-- Discussion containing changed information from previous version are highlighted. --
301
FXUS65 KTFX 130510
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1110 PM MDT Wed Jun 12 2024

Aviation Section Updated

.SYNOPSIS...

Warm and mostly dry weather is expected through Friday as upper
level ridging moves overhead. A cooler and more unsettled pattern
will develop next week, bringing multiple chances for rainfall
along with some higher elevation snowfall.

&&

.UPDATE...

This evening dewpoints and relative humidity across North-
central, Central, and Southwestern Montana were higher than
forecasted. As a result, they were lowered across the area to
better reflect current observations and trends. Only minor updates
were made to temperature, wind speed, wind gust, and sky grids.
The rest of the forecast is on track. Tonight winds will die down
across North-central, Central, and Southwestern Montana with
mostly clear skies. Thursday it will warm up to a few degrees
above normal with light winds across the area. -IG

&&

.AVIATION...

-- Changed Discussion --
13/06Z TAF Period

VFR conditions continue through the TAF period for North Central and
Southwest Montana airfields. Winds for KCTB continue to decrease for
the overnight period becoming lighter and variable. KWYS is still
experiencing breezy conditions but should continue to diminish as
well through the overnight hours. Webb

Refer to weather.gov/zlc for more detailed regional aviation
weather and hazard information.
-- End Changed Discussion --

&&

.PREV DISCUSSION...
/ISSUED 530 PM MDT Wed Jun 12 2024/

Key Points:

-Above average temperatures continue through the end of this week

-Cooler and wetter pattern expected next week with some snow in
the higher terrain

Short term (through Friday)... Warm and breezy conditions are
being observed across the Treasure State this afternoon as a broad
upper level trough and associated jet streak continue to work
their way through the Northwestern US today. With little cloud
cover to speak of, daytime heating is promoting a deep mixed layer
at the surface, which is helping to transport these winds aloft
to the surface, resulting in the widespread 20-30 mph wind gusts
that we have been seeing across North Central and Southwestern
Montana today. While the winds will linger through the afternoon
and evening, they will weaken and become light and variable
quickly around sunset as thermal mixing ceases.

Upper level ridging will push into the area for Thursday, which
will bring light winds as some sinking air keeps mixing notably
lower in the atmosphere where winds will be lighter. Even with
this ridge overhead, temperatures will generally be similar to
todays with most locations in the 70s with a few low to mid 80s
in the Southwestern valleys. Friday will be largely similar and
warmer, with just a few showers and thunderstorms in the Bozeman
to West Yellowstone area, thanks to some moisture moving through
the area. While some gusty winds cannot be ruled out thanks to
some notable instability (up to 1000-1500 J/kg of CAPE) and a
modest mixed layer, most areas will likely see a bit of a cap,
helping to limit the ability of storms to form.

Extended (Saturday through next Wednesday)... Cooler and
unsettled weather appears to be on the horizon as we head into the
weekend and next week. Saturday will bring the arrival of a broad
upper level low into the Northwestern US, which will bring a
surge of moisture and cooler temperatures into the area. Rain
showers (with a few areas of higher elevation snow) will begin to
push into Montana during the afternoon on Sunday, along with some
gusty winds as the color air surges into the area. We will have to
watch for some areas of locally enhanced winds with this front
thanks to some thunderstorms.

Looking into next week, upper level troughing will continue to
persist across the Northwestern US, which will keep us cool and
wet through at least the first half of next week. While the WPC
Cluster Analysis tool does show that there is much agreement in
the overall pattern, there are some slight differences with
regards to timing and placement of a few waves/disturbances
embedded in the flow around the low. Regardless of how exactly
this system sets up, it appears that the most likely scenario
(>75% chance) is that there will be two waves of precipitation
across the area, the first being the Saturday/Sunday time frame
with the arrival of the cold front, with a second round during the
Tuesday/Wednesday time frame. In addition to the rain, some snow
is looking likely in the higher terrain thanks to the cooler air
mass that will be in place next week. Ludwig

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  42  77  49  84 /   0   0   0  10
CTB  39  74  46  78 /   0   0   0   0
HLN  48  83  54  85 /   0   0   0  10
BZN  42  81  50  84 /   0   0   0  40
WYS  36  78  44  76 /   0   0  10  40
DLN  42  83  51  83 /   0   0   0  20
HVR  44  77  52  85 /   0   0   0  10
LWT  41  75  51  81 /   0   0   0  20

&&

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

$$

http://www.weather.gov/greatfalls