440 
fxus65 kggw 202058 
afdggw 


Area forecast discussion 
National Weather Service Glasgow Montana 
258 PM MDT Sat Mar 20 2010 


Short term...for northeast Montana...tonight through Monday... 
warming will continue into Sunday as the upper ridge pushes warm 
air east of The Rockies. Developing downslope will spread some 
stronger winds into the plains...but mainly over the higher 
terrain where mixing will be better...by Sunday afternoon. 
Moisture will also be spreading eastward ahead of next trough 
pushing into the Pacific northwest...but will generally result in 
high clouds for the region on Sunday as downslope keeps the low 
levels dry. 


Lee cyclogenesis develops on Sunday night then pulls away from the 
mountains on Monday as the shortwave trough pushes through the 
northern rockies. Moisture lowers and instability increases with 
cold air advection...leading to increased chance of showers by 
Monday. Temperature profiles suggest that precipitation will fall 
as rain for most of Monday. Ebert 




Long term...Monday night through Saturday... 
the polar vortex starts out over the Yukon territory and just to 
the west of the Hudson Bay. Pieces of shortwave energy rotate 
around the polar vortex and are ejected south southeastward towards 
the northern High Plains and Great Lakes region. The GFS European model (ecmwf) and 
the Gem are showing this pattern throughout the extended. As the 
short wave energy rounds the polar vortex it will pick up the 
Arctic air and trys to push it southward towards the lower 48. As 
it looks now the brunt of the Arctic air will remain north of the 
international border. This pattern could change with future model 
runs but the time of year and the dwindling snow pack across 
southern Canada is working against the really cold air making it 
too far south. 


So with this in mind the models show the Arctic frontal boundary 
wavering in and out of the northeast zones. Did not change tempertures 
very much at all in the extended but did tweak a few day time 
highs during the up coming week. Especially for Thursday as this looks 
like the best chance for a glancing blow of the Arctic air. Being 
this far out the precipitation is tough to call but a mix of rain 
and snow with mostly snow during the overnight hours is possible. 
Of course if the models change and send the blast of Arctic air 
through southern Montana...the precipitation type would be all 
snow. 


Models have been fairly consistent lately in the medium term showing 
a shortwave moving across western Montana on Monday night and 
Tuesday with enough instability and cold air working it way into 
the County Warning Area for snow showers Monday night and then a mix of rain and 
snow showers for Tuesday. This will come to an end as both models 
show an upper ridge building in from the west Tuesday night into 
Wednesday to put an end to the mixed precipitation through 
Thursday morning. By Thursday afternoon models show the the bulk 
of the polar vortex pushing down and glancing nemont in what 
quickly becomes northwest flow and a very strong gradient across 
the region. Overrunnung associated with teh cold air may lead to 
siome mixed showerrs acros the region. A weak front may help to 
produce some mixing and temperatures scouring around Friday. 


At this point models begin a breakdown in consistancy. Best guess 
at the moment is based around the ec with the Artic air mentioned 
earlier shoved well off to the east allowing for a strong ridge to 
build back into the intermountain west all the way up into Canada 
and raise current temperatures while dropping pop chances. 
Ghicks/rsmith 




&& 


Aviation... 
expect VFR conditions to prevail through tonight at all terminals. 
A few high cirrostratus clouds around 20 kft are likely. The winds 
from the southwest at 10 to 15 kts will back this evening slightly 
to the south and calm to under 10 kts after sunset. Ghicks 




&& 


Glasgow watches/warnings/advisories...none. 


&& 


$$ 


Weather.Gov/Glasgow