436 
fxus64 ksjt 200415 
afdsjt 


Area forecast discussion 
National Weather Service San Angelo Texas 
1115 PM CDT Tuesday Aug 19 2008 




Discussion... 
as in previous discussions the upper level low continues to spin 
over the northern Big Country. Widely scattered showers continue 
and are expected to continue across the eastern portions of the 
Big Country and Heartland during the overnight hours. The upper 
level low will begin to shift east Wednesday afternoon ... 
rain chances shifting to the east as the upper level low shifts to 
the east. For more details see the aviation discussion below. 


&& 


Aviation... 
current satellite is showing stratus moving into the Big Country 
and the Heartland. So have brought MVFR ceilings in at kabi starting 
at 06z ... clouds are expected to expand and affect kbbd 
and ksjt by 09z...and the kjct and ksoa by 10z. Have included IFR 
ceilings at kabi and kbbd near sunrise...similar to what occurred 
Monday morning. Widely scattered showers continue across the eastern 
portions of the Big Country and Heartland. Expect shower activity 
to continue during the overnight hour and shift to the east as the 
upper level low shifts east...don't think coverage will be more than 
widely scattered...so have left all terminals dry. Expect thunderstorm 
activity to stay east of west central Texas where better lift and 
instability is located. Northerly winds will shift to the east 
late Wednesday afternoon...but expect winds to remain at or below 
10 knots. 




&& 


Previous discussion... /issued 829 PM CDT Tuesday Aug 19 2008/ 


Update... 


Updated forecast this evening to remove probability of precipitation over the southwestern 
zones and to update the hourly grids based on latest observation. 


Discussion... 


The going forecast had chance probability of precipitation going for the Big Country and I 
do not disagree with this. An outflow boundary is approaching the 
region from the east and continues to fire up new showers/tshowers 
as it moves along. In addition...can't rule out some 
showers/tshowers in the vicinity of the upper low tonight which is 
sitting and spinning over northwest Texas. Probability of precipitation were removed from the 
forecast over the south and west farther from the upper low and 
with the loss of daytime heating. The rest of the forecast is on track. 


Previous discussion... /issued 634 PM CDT Tuesday Aug 19 2008/ 


Discussion... 
the persistent upper level low continues to spin across the the 
northern Big Country. This will keep the possibility of scattered showers 
across the Big Country...the Heartland and Northwest Hill country 
tonight into tomorrow. See aviation discussion for more details. 


Aviation... 
showers are beginning to decrease and weaken with the loss of 
daytime heating. With the upper level still around...widely 
scattered showers and isolated thunderstorms will continue to be 
possible tonight into tomorrow...mainly across the Big Country..Northwest 
Hill country and the Heartland...due to the scattered coverage 
only have cumulonimbus groups at kabi...kbbd and kjct terminals for tonight 
and overnight. Expect MVFR ceilings to move in to west central Texas 
for most terminals between 06z- 09z...then some IFR ceilings around 
sunrise. Expect VFR conditions to return at all terminals by 
18z/20. 


Previous discussion... /issued 302 PM CDT Tuesday Aug 19 2008/ 


Short term... 
WV imagery indicating upper level low just east of Childress. Middle 
and upper level dry slot over the southern 2/3 of west central 
Texas. Scattered showers and isolated thunderstorms moving southeast across the 
Big Country and Heartland. Will go chance probability of precipitation across the Big Country 
and eastern big Heartland tonight...and slight chance probability of precipitation across the 
remainder of west central Texas. 


Long term... 
the upper level low will move slowly east on Wednesday...and then 
north into Oklahoma on Thursday...and become an open trough across 
Kansas/Missouri on Friday. Looks like west central Texas will 
finally be on the dry side of this system Wednesday and Thursday. 
Will keep slight chance probability of precipitation across eastern County warning forecast area on Wednesday. The 
medium models are indicating an upper high pressure ridge building 
across The Four Corners this weekend into early next week. West 
central Texas will remain on the east side of the ridge with upper 
level northerly flow. Will go with mainly a dry forecast Thursday 
through next Tuesday. The GFS is indicating some quantitative precipitation forecast across the 
southern County warning forecast area on Sunday due to weak upper level tropical low 
developing on the south side of the ridge. Confidence is low on 
this scenario happening. Will keep the slight chance probability of precipitation across the 
Northwest Hill country and Heartland on Sunday. Temperatures will 
warm to around normal Thursday through next Tuesday...with highs 
mainly in the middle 90s. 


&& 


Preliminary point temps/pops... 
Abilene 74 65 85 65 92 / 60 30 20 10 10 
San Angelo 84 64 87 64 91 / 40 10 10 10 10 
Junction 89 65 88 67 91 / 40 10 20 10 10 


&& 


Sjt watches/warnings/advisories... 
none. 
&& 


$$ 


99/99/28