Area forecast discussion
National Weather Service Austin/San Antonio Texas
1134 PM CDT Tuesday may 21 2013
Aviation...
a 500 hpa trough moving to the eastern part of Texas tonight
opened The Gate for a cold front to move across south central
Texas from the north tonight. Scattered rain showers and isolated thunderstorms and rain
over the east to southeast part of south central Texas will move
southeast. As the 500 hpa trough moves further east on Wednesday
morning and to the lower MS valley by Wednesday afternoon...more
stable conditions will develop over south central Texas from the
west...with dry and warm weather expected Wednesday. Through 08z
ceilings near 4 thousand to 6 thousand broken vicinity of kaus to ksat and kssf and
a few clouds above 25 thousand feet vicinity of kdrt are expected. After
08z a few clouds at 5 thousand to 10 thousand feet vicinity of kaus to ksat
and kssf and scattered cirrus above 25 thousand feet vicinity of kdrt is forecast.
After 15z Wednesday VFR conditions will continue...with a few
clouds around 5 thousand feet and few to scattered cirrus above 25 thousand feet.
&&
Previous discussion... /issued 838 PM CDT Tuesday may 21 2013/
Update...
continued to show decreasing chances of showers and thunderstorms
from the west tonight...as the 700 to 200 hpa trough continues to
move east of south central Texas...taking the energy to produce
thunderstorms to the east. More stable conditions will continue
to increase across south central Texas late tonight through
Wednesday...bringing dry and warm weather for Wednesday and
Thursday. Removed the mention of severe thunderstorms from the
forecast for tonight...as the energy for severe storms has moved
east of south central Texas.
Previous discussion... /issued 805 PM CDT Tuesday may 21 2013/
Update...
adjusted probability of precipitation to show a trend of decreasing chances of rain from
the west and northwest this evening...and continuing through
tonight. The 500 hpa trough is beginning to move east of south
central Texas...taking the energy to produce thunderstorms to
the east. More stable conditions will continue to increase
across south central Texas late tonight through Wednesday...
bringing dry and warm weather for Wednesday and Thursday.
Previous discussion... /issued 627 PM CDT Tuesday may 21 2013/
Discussion...
See aviation for 00z tafs.
Aviation...
a 500 hpa trough from the northern plains to south central Texas
will move to eastern Texas by late this evening and to the
lower MS valley on Wednesday. This will open The Gate for a
weak cold front to move across south central Texas tonight.
Through 06z scattered rain showers/thunderstorms and rain are expected to develop over
south central Texas along and east of a line from near
kgtu to kaus to ksat to kpez. West of this line isolated
early evening rain showers/thunderstorms and rain are possible in wake of daytime
heating...and with the wind shift coming across the west
part of south central Texas from the north. After 06z more
stable conditions will develop over south central Texas...as
ridging aloft increases from the west. This will cause drier and
warmer weather for the area on Wednesday...with VFR conditions
across the area.
Previous discussion... /issued 255 PM CDT Tuesday may 21 2013/
Short term (tonight through Wednesday night)...
a frontal boundary stretching from near Denton to San Angelo to
Fort Stockton will be the primary focus of thunderstorm
development this afternoon and evening. The atmosphere is quite
unstable over south central Texas. Surface winds from the south
have brought moist Gulf air with dew points around 70. Cold air in
the middle-levels has steepened lapse rates. Storm Prediction Center mesoscale-analysis shows cape
above 3000 j/kg across much of the forecast area. Expecting storms
to move in to our County Warning Area late this afternoon and evening. Any storms may
become severe and the main threats will be for large hail and
damaging wind gusts with a slight threat for tornadoes. Most
convection should be over by 2am...but isolated thunderstorms
could linger overnight especially over the southeast. The front
will dissipate Wednesday and the upper level trough will move off
to the east. This will end any precipitation chances. A middle to upper
level ridge will begin to build over the Southern Plains Wednesday
evening.
Long term (thursday through tuesday)...
the middle to upper level ridge will build across the central part of
the country through the end of the week. The low level flow will
continue to be from the south to southeast. This will put US back
into the warm...moist pattern with overnight/morning clouds over
the eastern half of the area followed by afternoon/evening
clearing. Temperatures will be above normal. Rain chances will be
nearly zero. The one possibility for any rain is a short wave
trough models move through the upper pattern Friday/Saturday. Both
GFS and European model (ecmwf) show a chance for precipitation over the western part of
the County Warning Area. However...have discounted this since low level moisture
will be shallow and upper ridge looks strong.
&&
Preliminary point temps/pops...
Austin Camp Mabry 68 92 71 93 72 / 20 - 0 0 10
Austin Bergstrom international Airport 68 91 69 92 70 / 20 - 0 0 10
New Braunfels Muni Airport 68 92 70 93 71 / 20 - 0 0 10
Burnet Muni Airport 64 90 68 91 69 / 10 - 0 0 10
del Rio International Airport 71 97 74 98 75 / 10 10 0 0 10
Georgetown Muni Airport 66 89 71 90 72 / 20 - 0 0 10
Hondo Muni Airport 69 95 71 96 72 / 10 - 0 0 10
San Marcos Muni Airport 69 90 70 91 71 / 20 - 0 0 10
La Grange - Fayette regional 74 91 73 91 74 / 50 10 0 0 -
San Antonio International Airport 70 92 73 93 74 / 20 - 0 0 10
Stinson Muni Airport 70 92 72 93 73 / 20 - 0 0 10
&&
Ewx watches/warnings/advisories...
none.
&&
$$
Mesoscale/aviation...08
synoptic/grids...17
public service/data collection...33
