Helena, Montana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

141
FXUS65 KTFX 112332
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
532 PM MDT Sat Apr 11 2026

Aviation Section Updated.

.KEY MESSAGES...

 - Thunderstorms with gusty winds this afternoon and early evening.

 - Trending cooler and wetter for most areas Sunday night into
   Monday.

 - After a brief lull Tuesday, another cooler precipitation
   producing system moves in Wednesday and Thursday.

&&

.DISCUSSION...

 - Meteorological Overview:

A long fetch of southwesterly flow aloft is in place across the
Northern Rockies this afternoon, ahead of an upper level low diving
southeastward off the Northern California coast. The combination of
warmer surface temperatures, sufficiently cool temperatures aloft,
and a leading shortwave progressing across the region ahead of the
upper low is resulting in a few showers and thunderstorms already
early this afternoon. That trend looks to continue, with additional
showers and thunderstorms developing and moving northeastward
through the evening. While the overall magnitude of instability that
develops isn`t particularly high today, sufficiently deep mixing
will result in a gusty wind threat in the most robust thunderstorms
that do form. This activity wanes this evening as a cold front
begins to work in across the plains.

Looking toward Sunday, the upper level low progresses inland across
California. This positioning keeps a southwest to south flow aloft
across the region. Another round of showers and thunderstorms is
forecast as a result, though this time mainly across Southwest
Montana and portions of Central Montana. The progression of the
cooler air southward behind a front Sunday will ultimately
determine the north/south extent of showery activity Sunday
afternoon.

The core of the upper disturbance devolves into an open low with
several embedded waves by late Sunday. One of these waves drifts
northeastward toward the Northern Rockies Sunday night into Monday,
which will keep at least spotty precipitation around through the day
Monday. Snow levels look such that impacts from snow will be
reserved for areas above most passes.

Zonal flow aloft then develops behind the departing wave and ahead
of the next upper level system shifting southeastward from the Gulf
of Alaska along the BC coastline Tuesday. While some spotty
precipitation develops along the Continental Divide Tuesday, the
main concern will be for gusty westerly to southwesterly winds
developing ahead of the arrival of this system through Wednesday.

The main portion of the upper level system arrives Wednesday at some
point, though there remains some uncertainty with exact timing.
Additionally, there appears to be some splitting with this system as
it moves inland, which brings about additional uncertainty with
respect to where the best forcing for precipitation ultimately
tracks. A transition toward cooler and wetter conditions is forecast
late Wednesday into Thursday behind a cold front. Snow levels look
to drop to all elevations behind this front, though given the
aforementioned uncertainty with respect for the track of best
forcing for precipitation, it is too early to mention any specifics
for snow amounts.

Looking toward Friday and the weekend the main takeaway is for the
system to begin its departure. How quickly it departs, and how
quickly it warms back up as a result, depends on how much the
troughing splits. A more consolidated system looks to progress
quicker, while the more split scenario looks to linger across the
west a bit longer. -AM

 - Forecast Confidence & Scenarios:

Thunderstorms this afternoon and Sunday afternoon, along with
overall precipitation amounts through Monday:

Latest mesoscale analysis favors the greatest DCAPE environment, and
thus the area with the greatest risk for strong wind gusts from
thunderstorm outflow, near and east of US-87 this afternoon, with
decreasing risk for strong wind gusts the further you get from that
area.

Cooler air moving in Sunday will keep the threat for gusty outflow
winds across Southwest and portions of Central Montana Sunday.
Forecast soundings in these areas mix a touch deeper Sunday compared
to today, which would yield a slightly greater risk for gusty
outflow compared to today in these areas.

Precipitation transitions to be more stratiform Sunday evening across
the region, lasting into Monday. Areas with the greatest probability
to exceed a half of an inch of liquid through Monday evening largely
look to be north of the US-12 corridor and south of the MT-200
corridor. The probability for 3" snow at Kings Hill Pass over this
timeframe is roughly 40%.


Winds Tuesday into Wednesday:

Westerly flow aloft approaching or briefly exceeding 50 kts look to
develop Tuesday into Wednesday along the Rocky Mountain Front. Given
the marginal winds aloft, confidence is not yet high in strong winds
materializing at the surface. That said, both Tuesday and Wednesday
do look to be breezy days.


Precipitation and colder temperatures Wednesday into Thursday:

A wide range of scenarios exists for precipitation amounts across
the region for this event, largely related to the exact track and
any splitting that occurs. The main takeaway at this range is that
precipitation amounts trend higher from north to south across the
region. -AM

&&

.AVIATION...
12/00Z TAF Period

Main concern this evening is the potential for
showers/thunderstorms. Most storms will diminish by 04z, with
scattered showers continuing overnight. Showers redevelop on Sun
afternoon over Central and Southwest MT, with more widespread
rain/snow expected on Sun night. Mountains/passes will be obscured
at times through the period. Brusda

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  39  57  39  55 /  40  40  90  80
CTB  35  50  32  57 /  20  10  30  40
HLN  37  62  38  54 /  60  70  90  80
BZN  35  63  35  55 /  60  70  60  70
WYS  30  54  28  45 /  60  70  60  70
DLN  33  61  34  52 /  50  60  50  60
HVR  40  58  36  54 /  30  10  60  60
LWT  38  59  36  52 /  40  60  90  90

&&

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

&&

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