Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Austin/San Antonio Texas
520 am CST Sat Jan 31 2015
Aviation discussion...for 12z taf package...
rain already impacting kdrt this morning will slowly spread
eastward to the i35 corridor terminals by middle day. Expecting IFR
ceilings for all terminals while rain is falling. This rainfall will
push through and clear kaus by around midnight. Moist surface
conditions will lead to fog and continued low ceilings until at least
middle morning tomorrow. Included an improvement to MVFR for the 30
hour taf sites tomorrow morning. Taf amendments will likely be
needed throughout the period as conditions waver. Expecting IFR
conditions to prevail for the majority of the taf period.
Previous discussion... /issued 318 am CST Sat Jan 31 2015/
Short term (today through sunday)...large scale ascent increasing
across Val Verde County at the time of this writing...with the
approach of the middle and upper level shortwave. Low level warm air
advection was increasing ahead of the system...with lowering
cloud deck across the western 3rd of the County Warning Area and patchy light
drizzle developing. The low level moistening will increase through
the morning from SW to NE...with dew points modifying back into
the low to middle 50 across much of the County Warning Area by afternoon.
Aforementioned larger scale forcing combined with low and middle
level moistening will result in rain developing west to east
through the morning hours...west of I-35. The rain then expands
east of I-35 during the afternoon. The main forcing from the
shortwave and precipitation will skirt through the east and northeast County Warning Area
this evening...exiting northeast after midnight. Isolated showers
can not be ruled out west of I-35 tonight with embedded weaker
disturbances in the southwest flow aloft. Isolated thunder is also
possible tonight into Sunday.
A pre-frontal trough will move into northern and western areas of
the County Warning Area midday Sunday...with the actual cold front arriving late
afternoon across The Hill Country and Austin area...and through
southern areas and San Antonio Sunday evening. Low and middle level
flow turns west with the pre-frontal trough Sunday...resulting in
drying and the better moisture pool across the east/southeast County Warning Area.
Long term (sunday night through friday)...cold front pushes
through southern areas of the County Warning Area Sunday evening. Breezy
conditions likely Sunday night...especially along and east of the
Escarpment edge. Drying in the low levels takes places Monday.
The upper level low that will cut off across Baja California California by
Sunday night is forecast to open and eject northeast across north-
central Mexico Tuesday and south Texas Wednesday. The European model (ecmwf) and
GFS have trended slightly further north with the track of
this system...with potentially better rain chances now Tuesday
into Wednesday morning across the ewx County Warning Area. Still room for
significant error this far out...especially with systems this far
south coming out of Mexico...therefore no higher than 20-40 probability of precipitation
at the moment. Another cold front is indicated by the GFS and CMC
to drop south through the area...behind the departing upper level
system...Wednesday night into Thursday. European model (ecmwf) is much weaker with
the front. Have sided towards slightly stronger GFS solution.
Preliminary point temps/pops...
Austin Camp Mabry 61 57 66 37 51 / 90 80 30 10 -
Austin Bergstrom international Airport 63 56 66 37 50 / 90 70 30 10 -
New Braunfels Muni Airport 64 57 68 39 52 / 80 70 30 10 -
Burnet Muni Airport 58 53 62 33 49 / 90 80 30 10 -
del Rio International Airport 60 52 67 41 55 / 90 30 20 10 -
Georgetown Muni Airport 59 55 63 34 49 / 90 80 40 10 -
Hondo Muni Airport 62 55 69 39 55 / 90 60 30 10 -
San Marcos Muni Airport 63 56 67 38 51 / 90 70 30 10 -
La Grange - Fayette regional 65 57 67 39 51 / 60 70 50 10 -
San Antonio International Airport 63 56 68 39 53 / 90 70 30 10 -
Stinson Muni Airport 65 56 69 41 54 / 80 70 30 10 -