Rocky Boy, Montana Weather Forecast Discussion

624
FXUS65 KTFX 061736
AFDTFX
Area Forecast Discussion
National Weather Service Great Falls MT
Issued by National Weather Service Missoula MT
1136 AM MDT Sat Sep 6 2025
Aviation Section Updated.
06/18Z TAF Period
VFR conditions will predominately prevail throughout the
0618/0718 TAF period as upper level ridging remains in place over
the Northern Rockies; however, regional wildfire smoke may bring
periods of mainly low-VFR VIS to the KHLN, KBZN, KEKS, and KWYS
terminals. Additionally, monsoonal moisture lifting northeastward
beneath the ridge will bring increasing mid- and upper level
cloudiness to Southwest and into portions of Central Montana
through the afternoon and evening hours. While isolated showers
and thunderstorms are possible beyond 00z Sunday along and south
of the I-90 corridor in Southwest Montana the probability of any
one shower or storm directly impacting the KWYS, KEKS, or KBZN
terminals was too low to mention at this time.
&&
.DISCUSSION...
/Issued Issued by National Weather Service Missoula MT/
- Meteorological Overview:
Easterly breezes have generally kept temperatures a little warmer
than last night, but wind protected and cold prone areas will
still see lows dip into the upper 20s to middle 30s range by
sunrise. General warm and dry conditions continue today with
ridging aloft, but there will be increasing high clouds as monsoon
moisture and shortwave energy begins to undercut the ridge. Smoke
and haze from regional wildfires will also be on the increase and
will expand northward over the next couple of days.
A shortwave will bring an initial round of isolated shower and
thunderstorm activity into the southwest this evening and tonight.
This will head northward into Central/North-central MT in a
weakened state on Sunday while additional showers and storms
develop over the southwest. The primary concerns will be
localized strong, gusty winds and lightning, especially over the
drier vegetation of the southwest.
Ensembles continue to favor a Pacific Northwest trough deepening
and sending additional moisture into the region early next week
via an unstable southerly flow aloft. Afternoon temperatures will
continue to run around 10 to 15 degrees above average through the
mid- week period while daily rounds of scattered shower and
thunderstorm activity continue, especially Tuesday through
Thursday.
Cooler and showery weather settle in on the backside of the
trough heading into the weekend. Most ensembles weaken and slow
the trough as it moves through the state, but its trajectory
is now looking more favorable for at least light to moderate
widespread rain for the upcoming weekend. - RCG
- Forecast Confidence & Scenarios:
Shower and thunderstorm activity increasing this weekend into
next week...
Monsoon moisture slowly returns to the Northern Rockies this
weekend into next week. Isolated shower and thunderstorm activity
will initially moves into the southwest this evening and tonight
and then continues its trek northward on Sunday while weakening.
The primary hazards will be localized strong, gusty winds and
increased lightning activity. The latest HREF guidance highlights
Southwest Montana with a 50 to 70% for thunderstorm associated
wind gusts over 35 mph Sunday afternoon and evening. This combined
with lightning activity and some storms offering little in the
way of rainfall may cause some new wildfire starts.
Monday may be a slower thunderstorm day, but an unstable
southerly flow will bring scattered to numerous showers and
thunderstorms to all areas Tuesday through Thursday. Precipitable
water values nearing the 0.75 to 1.0 inch mark combined with
afternoon instability and forcing from the trough may be
sufficient for the development of a few stronger storms with
strong, gusty winds, heavy downpours, and some hail in addition to
lightning. Cooler, breezy, and showery conditions are expected
towards the end of the week as the main trough moves eastward
through the region. One trend change observed over the last 24
hours is the doubling of individual ensemble members favoring
more widespread and heavier rainfall for next Saturday and Sunday.
This increasing trend will continue to be be monitored. - RCG
&&
.AVIATION...
06/12Z TAF Period
Ridging aloft will maintain general VFR conditions and light
winds for much of the TAF period; however, regional wildfire
smoke will continue to compromise slantwise visibility and bring
some instances of low VFR or MVFR surface visibility. Monsoon
moisture will also slowly move in from the southwest and bring
increased higher level cloudiness today. Isolated shower and
thunderstorm activity will also begin to move into Southwest
Montana, mostly after 07/00Z. - RCG
Refer to weather.gov/zlc for more detailed regional aviation
weather and hazard information.
&&
.PREV DISCUSSION...
/Issued Issued by National Weather Service Missoula MT/
- Meteorological Overview:
Easterly breezes have generally kept temperatures a little warmer
than last night, but wind protected and cold prone areas will
still see lows dip into the upper 20s to middle 30s range by
sunrise. General warm and dry conditions continue today with
ridging aloft, but there will be increasing high clouds as monsoon
moisture and shortwave energy begins to undercut the ridge. Smoke
and haze from regional wildfires will also be on the increase and
will expand northward over the next couple of days.
A shortwave will bring an initial round of isolated shower and
thunderstorm activity into the southwest this evening and tonight.
This will head northward into Central/North-central MT in a
weakened state on Sunday while additional showers and storms
develop over the southwest. The primary concerns will be
localized strong, gusty winds and lightning, especially over the
drier vegetation of the southwest.
Ensembles continue to favor a Pacific Northwest trough deepening
and sending additional moisture into the region early next week
via an unstable southerly flow aloft. Afternoon temperatures will
continue to run around 10 to 15 degrees above average through the
mid- week period while daily rounds of scattered shower and
thunderstorm activity continue, especially Tuesday through
Thursday.
Cooler and showery weather settle in on the backside of the
trough heading into the weekend. Most ensembles weaken and slow
the trough as it moves through the state, but its trajectory
is now looking more favorable for at least light to moderate
widespread rain for the upcoming weekend. - RCG
- Forecast Confidence & Scenarios:
Shower and thunderstorm activity increasing this weekend into
next week...
Monsoon moisture slowly returns to the Northern Rockies this
weekend into next week. Isolated shower and thunderstorm activity
will initially moves into the southwest this evening and tonight
and then continues its trek northward on Sunday while weakening.
The primary hazards will be localized strong, gusty winds and
increased lightning activity. The latest HREF guidance highlights
Southwest Montana with a 50 to 70% for thunderstorm associated
wind gusts over 35 mph Sunday afternoon and evening. This combined
with lightning activity and some storms offering little in the
way of rainfall may cause some new wildfire starts.
Monday may be a slower thunderstorm day, but an unstable
southerly flow will bring scattered to numerous showers and
thunderstorms to all areas Tuesday through Thursday. Precipitable
water values nearing the 0.75 to 1.0 inch mark combined with
afternoon instability and forcing from the trough may be
sufficient for the development of a few stronger storms with
strong, gusty winds, heavy downpours, and some hail in addition to
lightning. Cooler, breezy, and showery conditions are expected
towards the end of the week as the main trough moves eastward
through the region. One trend change observed over the last 24
hours is the doubling of individual ensemble members favoring
more widespread and heavier rainfall for next Saturday and Sunday.
This increasing trend will continue to be be monitored. - RCG
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF  82  50  85  53 /   0   0  10  20
CTB  79  46  83  52 /   0   0  10  20
HLN  84  55  84  54 /   0  10  20  20
BZN  84  50  84  49 /   0  10  20  20
WYS  77  42  73  37 /   0  20  50  30
DLN  82  51  81  46 /  10  20  30  20
HVR  77  44  83  55 /   0   0   0  10
LWT  77  48  81  53 /   0   0  10  20
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
http://www.weather.gov/greatfalls

NWS TFX Office Area Forecast Discussion