Area Forecast Discussion
Issued by NWS Boise, ID
Issued by NWS Boise, ID
511 FXUS65 KBOI 130241 AFDBOI Area Forecast Discussion National Weather Service Boise ID 841 PM MDT Wed Jun 12 2024 .DISCUSSION...Another warm and dry evening across the forecast area. Satellite imagery indicates at least one active fire which is about 30 miles southeast of Jordan Valley, Oregon. Southwesterly winds aloft are carrying the smoke plume northeast towards Mountain Home this evening, resulting in hazy conditions across Owyhee County and parts of the Upper Treasure Valley. An upper- level ridge will strengthen late tonight through Thursday, particularly across southwest Idaho, in response to an approaching upper-level low anticipated to affect the region this weekend. This will lead to another day of above-normal temperatures with stable conditions. Smoke will likely be trapped in the southwestern valleys of Owyhee County, south of the Owyhee Mountains, overnight but shouldn`t affect the Western Snake Plain. The forecast will be updated to account for hazy conditions tonight into Thursday across Owyhee County. The latest models show better agreement in bringing the low center over the forecast area by Monday. If this trend continues, the probability of precipitation will increase above the current forecast precipitation chances across most of the forecast area. This will be further addressed in the next forecast package on Thursday morning. && .AVIATION...VFR and mostly clear except for smoke mainly south of KBOI and KMUO this evening. Surface winds: W-NW 5-15 kt becoming variable 10 kt or less late tonight. Winds aloft at 10kft MSL: W-SW 15-25 kt. KBOI...VFR under mostly clear skies. Smoke layers aloft, south of KBOI, should dissipate after sunset. Surface winds: NW 7-13 kt, decreasing later this evening and becoming variable 6 kt or less by 06Z/Thu. && .PREV DISCUSSION... SHORT TERM...Tonight through Friday night...Little change from previous forecast. Hotter Thursday as an upper ridge moves in from the west. Significant cooling beginning Friday as a deep upper trough in the Gulf of Alaska moves onto the northwest coast. Friday looks 6-10 degrees cooler than Thursday, and Friday night 6-10 degrees cooler than Thursday night (and even cooler after that). Models show limited moisture but enough instability for a slight chance of thunderstorms in Twin Falls County late Thursday/Thursday evening. Light winds tonight and most of Thursday, then westerly 20 to 30 mph in Harney County/OR Thursday afternoon and evening, and in southern Idaho Friday afternoon behind a surface cold front. LONG TERM...Saturday through Wednesday...An active pattern will develop over the extended period, offering a break from summer heat and a brief return to more springlike conditions. The core of an upper level trough will move by to our north Saturday into early Sunday, bringing a dry cold front with much cooler temperatures and breezy winds. Any chance (10-20%) for showers will be limited to the northern mountains. Highs on Saturday will be 10-15 degrees cooler than Friday with another 5 degrees cooling on Sunday. This will place lower valley highs in the upper 60s to near 70 on Sunday, which is 10-15 degrees below normal. Models continue to show a closed low moving through the Pacific Northwest and Northern Rockies Sunday through Tuesday. The exact track of this low will have a major impact on our weather, with a more southerly track bringing the potential for widespread rain (and high-elevation snow above 7000 feet MSL in the central Idaho mountains) and temperatures 15-25 degrees below normal. This southerly track is depicted by roughly half of the EC ensemble members but is much less prominent amongst the GFS ensemble. A more northerly track would limit chances of showers and thunderstorms to the northern mountains, but still bring continued cool temperatures and breezy winds. By late Tuesday and Wednesday, models project the upper level trough to lose amplitude and temperatures to rise closer to normal, with drier conditions and decreasing winds also expected. && .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...JDS AVIATION.....JDS SHORT TERM...LC LONG TERM....ST