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Letterhead and timestamp

000 FXUS65 KBYZ 150657 AFDBYZ Area Forecast Discussion National Weather Service Billings MT 1257 AM MDT Tue Sep 15 2026

KEY MESSAGES

- Cooler than normal through Wednesday, then seasonable temperatures.

- Increasing chances for showers and thunderstorms Thursday through Saturday. Locally heavy rain possible, especially east of Billings.

DISCUSSION

Through next Monday...

Satellite imagery shows the departing upper low over southern Manitoba and a flatter W-NW flow over the northern Rockies. There is an upstream shortwave along the BC coast that will be a player for us later this week. Winds are decreasing and will shift to easterly today. Overall it will be a tranquil day with high temps in the upper 60s to lower 70s (after a chilly start), and much less wind than Monday. There is also a low risk (<15%) of fog over our north and east early today, as post-frontal dew points are close to expected morning lows, but a west wind persisting beyond sunrise may prevent fog from developing despite the shrinking dew point depressions.

A weaker splitting shortwave from the NW will glance thru northern MT tonight into Wednesday. This looks mostly dry but another Canadian front will sag into the area reinforcing the below normal temps for another day. Temps should climb into the 70s across the area Thursday.

Aforementioned BC wave will eventually evolve into a cut off low over OR/CA/NV by Wednesday. This feature will then track slowly eastward, within a region of above normal heights, providing ascent for shower activity and allowing for another surge of high plains moisture. In fact, pwats are expected to climb back over an inch over the east half of our forecast area by Friday. Greatest potential for showers seems to be late Thursday through Saturday. Thunderstorms are possible Friday, with enough instability and slow storm motion to bring a risk of heavy rain, especially over the east. Shear will likely be too low for a risk of severe storms. Some showers could linger in the east into Sunday, but consensus is for rising heights and drying from the west by then. Latest NBM probabilities show a 20-40% chance of 1+ inches of rain over the east Friday thru Saturday night. Regarding temperatures, this is a seasonably warm system and snow levels will remain high, no lower than 10kft. Expect near to slightly cooler than normal temps Friday/Saturday, then warming into early next week with the ridging. Should see near 80F by next Monday, along with dry wx.

JKL

.AVIATION...

There is a small chance for fog/low stratus to develop this morning for eastern MT. Winds are expected to shift from west to east through the day with wind gusts to 25 kts in the evening. TS

PRELIMINARY POINT TEMP/POPS

Tdy Wed Thu Fri Sat Sun Mon ------------------------------------------------------- BIL 068 045/066 047/073 054/073 051/071 049/075 049/079 0/U 00/U 00/B 25/T 63/W 21/U 00/U LVM 069 040/070 042/075 047/071 044/072 044/076 045/079 0/U 00/U 02/T 57/T 43/W 11/U 00/U HDN 070 041/067 043/077 051/074 046/071 043/076 043/080 0/U 00/U 00/B 35/T 64/W 31/U 00/U MLS 067 050/070 046/075 056/075 051/070 047/074 047/080 0/U 00/U 01/B 35/T 65/W 32/W 00/U 4BQ 070 054/073 048/076 057/077 052/071 048/075 049/080 0/U 00/U 14/W 25/T 65/W 31/B 10/U BHK 068 045/077 041/073 051/077 047/071 042/075 043/079 0/U 00/U 02/W 56/T 75/W 41/B 10/U SHR 071 044/070 041/077 050/075 044/070 042/075 042/079 0/U 00/U 11/B 26/T 64/W 21/U 11/U

BYZ WATCHES / WARNINGS / ADVISORIES

MT...None. WY...None.

weather.gov/billings