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Area forecast discussion 
National Weather Service Cheyenne Wyoming 
300 am MST Friday Nov 21 2008 


Short term...today through Saturday night... 


Today...impressive surface Lee troughing developing early this 
morning across eastern Wyoming with three hourly pressure falls of 5 
to 7 millibars. Decent low level mixing has already developed across 
Carbon County with temperatures at 2 am already in the upper 30s to 
lower 40s at Rawlins and Arlington while 20s exist further east 
across our counties. 


Sharp shortwave trough moves east to eastern Wyoming by midday with 
a surface cold frontal passage across our counties. Areas of fog and 
low clouds will come to an abrupt end early this morning as winds 
become west. The shortwave trough aloft moves to western South 
Dakota by late afternoon. Our northern counties will be close enough 
to the moisture and dynamics associated with the system to warrant a 
small chance of light snow...elsewhere dry. Main challenge today 
will be the winds. Winds from Carbon County across Albany County to 
Laramie County will approach high wind criteria...especially at 
locales such as Arlington...vedauwoo and Bordeaux. However...surface 
through 700 mb gradients and isotachs look such that expect winds to 
remain just below high wind criteria...although this will need to be 
monitored. 


Tonight...decent surface pressure gradient will keep the low levels 
well mixed...thus keeping minimum temperatures locally higher in 
typically wind prone areas to the Lee of the Laramie range. 


Saturday...flow aloft becomes zonal. With 1000-500 mb thicknesses 
rising to 5560 meters and 700 mb temperatures warming to 2 celsius... 
maximum temperatures will soar into the upper 40s to middle 
50s...assuming high cloud opacity will be minimal. 


Saturday night...another quiescent overnight period with zonal flow 
aloft. Will be enough middle and high clouds and decent low level 
mixing to keep minimum temperatures locally higher to the Lee of the 
Laramie range. Rubin 


Long term...sun through Thursday...minor upper trough and its weak cool front 
pass through the region on sun with most clouds/precipitation staying to our north. 
Large upper ridge then shifts east into the region through Tuesday or Wednesday 
depending on the models. GFS may be a bit quick to bring in the 
next upper trough on Wed/Thu...European model (ecmwf) is a little slower. Upper air 
pattern becomes quite messy and convoluted by the late this week as a 
couple of weak upper lows spin around the region. Will lean towards 
European model (ecmwf) for now. 


&& 


Aviation...today...a cold frontal passage will bring west winds 
with speeds increasing. Expect mountain wave turbulence and Lee eddy 
effects. VFR. 


Tonight and Saturday...VFR. Rubin 


&& 


Cys watches/warnings/advisories... 
Wyoming...none. 
NE...none. 


&& 


$$ 


Short term/aviation...Rubin