Area Forecast Discussion
Issued by NWS Boise, ID
Issued by NWS Boise, ID
440 FXUS65 KBOI 081522 AFDBOI Area Forecast Discussion National Weather Service Boise ID 922 AM MDT Sat Jun 8 2024 .DISCUSSION...Mostly clear skies will prevail through early afternoon with light winds. Temperatures will warm rapidly reaching the low to mid 90s this afternoon in most valley location and the low 80s in mountain communities. This is about 15 degrees above normal for early June, but a little cooler than earlier projections and below records. The atmosphere will become unstable later this afternoon with isolated thunderstorm developing by early evening affecting about 20 percent of the area. These thunderstorms will produce gusty outflow winds in their vicinity. This is all handled well in the current forecast and no updates are needed this morning. && .AVIATION...Isolated to scattered showers/thunderstorms in SE Oregon mainly after Sat/23Z, then into SW Idaho beginning around Sun/05Z, continuing through Sunday evening. Gusty and erratic outflow winds up to 35-40 kt, as well as MVFR conditions due to brief heavy rain. Small hail possible. VFR outside of storms. Hot temperatures will increase density altitude today. Surface winds outside of storm activity: N to NW 5-15 kt. Winds at 10k ft MSL: W to S 10-20 kt. KBOI...VFR. Hot temperatures will increase density altitude today. Surface winds generally W to NW 5-12 kt this afternoon, then variable overnight. A 20 percent chance of showers and thunderstorms capable of strong outflow winds 30-40 kt hitting terminal around Sun/06Z-08Z. Light rain showers late Sunday morning. Sunday Outlook...Isolated to scattered showers and thunderstorms. Stronger storms will produce brief IFR/MVFR conditions with heavy rain, with potential for gusty winds up to 25-35 kt and small hail. VFR outside of storms. Surface winds generally W-NW 5-15 kt. && .PREV DISCUSSION... SHORT TERM...Today through Monday night...A minor mid-level disturbance pushing across SW Idaho early this morning has brought light showers as it`s moved through the lower Snake Plain. A few sprinkles are possible across the Boise mtns as it tracks east through mid-morning. Otherwise another hot early June day across the region with high temperatures around 15 degrees above normal. Southeast Oregon and portions of SW Idaho south of the Snake Plain will see afternoon showers and thunderstorms. Locally gusty winds to 45 mph are possible, but don`t expect widespread outflows from storms that develop today. Southwest flow sets up over the area tonight into Sunday as an upper trough pushes onto the Pac NW coast. Increasing dynamics and elevated instability will support a 15-25% chance of showers and thunderstorms over SE Oregon and far SW Idaho overnight. This coverage expands on Sunday as the wave moves inland and daytime heating (even through increased cloud cover) adds energy and instability. High moisture content (PW values around an inch or 90-95th percentile) will add the threat for locally heavy rain from showers/storms. The potential for stronger storms exists over s-central Idaho on Sunday where surface and mid-level conditions are most favorable. Showers and storms dissipate Sunday evening as the upper wave moves east, leaving dry and warm conditions on Monday under weak ridging aloft. The heat peaks today with a not as hot, but more humid day on Sunday. Monday is the `coolest` and driest day of the period with temperatures 5-10 degrees above normal (mid 80s for lower valleys). LONG TERM...Tuesday through Saturday...The long term period starts with zonal flow over the PacNW and extending well out into the Pacific, and this should last through Thursday. By Friday, the flow aloft shifts to SW as a large upper level low moves toward the coast of SW Canada. This low is forecast to move onshore Saturday with better-than-average model agreement. However, there is still some spread with the timing and location of the system. Models agree that we will be dry with temperatures around 10 degrees above normal through Friday, before cooling to near normal Saturday. It should be pointed out that even though the current model suite is in good agreement, there has been a significant amount of variability in the track and strength of this upper low over the past few days, and further adjustments are likely. At this time, the forecast is dry Saturday, but if the forecast track of the low shifts southward, that will change. && AVIATION...Isolated showers in the Lower Treasure Valley and over Owyhee County will end by Sat/11Z. Isolated to scattered showers and thunderstorms will redevelop around 20Z across southeast Oregon and in southwest Idaho mainly south of the Snake River. Gusty and erratic outflow winds to 40 kt possible, as well as MVFR conditions due to brief heavy rain. VFR conditions outside of thunderstorms. Surface winds: N to NW 5-15 kt, except gusty near storms. Winds at 10k ft MSL: W-SW 10-20 kt, becoming variable 5-15 kt by 09/06Z. KBOI...VFR. Surface winds W 10-15 kt, becoming variable 6 kt or less after 10Z, then becoming NW 6-12 kt after 19Z. Sunday Outlook...Isolated to scattered showers and thunderstorms, with the most coverage across the higher terrain. Stronger showers and thunderstorms will produce brief IFR/MVFR conditions with heavy rain and gusty winds. Outside of thunderstorms, VFR conditions expected. Surface winds generally W-NW 5-15 kt. && .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...JB AVIATION.....SH SHORT TERM...DG LONG TERM....SP