591
FXUS65 KTFX 100257
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
857 PM MDT Sun Jun 9 2024

.SYNOPSIS...

Showers and thunderstorms will continue to lift northeast from
Idaho and across Southwest and into Central Montana through the
afternoon and early evening hours. A few of the thunderstorms
this afternoon could be severe and produce damaging wind gusts.
Additional showers and thunderstorms are then expected to slide
east across the remainder of Central and North Central Montana
overnight and into the morning on Monday. Drier and breezy
conditions are expected through the first half of the work week,
especially on Tuesday and Wednesday.

&&

.UPDATE...

Main update for this evening was to bring showers into Central
Montana a bit sooner than previously forecast. Radar echoes are
spreading northeast out onto the plains as of this evening, so
have moved mention of showers there from around midnight to this
evening. Otherwise, the forecast is generally on track, as the
Pacific cold front continues to move into the area. The scattered
showers and thunderstorms have moved northeast out of Southwest
Montana, but another round of showers and storms may still move
into that area from Idaho around and after midnight.

&&

.AVIATION...

10/00Z TAF Period

VFR conditions are mostly expected through at least 11/00Z across
North Central (KCTB KHVR), Central (KLWT, KGTF, KHLN), and
Southwest (KBZN, KEKS, KWYS), unless otherwise specified.

A Pacific disturbance with an associated cold front will move
scattered showers and thunderstorms over the area through at
least 09Z, with the main threat being wind gusts of up to 40 kt.
The greatest threat for thunderstorms will mostly be along and
south of a KHLN-KLWT line, where periods of mountain-obscuring
MVFR conditions are possible with heavier downpours. As the
disturbance pushes the cold front east through the area between
09Z and 15Z, the breezy southerly to easterly winds will shift
more westerly, and the westerly winds aloft will cause some
mountain wave turbulence. Clouds and showers should also decrease
from the east after 12Z with this shift to more of a downslope
wind. Gusts of 20 to 30 kt over the plains could exceed 35 kt
along the Rocky Mountain Front. -Coulston

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

&&

.PREV DISCUSSION...
/ISSUED 615 PM MDT Sun Jun 9 2024/

Rest of today through tonight...primary forecast concern
throughout the period will be the threat for thunderstorms, some
of which could become severe and produce damaging wind gusts.
Thunderstorms have initiated over Northeast Idaho early this
afternoon and were beginning to lift northeast over the
Idaho/Montana border into Southwest Montana. BUFKIT soundings
across Southwest Montana, most notably in the Dillon and Bozeman
Areas, in advance of these initial storms show a classic
inverted-V beneath H600. Showers and thunderstorms, especially
collapsing ones, moving into this environment will be capable of
producing gusty/erratic winds and even a few isolated damaging
wind gusts through the afternoon hours. After the initial push of
showers and thunderstorms through the mid- to late afternoon the
threat for damaging winds should begin to subside as the column
becomes saturated and a transition to brief periods of heavy
rainfall occurs. Showers and thunderstorms will continue to lift
northeast and into Central Montana through the early evening
hours tonight, with additional showers and an isolated
thunderstorm or two sliding east from Western Montana and across
Central and North Central Montana from the late evening through
overnight hours tonight. - Moldan

Monday through Friday...Westerly winds increase and things dry
out on Monday following the passage of the shortwave, but another
weak perturbation does move across the region during the
afternoon hours for additional isolated to scattered showers and
thunderstorms, mostly along the Hi-Line and over and near areas
of higher terrain elsewhere.

Ensembles remain in fairly good agreement with a zonal flow aloft
settling in for the mid-week period. H700 to H500 flow will be on
the stronger side for this time of time of year, mostly between
40 and 50 kts or 2 to 3 standard deviations above climatology
according to the NAEFS (North American Ensemble Forecast System).
Deep layer mixing should encourage breezy to windy conditions,
especially over the plains and the Rocky Mountain Front on
Wednesday. Wind exceedence probabilities suggest that peak wind
gusts will mostly fall between the 35 and 55 mph range except
along the Rocky Mountain Front and adjacent high plains where
gusts up to and exceeding 60 mph will be more common. The primary
impact will be to summer outdoor recreation and travel; however,
afternoon temperatures in the 70s and 80s combined with the said
winds and minimum relative humidity values in the teens and 20s
is expected to accelerate the curing/drying of grassland fuels.
While no fire products are anticipated this time around, this may
set up fire weather concerns in the future.

Saturday through next Sunday...Uncertainty remains in terms of
forecast details for the upcoming weekend, but ensembles continue
to highlight a Pacific trough exerting an influence over the
Northern Rockies. At this time, there is an expectation for
breezy conditions, isolate to scattered shower and thunderstorm
activity, and a slight cool down for Saturday and Sunday. - RCG

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  56  80  50  84 /  60  20   0   0
CTB  51  77  49  81 /  50  20  10   0
HLN  59  84  51  86 /  80  10   0   0
BZN  55  78  45  84 /  90  60   0   0
WYS  47  71  39  74 /  80  40  10   0
DLN  51  76  45  82 /  90  20   0   0
HVR  53  77  49  84 /  70  60  30   0
LWT  54  76  46  79 /  60  60  10   0

&&

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

$$

http://www.weather.gov/greatfalls