Helena Valley, Montana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

559
FXUS65 KTFX 041136
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
536 AM MDT Fri Jul 4 2025

Aviation Section Updated.

.KEY MESSAGES...

 - Expect below normal temperatures through Saturday, with
   readings climbing near to slightly above normal on Sunday and
   Monday before rising well above normal through the remainder of
   next week.

 - Showers and thunderstorms will lift northeast across Southwest
   through North Central Montana through the day today, with
   lingering showers and storms persisting into the day Saturday.

&&

.DISCUSSION...
/Issued 305 AM MDT Fri Jul 4 2025/

 - Meteorological Overview:

Shortwave trough over Northern California will lift northeast over
the Great Basin through the day today (Friday) and Northern Rockies
on Saturday. This shortwave trough will help to spread showers and
thunderstorms across much of Southwest through North Central Montana
through the first half of the upcoming weekend, with showers and
thunderstorms initially developing over Northeast Idaho/Southwest
Montana through the morning hours today before lifting northeast
across Central and North Central Montana through the evening hours
tonight. Wrap around showers and scattered thunderstorms will then
linger into the day on Saturday as the main mid- and upper level low
move over the Northern Rockies, with the best areal coverage of
precipitation focused across eastern portions of Central and North
Central Montana (i.e. east of a Havre, to Great Falls, to White
Sulphur Springs line). High temperatures today will cool to near
normal in wake of a Pacific front, with below to well below normal
temperatures expected on Saturday as the aforementioned upper level
low moves overhead.

Quasi-northwest flow develops in wake of the departing shortwave
through the remainder of the weekend and into day on Monday before
becoming predominately zonal through the remainder of the work week.
This will allow temperatures to moderate back to near to slightly
above normal through Monday, with readings climbing well above
normal from Tuesday onwards. Predominately dry conditons will
accompany the transition of northwest to zonal flow; however, an
isolated shower or thunderstorm can`t be ruled out over the higher
terrain on any given day. - Moldan

 - Forecast Confidence & Scenarios:

Rainfall through Saturday night :

Showers and thunderstorms moving across Southwest through North
Central Montana will be capable of producing moderate to locally
heavy rainfall through the period, with the latest ECMWF EFIs
for QPF generally ranging from between 0.6 to 0.8 for a given
location over the next 48 hours. NBM probabilities for a wetting
rainfall (i.e. 0.10" or greater) are in excess of an 80% chance for
any given location within Southwest through North Central
Montana, with the probability for 0.5" or greater ranging from a
15-30% chance along and south of the I-90 corridor to a 30-60%
along and north of the I-90 corridor. Finally, NBM probabilities
continue to support between a 10-20% chance for rainfall amounts
to exceed 1" across predominately the Island Ranges of Central
Montana and along the Continental Divide where the most persistent
shower and thunderstorm activity is expected to occur. - Moldan

&&

.AVIATION...
04/12Z TAF Period

Primary aviation concern through 15z this morning will be LIFR/IFR
conditons at the KWYS terminal due to low VIS and/or CIGS.
Otherwise VFR conditions will prevail outside of this window
despite lowering CIGS and increasing precipitation coverage beyond
15-18z, with showers and thunderstorms lifting from southwest to
northeast beyond this timeframe. Biggest impact to terminal
operations from thunderstorm activity, which is generally expected
to occur between 04/18z to 05/06z, will be gusty and erratic
winds. Mountains will become increasingly obscured beyond 18z
this afternoon, especially those peaks at and above 9kft. -
Moldan

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  78  53  72  47 /  60  80  60  10
CTB  74  50  64  46 /  80  80  60  10
HLN  77  52  74  48 /  80  70  50  10
BZN  82  48  76  44 /  90  80  70  10
WYS  71  39  71  33 /  80  30  30  10
DLN  73  45  72  42 /  90  50  40   0
HVR  82  54  71  49 /  30  70  80  20
LWT  79  50  67  44 /  50  70  90  40

&&

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

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