Area Forecast Discussion
Issued by NWS Boise, ID
Issued by NWS Boise, ID
453 FXUS65 KBOI 231501 AFDBOI Area Forecast Discussion National Weather Service Boise ID 901 AM MDT Sun Jun 23 2024 .DISCUSSION...Temperatures across the valley are already in the low to mid 70s this morning, with the Boise airport at 79F as of 8:55AM MDT. Temperatures will steadily climb through the day bringing well above normal temperatures to most of the region. Most of the lower Treasure Valley will reach the upper 90s to low 100s. Breezy westerly winds will return by the afternoon as the upper level pressure gradient tightens due to a trough passage to the north. The highest winds (W-NW 20-30 mph) will be on ridgetops and above ~5000 feet. These winds, dry conditions, and hot temperatures will allow for active fire behavior on existing fires, promoting more smoke and haze development, especially across the Owyhee Mountains, with the smokiest conditions likely downstream near Mountain Home. Conditions will remain hot and dry through early next week with a slight chance of showers near the ID-NV border on Tuesday. No forecast updates necessary. && .AVIATION...VFR with clear skies. Hot temperatures will bring high density altitudes. Reduced visibilities from smoke near a prescribed fire in far SW Idaho. Surface winds: variable 10 kt or less becoming W-SW 10-20 kt with gusts to 30 kt after 18Z. Winds aloft at 10kft MSL: W-SW 15-30 kt. KBOI...VFR with clear skies. Hot temperatures will bring high density altitudes. Surface winds: NW 5-10 kt. && .PREV DISCUSSION... SHORT TERM...Today through Tuesday night...Temperatures in the Treasure Valley could reach 100 degrees again today. However, the arrival of the next Pacific system moving inland across British Columbia will increase westerly flow aloft, leading to breezy northerly surface winds in the valley and westerly winds elsewhere. Expect wind gusts of 25-35 mph in higher elevations, while winds will be lighter in lower elevations. This setup is likely to result in slightly cooler temperatures today. Ensemble probabilities for temperatures reaching 100 degrees or higher are between 30-70%, with Ontario having the highest probability at 70% due to warmer surface temperatures from northerly downslope winds. Hot, dry, and breezy conditions will promote active fire behavior this afternoon, potentially causing smoke plumes and hazy conditions, especially east-northeast of the fire in southwest Owyhee County. As the Pacific system continues east across West-Central Canada on Monday, a surface cold front will pass through, bringing cooler temperatures with valley highs around the mid-90s. However, the air mass will remain too dry for any precipitation with the frontal passage. A stronger Gulf of Alaska trough will approach the Pacific Northwest coast on Tuesday, causing the upper-level flow to shift to south-southwest, bringing hot temperatures back to the forecast area. Ensemble guidance indicates a 25% chance of high- based moisture from the southwestern U.S. reaching the Idaho/Nevada border Tuesday night, potentially leading to thunderstorms. Temperatures in the Treasure Valley will again approach 100 degrees on Tuesday, with a 20-30% chance of reaching or exceeding 100 degrees. LONG TERM...Wednesday through Sunday...The Gulf of Alaska trough will move inland across western Canada and the Pacific Northwest on Wednesday, keeping the forecast area in the warm sector for another hot and mostly dry day. The southerly flow might bring enough high-based moisture for afternoon thunderstorms in south-central Idaho. The associated cold front is expected to reach the forecast area on Thursday, bringing significantly cooler temperatures and breezy westerly winds. A temperature drop of about 20-25 degrees is possible, which could result in below-normal temperatures on Thursday and Friday. There is around a 90% chance that temperatures will remain below 90 degrees on both days. While the air mass will remain mostly dry, there could be enough moisture in the West Central Mountains of Idaho for showers and thunderstorms on Thursday and Friday. The strongest winds are expected on Thursday with the passage of the upper-level trough and jet. Temperatures will rebound into the low 90s next weekend as another ridge develops in response to another Pacific trough. && .BOI WATCHES/WARNINGS/ADVISORIES... ID...None. OR...None. && $$ www.weather.gov/Boise Interact with us via social media: www.facebook.com/NWSBoise www.twitter.com/NWSBoise DISCUSSION...SA AVIATION.....BW SHORT TERM...JDS LONG TERM....JDS