Weather

571 
fxus65 kmso 062056 
afdmso 


Area forecast discussion 
National Weather Service Missoula Montana 
256 PM MDT Sat Sep 6 2008 


Discussion...widespread cumulus clouds have developed this 
afternoon as the atmosphere under northwesterly flow aloft has 
become unstable. Radar imagery over the past hour or so suggest 
some scattered showers have developed in association with the 
convective development. Given that these showers are primarily 
driven by daytime heating...much of the activity will decrease 
soon after sunset. The best chance for measurable precipitation 
late this afternoon and evening will be over the mountains... 
especially closer to The Divide. Forecast models continue to 
remain in agreement with yet another short wave disturbance 
rotating south out of Canada after midnight. As has been the case 
for the past few days...subtle trends in satellite imagery and 
surface observations will lend a helping hand in determining when 
and where the best chances for precipitation will occur. At this 
time...the short wave trough is located in west central British 
Columbia which seems to be in fairly good agreement with the model 
consensus. The system will track south into Montana through the 
day on Monday with the best dynamics hugging the Continental 
Divide. Thus have kept the main focus of precipitation to Glacier 
National Park...western central and southwest Montana with a drier 
forecast for northwest Montana and central Idaho. This could 
change however depending upon how the upper level pattern changes 
overnight. 


Showers will diminish considerably Sunday evening as the 
atmosphere begins to show signs of stabilization and upper level 
dynamics associated with the short wave move into central 
Montana. Skies will rapidly clear which will lead to a very cold 
morning on Monday. Saturation will be likely in many valley 
locations across western Montana and central Idaho which will 
result in at least patchy fog. Some of the more "fog prone" 
locations will have areas or even widespread fog with the 
possibility of some locally dense fog. The upper level flow will 
become more westerly throughout the day Monday leading to 
additional warming. However maximum temperatures will be right in line 
with seasonal normals. Clear skies Monday night will lead to 
another cold morning Tuesday. 


Tuesday and Wednesday...a weak disturbance will move through 
northwest Montana. This instability and cooler northwest flow will 
combine to produce some scattered showers...mainly along the 
Continental Divide. Expect below normal temperatures with below 
normal temperatures. 


Thursday and Friday...a weak or Flat Ridge will develop across the 
region and produce ideal conditions with temperatures at or above 
normal in the middle and upper 70s under mainly clear skies and light 
winds. 




&& 


Aviation...convective showers have developed across western 
Montana and north central Idaho this afternoon and will dissipate 
by roughly 03z. Showers are expected to develop again Sunday as 
another short wave tracks over the northern rockies from the 
northwest. Mountain tops will be obscured by low VFR ceilings 
through Sunday. 




&& 


Mso watches/warnings/advisories... 
Montana...none. 
Idaho...none. 
&& 


$$ 


Short term...Dickerson 
long term....rpn 
aviation...derosa