Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 211754

Area Forecast Discussion
National Weather Service Great Falls MT
1155 AM MDT Fri Oct 21 2016

Aviation section updated

Current satellite imagery shows broad area of moisture in the
westerly flow aloft creating mostly high, thin overcast clouds
from north of Great Falls all the way to Bozeman/Dillon. As seen
in local webcams, there are some areas with lower clouds over the
central mtn ranges and parts of southwest MT. But other than a
few isolated showers along the higher elevations of the Rocky Mtn
Front, there`s no precipitation with this cloud cover and expect
the mostly dry conditions to continue across the region today. The
clouds may limit the number of sites reaching highs in the 60s
this aftn, but mid-upper 50s are right at our seasonal average for
the region. Current forecast is in good shape; no changes this
morning. Waranauskas


Updated 1755z.
A westerly flow aloft will reside over the region through the
period...with an upper level disturbance moving through later
tonight and on Saturday morning. Expect a band of precipitation to
affect the Rocky Mountain Front...then generally spread
northeastward along a line from Augusta to Havre from 07z to 17z
Saturday. Some MVFR conditions will be possible along that
line...with mountains obscured at times. Otherwise VFR conditions
should prevail. Brusda


/ISSUED 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


GTF  59  41  56  35 /  10  40  50   0
CTB  54  36  52  30 /  10  20  20   0
HLN  61  38  56  34 /  10  10  30  10
BZN  61  36  57  35 /  10   0  10  10
WEY  50  29  52  29 /   0   0  10   0
DLN  62  34  57  34 /   0   0  20   0
HVR  58  38  55  32 /   0  40  60   0
LWT  58  39  54  34 /  10  10  30   0




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