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000
FXUS65 KTFX 182040
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
240 PM MDT Thu Apr 18 2024

.SYNOPSIS...

A re-enforcing cold front will advance south across the Northern
Rockies late tonight and through the morning hours on Friday,
bringing another day of well below normal temperatures to
Southwest through North Central Montana. In addition to the cool
conditions, light snow or flurries are possible on Friday;
however, little to no accumulations are expected. Temperatures
warm somewhat on Saturday while remaining below normal, with
return to near normal temperatures expected by Sunday.

&&

.DISCUSSION...

Rest of today through tonight...Isolated to scattered snow showers
have develop this afternoon over the plains of Central and North
Central Montana where earlier clearing allowed surface temperatures
to warm sufficiently so that convective temperatures were reached.
Additionally, snow showers were also present along the Continental
Divide, with additional development expected further south and east
across the Central and Southwest Montana mountains through the
remainder of the afternoon and evening hours. While snow
accumulations will be minimal across most locations given the
brevity of the showers, brief periods of reduced visibility to below
1 mile are possible beneath the strongest showers. Where snow
showers are more persistent over the higher terrain of the
Continental Divide, mainly north of the MT Hwy 200 corridor and
south of the US Hwy 2 corridor, snowfall accumulations of 1-3" will
be possible through early this evening. While light snow may linger
through the overnight hours tonight across portions of Southwest
Montana and along the Continental Divide, most locations will see
decreasing chances for snow through the evening hours with the loss
of heating. Partial clearing over portions of the plains of Central
and North Central Montana during the late evening/early morning
(Saturday) hours ahead of southward advancing cold front will allow
temperatures to cool into the single digits to low teens above zero
by Friday morning, with the teens to 20s expected across most valley
locations in Southwest and Central Montana.

Friday through Friday night...North to northwest flow aloft will
prevail over the Northern Rockies through the period as a broad
longwave trough, which was draped over most of the CONUS and Canada
with an associated closed low over South Central Canada, slowly
lifts northeast to over Eastern Canada through Saturday morning. At
the surface, a re-enforcing cold front will back in from the north
to northeast late tonight through Friday morning as a strong surface
high (~1040mb) slides southeast along the Canadian Rockies (Friday
morning) to Northeast Montana (Saturday morning). This cold front
will bring additional chances for light snow/flurries to areas
predominately along and north of the US Hwy 12 corridor on Friday,
with widespread low level cloudiness expected over the plains of
Central and North Central Montana. These low clouds combined with
cold air advecting in across the Northern Rockies will help to keep
temperatures in the mid-20s to mid-30s across most plains locations
on Friday, with the upper 30s to low 40s expected in the valleys of
Southwest and Central Montana. The aforementioned low level clouds
will slowly dissipate through Friday evening/night as the low level
flow veers to the southeast and south. These clearing skies and
light surface winds will allow temperatures to fall into the single
digits to teens above zero, with a 20% chance that temperatures fall
below zero in the West Yellowstone Area through Saturday morning. -
Moldan

Saturday through next Thursday... Weak high pressure ridging is
forecast to develop over the western United States for much of this
period Saturday through Monday, warming temperatures to near
seasonal averages. However, a low pressure trough off the Pacific
coast of North America is also forecast to eject a shortwave trough
over Montana Sunday into Monday, bringing at least a chance of
precipitation to much of the area. Right now, though, probabilistic
guidance is giving less than a 20 percent chance of 4 inches of snow
accumulation in the mountains through this period. Forecast models
then indicate that the high pressure ridge will start to amplify
Tuesday into Wednesday, which should help warm temperatures to
around 10 degrees above normal through mid-week. Mostly dry
conditions are also expected on Tuesday, but the low pressure trough
is forecast to deepen off the Pacific coast Wednesday into Thursday.
This would shift the flow aloft more southwesterly and unsettled,
for an increasing chance of showers. - Coulston

&&

.AVIATION...
1205 PM MDT Thu Apr 18 2024 (18/18Z TAF Period)

A cold and moist northwesterly flow aloft will bring another round
of isolated to scattered snow showers this afternoon and evening.
Expect Low VFR/MVFR clouds during this time with some brief
degradations to IFR/LIFR with the heavier showers. This activity
diminishes after 19/03Z for most locations, but an H700 frontal
boundary may keep some light snow going into the overnight hours for
southwestern areas south of I90. Then another weak disturbance moves
into North-central MT Friday morning and brings a more persistent
MVFR/IFR stratus deck onto the plains. Northwesterly surface breezes
in northern areas will gust in the 25 to 30 kt range through this
evening. - RCG

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  17  35  15  48 /  20  10  10  10
CTB  16  33  17  44 /  10  10  10   0
HLN  23  41  21  54 /  20  10   0   0
BZN  20  42  15  51 /  20  10   0   0
WYS   5  41   4  52 /  20  10  10   0
DLN  19  40  18  53 /  20  10   0   0
HVR  20  38  18  49 /  20  20  10   0
LWT  13  31  15  44 /  20  20  10  10

&&

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

$$

http://www.weather.gov/greatfalls