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Area forecast discussion 
National Weather Service Austin/San Antonio Texas 
926 PM CDT Sat Mar 20 2010 


Update... 
changes to reflect Wind Advisory expiration...Fire Weather Watch 
cancellation...and freeze warning expansion as discussed below. 


&& 


Discussion... 
temperatures and winds were reviewed to assess a higher chance of 
freezing temperatures over areas fron drt to hdo...so the freeze warning 
was expanded for those areas. Min temperatures were raised slightly near 
aus where a stronger overnight breeze and a few lingering clouds 
should keep temperatures 1-3 degrees above freezing. This area just east 
of the Escarpment will be more likely to see a freeze Monday 
morning...so a freeze warning will likely be issued again 
tomorrow. Near Wind Advisory criteria is still occurring at 8 PM...but 
trends are down and the advisory was allowed to expire. A Wind Advisory 
for Sunday appears less likely for Sunday...but a few normally 
windy spots just east of i35 could see sustained winds reach the 
middle 20s during the early afternoon when mixing of winds aloft will 
be greatest. 


&& 


Fire weather... 
FWA cancelled instead of upgrading to a rfw for Sunday. The 
eastern counties had a low risk of reaching critical relative humidity 
values...but a much higher risk of reaching critical wind values. 
Western counties are most likely so see relative humidity values in the 
teens...but only an hour or two of near critical winds. Critical 
fire weather conditions are thus most likely for central 
sections...but recent rainfall and mild weather conditions has 
likely prompted at least a partial green-up for the Spring. Based 
on the tfs fuel dryness map for these higher threat areas...the 
potential for a rfw event is marginal. If winds are expected to 
become stronger than currently projected a blend of fuel 
dryness...fire danger...and recent rainfall trend maps would 
suggest a potential critical event generally south of a Pandale to 
San Antonio to Schulenburg line. 


&& 


Previous discussion... /issued 640 PM CDT Sat Mar 20 2010/ 


Aviation... 
stratocumulus with MVFR/VFR 025-035bkn-ovc ceilings will persist along 
and NE of a koza to kecu to kbaz to karm line this evening, then 
slowly lift NE of south central Texas during the overnight hours 
into Sunday as the upper low moves east to arklatex. Elsewhere, few 
VFR stratocumulus will persist into Sunday. Northwesterly winds 15 to 20 
kts with gusts to 30 kts will decrease due decoupling this evening 
to 5 to 12 kts overnight, increase to 15 to 20 kts with gusts to 
30 kts Sunday due mixing, then decrease to less than 10 kts Sunday 
evening due decoupling. 


Previous discussion... /issued 427 PM CDT Sat Mar 20 2010/ 


Discussion... 
middle to upper level ridging to keep south central Texas under a 
subsidence northwesterly flow for 24 to 36 hours before it turns 
more westerly (zonal flow) during Monday afternoon/evening. 


Surface high pressure will continue to build across central Texas 
tonight while it moves southeastern and then into the Gulf of 
Mexico late Monday into Tuesday. 


This weather setup will give US pleasant weather conditions for 
the next few days while northwesterly wind flow will keep the 
local area under a cold air mass...with high temperatures expected 
to be around the middle 60s on Sunday...but low temperatures to be 
near freezing on Sunday morning and once again on Monday morning. 


By Monday afternoon into Tuesday...the zonal flow mentioned above 
will build in while a surface returning flow is expected. This 
will bring back seasonal Spring temperatures for much of next week. 


A cold front is anticipated to come across the local area Wednesday 
afternoon/evening continuing through Thursday...increasing the 
chances for showers and isolated thunderstorms across south 
central Texas...but much likely to The Hill Country...northeast 
and east of the County Warning Area. Significant rainfall amounts are not expected 
at this time in association with this system. 


For the record...preliminary 24 hour storm total rainfall amounts 
measured as frontal passage went by the area: 


0.49 inches at New Braunfels Municipal Airport 
0.59 inches at San Antonio International Airport 
0.69 inches at Austin international Airport 
1.05 inches at Camp Mabry 


&& 


Preliminary point temps/pops... 
Austin Camp Mabry 37 62 33 75 45 / - 0 0 0 0 
Austin Bergstrom international Airport 33 62 31 73 35 / - 0 0 0 0 
New Braunfels Muni Airport 34 65 33 76 41 / - 0 0 0 0 
Burnet Muni Airport 32 60 34 72 43 / - 0 0 0 0 
del Rio International Airport 34 70 35 79 46 / - 0 0 0 0 
Georgetown Muni Airport 34 61 34 72 45 / - 0 0 0 0 
Hondo Muni Airport 32 65 30 77 38 / - 0 0 0 0 
San Marcos Muni Airport 34 65 33 75 42 / - 0 0 0 0 
La Grange - Fayette regional 37 60 37 70 43 / - 0 0 0 0 
San Antonio International Airport 34 67 34 77 43 / - 0 0 0 0 
Stinson Muni Airport 35 68 35 77 41 / - 0 0 0 0 


&& 


Ewx watches/warnings/advisories... 
freeze warning from 1 am to 9 am CDT Sunday for the following 
counties: Bandera...blanco...Burnet...Edwards...Gillespie... 
Kendall...Kerr...Kinney...Llano...Medina...real...Uvalde...Val 
Verde. 


&& 


$$ 


18/04