Area Forecast Discussion Issued by NWS Great Falls, MT
000
FXUS65 KTFX 222052
AFDTFX
Area Forecast Discussion
National Weather Service Great Falls MT
252 PM MDT Fri Mar 22 2024
.SYNOPSIS...
Areas of light snow will continue through tonight across north-
central Montana where a colder airmass remains in place. A Pacific
weather system then spreads more significant and widespread snow
across the area late Saturday and Sunday with a period of moderate
to heavy snow likely across some areas Saturday night.
Temperatures will continue to cool through the weekend with
coldest conditions likely Sunday and Sunday night.
&&
.DISCUSSION...
Rest of this afternoon through Sunday night...A potent spring storm
will bring accumulating snow to all of Southwest through North
Central Montana through the weekend, with below to well below normal
temperatures settling in across all of the region through Saturday
evening/overnight. Light to at times moderate snow has been on-
going over portions of Central and North Central Montana throughout
the day, with this snow expected to persist into the morning hours
on Saturday as mid-level frontogenesis pivots north to northwestward
ahead of the approaching upper level disturbance. Winter Weather
Advisories remain in effect for areas north/northwest of a Rogers
Pass, to Carter, to Hays line for this continued period of snow,
with additional accumulations of generally 1-2" expected through 6am
Saturday.
By Saturday morning the upper level trough will begin to move from
over the Eastern Pacific to over the Pacific Northwest before moving
east over the Rockies through the day on Sunday. A brief lull in
precipitation is possible during the mid- to late morning hours on
Saturday in wake of strong mid- to upper level warm air advection;
however, this will be short-lived as additional precipitation lifts
northeastward through the early to mid-afternoon hours.
Precipitation may initially begin as rain in Southwest and Central
Montana over this timeframe, but quickly transition to snow due to
strong cooling. The highest chance for moderate to heavy snow
falling across all of Southwest through North Central Montana will
be from the early evening hours on Saturday through the mid-morning
hours on Sunday as the best upper level divergence and mid-level
frontogenesis lifts and pivots across the region, especially for
areas southwest of a Dillon, to Helena, to Great Falls, to Chinook
line. With the exception of Northern Blaine, The Bears Paw
Mountains, Fergus County below 4500ft, and the Snowy Mountains where
a Winter Storm Warning is now in effect, a Winter Weather Advisory
now covers all of Southwest through north Central Montana from
18/21z Saturday through 00/06z Monday. One area that will need to be
watched will be across Southwest into portions of Central Montana as
Hi-Res guidance continues to indicate an intense band of
precipitation lifting northeastward Saturday evening and night,
generally east of a Dillon, to Helena, to Kings Hill Pass line.
Should this band actually materialize then snowfall rates in excess
of 1" per hour could be possible for a time, which may require an
upgrade from the Winter Weather Advisory to a Winter Storm Warning.
This spring storm will bring a multitude of impacts to the Northern
Rockies, including but not limited to hazardous driving conditions
and severe to extreme condtions to newborn livestock. - Moldan
Monday through Friday... Light mountain snowfall continues
throughout next week with a brief break in precipitation for
Wednesday as weak upper level ridging moves through our area then
ensemble member guidance is supporting for upper level troughing to
return for later next week. While still much uncertainty remains
for where troughing can occur exactly, probabilities from latest
National Blend of Models 4.1 data are above 50% for 24 hour
snowfall (Thursday into Friday) amounts exceeding 4 inches for
Southwest Montana mountain ranges. Lower elevations are near 50%
for a half inch of snowfall but with still much uncertainty this
far out, it will continue to fluxuate through the week with the
upcoming forecast model guidance. Temperatures for Monday will
still be colder than forecasted from the deterministic NBM for
Glacier county to Blaine County due to cloud coverage and recent
snowfall, so made minor adjustments to lower high temperatures
Monday 5 to 10 degrees. But I do want to mention that the National
Blend of Models 4.1 data is catching up to what we are thinking
for the long term, with a slow warm up across the Hi-Line and
everywhere else being near normal for temperatures next week until
later in the week where greater uncertainty remains for
temperatures. Webb
&&
.AVIATION...
1150 AM MDT Thu Mar 22 2024 (22/18Z TAF Period)
North Central Montana (KGTF, KLWT, KHVR, KCTB): Light scattered snow
showers continue throughout the TAF period that can bring a
reduction of visibility to below VFR conditions. WHile KHVR is
currently seeing clear skies at the beginning of this TAF period,
clouds will continue to move back in within the next hour. Low level
cloudiness continues to contribute to IFR and MVFR conditions as
well as light falling snow with these showers. There will be periods
of lesser snow shower activity late this afternoon and early
evening, but returns for tonight along with some breezy conditions
(mainly for KCTB) into tomorrow then through the end of the TAF
period.
Southwest Montana (KHLN, KBZN, KEKS): VFR conditions are forecasted
to continue through the TAF period with vicinity showers increasing
for tonight. There is a low probability (less than 30%) of snow
showers reaching the KEKS airfield during the TAF period, which can
bring conditions to MVFR status. But still kept it in the TAF as the
exact location and timing is still uncertain of where snow shower
activity will occur for tomorrow morning.
Widespread mountain obstruction continues through the TAF period.
Webb
Refer to weather.gov/zlc for more detailed regional aviation weather
and hazard information.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 22 29 13 21 / 60 90 100 90
CTB 15 23 12 20 / 90 90 90 60
HLN 26 38 19 25 / 30 80 90 70
BZN 26 47 18 29 / 20 80 90 70
WYS 25 45 21 30 / 30 80 90 70
DLN 31 52 23 31 / 20 90 100 60
HVR 13 24 10 21 / 60 90 100 80
LWT 17 30 10 18 / 60 70 100 90
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 6 AM MDT Saturday for Bears Paw
Mountains and Southern Blaine-East Glacier Park Region-Eastern
Glacier, Western Toole, and Central Pondera-Eastern Pondera and
Eastern Teton-Eastern Toole and Liberty-Hill County-Northern
High Plains-Southern High Plains-Southern Rocky Mountain Front-
Western and Central Chouteau County.
Winter Weather Advisory from noon Saturday to 6 PM MDT Sunday
for East Glacier Park Region-Eastern Glacier, Western Toole, and
Central Pondera-Eastern Pondera and Eastern Teton-Eastern Toole
and Liberty-Hill County-Northern High Plains-Southern High
Plains-Southern Rocky Mountain Front.
Winter Storm Warning from 3 PM Saturday to midnight MDT Sunday
night for Bears Paw Mountains and Southern Blaine-Fergus County
below 4500ft-Northern Blaine County-Snowy and Judith Mountains.
Winter Weather Advisory from 3 PM Saturday to 6 PM MDT Sunday
for Beaverhead and Western Madison below 6000ft-Big Belt,
Bridger and Castle Mountains-Canyon Ferry Area-Cascade County
below 5000ft-Elkhorn and Boulder Mountains-Gallatin Valley-
Gallatin and Madison County Mountains and Centennial Mountains-
Gates of the Mountains-Helena Valley-Judith Basin County and
Judith Gap-Little Belt and Highwood Mountains-Madison River
Valley-Meagher County Valleys-Missouri Headwaters-Northwest
Beaverhead County-Ruby Mountains and Southern Beaverhead
Mountains-Upper Blackfoot and MacDonald Pass-Western and Central
Chouteau County.
&&
$$
http://www.weather.gov/greatfalls