Weather

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Area forecast discussion 
National Weather Service Midland/Odessa Texas 
621 PM CDT Friday Aug 29 2008 


Discussion... 
see aviation discussion below. 


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Aviation... 
an upper level storm system across northern Mexico will impact 
the terminals with scattered to numerous showers and thunderstorms 
the next 24 hours. Do not think precipitation will last more than 
50 percent of the time but do think there is a better than 50 
percent chance of precipitation. Will have tempo groups for MVFR 
conditions for thunderstorms and rain at the terminals through the forecast cycle. 
Will mention br in many of the tafs in the tempo group late tonight 
and early Saturday morning. 


12 


&& 


Previous discussion... /issued 257 PM CDT Friday Aug 29 2008/ 


Discussion... 
a broad upper low in the vicinity of the central Baja California peninsula... 
Gulf of California and the state of Sonora in Mexico will remain 
nearly stationary through Saturday. An upper ridge resided to the 
north of this feature and extended from the West Coast across the 
southern rockies...southern and central U.S. Plains and into the 
Mississippi River valley. A plume of tropical moisture was 
funneling north and northwestward over the region and around the 
low...accompanied by several shortwave troughs. Surface dewpoints 
across southeast New Mexico and West Texas ranged from the upper 50s 
over the Guadalupe Mountains to the upper 60s over the lower trans 
Pecos this afternoon...with east to southeast surface winds 
advecting upper 60 to lower 70 dewpoints into the area. 
Precipitable water values ranged from 1.25 inches over the western 
County Warning Area to near 2 inches across the lower trans Pecos. 


A strong shortwave trough was translating northwestward over the County Warning Area 
this afternoon...resulting in an area of showers with embedded 
thunderstorms from the upper trans Pecos...southeastward across the 
Stockton plateau...lower trans Pecos and into west central Texas. 
More scattered showers and thunderstorms were developing over the 
western Low Rolling Plains into southeast New Mexico. Still more 
were developing south of The Big Bend region...likely ahead of the 
next shortwave trough Wheeling north and northwestward around the 
said cutoff low. Rainfall amounts of 1 to 2 inches have occurred 
over The Big Bend...with more sparse one half to one inch amounts 
from the southeast New Mexico plains...southward across the upper 
trans Pecos...Marfa Plateau...Presidio valley...Davis Mountains and 
lower trans Pecos in the last 36 hours or so. 


Expect scattered showers north to numerous showers south to occur 
through this afternoon and evening...then again Saturday as a series 
of shortwave troughs take a similar path as the current ones over the 
area. Considering the coverage of precipitation expected...precipitable water 
values stated above and less additional rainfall needed for flash 
flooding to occur along and west of the Pecos River...will continue 
the Flash Flood Watch there tonight and Saturday. 1 to 2 inch 
amounts will be possible...with isolated amounts of 3 to 4 inches. 
In addition...the heavy rainfall along the Rio Grande and it's 
tributaries will likely result in flooding along the Rio Grande 
River. Have included all of the above in the flash flood advisory and the severe weather potential statement. 
Further north over the Permian Basin and western Low Rolling 
Plains...some flooding could occur but think it will not be 
widespread enough at this time for a Flash Flood Watch. Will have 
later shifts monitor the situation though. 


An upper trough digging over the western Continental U.S. This weekend will 
absorb the cutoff low over Baja California...but precipitation chances will 
continue over the western half of the County Warning Area into Monday...if not 
Tuesday. Since precipitable waters  will remain high...additional flooding will be 
possible over these areas into next week. Have included at least 
chance probability of precipitation in the forecast over the west through these time 
frames. From Tuesday Onward...the upper flow remains somewhat 
muddled as the remnant of Gustav may not be too far east initially 
and the amplitude and timing of the West Coast trough as it moves 
eastward next week is by no means settled. Another consideration is 
the eventual arrival of a frontal boundary which could move into the 
area by middle next week. This would definitely affect rain chances 
and temperatures. Speaking of temperatures...expect highs..and to a 
lesser extent lows...to be below normal through Sunday before 
warming back near normal prior to the arrival of the front. 


&& 


Maf watches/warnings/advisories... 
nm...Flash Flood Watch through Saturday afternoon for the following 
zones... Eddy County plains...Guadalupe Mountains of Eddy 
County. 


Texas...Flash Flood Watch through Saturday evening for the following 
zones... Big Bend area...Davis/Apache Mountains area... 
Guadalupe Mountains...Marfa Plateau...Pecos...Presidio 
valley...Reeves County and upper trans Pecos...Terrell... 
Van Horn and Highway 54 corridor. 




&& 


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