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Area forecast discussion 
National Weather Service Glasgow Montana 
311 PM MDT Thursday Mar 18 2010 


Short term...for northeast Montana...tonight through Saturday... 
building upper ridge along West Coast is turning the flow more 
northerly and increasing over our area. This will keep cold 
advection going through Friday. Weak Arctic front from the north arrives 
this evening as well. 


This has caused upper trough to turn southeast across our area today. 
Mainly low overcast spreading S across our area as well. Slightly 
unstable airmass in lower levels has also caused afternoon 
cumulus to form in areas that had more sunshine. 
However...satellite channels indicate this is mainly all low 
overcast without that much vertical development...and any showers 
so far have been very isolated and weak at best. Main upper low 
circulation seen moving east-southeast across S mb. 


Secondary upper trough will be arriving from the north-northwest Friday. With 
similar conditions and airmass...expect only isolated light showers 
at best...in the form of snow though. Most of the area will not 
get much above freezing Friday for highs...or not even that high. Thicknesses 
drop to the upper 510s and lower 520s dm and 850 temperatures area -8c to 
-5c during the afternoon. 


Strong surface high of combined Arctic and Pacific air brings 
clearing skies and winds becoming light as it arrives directly 
over east Montana Friday night from the northwest. This will drop lows to the teens. 
Snowcover not much influence now...so will stay close to 
MOS...and models are in good agreement through the period. 


The surface high shifts to our S by Sat afternoon...and upper 
ridge shifts to our east. This will bring a day of sunny and warmer 
weather Sat...with afternoon SW wind at the surface after the 
morning inversions Burns off and mixes out. Simonsen 




Long term...Saturday night through Thursday... 
made some changes to the early portion of the period as models try 
to resolve what happens with introduction of Pacific trough. Models 
trending on bringing warmer temperatures into the area ahead of the said 
system Sunday. Raised temperatures as this would have a better chance of 
happening now that ground is bare of snow. But on Monday...decent 
cold front drops through the area which may mean that north to south 
temperature gradient may be greater. Therefore temperature gradient was tightened 
up a tad. Showers continue to look possible as instability looks to 
be sufficient. Rest of forecast looked good. Jamba 


Previous discussion... 
the extended period features an active weather pattern with some 
model uncertainty. Saturday night and Sunday has northeast Montana 
in a shortwave upper ridge that will give the area dry weather. A 
quasi-stationary front may split the area giving it a cool 
northeast and warm southwest temperature pattern. 


A shortwave trough coming inland from the Pacific northwest will 
affect Montana Monday bringing the front south as a cold front. 
Could see some light rain and/or snow with this system...models 
differ on placement of the moisture at this point. Will maintain 
slight chance probability of precipitation for now. The moisture will linger through 
Monday night. 


Another shortwave trough plows through the area on northwest flow 
aloft either Tuesday...Tuesday night or Wednesday keeping at 
least a slight chance of rain and/or snow across the area 
depending on temperatures. The GFS is stronger than the European model (ecmwf) with 
the upper level dynamics at this point but there has been run to 
run differences that makes the timing hard to Pin Point. 


Another wave is possible on Thursday as the flow turns more zonal 
aloft. Will not mention precipitation with this yet as moisture appears 
to be staying to the north. Forrester 


&& 


Aviation... 
low VFR/high MVFR ceilings look to linger across the area into 
Friday. A snow shower could also cross the area Friday bringing 
visibilities briefly into the MVFR range. Northwest winds are expected to 
diminish significantly later this afternoon/early this evening 
then increase a bit Friday...to about 10 to 15 kts. Jamba 


&& 


Glasgow watches/warnings/advisories...none. 


&& 


$$ 


Weather.Gov/Glasgow