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Area forecast discussion...updated 
National Weather Service Midland/Odessa Texas 
549 am CST Sat Nov 21 2009 


Discussion... 
see 12z aviation discussion below. 


&& 


Aviation... 
VFR conditions are expected at area taf sites through the next 24 
hours. Clear skies will continue through most of today...with some 
increase in high clouds this afternoon and evening. Mainly light and 
variable winds this morning will become south to southwesterly 
this afternoon as a surface low over southeast Colorado deepens. 


&& 


Previous discussion... /issued 428 am CST Sat Nov 21 2009/ 


Discussion... 
a progressive split flow regime will continue in place through the 
following week. A dry forecast will continue as forcing and 
moisture are limited. Shortwave ridging aloft this morning will 
give way to dampening overnight as a minor trough translates east 
over the central rockies. An increase in thermal ridging aloft and 
a return to southerly flow will result in a return to above normal 
temperatures areawide today and tonight. 


A stronger shortwave trough is forecast to amplify over the Great 
Basin/central rockies Sunday night and Monday. Return flow over 
eastern zones Sunday night may result in an uptick in low 
cloudiness in the predawn hours Monday across the far eastern 
basin/western Low Rolling Plains. Further amplification of this 
trough over the Central Plains Monday will lead to stronger 
southwesterly/westerly winds across the region...resulting in 
another above normal temperature day with windy conditions 
expected across the Guadalupe and Apache Mountains during the 
afternoon hours. A cold front will then translate south across the 
southern High Plains... knocking temperatures back down to near 
normal through Thanksgiving. 


GFS ensemble clustering seems to support the operational GFS run 
this morning...with a more progressive and farther north solution 
than what is suggested by the European model (ecmwf). Hard to completely dismiss the 
European model (ecmwf) solution...however...but the net effect here would be to 
increase winds Monday...and this is reflected in the grids. Have 
generally undercut MOS low guidance a few degrees while staying 
close to a blend of the GFS and GFS ensemble mean MOS numbers for 
highs. With little in the way of moisture and lift forecast... 
probability of precipitation are negligible through the end of next week. 


Fire weather... 
early morning RAWS observations show poor to fair relative humidity recovery across 
most of the Guadalupe Mountains. Dry air will remain in place 
today...and with temperatures warming to above normal levels...rh/S 
will likely drop into the 15 to near 25% range this afternoon. An 
increase in westerly winds in the middle-levels will likely bring gusty 
conditions to the higher elevations (above 6500 feet) and mountain 
gaps/passes. There could be brief...but isolated conditions of 
westerly 20 foot winds of 20 miles per hour along with relative humidity/S of 15% this 
afternoon. Given the brief and isolated nature of these 
conditions...a red flag warning will not be issued. 


For tonight...the winds in the middle-levels increase as an upper level 
trough moves through the southern rockies. This is expected to bring 
an increase in 20 foot westerly winds for elevations above 6500 feet 
across the Guadalupe Mountains. In addition...another night of poor 
to fair relative humidity recovery is anticipated. 


On Monday...a strong storm system will move into the central and 
southern U.S. Plains. Westerly winds will increase ahead of this 
system...likely resulting in windy conditions across the Guadalupe 
Mountains. Temperatures will remain above normal and minimum relative humidity/S 
may drop to near 15%. 


&& 


Maf watches/warnings/advisories... 
nm...none. 
Texas...none. 


&& 


$$ 


06