Ramsay, Montana Weather Forecast Discussion

479
FXUS65 KMSO 190824
AFDMSO
Area Forecast Discussion
National Weather Service Missoula MT
224 AM MDT Fri Sep 19 2025
.DISCUSSION...
KEY MESSAGES:
-  Warm, sunny, dry conditions continue through Saturday.
-  Westerly winds with gusts 30 to 40 mph Sunday could create
   hazardous, choppy conditions on area lakes, especially Flathead
   Lake where a wind advisory may be needed.
-  Low-lying areas could experience their first frost Monday
   and/or Tuesday morning (30-70% chance).
-  Brief ridge builds early next week before a more unsettled
   pattern could return from Thursday onwards.
The ridge over the region continues to provide sunny skies and
temperatures 10-15 degrees above average through Saturday. Patchy
fog is possible in some of the valleys. Frost is possible in the
high elevation valleys.
Attention then turns to a Pacific trough set to move across the
region on Sunday. There continue to be some timing differences in
the guidance regarding the main cold front passage, but the window
appears to be opening for the later morning through the afternoon
hours. Regardless of exact timing, winds are expected to ramp up
significantly through the afternoon and evening. Current numbers
suggest the potential for wind gusts ranging between 25 and 40 mph
across the region. Gusty, erratic winds are possible with showers.
Hazardous waves of 2 to 4 feet is possible on Flathead Lake and
this could necessitate a lake wind advisory.
Moisture remains limited, but forcing with the front and some
marginal instability with the trough, could support scattered
showers and a few weak thunderstorms. The best instability is
found across northwest Montana and from the Bitterroot Valley
south into Lemhi County and east towards Butte. Any showers that
develop will be capable of mixing down stronger gusts, potentially
to 40 mph.
Behind the front, a cooler air mass settles in for early next
week.There is some question as to how quickly clouds will clear
out Sunday night, which will be a key factor for overnight lows.
Have trended temperatures a little cooler, especially for Tuesday
morning, to highlight the potential for frost in the typical low-
lying, cold-prone valleys. A warm ridge quickly builds back over
the region for the middle of the week.
Ensemble forecasts continue to show the break down of the ridge
about a week away on next Friday or Saturday with 69% of ensemble
members showing a breakdown. There is however quite a range in how
the break down happens with about 27% of ensembles showing the
ridge flattening out into a breezy pattern, while another 29% show
a deep trough coming into the west coast and the remaining 13%
show a fast moving trough clipping along the Canadian border.
Current and forecast tropical activity in the west Pacific Ocean
is driving much of the uncertainty, but it is also more conducive
to an active pattern about a week out.
&&
.AVIATION...High pressure over the region will keep weather
impacts to aviation low today. Some patchy river fog may be seen
near terminals KMSO and KGPI, but it isn`t expected to spread into
either of the airports this morning.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...None.
&&
$$

NWS MSO Office Area Forecast Discussion