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Area forecast discussion...updated 
National Weather Service Austin/San Antonio Texas
539 am CST Friday Feb 27 2015

Update...
/12z tafs/
VFR category continues across the I-35 sites for the next several
hours before ceilings lower to MVFR around 17z/18z. MVFR conditions
will remain along the I-35 terminals for much of the period. Winds
will be from the northeast at 8 to 14 knots with ocassional gusts
up to 20 knots. Across kdrt...MVFR ceilings will remain through this
evening and then become IFR after midnight tonight. East winds to
shift to the southeast in the afternoon across kdrt with speeds of
8 to 14 knots.

&&

Previous discussion... /issued 346 am CST Friday Feb 27 2015/

Short term (today through saturday)...

Main focus this period continues to revolve around low-end chances
and low-impact winter precipitation for The Hill Country through
today into early Saturday morning.

Latest radar trends over west-central Texas towards Midland and San
Angelo coupled with surface observation indicate light snow is occurring and
reaching the ground. As anticipated...isentropic upglide ascent is
increasing across the region with very light radar returns seen over
the Rio Grande Valley streaming northeast towards The Hill Country.
Based on current observations...it appears at least a 4-5f dewpoint
depression is needed for precipitation to reach the surface. However...as
indicated by previous and current forecast soundings and the likely
detractor for winter precipitation amounts remains tied to surface
dewpoint depressions...which are currently 10-15f degrees over The
Hill Country. This large spread will be difficult to overcome
initially through the middle morning hours and possibly even through
the afternoon despite the cold temperatures. Latest hrrr/rap
guidance indicates continuing 7-10f dewpoint depressions through the
morning and afternoon...likely keeping vast majority of any winter
precipitation mix from reaching the ground. Yet...if top-down
moisturization and cooling from adiabatic processes occurs just
enough then some very light sleet or snow grain mix could result.
Only 20% probability of precipitation are are being forecast now through 6pm tonight. In
addition...overall temperature guidance as risen with spots in The
Hill Country briefly rising above freezing this afternoon...even
further reducing any winter precipitation risk.

However...by tonight into Saturday morning...dewpoint depressions
drop into the 1-4f range across much of the region as isentropic
upglide continues. Over-running southwest winds will actually warm
the 850 mb-700 mb layer above freezing but surface temperatures are expected
to fall back to and slightly below freezing for The Hill Country
overnight. As a result light freezing drizzle could result and probability of precipitation
are at 30% from 6pm through 6am Saturday. Some light patchy freezing
drizzle could be possible through 8-9am Saturday but temperatures
will warm above freezing by 10am and the winter weather risk will
end. Clouds will still remain in tact for another well below normal
temperature day as readings only make into the low 40s north to near
50 far southwest towards Eagle Pass. /Allen/

Long term (saturday night through thursday)...

A much warmer large scale pattern shift will begin by late weekend
and hold through at least Tuesday where the main highlight this
period will feature a frontal passage and the possibility of
thunderstorms.

Texas will be situated between a strengthening subtropical
Bermuda/Bahama high circulation and a digging trough across
Southern California late weekend through Tuesday. The pattern will
place weak ridging and warming S to SW flow over the region allowing
for a nice return to near normal and possibly above normal
temperatures. 20-40% rain chances will still be ongoing with weak
upglide over the region and at least partly cloudy skies remaining
intact. A cold front will attempt to approach the region Monday but
looks to hang up north of the region.

Rain and thunderstorm chances increase going into Tuesday afternoon
into Wednesday morning with the passage of a Pacific originated
front. Surface cape values 1000-1500 j/kg coupled with a surface
prefrontal trough and the frontal convergence should allow for
thunderstorms to develop mainly along and east of US 281. Precipitable waters of
1.3-1.5" /90-95 percentile/ could suggest thunderstorms capable of
high rainfall rates. Will need to monitor the prefrontal trough
development and how it merges with the actual frontal convergence
later in the evening and if flash flooding from training storms
could be possible.

Unfortunately...just behind the Pacific front appears to be another
secondary Canadian originated airmass that will likely bring much
below normal temperatures to the region late next week. /Allen/

&&

Preliminary point temps/pops...
Austin Camp Mabry 42 33 47 43 66 / 20 30 30 30 40
Austin Bergstrom international Airport 42 33 48 43 68 / 20 30 30 40 40
New Braunfels Muni Airport 42 36 48 45 71 / 20 30 30 40 30
Burnet Muni Airport 36 29 42 40 64 / 20 30 30 30 30
del Rio International Airport 44 36 49 45 71 / 20 30 20 20 10
Georgetown Muni Airport 38 31 46 41 64 / 20 30 30 30 30
Hondo Muni Airport 41 35 48 45 72 / 20 30 30 30 20
San Marcos Muni Airport 42 34 48 44 69 / 20 30 30 40 30
La Grange - Fayette regional 48 38 54 49 73 / 10 20 30 40 40
San Antonio International Airport 42 37 48 45 70 / 20 30 30 40 30
Stinson Muni Airport 43 38 50 46 72 / 20 30 30 40 30

&&

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

$$

Mesoscale/aviation...17
synoptic/grids...15

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