Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 221750
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1150 AM MDT Fri Mar 22 2024

Aviation Section Updated

.SYNOPSIS...

Areas of light snow will continue today across north-central
Montana where a colder airmass remains in place. A Pacific
weather system 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.

&&

.Update...

Morning update has been published, with only minor adjustments
made to PoPs to incorporate latest Hi-Res model guidance and radar
trends. Additionally, reduced temperatures by 1-3 degrees for most
areas along and north of the I-90 corridor as expansive cloud
cover and continued cold air advection across these areas should
aide in temperatures falling below earlier guidance. This will be
especially true over the plains of Central and North Central
Montana where observed high temperatures have been well below
guidance for the past several days now. Otherwise the remainder of
the forecast remains on track, and no adjustments are needed to
the current suite of Winter Weather Advisories in place over
portions of Central and North Central Montana through tonight. -
Moldan

&&

.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.

&&

.PREV DISCUSSION...
/ISSUED 535 AM MDT Fri Mar 22 2024/

Key Points:

--Periods of mainly light snow and minor impacts today and
 tonight

--More significant winter weather impacts likely late Saturday
  through early Sunday with moderate to heavy snowfall rates

--Cold temperatures becoming more widespread this weekend could
  create difficult conditions for newborn livestock

An expansive cold airmass and area surface high pressure remains
located across central Canada, sliding SE around the western
periphery of an anomalously deep large scale low/trough centered
near Hudson Bay. Meanwhile, a fairly vigorous upper level low
moving toward the OR coast today moves onshore tonight with a
portion of its mid-level circulation and associated surface low
tracking across SE ID and WY Saturday night, setting the stage for
a period of more impactful winter weather including significant
snowfall across the region late Saturday through early Sunday.

The leading edge of the cold airmass has made as far south as
Boulder Hill and Toston by 3AM and is likely to reach the I-90
corridor this morning before stalling. Deeper cold air is in place
across the N-central MT plains with bands of light snow
continuing today within a somewhat broad and nearly stationary
700MB frontal zone from NW to SE across the area. Coverage of
light snow across N-central MT may decrease some today as
frontogenic forcing weakens some but is likely to increase again
tonight with some help from a more favorable positioning beneath
the right entrance region of an upper level jet. Additional snow
amounts today and tonight across N-central MT are expected to
range from 3-4 inches along the continental divide west of the
Rocky Mtn Front to 1-3 inches along a swath through Pondera,
Teton, Chouteau and northern Fergus counties with amounts tapering
to an inch or less from Havre to the NE and along and south of
the MT-200/US-87 corridor. Winter weather advisories continue
through tonight for much of this area with primary impacts being
some slick roads this morning before late March solar heating
warms roads despite air temperatures remaining near or below
freezing. The same areas of north-central MT are likely to see
some slick roads develop again tonight through Saturday morning as
bands of light snow move across the area.

A period of more impactful winter weather develops by late
Saturday afternoon as deeper moisture and stronger mid-upper level
forcing shifts into the region with some locally moderate to
heavy snowfall rates possible Saturday night as this energy
lifts across the area. Focus for heavier snowfall amounts remains
across north- central MT but much of SW MT is likely to see a
period of accumulating snow as well. Total snow/QPF amounts have
decreased slightly (by around an inch) along with probabilities
for snowfall in excess of 6 inches (40%-Great Falls, 60%-Havre).
Have kept the Winter Storm Watch as is with higher resolution
models later today likely to shed some additional light on the
location of greater impacts and snow amounts Saturday night into
Sunday. Probabilistic Winter Storm Severity Index (pWSSI)
indicates primarily minor impacts but in addition to snowfall and
period of heavier rates/lower visibility Saturday night, cold/raw
conditions will create difficult conditions for newborn livestock
and those tending to them this weekend, especially on Sunday and
Sunday night as the coldest temperatures settle across the area.

An active and cool weather pattern looks to continue next week
with temperatures warming some by Tuesday but likely to remain
below seasonal averages for late March. Additional Pacific
disturbances are likely to move through the region later next
week, but timing and impacts are still uncertain. Hoenisch

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  31  20  28  13 /  40  60  70 100
CTB  24  14  22  10 /  70  80  90  90
HLN  43  27  38  18 /  30  30  60  90
BZN  47  26  48  16 /  20  20  70  90
WYS  45  25  45  21 /  20  20  90  90
DLN  53  31  51  24 /  20  20  70  80
HVR  25  13  24  11 /  30  70  90  90
LWT  28  16  29  10 /  80  70  70 100

&&

.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 Storm Watch from Saturday morning through Sunday evening
for Bears Paw Mountains and Southern Blaine-Cascade County below
5000ft-East Glacier Park Region-Eastern Glacier, Western Toole,
and Central Pondera-Eastern Pondera and Eastern Teton-Eastern
Toole and Liberty-Fergus County below 4500ft-Gates of the
Mountains-Hill County-Judith Basin County and Judith Gap-Little
Belt and Highwood Mountains-Northern Blaine County-Northern High
Plains-Snowy and Judith Mountains-Southern High Plains-Southern
Rocky Mountain Front-Western and Central Chouteau County.

&&

$$

http://www.weather.gov/greatfalls


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