Area Forecast Discussion
Issued by NWS Boise, ID
Issued by NWS Boise, ID
123 FXUS65 KBOI 042027 AFDBOI Area Forecast Discussion National Weather Service Boise ID 227 PM MDT Sat May 4 2024 .SHORT TERM...Tonight through Monday night...Major north Pacific storm now inland in OR and CA, preceded in our CWA by gusty southeast to southerly winds. Current Wind Advisory in the Upper Treasure Valley, Western Magic Valley, and Harney County is set to expire at 3 PM MDT /2 PM PDT/. Latest MOS guidance supports that expiration time with winds forecast to diminish. The Pacific storm`s cold front will then move into our CWA with moderate to heavy rain late today through tonight, with the front reaching central Idaho early Sunday morning. Latest forecast rain amounts through Sunday remain consistent with previous forecast: .15 to .50 inch in the Oregon valleys, .50 to 1.00 inch in the Oregon mountains, .40 to 1.00 inch in the Idaho valleys, and .80 to 1.75 inch in the Idaho mountains. Pcpn should decrease to lighter rain and mountain snow showers Sunday and Sunday night, then increase again Monday night as a weaker Pacific trough comes inland. The extra pcpn will add another .15 to 25 inch to the amounts stated above. Latest models now show little chance (less than 10%) of thunderstorms through Monday morning, but a 20 percent chance Monday afternoon and evening throughout our CWA. High temperatures Sunday will only be in the 40s to lower 50s. For Idaho that means about a 20 degree drop from today. Monday will be also be cold with the main upper trough still nearby (but east of our CWA). .LONG TERM...Tuesday through Saturday...After Monday`s system, we will be left with moist NW flow aloft and steadily decreasing chances of showers going from Tuesday through Tuesday night. The big story Tuesday will be strong winds, with gusts 30-50 mph possible. The strongest gusts are expected to develop from around Mountain Home south and east into the western Magic Valley. Wednesday, the only chance of precipitation worth mentioning (15-30%) will be in eastern Valley County as relatively dry northerly flow aloft builds in. Winds will still be breezy, but much weaker than Tuesday. Ridging aloft to our north, combined with a low to our south, will result in (relatively rare) easterly flow Thursday and Friday. Models begin to differ significantly late Friday and Saturday, but odds are we will be dry with temperatures near or a little above normal. && .AVIATION...Mainly VFR this afternoon into the evening, then areas of MVFR as precipitation becomes widespread. Mountains obscured at times this afternoon, then consistently tonight. There`s a 10% chance of thunderstorms from 22-04Z. Snow levels 7-9kft MSL, lowering to 3- 4kft SE OR and 4-6kft SW ID Sunday morning. Surface winds: S-E 10-25 kt, with gusts 25-40 kt becoming W-NW 10-20 kt tonight. Winds aloft at 10kft MSL: S 20-40 kt today, becoming W through S tonight. KBOI...VFR today with gusty SE surface winds. Rain will begin 22-24Z this afternoon and increase this evening. Wind will shift to NW between 01-03Z and there will be periods of MVFR. After 03Z probability of ceilings below 2kft increases to 40-60% with a 20-30% chance of IFR conditions developing. Sunday Outlook...Rain changing 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 until 6 PM MDT this evening IDZ014-016. OR...Wind Advisory until 5 PM PDT this afternoon ORZ061. && $$ www.weather.gov/Boise Interact with us via social media: www.facebook.com/NWSBoise www.twitter.com/NWSBoise SHORT TERM...LC LONG TERM....SP AVIATION.....SP