Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus64 kewx 201752 
afdewx

Area forecast discussion
National Weather Service Austin/San Antonio Texas
1152 am CST Mon Nov 20 2017

Aviation.../18z_tafs/
VFR conditions will continue today with southerly winds around 10
knots falling below 5 knots later tonight. Model guidance continues
to trend away from MVFR ceilings or patchy fog developing around
sunrise at the I-35 sites as flow will be too weak and most likely
too southwesterly to allow for enough Gulf moisture to return to the
region. Nevertheless, we have included a sct015 or sct020 deck at the
I-35 sites between 13-16z just in case onshore flow and moisture
return is greater than forecast. Winds will veer to the west with a
pre-frontal trough tomorrow afternoon ahead of a frontal passage
that will bring northerly winds late tomorrow afternoon or evening.



&&

Previous discussion... /issued 524 am CST Mon Nov 20 2017/

Aviation... /12z tafs/

A few cigs at around 17 kft are drifting quickly across Sat/ssf early
this morning; skies will remain VFR with almost cloud-free skies
later today. Some cirrus could return from the northwest later
tonight. Some models showing moisture return from south winds
tonight, but prefer the drier VFR sky forecasts given the fairly
light wind flow and broad area of dry low level air that still
extends into the northern Gulf. A few midday south breezes could
reach 12 knots around drt, but most winds should remain below 10
knots through tonight.

Previous discussion... /issued 335 am CST Mon Nov 20 2017/

Short term (today through tuesday)...
mostly clear skies with patches of high clouds continue to be in
place across south-central Texas at the present time. Temperatures
range from the middle 30s in The Hill Country to the lower 40s in the
southern counties. Dewpoints are only a few degrees off current
values and therefore do not anticipate temperatures dropping off too
much more from current values, especially across the western counties
where high clouds are thickest. The light and variable winds
currently in place will become southerly once again by this
afternoon, but weak flow will ensure warm-air advection stays minimal
this afternoon. Therefore, high temperatures today will still only
top out in the middle 60s to near 70 degree range.

With the continued rise in dewpoint values with the southerly flow,
lows tonight will be about 10 degrees warmer than current values.
With the increase in moisture and warmer temperatures, low-level
thermodynamic profiles within some forecast soundings show the
potential of patchy fog for the eastern half of the area and will
introduce the mention of patchy fog near daybreak Tuesday. Partly
cloudy skies with temperatures topping out in the middle to upper 70s
can be expected on Tuesday. A trough axis will be passing through
the Central Plains during the day Tuesday and this system will send a
cold front into the Southern Plains during the day. This front will
approach the County Warning Area late Tuesday afternoon and will have little to no
effect on the expected high temperatures.

Long term (tuesday night through sunday)...
the expected cold front will push through the County Warning Area by midnight and
cooler weather will once again be ushering into the region. At the
same time, the base of the trough axis will be passing through Texas
and will provide enhanced upper level synoptic lift over the region.
The limiting factor for precip production will be the inadequate
moisture in place for precipitation production. The main reason for
this is the progressive pattern in place which limits moisture return
within the brief periods of southerly flow. Latest model guidance
does show some moistening in the mid-levels Tuesday night that may be
sufficient enough to squeeze out some isolated showers across the
eastern counties. Will place a small area of 20 pops to cover this
low probability rainfall forecast. However, any rain that does fall
is not expected to amount to much. Highs Wednesday behind the front
will be back into 60s areawide, similar to the current conditions of
yesterday and today. Low temperatures on Thanksgiving morning will be
cold with temperatures back in the upper 30s to lower 40s across
much of the area. Southerly flow is expected to return by the morning
hours and highs on Thanksgiving should respond an be back into the
lower 70s.

Friday and Friday night are expected to be quiet with northwest flow
aloft in place with southerly flow continuing at the surface. Highs
Friday and Saturday will continue the warming trend with highs in
the middle to upper 70s. Models to continue to show a weak and brief
front moving into the region Saturday evening before lifting back to
the north. This front will have little effect on our weather despite
the north winds. Highs Sunday will top out in the lower to middle
70s.



&&

Preliminary point temps/pops...
Austin Camp Mabry 67 52 77 50 65 / 0 - 0 10 0
Austin Bergstrom Intl Airport 68 49 77 51 65 / 0 - 0 10 0
New Braunfels Muni Airport 68 49 78 51 66 / 0 - 0 10 0
Burnet Muni Airport 65 48 73 45 62 / 0 - 0 10 0
del Rio Intl Airport 68 45 79 48 67 / 0 0 0 0 0
Georgetown Muni Airport 66 49 75 48 63 / 0 - 0 10 0
Hondo Muni Airport 69 46 80 48 69 / 0 0 0 0 0
San Marcos Muni Airport 67 49 77 51 66 / 0 - 0 10 0
La Grange - Fayette regional 67 51 77 53 65 / 0 - - 20 -
San Antonio Intl Airport 70 51 78 51 67 / 0 - 0 - 0
Stinson Muni Airport 70 49 79 52 68 / 0 - 0 - 0

&&

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

National Weather Service Glossary of Abbreviations