Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 191816
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1116 AM MST Thu Jan 19 2017

Aviation Section Updated

.UPDATE...
Made minor updates this morning to update QPF and snow amounts
mainly south of I-90 and east of I-15. Issued a Special Weather
Statement to cover snow and localized blowing snow potential in
these areas through midday. Upped max temperatures as well over
the Plains as chinook winds have allowed for temperatures in some
locations to meet or slightly exceed forecast highs already,
despite mostly cloudy conditions. Cassell


&&

.AVIATION...
Updated 1816Z.
A moist, SW flow aloft continues to bring BKN low/mid clouds into
the area at this time. However, precipitation has mainly been
confined to the higher terrain of SW MT. Short term model guidance
suggests this trend will continue. That said, a few rain/snow
showers will be possible at KEKS/KBZN and maybe even as far north as
KLWT later this afternoon through tonight. Due to a lack of better
moisture and lift, confidence remains too low to include any
prevailing or TEMPO groups for precip, but we will continue to
monitor this through tonight. In general, VFR conditions should
prevail for most, if not all, sites through Friday morning. Martin

&&

.PREV DISCUSSION...
/ISSUED 450 AM MST Thu Jan 19 2017/
Today through Saturday...A slightly more active weather pattern is
moving through the Pacific Northwest over the next few days, but
because of downslope winds and the track of the storms, overall
precipitation amounts for North Central look to be mostly none
and generally on the low side over the Southwest. For today, and
tonight, an upper level trof will move from Washington towards
central MT, with an upper level disturbance moving through as
well. Expect scattered rain/snow showers over the Rocky Mountain
Front, while a better chance for light snow develops near the
MT/ID border in southern MT. The best area to receive accumulating
snow today/tonight looks to be south/east of a line from Lima to
Bozeman. About 1 to 2 inches is possible at lower elevations and 2
to 4 inches in the mountains in this region. For now, no advisory
will be issued. Additionally, some rain could mix in at times,
especially for showers that are further north towards Lewistown.
However, the chances for any freezing rain at this time look
low/isolated. Over the north, as the trof moves through today,
temperatures will be a touch cooler but still well above normal.
Expect more seasonable temperatures for Friday/Saturday with a
gradual cooling trend. Overnight lows will be cold by Saturday
morning, falling back into the single digits/teens. No
significant/widespread precipitation is expected Fri/Sat, other
than a passing snow shower mostly in the mountains. Brusda

Saturday Night through Thursday...Medium range models remain in good
agreement for Saturday night through Tuesday but diverge somewhat at
the end of the forecast period. Period is still expected to start
off with an upper level trough over the Four Corners Region that
progresses rapidly into the southern Great Plains. Shortwave ridging
develops behind this system but progresses into the central Rockies
by Monday morning. The next system to affect the western US drops
out of the Gulf of Alaska and deepens into a deep closed low off the
Pacific Northwest coast before moving inland and broadening into a
full latitude trough over the entire western USA Monday night and
Tuesday. Models appear to be in good agreement that the core of
energy associated with this trough will remain well south of Montana
before moving into the central Great Plains. Solutions diverge
beyond this but the overall trend points toward a ridge developing
along the West Coast Wednesday and Thursday. As this system builds,
the southern half of the upper trough is expected to remain in place
over the Four Corners region as the main portion ejects through the
Great Lakes for an elongated, positive-tilt trough and north to
northeast flow aloft over Montana. With good run-to-run continuity
and model agreement have once again made only minor changes to the
going forecast package. Temperatures should remain near seasonal
averages with the best chance for any precipitation expected to
favor the western mountains and southwest Montana through the entire
forecast period. mpj

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  44  28  37  19 /  10  20  10  10
CTB  45  23  36  16 /  10  10   0   0
HLN  34  19  27   8 /  20  20  10  10
BZN  34  18  29   6 /  30  50  30  10
WEY  23  13  23   1 /  60  60  30  20
DLN  37  15  29  10 /  30  20  20  10
HVR  42  28  36  20 /  10  10  10  10
LWT  41  30  37  18 /  30  40  20  10

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

weather.gov/greatfalls



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