222 
fxus65 kmso 191504 aaa 
afdmso 


Area forecast discussion...updated 
National Weather Service Missoula Montana 
904 am MDT Friday Mar 19 2010 


Update...decreased showers and sky cover this morning and added 
some patchy fog to the I-90 corridor from Drummond to just north 
of Butte. 




&& 


Discussion...showers have nearly ended across western Montana 
this morning with plenty of sunshine...the exception is The Butte 
region through the southern Bitterroot Mountains and Lemhi County. 
Did see a couple inches of snow from Drummond to Butte overnight 
and with the clearing behind the showers...received a report of 
some fog along the I-90 corridor from Drummond to just north of 
Butte. This is not expected to last much past 9 am. Still have a 
good north to south jet over western Montana today...so expect 
some mainly mountain showers to redevelop this afternoon. Despite 
the cooler air mass this morning...with good mixing and ample 
sunshine...temperatures are expected to warm to seasonal values...but 
will be a few degrees cooler than thursdays readings. 




&& 


Aviation...an upper level jet will help to redevelop mountain 
showers over western Montana this afternoon. These showers will 
obscure higher terrain at times...but are not expected to impact 
area airfields. High pressure will build in overnight tonight and 
through Saturday bringing pleasant Saturday flight conditions. 


&& 


Previous discussion... /issued 332 am MDT Friday Mar 19 2010/ 


Discussion... the shortwave trough that produced the exciting 
late winter weather last evening and through this morning has 
moved into southern Montana. Most of the precipitation has ended 
in western Montana but cloud cover lingers mainly from west central 
Montana through southwest Montana. This cloud cover will decrease 
from the north today though some fair weather cumulus may form 
this afternoon as daytime heating destabilizes the atmosphere. 
The sky should clear nicely by tonight with cool overnight 
temperatures expected...especially in southwest Montana. 


High pressure will build in on Saturday with above average 
temperatures and a very pleasant beginning to the Spring season. 
Sunday will also be a warm day but wind and cloud cover will increase 
ahead of an upcoming Pacific weather system which may help inhibit 
full warming potential in some locations. 


The next weather system to impact Montana and Idaho will move 
inland off the Pacific late Sunday and into the northern rockies 
region by Monday morning. Both the GFS and European model (ecmwf) continue to show 
a rather robust cold front that should be the focus for the 
heaviest precipitation. These models also show synoptic forcing 
along the front being enhanced over the Clearwater and Bitterroot 
Mountains...likely the result of additional lift produced by the 
positioning of an acceleration in the upper level jet. In addition 
a noticeable moisture feed coming off the Pacific Ocean is forecast 
to move into the inter-mountain west with this system. All these 
factors may combine to produce some heavier precipitation in the 
form of mountain snow (above 5000 feet) and lower elevation rain 
as the front moves through Idaho and Montana. Conditions overnight 
into Tuesday morning will also turn cooler with both models 
showing a decent amount of colder air associated with the upper 
level system. 


The upper trough will begin to exit to the south overnight Monday 
into Tuesday morning. Models differ in how this system exits so 
have erred on the side of caution and slowed the decreasing trend 
in precipitation to keep showers around into Tuesday afternoon. 
Thereafter the GFS and European model (ecmwf) are generally in agreement with a 
developing ridge for middle-week before yet another upper trough 
moves into the region late next week. This was reflected in the 
previous forecast by lesser precipitation chances Wednesday and Thursday 
but increasing back towards climatological chances by Friday. 
Temperatures also show a gradual warming trend with readings very 
close to seasonal normals. 




&& 


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


$$ 


Update...Mead 
previous discussion....Dickerson/kitsmiller 
aviation...kitsmiller