Area Forecast Discussion
Issued by NWS Glasgow, MT

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FXUS65 KGGW 181440 AAA

Area Forecast Discussion...UPDATED
National Weather Service Glasgow MT
840 AM MDT Sun Mar 18 2018


Sent an update this morning to include the latest observational
data, such as dense fog in Malta and snow likely through most of
Phillips County. Followed the best model consensus I could find
through the rest of the day. Expect the NW snow to diminish and
new snow to develop across our SE zones later this afternoon.

Previous Discussion: Synoptic Setup: Coldest air sets over
Quebec, The Hudson Bay and Canadian Shield. A trough juts west
from here through the Alberta front range where it gains a pacific
characteristic over southern British Columbia and the Pacific
Northwest. Weak ridging over the southern US Rockies and southern
US Plains contrasts this cold air in southwest flow that runs up
into eastern Montana. Upstream a meso-ridge resides over northern
BC with a meso-trough behind it in Yukon territory and the
Alaskan Panhandle.

Today through tonight: A closed low aloft has formed up in the
southwest flow and is driving many of the mesoscale features
over Montana including weak showers over low stratus. Further
showers will develop and slowly move northeast this afternoon and
overnight with more stratus, drizzle, and fog.

Monday through Monday night: By Monday a large chunk of the low
stratus should begin lifting and dissipating as the northern BC
meso-ridge moves through. A few light showers may exist into the
early evening. Meanwhile a ridge off the coast of California will
move inland.

Tuesday through Thursday night: Ridge over California will
amplify and spread over the western half of the CONUS. This will
warm temperatures and generate dry conditions. Look for highs in
the 30s and 40s by the end of these periods. A large pacific
trough will develop off the coast of the Pacific Northwest and
British Columbia.

Friday onward: Ridge will scurry eastward as the pacific trough
moves inland. Current model runs begin to break apart from here
onward decreasing certainty as to how the trough will move
through. Latest ensemble guidance actually has warmed Friday and
Saturday to even with the previous ridge, but this seems very
unlikely if the pacific trough does move in, so look forward to
future change downward in temperatures.    GAH




SYNOPSIS: A closed low over central Montana is sending waves of
light showers, low stratus, and fog into eastern Montana which
should last through Monday. Satellite trends in clouds are very
broken and disorganized. While near airport showdown ceilings are
occuring west of the terminals, they have yet to move into
northeastern Montana. Uncertainty is high this morning with
observations changing rapidly. Expect amendments.

WIND: Mainly light and variable.





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