805
FXUS65 KTFX 312330
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
530 PM MDT Fri May 31 2024

Aviation Section Updated

.SYNOPSIS...

Another cool night is in store tonight as skies clear and winds go
light, with temperatures on Saturday warming quickly beneath sunny
skies. A weak weather disturbance then brings a chance for
showers and isolated thunderstorms to some areas Saturday evening.
A more significant series of weather systems will bring wind and
rain to the area Monday and Tuesday with warmer and drier weather
developing later next week.

&&

.DISCUSSION...

Rest of today through the weekend...transient ridging sliding east
and over the Northern Rockies from this evening through early
Saturday afternoon will bring a period of lighter winds clearing
skies. Prior to this occurring, an isolated rain shower can`t be
ruled out through the early evening hours over northeastern portions
of North Central Montana as a shortwave slides east over the
Northern High Plains, but any rainfall amounts will be
inconsequential. Low temperatures tonight will once again fall into
the upper 20s to 30s across the CWA, with the potential for some
valleys and even a few plains locations to fall below freezing prior
to sunrise on Saturday. Highs on Saturday will warm to above normal
beneath the transient ridge, with chances for showers and even an
isolated thunderstorm or two returning by the late afternoon through
overnight hours as a fast moving wave slides east from the Pacific
Northwest. Once again transient ridging will follow Saturday night`s
shortwave, with continued above normal temperatures on Sunday
amongst increasing surface winds. - Moldan

Monday through Wednesday...an unusually strong (for early June)
Pacific upper level jet moves onshore with a fairly potent mid-level
wave and associated surface low kicking out across MT/AB Monday
night/Tuesday. H700 winds with this usually strong jet per NAEFS
analysis peak at between 2.5 to 3.5 standard deviations above normal
from 12z Monday through 12z Wednesday, with values of between 40-
50kts over much of the Central and North Central Montana from Monday
night through Tuesday night. EFI values for the day on Tuesday
continue to exceed 0.8 across much of the CWA, with a shift of tails
of 0 also encircling much of the CWA. 24hr maximum wind gusts
probabilities per the NBM also continue to increase throughout the
timeframe (Monday through Wednesday), particularly on Tuesday along
the Rocky Mountain Front and adjacent plains where the chance of
exceeding 48kts is 90%+ and 64kts is 30%; with the 25th percentile
for these 24hr maximum wind gust around 55kts. Additionally across
these areas the 24hr maximum sustained wind speed probabilities for
34kts are in excess of 80%. Further east over the remainder of the
Central and North Central Montana plains and into some of the wind
favored valleys in Central Montana the 24hr maximum wind gusts
probabilities for 48kts on Tuesday is generally between 30-50%.
Given this anomalous event, strong probabilistic support, and
favorability for mountain wave activity (BUFKIT soundings showing
strong ridgetop stability) I have elected to issue a High Wind Watch
for the Rocky Mountain Front and adjacent foothills and plains, and
Eastern Glacier, Western Toole, and Central Pondera Counties.
Impacts to those traveling, particularly those from out-of-state who
are operating high profile vehicles or towing trailers, and trees
which now have a majority of foliage are the biggest concerns with
this event. Further expansion of the High Wind Watch may be needed
with subsequent shifts should probabilities increase further and/or
deterministic guidance support high winds materializing.

In addition to the winds a plume of unusually deep Pacific moisture
(PWATs 150-180% of normal) streams across the area ahead of the wave
on Monday with the most widespread and persistent precipitation
focused along and west of the continental dive but showers are also
likely to the east, especially across central and southwest MT. -
Moldan/Hoenisch

Thursday through next weekend...there is strong model agreement to
build an upper level ridge across the interior western and NW US,
resulting in temperatures warming well above seasonal averages by
the weekend. Some uncertainty still exists with its amplitude and
the W/E placement of the ridge axis with larger differences arising
next weekend. - Hoenisch

&&

.AVIATION...

01/00Z TAF Period

VFR conditions prevail through the TAF period. Breezy west and
northwest surface winds along the Rocky Mountain Front and Central
MT decreases during the evening. Cloud cover increases tomorrow
morning ahead of some light precipitation, which best chances for
precipitation holds off until after the 24 hour TAF period. -Wilson

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  37  75  51  72 /   0  10  20   0
CTB  37  70  44  71 /  10  10  10   0
HLN  41  75  54  75 /   0  20  30  10
BZN  36  73  49  73 /   0  20  30  30
WYS  32  67  42  63 /   0  20  20  40
DLN  36  74  49  71 /   0  20  20  10
HVR  39  75  51  75 /  10  10  10  10
LWT  36  72  48  69 /   0  30  40  20

&&

.TFX WATCHES/WARNINGS/ADVISORIES...

High Wind Watch from Monday evening through Tuesday evening for
East Glacier Park Region-Eastern Glacier, Western Toole, and
Central Pondera-Northern High Plains-Southern High Plains-
Southern Rocky Mountain Front.

&&

$$

http://www.weather.gov/greatfalls