Area Forecast Discussion
Issued by NWS Boise, ID
Issued by NWS Boise, ID
900 FXUS65 KBOI 121624 AFDBOI Area Forecast Discussion National Weather Service Boise ID 924 AM MST Wed Nov 12 2025 .DISCUSSION...Continued mild and dry through most of Thursday in Idaho, but cooling in Oregon Thursday as a weakening Pacific cold front comes inland. The supporting upper trough off the coast has formed a closed low near 39N/139W. The low is headed for southern California while the northern portion moves rapidly eastward along near the Canadian border. The trough will be weakest as it passes through our area, and the cold front will also weaken Thursday night but still be able to scour the weak inversion. Pre-frontal south-southwest winds will reach 25-35 mph in gusts in southern areas Thursday afternoon. Current forecast is on track. No update. && .AVIATION...VFR under high clouds. Isolated light rain/virga showers this afternoon. Surface winds: Variable up to 10 kt. Winds aloft at 10kft MSL: SW 10-20 kt. KBOI...VFR. Surface winds: SE 5-10 kt. && .PREV DISCUSSION... SHORT TERM...Today through Friday night...Mild and dry weather through Thursday morning as an upper ridge and inverted conditions keep winds light and temperatures very warm for this time of year. High temps Wednesday and Thursday are as high as 15-20 degrees above normal, peaking Thursday with some Snake Plain locations potentially seeing just under 70 degrees. A persistent weak inversion will make for hazy conditions, with some morning mist possible. Off the West Coast, a low pressure trough amplifies, leading to increasing clouds through the first half of the short term. By Thursday morning, the leading edge of the moisture supports a slight chance of precipitation with snow levels still high at 8-9 kft MSL. The leading edge will also bring gusty winds on Thursday, with gusts 25-35 mph in SE Oregon and SW Idaho highlands and ridges. This, and a cold front Thursday night/ Friday morning with increased precipitation chances, will scour out the inversion. Some uncertainty is apparent amongst models as the front moves through, but the chance of precipitation for higher northern terrain is still 80-90% and 30-50% for lower elevations. The uncertainty has led to a slightly higher snow level forecast behind the cold front, with snow levels on Friday now 6-8 kft MSL and temps 5 degrees above normal, dropping expected snowfall on ridges significantly. The expected rainfall or liquid equivalent for mountains is still in the realm of 0.30-0.50 inch, and less than 0.10 inch for lower elevations. Precipitation continues through Friday, with the best chances in the morning. The high-amplitude trough becomes a closed low over SoCal by the end of Saturday, deamplifying the jet stream over the region and indicating a brief break in pcpn in the long term. LONG TERM...Saturday through Wednesday...With the region in the deformation zone of a closed low off the SoCal coast and the jet stream to the north on Saturday, only a slight chance of precipitation for Baker and Valley counties exists on Saturday. Model run-to-run variability has been significant in the track of the closed low Sunday onwards (as is usual with closed lows, much to my (and my forecast`s) dismay. The closed low amongst ensemble means seems to track northeastward, just clipping the area Sunday night with Pacific moisture. What would have been a fairly shortlived system, will be lengthened by a new trough developing almost immediately behind the closed low. The vast majority of models depict this trough, leading to high confidence in a wetter and cooler start to Monday as its cold front moves through. This will drop temps down to near normal Monday through Wednesday with snow levels at 4-5 kft MSL. This would give ridgelines and passes the couple of inches of snow they now miss out on in the Thursday system, possibly even impacting high elevation towns such as McCall with some snow accumulation. && .BOI WATCHES/WARNINGS/ADVISORIES... ID...None. OR...None. && $$ www.weather.gov/Boise Interact with us via social media: www.facebook.com/NWSBoise www.x.com/NWSBoise DISCUSSION...LC AVIATION.....NF SHORT TERM...JM LONG TERM....JM