Area Forecast Discussion
Issued by NWS Great Falls, MT

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900
FXUS65 KTFX 212347
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
545 PM MDT Thu Sep 21 2017

Aviation Section Updated.

.SYNOPSIS...

A developing weather system will bring widespread rain and snow to
Southwest and Central Montana tonight and Friday. North Central
Montana and the Hi-Line will see a chance for rain and snow as
well but accumulations will be much less than areas to the south.
High temperatures are expected to be only in the 40s but warmer
and drier conditions return for the weekend.

&&

.DISCUSSION...

Tonight through Friday night...A developing storm system will
bring widespread rain and snow to Southwest and Central Montana
overnight. Latest model runs have trended this system about 100
miles further north than earlier runs were indicating. As a
result, snow levels (and temperatures) are expected to be lower
than originally indicated so have introduced a mention of snow
over the plains of Central Montana, including at Great Falls and
Lewistown, on Friday morning. However, temperatures over the
plains will likely remain just a touch too warm to allow much
snow accumulation (if any), and the best accumulations are still
expected to be in the mountains. Lower snow levels and heavier QPF
have also trended snow accumulations higher for the mountains of
Fergus County so have expanded the Winter Weather Advisory to
include the Big Snowy, Judith and Moccasin Mountains. Periods of
precipitation will continue for much of the day on Friday and even
into Friday evening before the system begins to pull away from
the region and precipitation tapers off to showers. mpj

Saturday through Thursday...Spotty shower chances will continue into
the weekend with periods of clouds and sun as the upper-level low
slowly moves to the east and away from our area. Upper ridging
begins to slowly move toward the area from the west through the
week. The main challenge during the week will be watching for
relatively fast-moving disturbances bringing a few showers to the
region, especially the mountains, during this time. However, the
overall trend will be a trend toward warmer (near normal or
slightly above) and drier conditions. CC

&&

.AVIATION...
Updated 2345z.

Main concern for tonight through late Friday is a strengthening
weather system that will impact southwest and central Montana.
Surface winds are already shifting to the north/northeast across
North Central Montana in response to this developing system. Expect
developing widespread precipitation with significant mountain
obscurations and cigs lowering to IFR/MVFR overnight as rain mixes
with or completely changes to snow. Show will then change back to
rain by mid-day Friday, gradually tapering Friday evening. mpj/PN

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  32  40  31  51 /  70  80  60  20
CTB  31  40  30  52 /  10  50  40  20
HLN  33  40  31  51 /  70  90  50  20
BZN  33  44  29  49 /  80  80  40  20
WEY  27  39  21  45 / 100  80  30  20
DLN  32  39  27  45 /  90  90  40  20
HVR  35  46  33  55 /  20  60  50  20
LWT  33  39  30  49 /  80  80  40  20

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 6 PM this evening to midnight MDT
Friday night above 5500 feet for Beaverhead...Gallatin...
Madison...Meagher.

Winter Weather Advisory from midnight tonight to midnight MDT
Friday night above 4500 feet for Broadwater...Cascade...Central
and Southern Lewis and Clark...Fergus...Jefferson...Judith Basin.

&&

$$

weather.gov/greatfalls



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