Area Forecast Discussion
Issued by NWS Boise, ID
Issued by NWS Boise, ID
336 FXUS65 KBOI 311546 AFDBOI Area Forecast Discussion National Weather Service Boise ID 946 AM MDT Sun Aug 31 2025 .DISCUSSION...A strong ridge continues to build across the Pacific Northwest and will hold in place through Labor Day. Satellite imagery this morning shows increased cloud cover over central Oregon, signaling continued mid to high level moisture moving into southeast Oregon. Although CAPE values remain minimal at around 50 to 100 J/kg, temperatures will be a few degrees warmer today. Given the recent trend of thunderstorms developing over higher terrain, POPs have been adjusted to include a thunderstorm mention across Harney County and the higher terrain of Baker County, in line with the majority of high resolution guidance. Any storms that do form will be high based, capable of producing gusty outflow winds up to 40 MPH with little rainfall. Across southwest Idaho, conditions appear stable enough to limit thunderstorm development, though cumulus buildups can still be expected over the mountains. Smoke from fires in central Oregon has increased across the area this morning as it is being recirculated around the ridge from the east. Strengthening southwesterly flow tonight into Monday should keep additional smoke from the Emigrant Fire northwest of the area, but smoke from larger fires in California and Nevada will move in. As a result, little improvement in smoke and haze is expected for Labor Day. && .AVIATION...Generally VFR. Smoke layers aloft through around 20kft MSL. A 15-20% chance of showers/thunderstorms in Harney County (KBNO) and across higher terrain west of KBKE this afternoon. Surface winds: S-E 5-15 kt with localized gusts to 25 kt in the Snake Plain. Winds aloft at 10kft MSL: S-SE 5-15 kt. KBOI...VFR. Smoke Layers aloft. Surface winds: Variable under 10kt this morning, becoming SE 8-12 kt with gusts to 20 kt this afternoon. && .PREV DISCUSSION... SHORT TERM...Today through Tuesday night...Heat will build over the region through Monday as an upper ridge amplifies across the interior western US. Conditions are a touch more stable today across Baker County and the w-central ID, so while mtn cumulus development is likely, don`t expect it to be deep enough to produce lightning. Do expect to see some taller buildups over Harney County this afternoon and have edged up the chance of a shower or thunderstorm to around 10%. Given the development the last few days, honestly wouldn`t be surprised to see a cell overachieve this evening. Today will run 1-3 degrees warmer than yesterday, with another 1-3 degrees of warming into Monday. This will place lower elevations in the upper 90s, and wouldn`t be surprised to see a couple of 100 degree highs on Monday as a surface thermal trough over Oregon pulls SE winds through the Snake Plain. A more southerly flow aloft sets up Monday into Tuesday as the ridge axis shifts eastward. This will draw moisture northward, lifting precipitable water values to over 0.75 inches, which is certainly enough to support shower/storm development. Thus have increased precipitation chances across SE Oregon and areas south of the Snake Plain in Idaho starting Monday, but more so for Tuesday. Will also be watching the timing of a weak low lifting northward through CA late Tue/Wed which could enhance afternoon development or even introduce a nocturnal threat Tuesday night. LONG TERM...Wednesday through Sunday...The CA low will likely still be in play over the area on Wednesday. Models favor tracking the low center through Oregon, which would favor SE Oregon and far SW Idaho for a continued chance of showers and thunderstorms. From there we`ll be looking for a potential breakdown of the upper ridge late in the week into next weekend. While there are differences in how it evolves, both the GFS and ECMWF show a break in the heat and increased chances of rain unfolding by the weekend. These solutions lineup with the ensemble consensus which has temperatures returning to near normal and a broad 20-30% chance of showers/storms starting on Saturday. Interestingly the operational Canadian model keeps the ridge and summer heat in place through the period. && .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...JDS AVIATION.....NF SHORT TERM...DG LONG TERM....DG