Helena Valley Northeast, Montana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

654
FXUS65 KTFX 222349
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
549 PM MDT Sun Jun 22 2025

Aviation Section Updated.

.KEY MESSAGES...

- Scattered to widespread showers/mountain snow showers and
  isolated thunderstorms this afternoon.

- Temperatures remain well below normal for Monday, with a gradual
  warm up through the week.

- Slight chances for precipitation most days during the forecast
  period.

&&

.DISCUSSION...
/Issued 244 PM MDT Sun Jun 22 2025/

 - Meteorological Overview:

Throughout the morning, precipitation has been slowly building in
around the low pressure system in southern Saskatchewan/northern
MT. This will continue to bring in scattered to widespread
precipitation through the afternoon. Snow levels are rising to a
little less than 7,000ft in Southwest MT and to 6,000ft towards
McDonald`s Pass. There will be additional mountain snow this
afternoon, but only minor accumulations expected on grassy
surfaces. Weak instability in the area will allow for some
convective snow showers as well. Coverage in precipitation will
decrease in the evening with high pressure trying to build in
Southern MT. Clearing overnight with subsidence from high pressure
and lingering low level moisture from precipitation today will
try to develop fog, particularly in Southwest MT. Another concern
will be low temperatures dropping to the low 20s to low 30s in
Southwest MT valleys and mid to upper 30s across the north-
Central MT plains. If there is good clearing in the clouds
overnight, then frost will develop along wtih fog.

Remnants of this upper level wave Monday will allow for some
isolated showers and thunderstorms, mainly across the Hi-Line
region. Weak troughing in the region will allow for low end to
slight chances of precipitation through the forecast period. We
will have to watch the potential for a few organized storms
towards the second half of the week/weekend. Southwest flow aloft
will allow for a gradual warm up in temperatures.


 - Forecast Confidence & Scenarios:

Precipitation this afternoon will be more uniform across the North-
Central MT plains. Showers and thunderstorms across Southwest MT
this afternoon will bring heavier bursts of rain. The 25th-75th
percentile brings 0.05-0.25" of additional precipitation amounts across
the lower elevations. Slightly higher amounts are expected in the
mountains/areas that get a few moderate showers. With the closed
low bring in colder air loft and increased vorticity (enhanced
stretching of showers), I can`t rule out the potential for cold
air funnels near the ID/MT border.

Snow levels have risen to just short of 7,000ft this afternoon in
Southwest MT and to 6,000ft along and north of Mcdonalds`s Pass.
Webcams show snow struggle to accumulate, so only minor
accumulations are expected on non pavement surfaces.

In terms of the frost/fog potential tonight, models show a little
bit of low level moisture lingering overnight. The main question
is if cloud cover clears enough for fog development, particularly
over the North-Central MT plains. If clouds clear, then cold
morning temperatures of 30s in the lower elevations can develop
frost in addition to fog. Higher confidence for fog will be across
Southwest MT where more clearing is expected.

Precipitation development over the rest of the forecast period
look to be isolated to scattered. With an upper-level shortwave
and a front moving through Thursday, we will have to watch for a
few organized thunderstorms with an increase in deep layer shear
magnitude and directional. -Wilson

&&

.AVIATION...
23/00Z TAF Period

An area of rain and associated MVFR/IFR conditions will slowly
diminish through 23/06Z, though some isolated showers and low
VFR/MVFR clouds may linger into the overnight hours. Patchy fog
may develop between 23/09 and 23/15Z. Lingering low clouds look to
keep the most impactful fog over the river valleys, but some
prevailing groups were added for 6sm BR.

In southwest Montana scattered showers will also diminish through
23/04Z. Patchy fog development can be expected here as well,
especially for KWYS. Lingering clouds reduces confidence for
impactful fog for KEKS, KHLN, and KBZN, especially with
probabilities for visibility reductions below a half mile running
less than 20%. Similar to most of the northern terminals, 6sm BR
groups were added for KBZN and KHLN 23/09 and 23/15Z. - RCG

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  38  68  42  78 /  60  30   0   0
CTB  36  66  40  75 /  30  40  10  10
HLN  38  70  44  78 /  50  30   0   0
BZN  33  71  39  78 /  50  10   0  10
WYS  23  61  25  68 /  50   0   0  20
DLN  30  64  36  71 /  40  10   0   0
HVR  38  71  45  79 /  80  20  10   0
LWT  33  66  41  74 /  70  20  10  10

&&

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

$$
http://www.weather.gov/greatfalls