Area Forecast Discussion
Issued by NWS Boise, ID
Issued by NWS Boise, ID
471 FXUS65 KBOI 210913 AFDBOI Area Forecast Discussion National Weather Service Boise ID 313 AM MDT Fri Jun 21 2024 .SHORT TERM...Today through Sunday night...Satellite this morning shows an upper-level trough over northern Idaho, which will move east into Montana this afternoon. This shift will bring drier air and westerly flow aloft, limiting warming across the forecast area. Temperatures are expected to rise by about 2-4 degrees above yesterdays highs. While moisture will be limited, there will be enough to support cumulus cloud development across southwest Idaho. The next Pacific system is set to reach the British Columbia coast on Saturday, potentially bringing the warmest temperatures of the year so far. Forecast models now indicate a 50-70% chance of temperatures reaching 100 degrees or more in the Treasure Valley on both Saturday and Sunday. Historically, Boise`s first 100-degree day occurs around July 9th, though in 5 of the last 11 years, it has happened in June. .LONG TERM...Monday through Friday...A brief break in the hot temperatures is expected on Monday with the passage of a Pacific system. Although the core of the system will remain well north in Western Canada, an associated surface cold front will move across the forecast area, bringing slightly cooler temperatures. Highs will drop into the mid-90s on Monday. The air mass will remain too dry for any precipitation with the frontal passage. A much stronger Gulf of Alaska trough is expected to move inland, potentially as early as Thursday. The latest ensemble guidance shows much better agreement, with 93% of the members favoring a Thursday/Friday timing for the cold frontal passage. This setup will build a ridge across the forecast area for Tuesday into Wednesday, bringing back the hot temperatures. Current guidance indicates temperatures between 99-101F for the Treasure Valley. However, these temperatures could be too low due to the likelihood of stronger east-southeasterly winds ahead of the approaching cold front. Although guidance does not currently show these winds, they are typical with this type of synoptic pattern. Temperatures will drop about 20-25 degrees behind the front, potentially leading to below-normal temperatures on Friday. While the air mass will remain largely dry, there could be enough moisture across our northern mountain zones for showers and thunderstorms on Friday. && .AVIATION...VFR. Mostly clear skies. Surface winds: E-SE 5-15 kt. Winds aloft at 10kft MSL: S-SE 10-15 kt. KBOI...VFR. Mostly clear skies. Surface winds NW 5-10kt, switching to SE 5-10kt around 21/06Z. Weekend Outlook...VFR. Hot temperatures will bring high density altitudes Saturday and Sunday. Surface winds W-SW 10-20kt during the afternoons, light during the night. && .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 SHORT TERM...JDS LONG TERM....JDS AVIATION.....JDS