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Area forecast discussion...updated 
National Weather Service Austin/San Antonio Texas 
1124 PM CST Tuesday Dec 2 2008 


Aviation... 
conditions are forecast to deteriorate early Wednesday morning 
along the I-35 corridor with MVFR ceilings forecast. Otherwise...VFR 
conditions are forecast at south central Texas terminals. A 
moderate southerly low level flow will become gusty late Wednesday 
morning along the I-35 corridor...then turn to the northwest 
between 00-01z when a cold front pushes through. 


&& 


Previous discussion... /issued 753 PM CST Tuesday Dec 2 2008/ 


Discussion... 
the strong boundary layer winds have pushed 45 degree dewpoints 
up to Interstate 10, east of San Antonio. Infrared satellite images 
Show Low clouds developing along the middle coast as warm air 
streams over the cold waters. Ribbons of low clouds are shearing 
northward from the coastal Bend through the eastern County Warning Area. Dewpoint 
increase is slower over the western County Warning Area. The digging upper low 
over The Rockies will keep the strong boundary layer winds going 
through the night. However, boundary layer winds will become more 
southwesterly by morning and weaker over the western half of the 
County Warning Area. Expect there could be some patchy fog south of the 
Escarpment. Will add this element in the forecast. Otherwise only 
minor adjustments to the ongoing forecast. Updates are available. 


Previous discussion... /issued 533 PM CST Tuesday Dec 2 2008/ 


Aviation... 
VFR conditions will deteriorate late tonight at I-35 terminals 
with MVFR ceilings forecast to develop. VFR conditions are forecast to 
persist through the next 24h at kdrt. A moderate southerly low 
level flow will become southwest and gusty late Wednesday morning 
along the I-35 corridor. At kdrt...the low level flow will become 
northwest by middle day with gusts during the afternoon. 




Previous discussion... /issued 340 PM CST Tuesday Dec 2 2008/ 


Discussion... 
low pressure continues to deepen across the plains this afternoon 
with moderate southerly flow. Dewpoints began to increase earlier 
today, however drier air has mixed in this afternoon. Moisture 
rapidly increases tonight with stratus by early morning. Do not 
expect fog due moderate low level jet. Lows tonight are expected 
to be 15 to 25 degrees warmer than last night. Upper trough moving 
through the Great Basin this afternoon will move across Southern 
Plains on Wednesday. This drags a prefrontal trough into the area 
during the afternoon with a cold front moving through in the late 
afternoon and evening. Southwesterly boundary layer winds will 
rapidly dissipate the stratus by afternoon leading to highs in the 
middle 70s to near 80. Records at the climate sites are in the middle 
80s. Some moisture convergence is possible along the front and 
have slight probability of precipitation across the far eastern counties during the early 
evening. Surface high and upper ridge builds into the area 
Wednesday night and persists through Friday. Well below average 
temperatures and low dewpoints can be expected. Some middle level 
cloudiness is possible as a southwesterly flow aloft brings some 
moisture over the cool surface ridge. Over the weekend, surface 
high moves off to the east as low pressure develops in the plains. 
Southerly winds will return leading to increased moisture and a 
warming trend. For next week, models are inconsistent and lack a 
consensus. An upper trough currently in the Gulf of Alaska drops 
south along the West Coast and develops into a closed low west of 
Baja California California by this weekend. Models are having difficulty with 
how fast the low is picked up. Some show a stronger upper trough 
moving into and across the northern states picking up the low and 
bringing it across Texas by middle week while others have a weaker 
trough that does not pick it up. There is disagreement even among 
the ensembles. Will go with ongoing forecast, however have 
introduced slight chance of showers for Monday and Tuesday for 
eastern areas due possibility of streamer showers on stronger low 
level jet. Mex temperatures seem reasonable, however have gone up 
to a category cooler on lows tonight and Thursday night due lower 
dewpoints. 


Fire weather... 
red flag conditions are ongoing across much of south central Texas 
this afternoon and will let red flag warning go until 6 PM CST as 
scheduled, then winds diminish and relative humidities recover. 
Prefrontal trough will move east into the lower Pecos Valley and 
Hill Country Wednesday afternoon. Breezy conditions and drier air 
may lead to near critical fire weather conditions for a few hours. 
Relative humidities will stay more moist for the remainder of the 
forecast. 


&& 


Preliminary point temps/pops... 
Austin Camp Mabry 54 76 44 59 40 / - - - 0 - 
Austin Bergstrom international Airport 50 74 42 62 34 / - - - 0 - 
del Rio International Airport 48 76 45 64 43 / 0 0 0 0 - 
San Antonio International Airport 52 79 42 62 40 / - - 0 0 - 


&& 


Ewx watches/warnings/advisories... 
none. 
&& 


$$ 


06/11/05