Area Forecast Discussion
Issued by NWS Boise, ID
Issued by NWS Boise, ID
285 FXUS65 KBOI 220949 AFDBOI Area Forecast Discussion National Weather Service Boise ID 349 AM MDT Wed May 22 2024 .SHORT TERM...Today through Friday night...Widespread precipitation will continue this morning as a closed low approaches east Oregon and southwest Idaho from the north- northwest. Snow levels are currently around 6500-7000 ft MSL, but will quickly lower to around 4500-5000 ft MSL as the cold front arrives late this morning/afternoon. Conditions will become unstable and promote convective shower activity and isolated/scattered thunderstorms, mainly for far eastern Oregon and over southwest Idaho. Meanwhile, a swath of drier air will start to move into southeastern Oregon late this afternoon/eve, shunting much of the shower activity toward the east and south for the remainder of the day. The exception will be the wrap- around showers from the closed low continuing over east-central Oregon and central Idaho through early Thursday. Latest model runs move this low eastward out of the area more quickly on Thursday, but a slight chance (20%) of showers will linger over central Idaho mountains through Thursday afternoon. Overall, precipitation totals will be highest over southwest Idaho where around 0.2 to 0.5 inches of rainfall is forecast for the valleys, and up to 0.75 to 1.25 inches of liquid equivalent over the higher terrain. Light snow accumulations may be possible down to 4500-5000 ft MSL today and tonight, while several inches of late season snow can be expected generally above 7000 ft MSL. In addition to the precipitation, west and northwest winds will ramp up late this morning/afternoon across the area, especially over south-central Oregon. As a result, a Wind Advisory has been issued for southern Harney County due to wind gusts up to 45-50 mph possible in the afternoon and early evening. Temperatures will be much colder today compared to Tuesday, roughly 10-15 degrees below normal. Drier, northwesterly flow aloft will replace the low on Thursday, with temperatures rebounding by a few degrees. Further warming anticipated Friday ahead of a weak shortwave trough forecast to arrive late Friday. This shortwave will come ahead of the next low pressure system, and introduce a chance of (20-35%) of showers for east-central Oregon and west-central Idaho by Friday evening. Snow levels late Friday will begin around 7000-7500 ft MSL. .LONG TERM...Saturday through Wednesday...Cloudy and unsettled conditions will continue to spread throughout most of the region as the leading edge of a North Pacific low pressure system packed full of inclement weather treats quickly slides across. Lower probabilities (10-30%) for showers are anticipated across most of the valleys and other regional low lying areas while higher values (40-80%) dominate the Boise, West Central and Owyhee Mountains. As the associated cold pool of moist air temporarily blankets primarily the northern zones, snow levels will lower enough to bring snowfall possibilities back into the picture - mostly in areas with elevations 5000ft and above during the low`s brief stay. This same cooling condition will also destabilize the local atmosphere enough (as reflected in borderline CAPE, LI`s accompanied by orographic lift and surface heating converging during that time) to encourage a slight chance for afternoon through evening thunderstorms across Baker county, Oregon and the Mountains of Southeastern Idaho on Saturday. Breezy winds will also be a weather factor across the major valleys and Owyhee and Steens Mountain areas and especially near showers and thunderstorms. By Sunday afternoon, conditions will dramatically improve to sunny and warmer as the low exits and drier, warmer ridging builds in. This warming trend will continue throughout the remainder of the period with highs increasing and ranging from mid 70`s thru mid 80`s. However, these improving conditions will be short lived as starting Tuesday conditions will slowly deteriorate as pockets of moisture and instability begin trickling into northern Oregon increasing the chances once again for precipitation. && .AVIATION...Numerous rain and snow showers. Isolated to scattered thunderstorms after Wed/15Z. Periods of MVFR/IFR in precip. Mountains obscured. Snow levels around 6000-7000 ft MSL will lower to 4500-5000 ft MSL this afternoon. Surface winds: variable 5-15 kt this morning, then generally W-NW 10-25 kt with gusts 25-35 kt late this morning through tonight with cold front. Winds aloft at 10k ft MSL: W-NW 20-35 kt. KBOI...Steady rain with periods of MVFR ceilings and visibility this morning. Transitioning to showers after Wed/13Z. A 30% chance of thunderstorms hitting KBOI late morning through around Wed/22Z. Winds: variable or northwest 5-10 kt, then W to NW 10-20 kt with gusts up to 25-30 kt this afternoon with cold front. Decreasing around sunset. && .BOI WATCHES/WARNINGS/ADVISORIES... ID...None. OR...Wind Advisory from 11 AM this morning to 8 PM PDT this evening ORZ061. && $$ www.weather.gov/Boise Interact with us via social media: www.facebook.com/NWSBoise www.twitter.com/NWSBoise SHORT TERM...SH LONG TERM....WH AVIATION.....SH