053 
fxus64 ksjt 231150 aaa 
afdsjt 


Area forecast discussion...updated 
National Weather Service San Angelo Texas 
550 am CST Monday Nov 23 2009 


Discussion... 
see aviation section. 


&& 


Aviation... 
low clouds developing over the Edwards Plateau will expand 
north into roughly the southern third of west central Texas 
early this morning. Patchy fog is possible across most of west 
central Texas. Cloud ceilings will be mostly in the LIFR 
category...and visibility could drop into the IFR or LIFR at 
times. The clouds and fog will dissipate around mid-morning... 
with generally clear skies and VFR conditions expected from 
late morning through early evening across west central Texas. 
Light winds will become south to southwest at 10-15 knots...and 
some gusts to 20 knots are expected at the kabi and ksjt terminals. 
Winds will shift to the north with the cold frontal passage 
tonight. Per the model low-level moisture fields...low clouds 
will likely redevelop across roughly the southern half of west 
central Texas tonight...and expect ceilings to mostly be in 
the MVFR category. 


&& 


Previous discussion... /issued 453 am CST Monday Nov 23 2009/ 


Short term... 
GOES 11-3.9 micron satellite imagery shows fog and some low cloud 
development just north and east of the Big Country. Other patchy low 
clouds developing just southwest of Crockett County. Taking into 
account radiational cooling and current surface dewpoints...have 
expanded the patchy fog mention to include the northern and eastern 
Big Country early this morning. Some low cloud development is 
possible into the southern third of our area during the early 
morning. 


A mainly clear sky is expected from middle-morning through early 
evening. Warmer 850 mb temperatures and some compressional warming 
effects ahead of approaching front will favor temperatures climbing 
into the middle to upper 70s for highs this afternoon. 


Upper trough over the northern rockies will dig into the Central 
Plains later today and tonight. Associated cold front will drop 
south across west central Texas tonight. Per the low-level model 
moisture fields...low cloud development is expected across the 
area roughly southeast of a Brownwood to Mertzon line tonight... 
as the front moves down into the area. Lee troughing and a 
slightly increased surface pressure gradient will support higher 
wind speeds today. With the frontal passage winds will shift 
to the north...and winds may be somewhat gusty for a few hours 
after the frontal passage. 


Long term... 
cooler temperatures expected following the frontal passage early 
Tuesday as strong high pressure builds southeast into the area. 
Highs on Tuesday will only manage to reach the upper 50s and lower 
60s as low level cold air advection develops over the area. The 
strong cold air advection will result in sustained north to 
northwest winds 15 to 20 knots with higher gusts into the early 
afternoon hours before subsiding late. Clear skies along with 
light surface winds and the very dry low levels will result in 
excellent radiational cooling Tuesday night with overnight lows 
dropping into the upper 20s and lower 30s areawide. Would not be 
surprised to see some middle 20s in some of the lower lying areas if 
surface winds are able to fully decouple. 


Very pleasant weather is expected across west central Texas 
through the end of the week and into the first part of the 
upcoming weekend. Exiting short wave on Tuesday will move into the 
Ohio Valley by early Wednesday with a much stronger wave diving southeast from 
the upper Midwest on Wednesday...then into the tenn valley on Thursday. 
This will result in a deep trough being carved out across the 
eastern Continental U.S. With a strong upper ridge to our west with northwest 
flow aloft over west central Texas through the end of the week. Highs 
through Sat will be in the 60s with overnight lows in the 30s both 
Wednesday and Thursday then upper 30s and lower 40s by Sat. 


Forecast becomes more of a challenge late in the extended period 
as both the GFS and European model (ecmwf) indicate a deep trough developing over 
the southwest states over the weekend which could begin affecting 
our weather sun into Monday of next week. Cursory look at the 06z 
GFS shows that it may be trending towards the 00z European model (ecmwf) with a 
closed low forming over Arizona late sun but timing/strength 
issues continue to be a problem. Both show a cold front crossing 
the area on sun with some precipitation associated with it and much 
cooler temperatures for the start of next week. Have introduced slight 
probability of precipitation over the area in association with the front and upper trough 
sun into Monday and trended towards lower temperatures on Monday with 
highs in the upper 50s. Latest mex numbers now showing middle 50s 
across much of the area by this time. 


&& 


Preliminary point temps/pops... 
Abilene 77 41 62 34 61 / 0 10 10 0 0 
San Angelo 78 43 62 29 64 / 0 10 10 0 0 
Junction 76 48 64 29 68 / 0 20 10 0 0 


&& 


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


$$ 


19/24/19