Lewistown, Montana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

757
FXUS65 KTFX 031650
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
950 AM MST Tue Dec 3 2024

.KEY MESSAGES...

 - Afternoon temperatures warm to as much as 10 to 20 degrees
   above average by Saturday, though areas near the river valleys
   along the Hi- Line and in Chouteau County will see a much
   slower warm up.

 - Winds will become strong again along the Rocky Front Thursday night
   into Friday, with more widespread strong wind potential this
   weekend.

 - Little in the way of precipitation is expected until later in
   the weekend and early next week when accumulating snow
   potential returns.

&&

.UPDATE...

Morning update has been published, with the main adjustment being
to cancel the High Wind Warning early as winds speeds and/or
gusts have fallen below criteria. None-the-less, breezy and gusty
winds will continue along the Rocky Mountain Front through the
remainder of the morning, with decreasing winds through the late
afternoon hours. Southwest to west winds will continue to push
warmer air further northeast towards the stubborn cold prone
areas of North Central Montana. With that being said, these areas
will still be the "coolest" across Southwest through North Central
Montana today. - Moldan

&&

.DISCUSSION...
/Issued 410 AM MST Tue Dec 3 2024/

 - Meteorological Overview:

A tightening pressure gradient coupled with mountain wave activity
will maintain bouts of strong, gusty winds along the Rocky Mountain
Front and neighboring high plains through the morning hours. The
shallow layer of cold air has mostly been scoured out the plains,
but will be reluctant to exit some of the normally colder Milk River
Valley locations and neighboring areas over the next few days,
especially with an expected reinforcing shot of colder air moving in
later today through early Thursday.

Otherwise, temperatures are expected to surge while winds increase
again along the Rocky Mountain Front during the second half of the
workweek. Then a prospective deepening trough dives southeastward
from BC/AB and brings widespread strong wind potential Saturday
through early Sunday. This looks to be followed by a cool down with
accumulating snow chances Sunday into Monday depending on the depth
of the said trough. - RCG

 - Forecast Confidence & Scenarios:

Winds :

Winds along the Rocky Mountain front and the high plains are
expected to peak in strength early this morning before diminishing
heading towards the early afternoon hours. No changes were made to
the ongoing high wind warnings which are scheduled to expire at 11
am MST.

Although breezy conditions are generally expected for much of the
week, the strongest and most widespread winds hold off until the
weekend. Winds initially strengthen again along the Rocky Mountain
Front Thursday night amid a tightening pressure gradient for more of
a `run of the mill` event before the potentially higher impact winds
move in Saturday through early Sunday. Around 55% of the ensembles
now favor a vigorous trough diving into the Northern Rockies this
weekend, though there are slight time differences among the
supporting members. Climate anomaly indicators such as the NAEFS and
the EC EFI are now picking up a signal for a stronger end wind event
and NBM probabilistic guidance is now highlighting over an 80%
chance for wind gusts over 55 mph along the Rocky Mountain
Front/high plains and over a 50% chance for locations along the MT
highway 200 corridor and portions of the Hi-Line.

Snow this weekend into Monday:

More seasonable temperatures and accumulating snow potential are
expected to follow the winds Sunday into Monday. Most ensemble
members continue to forecast H700 temperatures falling to around -
15C Sunday night into early Monday for at least some light snow at
all elevations, particularly the northerly upslope areas
Central/North-central and Southwest MT. Overall, mountain areas are
favored for the higher amounts. Of course this will all depend on
the 55% chance that the trough will be deep and cold enough to
materialize this scenario.

Temperatures :

Temperatures will overall be warming well above average through
Saturday, though the colder air will linger in the river valleys of
Hill, Blaine, and Chouteau counties through Thursday. I lowered
temperatures toward the Canadian models in these areas to account
for slow warming today and the cold front moving in later today into
Wednesday. - RCG

&&

.AVIATION...
03/12Z TAF Period

The primary concern this TAF period will be for gusty winds and
mountain wave activity, primarily along and adjacent to the Rocky
Mountain Front through the morning today. VFR conditions prevail
otherwise under mostly clear skies. -AM

Refer to weather.gov/zlc for more detailed regional aviation
weather and hazard information.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  47  22  40  19 /   0   0   0   0
CTB  40  18  31  19 /   0   0   0   0
HLN  48  25  46  23 /   0   0   0   0
BZN  47  22  46  18 /   0   0   0   0
WYS  39  10  38   6 /   0   0   0   0
DLN  48  19  46  18 /   0   0   0   0
HVR  35  15  26  11 /   0   0   0   0
LWT  48  25  42  22 /   0   0   0   0

&&

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

$$
http://www.weather.gov/greatfalls