Marine Weather and Tide Forecast for Boise City, ID

FXUS65 KBOI 152145 AFDBOI

Area Forecast Discussion National Weather Service Boise ID 245 PM MST Mon Dec 15 2025

SHORT TERM
Tonight through Wednesday night...At 2 PM MST a weak cold front was in western ID with a band of light rain extending north-south along the OR/ID border. The front was moving steadily east with slightly more pcpn than models predicted but should total less than .15 inch even in the wettest locations. The front will stir up the stagnant air but not enough to end the Air Stagnation Advisory which will continue until 5 AM Tuesday. Clouds and light winds will moderate low temps tonight, and increasing southeast winds will boost max temps to near record highs Tuesday. Tuesday night will be windy and very mild ahead of a very strong Pacific cold front due in the pre-dawn hours Wednesday in OR, and early Wednesday morning in western ID. South/southeast winds will shift abruptly to west/northwest as the front passes and increase to 30 to 40 mph with possible gusts as high as 60 mph in southern zones. A High Wind Watch has been issued in those zones (listed below) for Wednesday morning in OR and through 2 PM MST Wednesday afternoon in western ID. Strongest winds are expected in the western Magic Valley and Camas Prairie. Pcpn will be heavier with the strong cold front with greatest amounts (near 1.00 inch) in eastern Valley County and northern Elmore County in ID late Tuesday night through late Wednesday night. Heaviest pcpn will fall as the cold front passes and may result in rock slides in steep terrain. Travelers would be wise to avoid the Banks-Lowman road in ID and be wary on ID state highway 21 northeast of Idaho City. The rest of ID north of the Snake Basin should have .25 to .50 inch liquid equivalent, while southern areas including the Snake Basin receive .10 to .25 inch, with similar amounts in eastern OR. The snow level will lower rapidly to valley floors later Wednesday in northern zones and to near 5000 feet in southern zones.
Snowfall 3 to 6 inches is expected in the higher ID mountains late Wednesday through Wednesday evening. Wednesday night should be calming, drying, and significantly cooling.

LONG TERM
Thursday through Monday...Precipitation chances continue through the extended, with a hefty push during Thursday, Friday, and early Saturday. This comes as another atmospheric river event impacts the Pacific NW from an elongated disturbance, courtesy of the Gulf of Alaska low. A strong, westerly mid-level jet will accompany this disturbance. As a result, this system will pull in a long fetch of considerable subtropical moisture, spreading moderate/heavy precipitation into the area. Snow levels will oscillate quite a bit during this period, associated with the tight temperature gradient, making snowfall accumulations a significant forecast challenge during this period. Overall, snow levels are expected to be lowest across the north, gradually rising from south to north throughout the day Thursday. Snow levels will then gradually lower from north to south as a cold front moves in late Friday/early Saturday.
Overall, mountains could see 1 to 2 inches of liquid equivalent throughout this period, along with snowfall totals 1 to 2 feet at the ridgetops (depending heavily on the snow level). The period of rainfall over saturated, steep terrain will also introduce rockslide concerns.

In addition to precipitation, strong surface winds are expected to develop across much of the area, particularly Friday, ahead of/along the cold front. Gusts will be strongest across southeast Oregon, the ID/NV border, and the mountains of southwest Idaho.
Meanwhile, temperatures are forecast to stay above normal Thursday and Friday, with the coldest air expected across west-central/central Idaho and eastern Oregon.

Once the aforementioned system exits, there will be a brief respite from precipitation late Saturday into Sunday morning.
This will occur before yet another push of precipitation comes ahead of a upper-level long wave trough slowly moving inland Sunday and Monday. Models currently disagree on how much of the polar air to the north will penetrate E Oregon and SW Idaho, resulting in poor forecast confidence on temperatures and snow levels this far out. Regardless, ample moisture will yield a new round of notable precipitation amounts for the area, with upslope flow favoring the mountains of west-central/central Idaho once again.
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