FXUS65 KTFX 211127

AFDTFX



Area Forecast Discussion

National Weather Service Great Falls MT

527 AM MDT Mon Sep 21 2026



Aviation Section Updated.



.KEY MESSAGES...



 - Areas of fog this morning. 



 - Mild and mainly dry conditions prevail through Thursday.  



 - Pacific weather system brings windy and cooler conditions by the 

   weekend 



&&



.DISCUSSION...

/Issued 236 AM MDT Mon Sep 21 2026/ 



 - Meteorological Overview:



An upper level ridge centered over MT and surface high pressure 

over the northern US plains will maintain very light flow aloft and 

at the surface across the region through tonight. Except for some 

areas of fog this morning, primarily across the plains but also in 

some SW MT valleys, mainly clear skies and light winds will prevail 

with afternoon temperatures reaching the 70s. A southwesterly flow 

develops Tuesday through the rest of the week, bringing some 

additional warming with afternoon temperatures as much as 10-15 

degrees above average through Thursday. A weakening upper level

disturbance tracking out of the Southwestern US across WY by mid-

week will bring risk for showers and perhaps an isolated thunderstorm

to portions of SW MT late Tue/Tue night. A larger scale upper 

trough from the North Pacific begins to move onshore Friday with a

cold front sweeping east across the Northern Rockies and MT late 

Friday or early Saturday. Gusty winds are likely to accompany and 

follow the frontal system along with cooler temperatures by the 

weekend.



 - Forecast Confidence & Scenarios:



Looking ahead to the late week/weekend system, there is reasonable 

model agreement on a potent shortwave ejecting across the Northern 

Rockies, which would favor a fairly energetic frontal passage and 

associated winds. Probabilistic model guidance keeps the risk for 

strong (>50mph) winds around 20% less, and there is still a fair 

amount of timing uncertainty, but this will continue to be monitored 

as the week progresses. Hoenisch.



&&



.AVIATION...

21/12Z TAF Period 



Main concern this morning will be areas fog with dense (VLIFR) 

fog being observed early this morning at KWYS and KHVR, where it

will be most persistent/dense through 16z. Patchy fog or low 

clouds with MVFR/IFR conditions are possible in the vicinity of 

most terminals with the exception of KGTF this morning. Otherwise,

VFR conditions with clear skies and light winds are expected at 

all terminals this afternoon/evening. Hoenisch 



&&



.PRELIMINARY POINT TEMPS/POPS...

GTF  79  48  80  49 /   0   0   0   0 

CTB  76  44  77  47 /   0   0   0   0 

HLN  76  45  77  49 /   0   0   0  10 

BZN  73  41  75  45 /   0   0   0  10 

WYS  67  30  68  34 /   0   0   0  30 

DLN  72  41  73  42 /   0   0  10  20 

HVR  79  46  80  49 /   0   0   0   0 

LWT  75  44  79  48 /   0   0   0  10 



&&



.TFX WATCHES/WARNINGS/ADVISORIES...

None.

&&



$$

http://www.weather.gov/greatfalls