Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Austin/San Antonio Texas
925 am CDT Monday may 25 2015
Update...coordinated with Storm Prediction Center on Tornado Watch until 4 PM. Storms
will continue to develop and increase in coverage as they move
east through The Hill Country into the I-35 corridor. Ongoing
supercell tracking through Edwards County has produced large hail
reports all they way back through Val Verde County...and
significant wind damage reported back into Mexico where it began.
Discrete storm cells with large hail and isolated tornado
potential will be a threat with storms through at least The Hill
Country and I-35 corridor.
In addition...Flash Flood Watch remains in effect through late
tonight. 1-3 inches possible with isolated amounts up to 5 inches.
Any additional heavy rainfall will result in dangerous flash
flooding...with stream flows through The Hill Country still
elevated and grounds east saturated.
Previous discussion... /issued 628 am CDT Monday may 25 2015/
Aviation discussion...for 12z taf package...
severe thunderstorm in vicinity of kdrt at taf issuance. This
storm should be clear of the terminal by 12z so only included thunderstorms in the vicinity
in the taf. No development seen yet behind it. Otherwise...not
much change to the tafs from the 06z issuance...timing still looks
good for thunderstorms and rain at i35 corridor terminals. Expect activity to be
clear of the terminals by around 00z. Isolated storms may clutter
approach and departure routes from middle morning through the
Previous discussion... /issued 340 am CDT Monday may 25 2015/
Short term (today through tuesday)...
the atmosphere is getting ready for another round of showers and
thunderstorms for this morning and afternoon...some of which could
have heavy rain and be severe. Currently on water vapor imagery
and per 00z upper air analysis a compact but strong shortwave
trough can be seen beginning to move into West Texas. Looking at
water vapor shows US that there are two areas where upper lift
will be maximized with the first being over West Texas is closer
proximity to the low. The second area of enhanced lift is farther
south...just west of our western counties. Per latest radar
imagery...we are already seeing convective development about 40
miles west of del Rio. Morning high-res model guidance shows these
two areas of lift quite well and keep an axis of the most activity
following a west-southwest to east-northeast track from the respective origins. This
would bring high coverages of showers and storms to north of our
County Warning Area from the northern piece and a good swath of showers and storms
across our County Warning Area later this morning and afternoon. The timing of
this is a bit faster than previous thought with the main activity
to the I-35 corridor around 18z. For the morning hours...think the
activity will follow the expected motion quite well...but by the
afternoon...convective outflow boundaries could lead to more
chaotic development and storm motions...and coverage of activity
is expected to increase across the eastern counties. With this
expected scenario...the best coverage would be across the Edwards
Plateau and Hill Country through the late morning hours...before
encompassing much of the area this afternoon.
Current GOES precipitable water analysis shows the atmosphere is slightly drier
than the last rainfall event and this will help keep rain totals
down. However...given the expected coverage of convection...1-4
inches of rain will be possible with isolated higher amounts.
These amounts will not occur for everyone...but the potential is
there. It will not take a lot of rainfall to cause additional
flooding so everyone needs to be weather aware today. Given the
convection already ongoing west of the Rio Grande...went ahead and
included the rest of the County Warning Area in the Flash Flood Watch and moved up
the start time to 11z or 6am.
The atmosphere will be extremely unstable today and with plenty
of shear...severe storms are likely. The main threats will be
large hail initially...but damaging winds can also be expected.
The kdfx VAD wind profile and Storm Prediction Center mesoanalysis indicate plenty of
low-level shear with turning for isolated tornadoes as well. The
threat for tornadoes will continue east through the afternoon
hours. In addition to the flooding threat we will have a decent
severe threat and Storm Prediction Center has placed much of the County Warning Area in an enhanced
risk with the rest of the area in slight. With the activity
currently just west of the Rio Grande...some sort of convective
watch may be needed later this morning. Again...be weather aware
on the Holiday with multiple ways to get weather information.
Storms are expected to be east of the County Warning Area by the late evening and
will keep small chances of rain in the forecast for the overnight
period. There will be a small chance of diurnally driven
convection Tuesday afternoon...but most of the forecast area
should remain dry.
Long term (tuesday night through sunday)...
shortwave ridging is expected on Wednesday...keeping much of the
area dry. Wednesday will be one of the warmest days so far this
Spring with highs reaching the upper 80s and 90s for much of the
area. By Thursday....the ridging is expected to break down and
move east and we should cool a couple of degrees for highs. As the
high shifts east...another upper trough is expected to be moving
east across the western Continental U.S.. as this system nears the
area...rain chances will be on the increase once again beginning
Thursday. Models are keeping this low around the area through the
weekend...so another wet period is possible although it is too
early to tell how much rain will fall or exactly where.
Preliminary point temps/pops...
Austin Camp Mabry 81 68 88 73 89 / 80 30 20 20 20
Austin Bergstrom international Airport 81 67 87 72 88 / 80 40 20 20 20
New Braunfels Muni Airport 82 69 87 73 89 / 70 40 20 20 20
Burnet Muni Airport 80 66 87 71 87 / 80 30 20 20 20
del Rio International Airport 90 70 91 74 90 / 60 10 - 20 20
Georgetown Muni Airport 80 68 87 72 88 / 80 30 20 20 20
Hondo Muni Airport 84 70 88 73 88 / 60 20 20 20 20
San Marcos Muni Airport 81 68 87 73 88 / 70 40 20 20 20
La Grange - Fayette regional 82 71 87 74 88 / 80 60 20 20 20
San Antonio International Airport 83 70 87 74 88 / 70 30 20 20 20
Stinson Muni Airport 82 70 88 74 89 / 70 30 20 10 20
Flash Flood Watch through late tonight for the following counties:
public service/data collection...33