Area Forecast Discussion
Issued by NWS Austin/San Antonio, TX
FXUS64 KEWX 262358 AAA
Area Forecast Discussion...UPDATED
National Weather Service Austin/San Antonio TX
658 PM CDT Sun Mar 26 2017
VFR conditions will prevail across area terminals through late
evening. Clouds will develop along the Coastal Plains and then move
toward the north this evening and over the I-35 sites by midnight
tonight. MVFR cigs are anticipated by 05Z with IFR cigs starting
around 08Z/09Z across Austin and San Antonio airports. There are
indications from several HiRes models and guidance for cigs to go
down as low as LIFR for Austin around the 12Z time frame and have
included this as such for KAUS. MVFR are forecast to linger around
through 16Z for the I-35 terminals with VFR returning by 17Z and
staying that way through Monday evening. Southeasterly winds will
prevail through the forecast period with 5 to 15 knots overnight into
Monday morning and decreasing 5 to 10 knots Monday afternoon.
KDRT should remain VFR through late tonight with MVFR expected by
11Z. There is a chance for cigs to lower to LIFR for an hour or two
just like this morning and have added it to this forecast cycle.
Good mixing takes place out west along the Rio Grande by late morning with
VFR returning by 16Z Monday.
.PREV DISCUSSION... /ISSUED 319 PM CDT Sun Mar 26 2017/
SHORT TERM (Tonight through Monday Night)...
Severe weather risk this afternoon remains non-zero but is still
extremely marginal. Currently, satellite imagery is showing some
bubbling cu from Mason County to Fayette County. Latest LAPS
soundings show a weak cap struggling to hold on this afternoon and
RAP forecast soundings keep it holding on through out the afternoon.
Also of note is the presence of about 20-50 J/KG of CIN working
against heated parcels at the surface. If a surface boundary of some
kind were present, concerns would be much higher for the chance for
CI this afternoon, but with surface dewpoints in the 50s west of I-35
and lack of lifting mechanism present east, think its very unlikely
parcels will be able to tap into the ripe conditions aloft. SPC
mesoanalysis shows LFC heights over 4000m thus surface parcels will
need to overcome inhibition, weak surface moisture, and without any
help to lift it to get to that height. Thus, confidence is extremely
low for the chance for storms.
Should one occur though, effective bulk shear, lots of instability,
and strong mid level lapse rates all mean the possibility for strong
to severe storms with large hail and damaging winds.
LONG TERM (Tuesday through Sunday)...
The focus for the short term will be the prospect of severe weather
with our next upper low Tuesday and Wednesday. SPC has already
outlined marginal to slight risk for large hail, damaging winds, and
tornadoes Tuesday and a day 4 area outlined for the Austin area and
northeast Wednesday. Our best timing for severe potential will likely
be late Tuesday night, and maybe as late as early Wednesday morning
(after midnight) as we inherit a mature system that develops near
Abilene. Latest ECMWF shows convection initiating along the dry line
near the Childress area and unzipping southward to Del Rio by
midnight Tuesday night. Overnight, these cells become more
dynamically driven and likely coalesce into a linear system that
pushes across the CWA from the west and impacts the I-35 corridor by
12Z Wednesday morning. While PWAT values over 1.5" have been
advertised thus far, both GFS and ECMWF quickly exit the system after
18Z Wednesday and should limit flash flooding potential. Should this
system indeed become a linear system as advertised, the principle
threat should be damaging straight line winds and hail.
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 67 88 67 84 67 / 10 10 - 20 40
Austin Bergstrom Intl Airport 66 88 67 84 67 / 10 10 - 20 40
New Braunfels Muni Airport 66 88 67 84 67 / - 10 - 20 40
Burnet Muni Airport 63 85 63 80 64 / 10 - - 30 70
Del Rio Intl Airport 60 92 66 87 62 / - 0 - 30 50
Georgetown Muni Airport 66 87 65 81 65 / 10 - - 30 50
Hondo Muni Airport 65 92 66 85 66 / - - - 30 40
San Marcos Muni Airport 66 89 66 84 68 / 10 10 - 20 40
La Grange - Fayette Regional 68 87 67 84 69 / 10 10 - 10 30
San Antonio Intl Airport 67 89 68 84 68 / - - - 30 40
Stinson Muni Airport 67 89 67 84 68 / - - - 20 40
Public Service/Data Collection...Williams