Area Forecast Discussion
Issued by NWS Glasgow, MT

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FXUS65 KGGW 210921

Area Forecast Discussion
National Weather Service Glasgow MT
321 AM MDT Thu Jun 21 2018


Synoptic Setup: Short term begins with a large area of hot high
pressure over the Desert Southwest. A warm ridge rises out of
this airmass toward the north and stretches through eastern
Montana and into Alberta and the Yukon Territory. A surface trough
over the Gulf of Alaska drops south off the coast of British
Columbia and turn inland over the Pacific Northwest. The base of
this trough is digging into the weakest point of this ridge in
Montana and will begin crossing over soon.

Today and tonight: With the ridge in place conditions will warm
and remain dry until the afternoon hours when lift from a jet
streak passes over the central Montana mountains. This may spark a
few thunderstorms that could exit into our far western zones by
the afternoon and evening hours. During the overnight hours the
ridge will have broken in two with a steady stream of pacific
moisture entering the area and showers increasing.

Friday through Saturday: Models have limited mesoscale specifics
but on the synoptic level each model seems to indicate that the
base of the trough over the PCNW will break off and move over
Montana which should increase chances for rain showers, even if
QPF totals will be low.

Sunday through Monday: As the disturbance exits a new ridge will
build up into Monday. Showers across the region should decrease
into Monday as well while temperatures are expected to warm

Monday night onward: The ridge breaks down rather fast with a
large trough moving across southern Canada and the base skirting
the south of the International Border. This seems to be the set up
for convective weather with the potential for some severe
elements initially. After which the high pressure to the south
moves farther north placing Montana on the edge of the most active
weather pattern through mid-week. GAH



DISCUSSION: Excellent flying weather expected throughout the next 24
hour TAF period with a CU deck around 10 kft. Clouds will scatter
out this morning into tomorrow.

WIND: south to southeast at 5 to 15 kts through midnight...
backing to the east to southeast and becoming light Friday





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