015
FXUS65 KTFX 162048
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
248 PM MDT Thu May 16 2024

.SYNOPSIS...

Gusty west winds will increase and become more widespread through
Friday as a Pacific weather system moves into the region with its
associated cold front crossing the region by Friday afternoon.
Scattered showers and isolated thunderstorms are possible in some
areas through Friday evening, with cooler temperatures following
through the weekend while an active weather pattern brings
additional chances for precipitation late this weekend into next
week.

&&

.DISCUSSION...

An upper level trough digging into BC today will progress east
across western Canada tonight through Friday. Meanwhile, A fairly
vigorous shortwave and strong upper level jet (for May) move onshore
in the Pacific NW tonight and across the Northern Rockies Friday
with an associated Pacific cold front at the surface. Surface low
pressure emerging ahead of these features in southern AB will move
off to the east into western SK by Friday morning with the
Pacific cold front trailing SW across central and western MT.
Breezy to windy conditions persist through this evening across
much of the area with 30-40 mph gusts over the mountains and
across western portions of north-central MT. These areas will see
winds persist through the overnight period while areas further
east across north-central MT and in the SW MT valleys should see
winds diminish some overnight. Showers and a few thunderstorms are
possible near the Canadian border (mainly northern Hill/Blaine
counties) through this evening with showers increasing later
tonight along northern portions of the Continental divide near
Glacier NP. Better support for organized thunderstorms will exist
north of the border through this evening, but there may be some
potential for wind gusts from storms in far SE AB and SK to reach
into portions of Hill and Blaine counties.

Wind continues to be the primary concern for tomorrow across much of
the area with most areas likely (>60% probability) to see gusts
in excess of 40 mph with a reasonable chance (30-50%) for
localized gusts in excess of 50 mph, especially across areas
adjacent to the Rocky Mtn Front and mountains of central and
southwest MT. Strong winds (gusts in excess of 50kts) are not
expected to be widespread but a few isolated higher gusts are
possible, piratically with the passage of the cold front across SW
MT Friday afternoon. Westerly/downslope flow will be a limiting
factor for precipitation coverage/amounts on Friday, however there
will be ample mid to upper level support from the incoming
shortwave, upper jet energy and modest instability for showers,
particularly across southwest MT and increasing in the afternoon
and evening as moisture and another disturbance move southeast
from AB. Hoenisch

Saturday through Sunday...ensemble clusters strongly favor longwave
troughing over the Northern Rockies throughout the weekend, with the
leading mode of uncertainty being the overall amplitude of the
longwave trough, specifically on Sunday. A deeper longwave trough on
Sunday, which is overall favored in 3 of the 4 clusters, would
result in cooler and "wetter" conditions through the weekend across
much of Southwest through North Central Montana. Latest NBM
probabilities for a 0.25" of precipitation from 12z Sunday to 12z
Monday generally range from 20-40% south of the US Hwy 2 corridor
and north of the US Hwy 12 corridor. Additionally, the probability
for snowfall of 2" or more along the Continental Divide and across
the mountains of Central Montana over this timeframe is
approximately 30%, with 48hr probabilities (including Saturday and
Saturday night) ranging from 30-50% for these same areas. High
temperatures on Saturday in wake of Friday`s Pacific front will fall
into the 60s, with Sunday only seeing highs rise into the 50s.

Monday through next Thursday...an unsettled and "cooler" pattern is
favored through the upcoming work week, with the multi-model
ensemble cluster suggesting overall longwave troughing over the
Western CONUS and Western Canada and inconsequential periods of
transient shortwave ridging moving over the Northern Rockies. Some
uncertainty exists with the timing, position, and amplitude of
individual shortwaves troughs rotating through the longwave trough,
but the main message to put forward will be that their exists
multiple chances for precipitation (some of which may fall as
mountain snow) and below normal temperatures through the upcoming
work week. - Moldan

&&

.AVIATION...
16/18Z TAF Period

Expect VFR conditions across North Central and Southwestern Montana
over the next 24 hours, even as winds increase and upper level cloud
cover increases. Winds will be strongest across the plains,
particularly at KCTB and KGTF during the afternoon hours. There is a
slight chance of showers during the overnight and early morning
hours at all terminals which may temporarily reduce conditions down
to MVFR. Winds will diminish a little overnight before picking back
up Friday morning and continuing through most of the day.

-thor

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  50  61  40  64 /  10  40  30  10
CTB  45  55  35  60 /  10  70  40  10
HLN  51  62  39  67 /  10  40  10   0
BZN  43  65  30  66 /  10  50  10   0
WYS  37  61  24  57 /  20  30  10   0
DLN  43  63  29  66 /   0  20   0   0
HVR  50  64  39  65 /  20  60  80  10
LWT  45  61  36  61 /  10  60  40  10

&&

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

$$

http://www.weather.gov/greatfalls