Area Forecast Discussion
Issued by NWS Boise, ID
Issued by NWS Boise, ID
920 FXUS65 KBOI 041031 AFDBOI Area Forecast Discussion National Weather Service Boise ID 431 AM MDT Sat May 4 2024 .SHORT TERM...Today through Monday night...A deep closed low positioned off the Oregon coast will come onshore near the OR/CA border this evening. Showers will break out today in the increasingly unstable airmass ahead of the low center. A minimal threat for thunderstorms exists over s-central Idaho where instability and surface heating overlap with a strong shear environment. Gusty easterly winds will strengthen through the morning, channeling through the Snake Plain and Baker Valley while a strong southerly flow aloft (30-40kt at ~5kft MSL) mixes to the surface across higher terrain of SE Oregon. The focus of strongest winds will be across Malheur County in Oregon and portions of the Treasure Valley where sustained winds of 25-35 mph and gusts of 40-50 mph are expected. These areas remain covered by a Wind Advisory. A band of heavier, steady precipitation will develop along a cold front which will track into SE Oregon early this afternoon and SW Idaho by this evening. Precipitation rates of 0.10-0.20"/hr are expected along this line which will be accompanied by a wind shift to the W-NW. Snow levels of 7-9kft MSL ahead of the front today will drop to 3-4kft across SE Oregon and 4-6kft over SW Idaho by Sunday morning. Areas of Harney county and the western Magic Valley could see precipitation mix with or change to snow, though surface temperatures will likely be too warm for any accumulation. Widespread showers continue in the mountains through Monday night as the main upper low is followed by a weaker trailing trough. Lower valleys catch a brief break Sunday night into early Monday, before the trailing wave brings another round of rain/snow. The axis of heavier precipitation totals through Sunday night arcs from Baker County into the w-central ID mtns south into lower Snake Plain. These areas will see totals of 0.5-1.0" in the valleys and 0.75-1.5" in the mountains. Otherwise a widespread 0.2-0.5" of liquid is expected through Sunday night. The heaviest snow will be above 5500 feet where total accumulation of 4-8 inches with locally higher amounts is possible. .LONG TERM...Tuesday through Saturday...Showers continue Tuesday as the low gradually shifts eastward. An upper ridge builds along the West Coast on Wednesday while the recently departed low will circle over the upper Great Plains through the remainder of the week. Models show some variability in how far west the low will retrograde and introduce the possibility of a piece splitting off and resettling over the eastern Great Basin late in the week. While much of the area dries out starting Wednesday, a slight chance of showers (~20%) remains over w-central Idaho through Thursday. Temperatures will slowly warm through the end of the week. && .AVIATION...VFR today. Rain and high mtn snow moving into SE OR by late morning and into SW ID late afternoon. Isolated thunderstorms across SW ID Saturday afternoon. Local MVFR/IFR conditions limited to mountains through this afternoon, increasing across lower elevations overnight. Mountain obscuration in precipitation becoming widespread tonight. Snow levels 7-9kft MSL, lowering to 3-4kft SE OR and 4-6kft SW ID by Sunday morning. Areas of LLWS this morning, mostly in corridor from KBKE-KBOI with winds S-SE 35-45 kt at 2000 ft AGL. Surface winds: S-SE 10-25 kt, with gusts 25-40 kt becoming W-NW 10-20 kt this evening. Winds aloft at 10kft MSL: S 20-40 kt. KBOI...VFR today with gusty SE surface winds. Rain this evening will bring wind shift to NW and periods of MVFR conditions. After 03Z probability of ceilings below 2kft increases to 30-50% with a 20-30% chance of IFR conditions developing. Sunday Outlook...Change to snow in the mountains will produce widespread IFR and obscure terrain across w-central Idaho and e-central Oregon. Snow levels 3500-5500 feet, lowest in SE Oregon Sunday morning. Elsewhere low VFR-MVFR with showers continuing through the day. Surface winds: W 10-20 kt with gusts 20-30 kt. && .BOI WATCHES/WARNINGS/ADVISORIES... ID...Wind Advisory from 9 AM this morning to 6 PM MDT this evening IDZ014-016. OR...Wind Advisory from 8 AM to 5 PM PDT Saturday ORZ061. && $$ www.weather.gov/Boise Interact with us via social media: www.facebook.com/NWSBoise www.twitter.com/NWSBoise SHORT TERM...DG LONG TERM....DG AVIATION.....DG