Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 220440

Area Forecast Discussion
National Weather Service Great Falls MT
1040 PM MDT Fri Oct 21 2016


Water Vapor and IR satellite imagery both reveal a characteristic
baroclinic leaf pattern over the PacNW. This indicates a broad
area of lift associated in this case with weak mid-level
frontogenesis. The combination of ascending air and cooler mid-
level temperatures will produce a band of light rain showers
across portions of north-central MT later tonight into early
Saturday. Short-term models have shifted this band of rain
slightly further north. Hence, POPS have been raised a bit across
the Hi-Line. The forecast continues to indicate a rapid
progression of this wave, with showers ending by mid-day Saturday.
Beyond this slight northward shift in POPs, freshened the hourly
forecast grids to better match observed trends. PN


.AVIATION...Updated 0440z.

A weak upper level disturbance will cross the Rockies tonight and
bring a chance of showers across central and northern portions of
the region. Most areas affected by precipitation will remain VFR
although local MVFR near showers is possible as well as mountain
obscuration. Dry conditions and brisk west winds will develop
Saturday behind the associated cold front.


/ISSUED 510 PM MDT Fri Oct 21 2016/
This Afternoon through Sunday Evening...Latest analysis shows high
overcast clouds from earlier today have thinned quite a bit,
allowing more sunshine and temps to warm close to forecast highs of
upper 50s/low 60s. Forecast is on track for the next shortwave trof
(currently over central WA) to reach the Rocky Mtn Front tonight.
Scattered rain showers develop initially over western parts of the
Hiline and then expand south/east into the central counties through
the morning hours on Sat. Southern edge of the precip will be
along/north of a Helena to Lewistown line, with the main swath of
rainfall expected from near Lincoln northeast toward Ft Benton and
out to Hill/northern Blaine counties. Short-term models remain
consistent on rainfall projections of a tenth- to a quarter-inch of
rain in the main swath, with lighter amounts on the northern/
southern edges. Locations from Townsend south to the MT/ID stateline
will remain dry through the day.  The shortwave makes a quick exit,
heading into eastern MT by mid-aftn tomorrow, with gradually
clearing skies from west to east.  High pressure ridging returns on
Sun with a mix of clear skies and scattered high clouds; no precip
is expected anywhere in our region on Sun.

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  43  57  34  59 /  30  60   0  10
CTB  39  53  29  53 /  30  10   0  10
HLN  41  57  34  59 /  10  20  10   0
BZN  39  57  34  61 /   0  10  10   0
WEY  32  50  29  55 /   0   0   0   0
DLN  37  57  33  60 /  10  10   0   0
HVR  42  57  31  56 /  40  70   0  10
LWT  41  55  34  57 /  10  20   0  10



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