Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 151706
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1006 AM MST Wed Nov 15 2017

.UPDATE...

The forecast remains in good shape this morning, so only minor
adjustments were made to better align with observed trends. There
are areas of freezing fog that have developed along the HiLine.
These should continue to erode through noon. PN

&&

.SYNOPSIS...

Generally quiet weather is expected through this afternoon across
the area with temperatures running close to or just above normal.
A Pacific cold front will move through Thursday and Friday
bringing gusty winds to the plains and snow in the mountains. The
valleys of Southwest Montana will see some snow as well, mainly
Thursday evening through Friday.

&&

.AVIATION...
Updated 1118Z.

VFR conditions are expected to prevail through the current TAF
cycle, but a stratus deck may lead to lower CIGS/VIS along the Hi-
line.

The main concern this morning is the potential for lower CIGs/VIS at
KCTB/KHVR due to a stationary front in the area. This front isn`t
expected to move much today and there is a decent amount of low
level moisture on the cool side which could allow a lower stratus
deck develop this morning or afternoon. For now, I kept KCTB and
KHVR at VFR, but this will be closely monitored. The next system to
impact the area approaches late tonight, but most aviation impacts
should hold off until after the current TAF cycle (and mainly be
confined to SW MT). MARTIN

&&

.PREV DISCUSSION...
/ISSUED 418 AM MST Wed Nov 15 2017/

Today through Friday...Morning surface analysis shows high pressure
over central SK building in behind a surface front that stretches
from SE MT back NW to near Cut Bank and up into southern AB. As the
high slides SE today, the surface front will more or less stall,
then eventually begin to lift back north as a warm front. However,
the low-level cold air in place along the Hi-line may prevent the
front from moving completely through that area until late tonight or
THU, making the temp forecast there a bit tricky. The colder temps
will hold on longest in the Milk River Valley. Across the plains
west of the front, downsloping should help temps warm above normal.

Attention then turns towards the next Pacific front, which will
sweep across the plains on Thursday with gusty winds, then stall
for a short time in the vicinity of SW MT, before finally pushing
east on FRI. Like the last front, precip will be focused along the
Continental Divide and across SW MT. Also, once again, there are
indications that low-level instability will be present and at
least modest convergence, which may lead to another round of
heavier snow bands across parts of SW MT (perhaps even a few
lightning strikes). Given the uncertainties regarding where the
heaviest snow will occur, we`ll hold off on issuing any winter
weather products at this time, but this will be closely monitored
in later forecasts. The greatest impacts are expected over Marias
Pass as well as passes along the MT/ID/WY border.
Dillon/Ennis/Bozeman areas will likely see some snow as well,
especially Thursday evening through Friday morning with at least
minor impacts. MARTIN

Friday night through Wednesday...Weather system expected to move
through the region on Friday will move rapidly eastward Friday night
with northwest flow aloft setting up over Montana. This is expected
to set up a dry and windy period for Montana with temperatures
rebounding back to near or above seasonal averages through the
weekend. Unfortunately, once again, the model solutions diverge
significantly by Monday morning and remain so through Tuesday before
slowly trending back toward loose agreement as they build an upper
level ridge over the western USA on Wednesday. Have once again
trended the uncertain portion of the forecast period toward a
SuperBlend/NBM blend of models solution for Monday and Tuesday. This
introduces a slight chance for precipitation over the plains with
higher PoPs in the western and Southwest Montana mountains. The good
news with regard to models trending toward ridging for Wednesday
suggest that mostly and relatively warm conditions look favorable
for the travel days leading up to Thanksgiving. mpj

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  44  36  47  27 /   0   0  10  10
CTB  32  25  37  22 /   0   0  20  10
HLN  36  30  45  25 /   0  10  30  20
BZN  32  31  46  22 /   0  10  40  50
WEY  30  28  38  21 /  10  90  80  60
DLN  38  34  48  23 /   0  10  30  40
HVR  32  25  42  19 /   0  10  10  10
LWT  39  34  48  26 /   0   0  20  20

&&

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

$$

http://www.weather.gov/greatfalls



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