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fxus65 kcys 152015 
afdcys 


Area forecast discussion 
National Weather Service Cheyenne Wyoming 
215 PM MDT Wednesday Oct 15 2008 


Short term...tonight through Friday... 
fairly fast westerly flow aloft will become more northwest by 
Thursday night as heights rise through Friday night over The Rockies. 
A broad ridg aloft will be over The Rockies by 12z Saturday. Models 
depict several weak shortwave troughs will move across the County Warning Area 
tonight and Thursday. The shortwave troughs will bring mainly and 
high level clouds over mainly of the north part of the County Warning Area during 
that time. A weak front will move across the region late Thursday. 
Wind speeds aloft increase and the surface pressure gradient 
tightens late tonight and continue for Thursday. The result will be 
an increase in wind speeds over the County Warning Area...especially along and west 
of the Laramie range. Winds should diminish some for Thursday night 
and Friday. Will leave the County Warning Area dry for now...although light 
precipitation is possible over the higher elevations of the Snowy 
Range on Thursday. Temperatures will warm up to 10 degrees ahead of 
the front on Thursday and then several degrees warmer for Friday. 
Westerly surface pressure gradient will keep lows above normal for 
tonight through Friday night. 


Long term...Friday night through Wednesday... 
the ridge aloft will be over The Rockies through Saturday before 
being flattened by a shortwave trough moving across southern Canada 
Sunday and Sunday night. The models do bring a 300 mb jet segment 
and weaker shortwave energy over the County Warning Area Sunday through Monday. A 
cold front backs into the County Warning Area as well Sunday. Models...especially 
the 00z European model (ecmwf) develop quantitative precipitation forecast behind the front which lingers in the 
upslope wind flow through Monday. At this time will introduce low 
probability of precipitation behind the front...and moving from north to south...Sunday 
through Monday. Low clouds will be a possibility late Sunday night 
and Monday morning and again late Monday night and Tuesday morning. 
Temperatures will be mild through Saturday night ahead of the front 
with readings falling to around normal for Sunday and Monday. A 
large amplitude shortwave trough will affect the County Warning Area Tuesday and 
Wednesday after moving in from the Pacific. In fact...the GFS and 
European model (ecmwf) close off a deep upper low near The Four Corners area on 
Wednesday. The 12z GFS has been consistent is being further east 
with the shortwave trough and upper low and places the feature over 
cwentral Kansas 00z Thursday. Based on discussions from HPC will 
favor a compromise timing of the upper low for Tuesday and next 
Wednesday. The resulting surface upslope and increased moisture and 
cyclonic flow aloft should produce some precipitation over 
especially the south half of the County Warning Area Tuesday and Wednesday. At this 
time the temperatures look to be warm enough for the precipitation 
type to be mainly in the form of rain below 9000 feet mean sea level. The 
associated surface cold front will move across the County Warning Area Tuesday or 
Tuesday night with below normal temperatures behind the front. 


&& 


Aviation...VFR conditions will continue across the County Warning Area through 
Friday night. An expected increase in the winds for late tonight 
and Thursday...mainly along and west of the Laramie range will 
produce gusts as high as 35 knots. Turbulence below 700 mb can 
be expected through Thursday with weak mountain wave activity near 
the mountains. 


&& 


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


&& 


$$ 


Weiland