Area Forecast Discussion
Issued by NWS Boise, ID
Issued by NWS Boise, ID
510 FXUS65 KBOI 252029 AFDBOI Area Forecast Discussion National Weather Service Boise ID 229 PM MDT Thu Apr 25 2024 .SHORT TERM...Tonight through Saturday night...A shortwave trough pushing in from the coast will advance a line of showers and isolated thunderstorms as it moves through the region overnight. For now have limited the mention of thunder to SE Oregon zones as later timing is less favorable east of the ID/OR border. Gusty outflow winds of up to 40 mph will accompany the line of precipitation. The upper trough slows its eastward movement on Friday as energy closes off over the Great Basin. Daytime instability will feed shower and thunderstorm development mostly over higher terrain. The cold air aloft could support graupel or small hail on strong cells with wind gust potential to 35 mph. For the bulk of the precipitation snow levels will be above 6kft MSL which will limit accumulation to the higher peaks. Through Saturday morning snow totals of 2 to 4 inches are expected above 6500 feet in the w-central Idaho mtns and eastern Boise mtns. Much of the area dries out on Saturday while moisture wrapping around the exiting trough keeps a 20-40% chance of showers over w-central Idaho through the afternoon. The dry westerly flow continues into Saturday night with any small chance of showers (15-25%) limited to northern Valley County. Temperatures are near normal through Saturday. .LONG TERM...Sunday through Thursday...Models are in excellent agreement starting the long term off with WNW flow aloft Sunday, becoming zonal Monday into Tuesday. This will bring in a chance (10-30%) of showers mainly in the northern mountains and along the ID/NV border on these days. The first notable disagreement in the latest deterministic runs arrives Wed, as the EC depicts a strong upper low moving across northern ID while the GFS shows dry zonal flow. Comparing these to the available ensemble runs shows that the EC is an outlier (15% of the spread). Therefore, the forecast favors the drier GFS, but still holds on to a chance (still 10-30%) of showers mainly in the northern mountains. Models remain out of synch with each other into Thu, but there is general agreement that another upper low will approach the Pacific Coast Thu. This is likely to bring cooler and wetter weather late next week and into next weekend. Overall, temps will be near normal Sun-Tue, then above normal Wed and Thu, with Wed the warmest day next week. && .AVIATION...Generally VFR, then areas of MVFR moving into eastern Oregon this afternoon as showers/weak thunderstorms develop. This area will move into southwest Idaho this evening. Surface winds: W to NW 5-15 kt. Gusts to 30 kt in stronger showers, and along/just behind the cold front tonight. Winds aloft at 10kft MSL: W-NW 15-25 kt. KBOI...VFR under mid to high level clouds today. Surface winds: NW 5- 15 kt, with gusts near 20 kt this afternoon. A cold front will arrive this evening with light rain showers along and behind the front. The front will also lower ceilings to 5000-7000 ft AGL and bring brief wind gusts to 30 kt. Thunderstorm chances less than 15% tonight. Weekend Outlook...Scattered to numerous showers and isolated thunderstorms will continue into Friday, with the highest coverage in the mountains. Periods of MVFR conditions and mountain obscuration in showers. Snow levels 5500-6500 ft MSL. Scattered showers will continue into Saturday and Sunday over the mountains, with mostly dry conditions and decreasing clouds elsewhere. Surface winds generally W-NW 10-25 kt, with the strongest winds Friday night and Saturday from KMUO east through the Magic Valley where gusts up to 40 kt will develop. && .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...DG LONG TERM....SP AVIATION.....SP