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fxus65 kcys 220309 
afdcys 


Area forecast discussion 
National Weather Service Cheyenne Wyoming 
909 PM MDT sun Mar 21 2010 


Update... 
based on current observation cooled temperatures in the Laramie valley 
and warmed temperatures in the northern Nebraska Panhandle and 
east central Wyoming. With current trending of infrared satellite 
image...increased sky cover in the west especially along the Lee 
of the mountains and trended to clearer skies over the 
Panhandle. 


Jtl 


&& 


Previous discussion... /issued 153 PM MDT sun Mar 21 2010/ 


Short term...tonight through Tuesday... 


Forecast challenges in the short term deal with precipitation chances 
Monday afternoon and evening...convective chances for the same 
time...and temperatures. 


Currently...surface high pressure over northern Colorado this 
afternoon with mainly a light westerly wind across the state of 
Wyoming and northwesterly flow across the Nebraska Panhandle. 
Upper level ridging persists across The Rockies with our next 
weather system pushing into the Pacific northwest. 


For tonight...westerly winds are forecast to stay up 
overnight...which should help keeps temperatures mild. Followed 
adjmavbc guidance on temperatures...which keeps low 30s across the 
central portions of the County Warning Area and middle 20s across south central 
Wyoming near Rawlins. Assisting in the warmer temperatures will be 
cloud cover...that is expected to thicken as debris from upstream 
storm system moves into the area overnight. 700mb temperatures 
rise from -2c this morning to around 0c across southern Wyoming 
early this evening...which would favor warmer lows tonight as well. 


By Monday afternoon...we start to see the influence of the storm 
system as cold front approaches eastern Idaho around noon 
time...then into central Wyoming by late afternoon. Models 
continue to paint some fairly unstable conditions...especially 
across the Nebraska Panhandle. GFS showing elevated convective available potential energy around 
100 j/kg while WRF showing anywhere from 400 to 800 j/kg. This is 
substantially less than previous model runs. Will continue just 
mentioning showers in the forecast for tomorrow afternoon...though 
we could still see a few lightning strikes as the front pushes 
through late in the day. Best chances for precipitation look to be late 
Monday night into Tuesday associated with the upper low pressure 
system. Model soundings across the area showing significant 
cooling Monday night into Tuesday...so looks like most precipitation 
should fall as snow. Through this time period. 


Long term...Tuesday night through Sunday... 


Some lingering light snow/flurries possible over the southeast part of the 
County Warning Area Tuesday evening but will be ending as upper trough continues to 
sink south away from the area. Upper ridging then expected to take 
overall control of the weather for the middle to late part of the week 
allowing for warmer and mainly dry conditions. Next upper system 
will take shape over the central and southern rockies next weekend. 
GFS seeming a little too fast and will lean toward the somewhat 
slower European model (ecmwf). This should spread precipitation into the northwest part of the County Warning Area 
Friday night and across the rest on Saturday before clearing the 
area Sat night. Mainly dry and mild Sunday. 


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...re