textproduct: Great Falls

KEY MESSAGES

- Patchy fog is expected in Southwestern Montana this morning.

- Cool (below seasonal-average) temperatures are expected through this upcoming work week.

- There will be periods of precipitation from Monday evening through the rest of the work week.

UPDATE

/Issued 444 AM MDT Sun Oct 25 2026/ The main early morning adjustment was to issue a dense fog advisory for portions of North Central and Southwest MT until 11 AM this morning. Web cams show the dense fog widespread enough for a dense fog advisory. The fog should begin to dissipate by late morning. Otherwise, the rest of the forecast is on track. Brusda

DISCUSSION

/Issued 444 AM MDT Sun Oct 25 2026/

- Meteorological Overview:

Today there will be an upper-level ridge over North-central, Central, and Southwestern Montana. This will allow skies to be clear with light winds. As a result at some lower-elevation locations there is the potential for patchy fog to form. See the Forecast Confidence and Scenarios section for details. Today it will be dry with well-below normal temperatures across North-central, Central, and Southwestern Montana. On Monday the upper-level ridge remains over North-central, Central, and Southwestern Montana. By Monday evening an upper-level trough begins to move over the area. This will bring slightly warmer and dry weather to North-central, Central, and Southwestern Montana through the day on Monday. Monday evening snow-levels will begin to fall and snow will begin across the mountains of Southwestern Montana.

On Tuesday the upper-level trough remains over North-central, Central, and Southwestern Montana. This will bring widespread precipitation primarily in the form of lower-elevation rain and Mountain snow. See the Forecast Confidence & Scenarios section for details. Due to lingering southerly flow temperatures will warm up a few degrees on Tuesday but remain below seasonal averages. On Wednesday an upper-level ridge briefly builds in over North-central, Central, and Southwestern Montana. This will allow warm temperatures to persist with mostly dry weather. Thursday through Saturday an upper-level trough returns to North-central, Central, and Southwestern Montana. This will bring multiple rounds of precipitation to the area with cooler temperatures. -IG

- Forecast Confidence & Scenarios:

For fog this morning there is around a 30 - 50% chance along the Rocky Mountain Front, the lower-elevations of Cascade County, and the West Yellowstone area. However based on current satellite imagery and model soundings this is most likely due to low clouds and not fog. In the Helena and Gallatin Valley there is a low chance for fog to form this morning as well, which is suggested in some model soundings. Based on current satellite imagery the Gallatin Valley and West Yellowstone area have the highest chance for fog to form out of any of the areas listed above.

For the Monday evening through Tuesday morning system there is a 50 - 80% chance for 4 inches of snow or greater across the higher peaks of the Madison and Gallatin Mountains. For the Monday evening through Tuesday morning system there is a 40 - 70% chance for 2 inches of snow at pass-level in the Madison and Gallatin Mountains. From Monday evening through Tuesday there is a 40 - 80% chance for a quarter inch of liquid precipitation or greater across Southwestern Montana. From Monday evening through Tuesday morning across the Gallatin and Madison River Valleys and the Lewistown area there is greater than a 60% chance for a tenth of an inch of snow or greater. On Tuesday across Blaine and Fergus Counties there is a 40 - 60% chance for a quarter inch of total liquid precipitation or greater. -IG

AVIATION

25/18Z TAF Period

Low clouds and fog will continue to linger during the early afternoon across Southwest MT. Fog and an overcast/broken IFR to LIFR cloud deck will slowly lift this afternoon, though a few lower clouds will remain in the area for the rest of the day. Confidence is increasing for another round of lower clouds and fog in Southwest MT Monday morning. Up in North-Central MT, MVFR clouds continue into the early afternoon before lifting. There is a slight chance for low stratus and fog in North-Central MT Monday morning, though confidence isn't high enough to include in this TAF cycle. -Wilson

PRELIMINARY POINT TEMPS/POPS

GTF 38 18 43 30 / 0 0 0 40 CTB 41 19 43 25 / 0 0 0 30 HLN 40 22 48 32 / 0 0 0 80 BZN 39 19 52 28 / 0 0 0 90 WYS 47 17 49 18 / 0 0 10 100 DLN 43 22 52 30 / 0 0 0 90 HVR 45 23 52 28 / 0 0 0 40 LWT 41 22 50 29 / 0 0 0 60

TFX WATCHES/WARNINGS/ADVISORIES

None.