Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 211123

Area Forecast Discussion
National Weather Service Great Falls MT
523 AM MDT Fri Oct 21 2016



Today through Saturday...A shortwave high pressure ridge will move
eastward over our CWA today, providing many places with mostly
cloudy skies and dry conditions. The exception will be the Rocky
Mountain Front, where a few upslope rain showers and higher-
elevation snow showers may spill-over the Continental Divide.
Tonight, a weather disturbance will move onshore western WA and OR
and near the Continental Divide around daybreak Saturday. This
disturbance should then reach the MT/ND border by nightfall.
Expect mostly cloudy skies and scattered rain showers/higher-
elevation snow showers to accompany this disturbance, especially for
areas north of I-90. In addition, high-resolution model data suggest
a mesoscale rain band may impact portions of North-Central Montana
Friday night into Saturday morning along and ahead of the
disturbance. This mesoscale band looks to result from confluent flow
and frontogenesis amidst ample moisture within the 850-500 mb layer.
While rainfall amounts should generally be a few hundredths to a
tenth of an inch, the mesoscale band may produce a tenth to a
quarter of an inch of rainfall. Latest indications suggest this band
will develop over the Chouteau to Havre corridor and then impact
locations such as Great Falls, Fort Benton, Chinook, and Roy as it
moves eastward. However, confidence in the occurrence and location
of this band is low at this time. Most places will have highs in the
mid 50`s to lower 60`s today, lows in the mid 30`s to lower 40`s
tonight, and highs in the 50`s Saturday. Snow levels will vary
between about 6000 and 8000 feet MSL throughout the period, with the
lowest (highest) snow levels near Glacier Park (the Idaho border and
Yellowstone Park).

Saturday Night through Sunday...Dry weather should return to our CWA
by Saturday evening and then continue through Sunday as another
shortwave high pressure ridge moves in from the Pac NW. Under partly
to mostly cloudy skies, lows should reach the low to mid 30`s for
most places Saturday night and be followed by highs in the mid 50`s
to lower 60`s Sunday afternoon. Temperature readings will be near-
normal to about 10 degrees above normal during the short-term
forecast period. Jaszka

Sunday night through Friday...Large scale weather pattern next week
generally features a trough off the west coast with a ridge
downstream over the Northern Rockies and MT. Early next week models
are in fair agreement in the upper ridge amplifying over the
region and bringing milder than average temperatures and generally
dry conditions. By Tuesday night, weakening Pacific energy ejecting
out of the offshore trough moves through the region for some showers,
though precipitation amounts look to be fairly light. Slight cooling
is anticipated behind this feature for Wednesday. Models diverge some
with the degree of ridging that will follow for latter portions of
next week with the ECMWF/CMC models bringing a quick re-
amplification of the ridge while the GFS brings several northern
stream shortwaves across the Canadian Prairies and northern Plains
states, which results in suppressed ridging and delayed warming.
Leaning more towards the ECMWF/CMC solution at this point but both
scenarios are relatively dry for the region with temperatures near
or somewhat above seasonal averages. Hoenisch


Updated 1123Z.

Westerly flow aloft and predominantly VFR expected through 12Z/Sat.
Within the westerly flow aloft, the next weather disturbance is
expected to move onshore western WA/OR by 06Z/Sat and then near the
Continental Divide by 12Z/Sat. Accordingly, broken mid- to upper-
level cloud cover will persist over the area. Scattered rain showers
should develop and CIGS should lower over portions of North-Central
Montana around and especially after 06Z/Sat. This includes KHVR and
KGTF. Periods of mountain obscuration should be expected between
about 06Z and 12Z/Sat. Jaszka


GTF  60  42  57  36 /  10  30  40  10
CTB  56  37  54  32 /   0  20  20   0
HLN  62  39  57  35 /  10  20  30  10
BZN  61  37  59  36 /   0  10  10  10
WEY  50  30  53  30 /   0   0  10   0
DLN  61  35  58  35 /  10  10  20   0
HVR  59  39  56  32 /   0  20  30   0
LWT  60  40  55  36 /   0  10  40  10



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