737 
FXUS65 KTFX 061027 CCA
AFDTFX

Area Forecast Discussion...Corrected 
National Weather Service Great Falls MT 
325 AM MST Sun Nov 6 2022

.SYNOPSIS...

Temperatures remain well below average through mid-week as a 
colder airmass settles in from Canada. Widespread snow develops 
late tonight and continues through Monday and Tuesday, as Pacific 
moisture lifts over the low level cold air. Snow gradually ends on
Wednesday. Although not as cold, temperatures remain well below 
normal through the end of the week.

&&

.DISCUSSION...

Areas of light snow persist early this morning, but overall
continue to gradually dissipate as the atmosphere stabilizes under
shortwave ridging aloft. Surface winds have turned northerly
across North-central Montana as colder air settles in from Canada.
Temperatures will remain below average today with continued cold
advection producing a few light snow showers.  

Widespread snow returns to the forecast late tonight through 
Monday. A mid-level warm front will lift Pacific moisture from the
southwest late tonight, spreading light snow across much of 
North-central Montana through Monday. 25th-75th percentile 
snowfall amounts from the NBM range from around 1 to 3" for much 
of North-central Montana, trending upward a bit toward 2 to 5" 
north and west of Great Falls where the low level easterly flow 
will enhance the upslope flow into the Northern Rocky Mountain 
Front. This is only part of a complicated forecast. After the 
initial warm frontal passage aloft, an upper level jet streak 
arrives and begins to produce a band of heavier snow from northern
Nevada, across southern Idaho, and into Southwest Montana. The 
combination of surface convergence, upper level divergence, and 
orographic lift will combine to produce deep dendritic growth 
layer within this snowband. While confidence is high enough to 
issue a winter storm watch for the Southwest Montana mountains, 
there remains considerable uncertainty in the position, and 
northward extent of the snow band further north into central 
Montana later Monday night. It is anticipated that winter weather 
advisories will be posted on a later forecast, but are withheld 
for now due to lack of confidence in the position and extent of 
the secondary snowband for areas north of I-90 later Monday night.

The Arctic airmass deepens over the region on Tuesday, with an 
elongated cutoff trough over the western CONUS. Wind chill 
advisories may be needed as wind-chill temperatures dip toward 
-20F early Tuesday for portions of North-central MT. In the 
Southwest, snow is likely to continue as the upper level low 
slowly rotates through the interior west. Areas around West 
Yellowstone could be looking at a 4-day continuous snowfall from 
Monday through Thursday. Even further north, periods of light snow
may occur on Wednesday as embedded shortwave energy moves through
the southwest flow aloft. 

Snowfall comes to an end on Thursday, but cold air remains in
place through late week and on into the weekend ahead. 

&&

.AVIATION...
1148 PM MDT Sat Nov 5 2022 (06/06Z TAF period)

The main concern this TAF period is scattered snow showers across 
western portions of the region through 10Z, and low level clouds at 
terminals across North-central Montana through much of the morning. 
Periods of MVFR or IFR cigs/vis will be possible with snow showers 
through the early morning at KGTF and KHLN. Elsewhere across North-
central Montana, where low level clouds are moving in behind a 
Canadian front, MVFR cigs are expected at times through the morning. 
Otherwise, expect a largely quiet 24 hours, before the opportunity 
for additional snow moves into Southwest Montana late tomorrow 
night. Terrain may be obscured through the morning. -AM

KWYS TAF will not be issued again until airport operations resume
next spring.

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  27  12  22   0 /  10  40  80  60 
CTB  19   4  12  -6 /  20  80 100  40 
HLN  37  16  25   7 /   0  40  80  70 
BZN  40  19  36  13 /   0  60  80  90 
WYS  31  17  38  19 /   0  90 100 100 
DLN  36  20  35  15 /   0  60  90  80 
HVR  25  10  25   5 /   0  20  80  70 
LWT  30  12  30   5 /  10  20  70  80 

&&

.TFX WATCHES/WARNINGS/ADVISORIES...

WINTER STORM WATCH IN EFFECT FROM LATE TONIGHT THROUGH TUESDAY 
MORNING FOR Ruby Mountains and Southern Beaverhead 
Mountains...Gallatin and Madison County Mountains and Centennial 
Mountains

&&

$$

http://www.weather.gov/greatfalls