Area Forecast Discussion
Issued by NWS Boise, ID
Issued by NWS Boise, ID
171 FXUS65 KBOI 181540 AFDBOI Area Forecast Discussion National Weather Service Boise ID 940 AM MDT Sat May 18 2024 .DISCUSSION...Relatively stable conditions prevail across the region this morning, with high cirrus clouds over Baker County, OR and the West Central Mountains. Temperatures will be slightly above normal today, with the frontal passage still anticipated later tonight (11 pm MDT-3 am MDT). Winds will pick up this evening, especially along the Snake River Valley with brief gusts to 30-35 mph, with ridgetops seeing gusts to 45 mph. This front will cool temperatures for tomorrow by about ten degrees, beginning the slight cooling trend next week. Light precipitation across the West Central Mountains still looks possible (30% chance), although hi-res model guidance now suggests it will stay mostly to the north of the county warning area. No forecast updates necessary. && .AVIATION...VFR with some high clouds over the region. Surface winds: light and variable this morning, becoming SW to NW 5-15 kt with afternoon gusts to 20-30 kt. Then, NW gusts up to 30- 40 kt spreading through the Snake Plain from KBKE/KONO to KMUO/KTWF this evening/overnight with cold front. Winds aloft at 10k ft MSL: W 20-35 kt. KBOI...VFR. Increasing high clouds. Winds light and variable, becoming NW 5-10 kt around Sat/21Z. Increasing to 10-15 kt with gusts 20-30 kt around Sun/05Z, due to cold front. Sunday Outlook...VFR. Increasing clouds for northeast OR and w- central ID mountains Sunday, and 20-50% of showers. Snow levels 4500- 5500 ft MSL. Surface winds: W to NW 10-20 kt on Sunday. Local gusts to 25-30 kt in the Snake Plain. && .PREV DISCUSSION... SHORT TERM...Today through Monday night...An upper-level trough situated just north of the forecast area today will continue to bring breezy conditions and below-normal temperatures. Winds are expected to lighten this afternoon, with valley temperatures reaching the low to mid-70s. This evening, an approaching shortwave and its associated cold front will move across southeast Oregon and into southwest Idaho by early Sunday morning. The front will bring brief gusty winds, with gusts up to 45 MPH. The strongest winds are anticipated between Baker City and Ontario from 6 PM MDT to midnight, and from Ontario to Mountain Home from midnight to 5 AM MDT. Breezy conditions will persist from Mountain Home through the Western Magic Valley from about 3 AM MDT until sunset on Sunday. While the latest guidance indicates increased wind speeds, they remain below advisory levels. Temperatures will drop to approximately 10 degrees below normal for this time of year. Additionally, there is a 30% chance of showers in the West Central and Boise Mountains of Idaho, with light snow possible above 6000 feet. The shortwave and cold front will exit the region by Sunday night. However, the upper-level trough will remain, expanding southward across the entire forecast area by Monday. This shift will increase instability and moisture, supporting a 30% chance of convective showers in the afternoon and evening over the higher terrain. Though overall instability and dynamics are relatively weak, its still sufficient to support a 15% chance for thunderstorms. Breezy northwest winds will persist, maintaining below-normal temperatures across the area. LONG TERM...Tuesday through Saturday...Dry conditions with slightly warmer temperatures are expected with a brief, weak ridge Tuesday. Winds will become breezy Tuesday night into Wednesday as the next trough arrives over the Pacific Northwest. Shower chances will increase over east Oregon and southwest Idaho Wednesday, with the best chance (60-80%) of precipitation occurring over the central Idaho terrain. In addition, instability will increase Wednesday afternoon and promote a slight chance (15%) of thunderstorms across the area. Temperatures are anticipated to drop several degrees below normal with the trough, with snow levels lowering to approximately 5500-6500 ft MSL by late Wednesday. As a result, snow accumulations are possible at high elevations through early Thursday. Models begin to vary significantly on the path and evolution of this trough, and subsequent troughs, for the remainder of the week. However, the overall pattern will support unsettled and cooler than normal conditions. && .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.....SA SHORT TERM...JDS LONG TERM....SH