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Area forecast discussion...updated 
National Weather Service Austin/San Antonio Texas
601 PM CST Friday Dec 26 2014

Aviation.../00z taf cycle/

Afternoon stratus deck was able to mix out to VFR for all sites
which is ongoing as of 00z. However, expect a drop back to MVFR and
IFR overnight with hi-res guidance indicating MVFR stratus
developing next 2-4 hours over central taf sites and lower towards
IFR through 08-12z. Some visible reductions to 1-2sm will also be
possible for ksat/kssf 08-12z. Winds will initially be S/southeast around
5-10 knots overnight but then become north as a cold front moves
through the region. Front will arrive at kdrt 07-09z time frame and
may hinder stratus development from reaching west-central Texas.
Wind shift should arrive at kaus 10-12z and ksat/kssf 12-14z. Expect
MVFR to prevail much of Saturday and isolated light showers. Winds
will also be elevated with near 15 knots sustained winds and gusts
near 25 knots during the afternoon and early evening hours Saturday.
/Allen/

&&

Previous discussion... /issued 257 PM CST Friday Dec 26 2014/

Short term (tonight through Saturday night)...
south winds will decrease this evening and leave temperatures to
cool to saturation across many locations tonight. An upper trough
carving into northern Mexico will also provide some lift that could
result in scattered mostly light rain showers. The buoyancy and
shifting of the surface pattern should limit the formation of a
sustained dense fog pattern...so will keep the mention of dense
fog possibilities confined to the severe weather potential statement. The fog kicker will be a
cold front now expected to move through most area after daybreak
Saturday. The slower trend of the front means some southern
counties could have a nice late morning warm-up before temperatures
level off. Light showers behind the front and isolated
thunderstorms near and ahead of the front are not expected to
produce significant rains...but far east counties could see spotty
amounts over 1/2 inch. A shearing out upper trough still looms
just to the west Saturday night...so light overrunning showers
will remain possible in Sunday morning. NAM model soundings
around drt suggest the potential for a few flurries...but will
keep out of the forecast for now.

Long term (sunday through friday)...
the above mentioned upper trough axis passes over Texas during the
day Sunday with decreasing rain chances and clearing skies
enabling some sunshine and warming over western counties. Drier
air and light winds in the wake of the trough will enable cool
morning lows mostly in the 30s for Monday. After one more mild
afternoon Monday...a sustained cold and dreary pattern begins with
the next front set to arrive early Tuesday.

A high amplitude upper ridge develops over the Pacific coast of
Canada by Monday and results in a southward surge of Arctic air.
Aided by a broad snowpack already developing over the High Plains
near the central rockies...the Tuesday front should bring a thick
and dense layer of cold air and enter an overrunning pattern
aloft that is enhanced by an upper low digging over the southwestern US.
Will keep slightly cooler than model consensus on temperatures for
Tuesday into early Wednesday and fall into alignment with model
temperatures afterwards. The overrunning pattern and temperatures near or
below freezing means light winter precipitation is possible...but
low probabilities and very light amounts are expected through
Wednesday.

Model temperature trends are flat for Wednesday night...with near
freezing conditions possible for northern counties. The trends GFS
and parallel run of higher resolution output shows increasing quantitative precipitation forecast
potential for Thursday morning...which would be a concern for Jan
1 should freezing temperatures hang around. With the associated lift
being mostly isentropic...the current thinking is that the
increasing precipitation modifies the air mass to move surface temperatures above
freezing. This assumes the model track of the upper low does not
deviate much from the preferred 12z GFS ensemble mean
forecast...which is a shallower compromise between the GFS and
European model (ecmwf). Next Saturday has a chance to be fair and mild in the wake
of the passing upper low...but the high amplitude pattern
persists and suggest more colder than normal periods are on the
way for early January.

&&

Preliminary point temps/pops...
Austin Camp Mabry 56 56 38 54 36 / 20 40 20 10 10
Austin Bergstrom international Airport 57 57 38 53 31 / 20 40 20 10 10
New Braunfels Muni Airport 58 58 40 55 35 / 20 50 20 10 10
Burnet Muni Airport 50 50 35 52 34 / 20 30 20 10 10
del Rio International Airport 49 59 39 60 37 / - 10 20 - -
Georgetown Muni Airport 53 53 37 51 34 / 20 40 20 10 10
Hondo Muni Airport 54 57 37 58 33 / 10 30 20 10 10
San Marcos Muni Airport 58 58 38 53 33 / 20 50 20 10 10
La Grange - Fayette regional 61 63 41 52 35 / 30 60 30 20 10
San Antonio International Airport 56 57 40 56 37 / 20 40 20 10 10
Stinson Muni Airport 57 60 41 57 36 / 20 40 20 10 10

&&

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

$$

Mesoscale/aviation...15
synoptic/grids...12
public service/data collection...33

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