Weather

482 
fxus65 kcys 070855 
afdcys 


Area forecast discussion 
National Weather Service Cheyenne Wyoming 
255 am MDT sun Sep 7 2008 


Short term...today through Monday night. 
Little change to the forecast with this package...as the models 
have been quite consistent with the approaching precipitation 
producing system. 


Early this morning and today...there will continue to be isolated 
very light showers across the northern half of the southeast 
Wyoming zones and across much of the northern two-thirds of the 
Nebraska Panhandle before sunrise. This precipitation is occurring 
along a boundary layer convergence zone which will linger before 
being pushed southwest across the area as a frontal boundary. The 
southeast flow into the convergence zone is resulting from surface 
pressure falls due to the right entrance region to the jet streak 
north of the forecast area. 


Tonight...the next north-south oriented jet streak will add 
support for numerous showers as the left exit region becomes 
Colorado-located with the right exit region of the ejecting east-west 
oriented jet streak move over east central Wyoming. The 
combination of the excellent difluence aloft with cyclonic 
curvature aloft and surface frontal boundary will create the 
widespread precipitation event...with the best chances located 
across the northern half of the area. Model guidance suggests that 
one-half to three-quarters of an inch of precipitation may be 
observed from Converse County east to Dawes and Box Butte 
counties...with gradually lower precipitation amounts across the 
southern and western forecast zones tonight. 


Monday and Monday night...precipitation will exit to the east of 
the forecast area by midday Monday as a short-wave ridge develops 
along the Pacific coast. Upper flow will back to a westerly 
direction during this period. Temperatures Monday will be slightly 
cooler than Sunday...behind the cold front. The WRF-nmm is 
suggesting much cooler temperatures than the GFS for Monday...but 
for now have gone just slightly cooler than the GFS guidance 
values. 


Long term...Tuesday through Saturday. 
Dry and warmer weather expected for Tuesday as return flow sets up 
under backing upper flow. By late Wednesday next upper low forecast to 
drop into the northern rockies then slowly drift east-northeast into the 
northern plains through Friday. Shortwave energy ejecting ahead of 
upper low should bring scattered showers to the County Warning Area primarily 
Wednesday night and again Thursday night. Dry and seasonal weather 
expected Friday and Saturday as upper trough moves east of the County Warning Area 
leaving a general westerly flow over the region. 


&& 


Aviation... 
VFR ceilings will be present this morning...with localized areas 
of MVFR ceilings Colorado-located with shower activity this morning. 
Patchy fog will also be present east of a line from 30 miles west 
of kcys to kcpr. MVFR and IFR ceilings with increased shower 
activity will increase in coverage late this afternoon into 
tonight as widespread precipitation will develop north and east of 
a krwl to klar to kcys line. 


&& 


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


&& 


$$ 


Short term/aviation...CArpenter 
long term...re