544 
fxus65 kmso 220314 
afdmso 


Area forecast discussion 
National Weather Service Missoula Montana 
914 PM MDT sun Mar 21 2010 


Update...adjusted precipitation timing and location for the rest 
of the night. 




&& 


Discussion...had the first wave of precipitation associated with 
an occluded front move through the intermountain region earlier 
this evening. Strong West Ridge top winds accompanied this first 
batch of precipitation and many of the north/south valleys of 
western Montana saw little to no precipitation with this first 
wave. The next batch of precipitation associated with the surface 
cold front is already pushing into the Idaho Panhandle this hour 
and is expected to move through western Montana between 10 PM and 
2 am MDT. Some light showers will be experienced in the valleys 
before the front...but best precipitation is expected right along 
the front. Drying returns to valley locations as winds increase 
again behind the front. Also expect some breezy winds again along 
the cold front. Have adjusted the winds and probability of precipitation tonight to 
account for this timing. Temperatures look on track. 




&& 


Aviation...surface cold front and parent Pacific trough continue 
to keep widespread showers and periods of breezy surface winds 
going this evening across the northern rockies. Gusty winds still 
linger at locations along the Continental Divide...including 
kbtm...and may continue through 22/0400z. Winds along the Salmon 
River Valley in Lemhi County near ksmn will continue to decrease 
throughout the evening as the lower atmosphere begins to saturate 
courtesy of nearby mountain showers. Some breezy gusts could still 
occur with frontal passage expected to occur early in the morning. 
Elsewhere...ceilings will begin to push 3000ft above ground level by early 
morning. Periods of a rain snow mix are possible through Monday 
middle morning. Low clouds and showers may block terrain through 
Monday. 


&& 


Previous discussion... /issued 244 PM MDT sun Mar 21 2010/ 


Discussion... 


Tonight through Tuesday night...north central Idaho and western 
Montana will be impacted by a Pacific storm system from this evening 
through early Tuesday. Mild temperatures and increased southwesterly 
flow will exist ahead of a surface cold front moving across the 
region during this evening. Precipitation will develop along and 
behind this cold front...with snow levels lowering throughout 
tonight. The most significant weather impact will be accumulating 
snow over nearby mountain passes creating hazardous driving 
conditions for a time from tonight through Monday evening. Very 
little in the way of low elevation accumulations are 
anticipated...with the exception of southwest Montana Interstate 90 
corridor. In southwest Montana...light accumulations are anticipated 
at low elevations from tonight through Monday afternoon. By 
Tuesday...high pressure is expected to return to the region...with 
mountain snow shower activity lingering throughout the day and 
warmer temperatures. 


Wednesday the ridge of high pressure will keep conditions warm and 
dry. For Wednesday night...have decreased the probability of precipitation as the Pacific 
system appears to be about 12 hours slower. We will see increasing 
clouds early Thursday with some showers moving into north central 
Idaho Thursday morning. These will move across western Montana 
Thursday and remain into Friday night. Some showers will linger 
into Saturday as another ridge of high pressure builds in from the 
west. 


&& 


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


$$ 


Update...Mead 
previous discussion....zumpfe/kolata 
aviation...Nolte