm was to
break through, it could go strong/severe quickly. Stronger forcing
and height falls will occur over north and West Texas Saturday
morning that should initiate convection and shift into the Red River
valley in NE Texas. Much of this activity looks to remain north of
the area but as the trough axis shifts across North Texas Saturday
morning, it will also shift the dryline into the region. Isolated/
scattered showers trapped under the cap may be ongoing Saturday
morning but by the afternoon, the cap could erode just enough along
and east of I-35 to aid in thunderstorm development. Areas along and
east of this environment could be favorable for isolated
strong/severe storms. The location of the troughing and dryline
indicate that rainfall will not be widespread over the region but
confined to areas just along it and east.

By Sunday, the main trough axis will shift east and bring a secondary
cold front from the north. The big question at this stage will be
where is the dryline when the front moves south? Ec has the dryline
farther west - allowing more moisture pooling ahead of the stronger
front. The GFS is farther east with the dryline and has moisture
confined to coastal plains with less rain coverage than ec depicts.
Have placed 30-40% chances for late Saturday to early Sunday
timeframe and will monitor for better agreement to refine timing and
chances. Both models do clear the stronger front south and east Sunday
afternoon with cooler and dry conditions likely early next week.

&&

Preliminary point temps/pops...
Austin Camp Mabry 88 71 90 54 86 / - 10 10 0 0
Austin Bergstrom Intl Airport 88 71 90 52 85 / - 10 10 0 0
New Braunfels Muni Airport 88 70 90 52 86 / - 10 - 0 0
Burnet Muni Airport 89 67 84 49 84 / - 10 - 0 0
del Rio Intl Airport 98 68 89 57 92 / 0 0 0 0 0
Georgetown Muni Airport 88 70 87 52 84 / - 10 10 0 0
Hondo Muni Airport 92 66 90 52 89 / 0 0 0 0 0
San Marcos Muni Airport 88 70 90 52 86 / - 10 10 0 0
La Grange - Fayette regional 86 72 90 52 86 / - 10 10 0 0
San Antonio Intl Airport 89 70 90 54 87 / 0 - - 0 0
Stinson Muni Airport 90 70 90 54 88 / 0 - - 0 0

&&

Ewx watches/warnings/advisories...
none.
&&

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