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Area forecast discussion 
National Weather Service Cheyenne Wyoming 
1139 am MDT sun Mar 21 2010 


Update to aviation... 




Previous discussion... /issued 334 am MDT sun Mar 21 2010/ 


Short term...today through Monday night... 


The majority of the short term and the first two days of Spring 
look great. An upper level ridge will move across the County Warning Area today 
and Monday bringing mainly sunny skies and warming temperatures. 
However by Monday night and into Tuesday morning an upper low will 
move into southwest Wyoming with a trough extending northeast into 
eastern Montana. Associated with this upper system will be a 
surface cold front that will push across the County Warning Area by Tuesday middle 
morning. At this time the main question will the timing of the front 
and the associated precipitation. It appears it will be cold enough 
that when the precipitation begins it should be in the form of snow. 
Models showing that snow totals will probably be in the advisory 
category for now. 


Long term...Tuesday through Saturday. NAM...GFS and European model (ecmwf) in decent 
agreement on synoptic pattern...thus moderate to high confidence in 
their solutions. 


Tuesday...shortwave moves across eastern Wyoming and Colorado. 
Combination of deeply saturated atmospheric column...upslope lift... 
dynamic lift will produce good chances for precipitation... 
especially southeast of a Laramie to Scottsbluff line. Expect 
precipitation chances will need to be increased by later shift teams. 


Wednesday...drying out period in the wake of the shortwave. Still 
some orographic snow showers across the Snowy Range. High 
temperatures in the 40s to middle 50s at lower elevations with 1000-500 
mb thicknesses near 5460 meters. 


Thursday...warming trend in full force with transitory shortwave 
ridge across Wyoming. Maximum temperatures in the upper 40s to lower 
60s with 1000-500 mb thicknesses near 5520 meters. 


Friday...next progressive shortwave trough moves across Wyoming and 
Montana with associated cold front across our region. GFS likely too 
aggressive with precipitation shield and thus will keep 
precipitation chances west of a Scottsbluff to Laramie line. High 
temperatures in the middle 40s to middle 50s with 1000-500 mb thicknesses 
near 5520 meters. 


Saturday...brisk northwest flow aloft develops. With deep 
unidirectional northwest flow and decent surface through 700 mb 
gradients...expect brisk and windy day with northwest winds. Maximum 
temperatures in the middle 40s to middle 50s with 1000-500 mb thicknesses 
near 5400 meters. 


Aviation...for the 18z southeast Wyoming and Nebraska Panhandle 
tafs...VFR conditions expected through next 24 hours as westerly 
winds persist. Should see a gradual lowering of ceilings overnight 
as clouds from an approaching system move into the area from west 
to east. Still...VFR conditions expected. 


Fire weather...no fire weather concerns at this time. 


&& 


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


&& 


$$ 


Short term/aviation...claycomb 
long term...Rubin