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000
FXUS65 KTFX 150236
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
836 PM MDT Sun Apr 14 2024

.UPDATE...

Showers and a few isolated thunderstorms continue to track N/NE
across primarily central MT this evening. While most of these
cells are weak, there is pocket of higher instability (CAPE) and
wind shear that lies along the north slopes of the Little Belts
and Snowies where a few stronger cells developed this evening.
Still some potential for thunderstorms across Cascade county and
vicinity through 10pm, but loss of heating and instability
through the rest of this evening should limit the risk for
additional thunderstorms elsewhere and a few showers will linger
after midnight. Hoenisch

&&

.SYNOPSIS...

A few showers and thunderstorms will track from Southwest Montana
into North-central Montana this evening. On Monday, expect
similar conditions across eastern portions of north-central and
southwest Montana. After one more day of mild temperatures on
Monday much colder temperatures develop by the middle of the week,
along with rain changing to snow at all elevations by Tuesday
night.

&&

.AVIATION...
620 PM MDT Sun Apr 14 2024 (15/00Z TAF Period)

Scattered showers and a few isolated thunderstorms will continue to
track slowly north across central and portions of southwest MT this
evening. Expect some local mountain obscuration in the vicinity of
showers in addition to erratic winds. VFR conditions prevail
otherwise with mid-level cloud-cover increasing some overnight and
additional showers developing later tonight through Monday across
eastern portions of north-central and southwest Montana. Hoenisch

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

&&

.PREV DISCUSSION...
/ISSUED 620 PM MDT Sun Apr 14 2024/

Key Points...

--Turning Windy and Cooler by Tuesday
--Areas of Snow and Much Colder temperatures Developing Tuesday
Night through Wednesday
--Unseasonably Cold Temperatures Linger Through Late in the Work
 Week

Satellite imagery this afternoon shows mainly clear skies across the
north-central MT with cumulus cloud initiation and showers
developing across SW MT beneath diffluent flow aloft to the north of
a closed mid-upper level low tracking east across the Northern Great
Basin. Hi-res model ensembles are in fairly good agreement depicting
the shower activity to lift north through central and north-
central MT this evening. In addition to isolated lightning, dry
lower levels will support some brief gusty/erratic winds near
showers. Later tonight through Monday, an axis of deformation
(stretching/shearing winds) to the north of the upper low, sets
up from N to S across eastern portions of N-central and SW MT and
will be a focus for additional showers.

Gusty west winds develop late Monday through Tuesday as low pressure
associated with the upper low tracking by to our south emerges and
deepens across Nebraska while westerly flow aloft strengths across
the Northern Rockies in advance of a strong upper level trough
digging southward through BC. Models are in fairly good agreement
now with the larger scale trough continuing to dig SE through MT
Tues night and Wed. Within the larger trough a closed mid-upper
level center develops and tracks east across southern AB/SK Wed
while an embedded wave and associated upper jet also circulate
through the SW periphery the trough across ID into WY by late
Wednesday.

Winter weather impacts begin Tuesday afternoon near Glacier NP as
precipitation develops with the arrival of the larger scale trough
and a colder airmass from Canada begins to surge south along the
Rockies. Most of the forecast area is likely to see at least a
period of snow with some minor accumulations as the upper trough and
colder airmass dig through the area Tuesday night through Wednesday
morning with precipitation decreasing by Wednesday night. Snowfall
amounts are only one aspect of this system and forecasts have not
changed significantly over the last few forecast cycles with amounts
in excess of 4 inches primarily confined to the mountains with 1-3
inch snowfall amounts in the valleys of SW MT and areas adjacent to
the mountains in N-central MT and generally less than in inch
forecast elsewhere across the N-central MT plains. A winter weather
advisory continues for eastern portions of Glacier NP and adjacent
portions of GLacier county, where gusty north winds may also cause
additional visibility and travel impacts Tuesday night through early
Wednesday. A Winter Storm Watch continues for the mountains of
Madison and Gallatin counties where the highest snowfall amounts are
now forecast in association with the previous mentioned wave moving
across southern ID into WY. Latest forecasts give a 50-80%
probability of snowfall amounts in excess of 12 inches across
northern portions of the Gallatin Range including the Hyalite area.
Additional winter weather statements may be needed for the mountains
of central MT where at least some minor impacts to travel over
passes is likely Tuesday night into Wednesday. Current forecasts
have a 50-70% probability for 4 inch or greater snowfall amounts at
Rogers Pass, Kings Hill and Bozeman Pass.

Windy and colder temperatures are the other aspects of this storm
system with gusty northwest winds particularly across north-
central MT Tuesday night through Wednesday from both the incoming
surge of higher pressure and colder airmass as well as the
gradient across the region as low pressure tracks east across the
Canadian Prairies Wednesday. While very little accumulating snow
is expected across NE portions of the forecast area, northwesterly
wind gusts in excess of 45 mph are likely (50-70%) across
portions of Blaine county with 30-40 mph wind gusts widespread
across the rest of north-central MT. This will be in combination
with daytime temperatures only in the upper 30s to near 40.
Precipitation and winds decrease Wednesday night but medium range
model ensembles are coming into better agreement supporting an
upper level pattern that would keep the cold airmass across the
region through the rest of the work week with daytime temperatures
in the upper 30s to around 40 with overnight temperatures in
upper teens to low 20s. Hoenisch

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  45  69  39  53 /  50  30   0  20
CTB  39  64  34  45 /  10   0  10  50
HLN  46  66  39  53 /  30  30   0  10
BZN  42  63  31  55 /  40  70  20  20
WYS  31  56  25  47 /  40  70  20  30
DLN  39  59  32  56 /  10  50   0  10
HVR  44  71  41  54 /  10  20  10  30
LWT  43  63  36  52 /  50  60  10  10

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from noon Tuesday to 6 AM MDT Wednesday
for East Glacier Park Region-Northern High Plains.

Winter Storm Watch from Tuesday evening through Wednesday
afternoon for Gallatin and Madison County Mountains and
Centennial Mountains.

&&

$$

http://www.weather.gov/greatfalls