533
FXUS65 KTFX 040431
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1031 PM MDT Tue Jun 3 2025

Aviation Section Updated.

.KEY MESSAGES...

 - Daily chances for showers and storms through the work week,
   with the highest coverage of showers and storms expected today
   and Wednesday.

 - Below normal temperatures through Wednesday will gradually warm
   to above normal temperatures by the end of the work week with
   warmer temperatures lasting through at least early next week.

 - Predominately light winds are expected through Thursday.

&&

.UPDATE...
/Issued 749 PM MDT Tue Jun 3 2025/

A shortwave trough and lingering diurnal instability will
maintain scattered showers and a few rumbles of thunder through
this evening with the most widespread activity over Central and
North- central Montana. Gusty winds over 30 mph have been the
most significant impact so far. Although a few showers will
persist into the overnight hours, expect a decrease in coverage
over the next few hours. A modestly unstable northwesterly flow
aloft will remain over the region on Wednesday and bring another
round of mostly afternoon and evening scattered showers/thunder.
- RCG

&&

.DISCUSSION...
/Issued 749 PM MDT Tue Jun 3 2025/

 - Meteorological Overview:

Moist, and unstable, northwest flow aloft will help to support daily
chances for showers and thunderstorms across much of Southwest
through North Central Montana through the remainder of the work
week. Within this northwest flow subtle shortwaves, specifically
today and Wednesday, will help to provide the "best coverage" for
showers and storms as compared to Thursday and Friday when coverage
will be more isolated to widely scattered in nature. With H700-H500
temperatures running anywhere 1 to 2.5 standard deviations below
normal through Wednesday will support an environment conducive for
cold air funnels, especially over the plains of Central and North
Central Montana where surface heating will be the strongest in
conjuction with the coldest air aloft. High temperatures will remain
below normal through Wednesday, with temperatures moderating back
above normal through the remainder of the work week.

Transient upper level ridging then looks to overspread the Northern
Rockies through the weekend and Monday before being flattened and
replaced with predominately zonal flow. This aforementioned ridging
will bring generally dry conditions to much of the Northern Rockies
over the weekend; however, and isolated shower or storm can`t be
ruled out over the mountains. Temperatures continue to moderate
through the weekend, with well above normal temperatures expected as
highs peak in the mid-70s to mid-80s. -Moldan


 - Forecast Confidence & Scenarios:

Rainfall Today and Wednesday:

In general, showers will remain light across the region through
Tuesday afternoon. However, HREF guidance still shows the potential
for some stronger storms to develop which could bring rainfall rates
of 0.10" or greater west of the I-15 corridor (20-40%) with lower
probabilities (10-30%) along the Island Ranges.

On Wednesday, the HREF shifts its focus for heavier precipitation
more towards the Island Ranges and particularly the Little Belts.
Wednesday afternoon could see another round of isolated to
scattered afternoon thunderstorms with some potential for some
heavier downpours. At this time there is a low potential for
severe weather for both Tuesday and Wednesday. However, an
isolated stronger storm cannot be ruled out.


Warmer Temperatures Next Week:

The ECMWF EFI has been strongly hinting towards well above normal
temperatures returning by Sunday and lasting through at least
Monday. Currently the NBM has a 40-60% of highs exceeding 90
degrees along portions of north-central Montana including Havre,
Shelby, Fort Benton, and Great Falls. Tuesday is expected to be
slightly cooler however there is still a 10-30% chance for the
same locations exceeding 90 degrees. The good news is, at this
point in time, good overnight temperature recovery is expected
with lows dipping into the 50s. Thus, the concerns for prolonged
heat are minimal at this time.  -thor


&&

.AVIATION...
04/06Z TAF Period

VFR conditions will prevail beneath northwest flow aloft;
however, another round of showers and isolated thunderstorms will
develop between 15z Wednesday and 03z Thursday, most notably
northwest of a line from KHLN to KBZN and southwest of a KHVR to
KLWT line. Main impact from any shower that impacts or is within
the vicinity of a given terminal will be a brief period of gusty
and erratic winds. Otherwise, the only other concern to terminal
operations during the 0406/0506 TAF period will be the potential
for fog developing at/near the KCTB, KHVR, and KGTF terminals
through 15z Wednesday; however, confidence in impacts below VFR
remain very low (i.e. less than a 10% chance of occurring). -
Moldan

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

&&

.HYDROLOGY...

The Gallatin River, specifically at Logan, continues to run near
or above Action Stage thanks to increased snowmelt and recent
precipitation across the Madison and Gallatin Ranges in Southwest
Montana. Latest river forecasts from the Missouri Basin River
Forecast Center (MBRFC) keeps the Gallatin River below Minor Flood
Stage at all forecast points, but users and those with interest
along the river should be prepared for increased spring flows. -
Moldan

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  40  67  42  73 /  50  30  10  10
CTB  38  66  39  74 /  60  20  10   0
HLN  42  70  44  76 /  40  30  10  10
BZN  37  67  39  71 /  40  10  10  10
WYS  29  62  30  66 /  30  10  10  20
DLN  37  64  37  69 /  20   0   0  10
HVR  39  70  42  77 /  50  20  10  10
LWT  37  62  41  68 /  40  50  20  20

&&

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

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