542 
fxus65 kgjt 212155 
afdgjt 


Area forecast discussion 
National Weather Service Grand Junction Colorado 
300 PM MST Sat Nov 21 2009 


Short term...tonight through Monday... 
infrared satellite imagery showing second of three disturbances just 
entering County Warning Area over eastern Utah at this time. Latest 20z surface observation not showing any 
precipitation over central Utah currently. Even so...kept mention of showery 
precipitation for extreme northestern Utah/northwestern Colorado and central mountains this evening as 
models do highlight enough instability for some minor precipitation. Small 
reprieve during the day Sunday between open waves until late Sun 
afternoon/evening as the next system digs down. 


Approximately 100kt jet digs down over intermountain west leaving 
Utah/Colorado in divergence sector...or area of favorable upward motion...and as 
jet continues to dig southward...chance for precipitation increases with 
passage of surface cold front. Previous grids caught this thinking very 
well with chance to schc snow noon Sunday through afternoon Monday so made 
almost no changes to current forecast aside from bumping up probability of precipitation for 
cen/northern mountains Sun night into Monday. Snow amounts should be between 3 to 
4 inches above 5000ft or so. Remaining areas will see mostly cloudy 
skies with temperatures a few degrees cooler than seen lately due to incd 
cloud cover. 


Long term...Monday night through Saturday... 
a drying nwrly flow will occur Monday night as exiting upper low moves 
into the plains and ridge builds over the Great Basin. Little change 
is expected Tuesday and Wednesday with ridge to our west producing a generally 
dry northwesterly flow. There may be a few clouds at times especially 
across the north...otherwise fair conditions amend mild temperatures 
are expected. 


The ridge line shifts eastward over our County Warning Area Thursday with mild 
conditions continuing...along with light winds. Toward the end of 
the week the GFS and ec diverge significantly with the ec showing a 
digging trough into Nevada and Utah. The GFS solution shows a short 
wave flattening the ridge but keeps the forecast area dry. No 
changes to the dry forecast until models show better agreement. 


&& 


Aviation... 
VFR conditions will remain as high clouds stream over the area for 
the remainder of today. Some snowshowers later this evening 
and tomorrow may cause some IFR...possibly even LIFR...due to 
dropping visible and lowered ceilings in heavier snowshowers. Kege and kase 
will be susceptible to these snowshowers while remaining taf sites 
should say above VFR. 


&& 


Gjt watches/warnings/advisories... 


Colorado...none. 
Utah...none. 


&& 


$$ 


Short term.....Tgr 
long term......mc 
aviation.......tgr