Area Forecast Discussion
Issued by NWS Boise, ID
Issued by NWS Boise, ID
365 FXUS65 KBOI 290237 AFDBOI Area Forecast Discussion National Weather Service Boise ID 837 PM MDT Fri Jun 28 2024 .DISCUSSION... A warm and dry evening is expected as a weak upper-level ridge develops over the forecast area in response to an approaching upper-level trough anticipated late Saturday. Light winds and mostly clear skies are forecasted overnight. Temperatures will rise above normal on Saturday, with lower valleys expected to reach the mid-90s. The next upper-level trough and associated cold front will move across the Pacific Northwest, reaching southeast Oregon around 6 PM MDT. Ahead and behind the front, clouds and wind will increase as it continues eastward, reaching southwest Idaho between midnight and 1 AM MDT on Sunday. Models suggest weak instability along and behind the front; however, moisture remains limited with PW values approaching 0.75. This will be sufficient for a few high-base showers on Sunday morning with little to no precipitation. Cooler temperatures are expected Sunday afternoon post-frontal, with northwesterly flow. There may still be enough moisture and instability for showers and thunderstorms Sunday afternoon, with the best chance (30 percent) along the Idaho/Nevada border and in the West Central Mountains of Idaho. The current forecast covers this well, so no updates are needed at this time. && .AVIATION...VFR and mostly clear. Surface winds: W-NW 5-15 kt becoming SE less than 10 kt after sunset. Winds aloft at 10kft MSL: W 5-15 kt. KBOI...VFR and mostly clear. Surface winds stay NW 6-12 kt through the day and turn SE 5-7 kt around midnight. Weekend Outlook...Generally VFR. Increasing clouds late Saturday and Sunday. A 15-30% chance of showers and thunderstorms will develop over northeast Oregon Saturday night, spreading to southeast Oregon and the higher terrain of southwest Idaho on Sunday. Surface winds: SE-SW 5-15 kt on Saturday, becoming NW 10-20 kt Saturday night and Sunday. && .PREV DISCUSSION... SHORT TERM...Tonight through Sunday night...Dry, cool northwest flow will continue to bring seasonable temperatures to the region tonight, with overnight lows in the upper 30s to low 40s in many higher elevation locations. A weak ridge will begin to build in tomorrow, bringing a return to hot, above normal temperatures by the afternoon. Light winds will remain throughout the region through tonight, the only exception being the Snake River Valley, where some westerly gusts could reach 20-25 mph by the evening. The pattern shifts as another upper level shortwave trough moves through the region on Sunday morning, advancing a cold, moist airmass into the region. The cold front will move through southeast Oregon on Sunday morning and then through southwest Idaho on Sunday afternoon. Isolated showers and thunderstorms will move in with the cold front, mainly over high terrain. Winds will be breezy ahead of the front early Saturday, with gusty outflow winds increasing outside of any showers or thunderstorms. Temperatures will moderate to just slightly above normal on Sunday after the front moves through. LONG TERM...Monday through Friday...A Pacific High will build over the Eastern Pacific Ocean, bringing northwest flow into the region on Monday. Temperatures will dip down to just about 5 degrees above normal, along with dry conditions. Models then vary significantly on the evolution of this broad high. Deterministic GFS/ECMWF solutions show the high building into the desert southwest and bringing extremely hot temperatures into our region, with 99th percentile highs in the valleys reaching near 110F on Friday.The ECMWF AI and some of the cluster ensembles however shows the ridge staying off the coast which would moderate temperatures sufficiently. Current forecasts show the valley reaching near the upper 90s, but if the deterministic solution pans out, we could reach well over 100F. Conditions will be dry through next week, with the 8-14 day CPC outlook favoring below normal precipitation and above normal temperatures for the region. && .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...SA LONG TERM....SA