


Area Forecast Discussion
Issued by NWS Boise, ID
Issued by NWS Boise, ID
514 FXUS65 KBOI 041608 AFDBOI Area Forecast Discussion National Weather Service Boise ID 1008 AM MDT Fri Jul 4 2025 ...MARGINAL RISK FOR SEVERE THUNDERSTORMS AND FLASH FLOODING THROUGH THIS EVENING... .DISCUSSION...Instability and moisture along with dynamics associated with an upper trough will promote rounds of showers and thunderstorms across the region through this evening. There is a marginal risk for severe thunderstorms capable of producing damaging winds and large hail. There is also a marginal risk for heavy rainfall that may cause flash flooding on burn scars. The Flash Flood Watch for central Idaho was extended through this evening, and expanded to include all of SE Oregon. && .AVIATION...Mostly VFR. Rain showers continue to move north with clouds clearing behind. Scattered thunderstorms in E Oregon, with coverage increasing into SW Idaho as early as 18z. Thunderstorms capable of producing heavy rain, hail, 50 kt wind gusts, and MVFR/IFR conditions. Mtns obscured in precipitation. Surface winds outside of storms: W-NW 10-20 kt with gusts to 25 kt in the Snake Plain. Winds aloft at 10kft MSL: Variable 10-20, becoming SW 15-30 kt after 18z. KBOI...Mostly VFR. 30-40% chance of thunderstorms this afternoon. Most likely time frame for thunderstorms at terminal are between Fri/20z-Sat/00z. Hazards with thunderstorms include: heavy rain, hail, wind gusts of 50 kt, and MVFR/IFR conditions. Outflows may travel from distant storms. Surface winds outside of thunder: NW 10- 16 kt with gusts up to 25 kt this afternoon. Weekend Outlook...Generally VFR. A 15-25% chance of showers and thunderstorms Saturday morning in W-central Idaho mountains, then clearing through Sunday. Surface winds variable or NW 5-15 kt. && .PREV DISCUSSION... SHORT TERM...Today through Sunday night...A strong upper level positively-tilted shortwave will move into the region today and help keep thunderstorms going. Most areas can expect multiple rounds of showers and storms. As of 2 AM MDT, showers and storms were most numerous south of Boise, but there were additional showers and storms in the mountains. Mesoscale models are reasonably consistent showing this activity increasing through sunrise as storms continue to move north. Latest QPF guidance continues to show the possibility of high rainfall rates in the mountains this morning, and the Flash Flood Watch will be maintained as issued. We considered moving the start time up a couple hours, but it appears that the strongest rain rates will occur around and after 12Z, so a change is not needed. Red Flag Warnings continue across eastern Oregon today, and seem appropriate based on several bands of thunderstorms that should move across the region this morning through early evening. Instability will be extreme for this area, with CAPE values forecast over 1000 J/kg over a sizable area around midday. Shear increases today compared to yesterday as the shortwave trough moves through, and supercells may form, especially this afternoon. Not coincidentally, SPC has put nearly our entire CWA into a marginal risk for severe thunderstorms. Some storms are expected to produce wind gusts 40-60 mph, hail up to 1 inch in diameter, and brief torrential rain. PW values near 0.90 inch put us near the 90th percentile this morning, before drier air moves in this afternoon into the evening. Showers and storms should continue into the evening before diminishing around midnight tonight. There is still a slight chance of showers and thunderstorms in eastern Valley County Saturday, but Sunday will be dry with a warming trend as temperatures return to near normal. Temperatures today and Saturday are expected to be relatively cool for this time of year, with readings in the lower to mid 80s at lower elevations. Winds should mainly out of the NW at 5-15 mph today and Saturday except near showers and thunderstorms. LONG TERM...Monday through Friday...Strong ridging will build into the area from the four corners region throughout the long-term, sustaining hot and dry conditions Monday to Friday. A trough off the coast of California is expected to keep our area in southerly flow aloft. As the ridge builds, temperatures take on a significant warming trend reaching roughly 10 degrees above normal, with valley daytime temperatures reaching or exceeding the upper 90s throughout the week. Heat headlines may be needed in the week to come as a result of the prolonged hot temperatures. Influxes of upper-level monsoonal moisture steered by this pattern interaction cannot be ruled out for the extended period. A slight ridge breakdown is possible Thursday as the trough off the California coast is expected to briefly dig across the northwest as a shortwave towards the end of the week. && .BOI WATCHES/WARNINGS/ADVISORIES... ID...Flash Flood Watch until 9 PM MDT this evening IDZ011-013. OR...Red Flag Warning until 8 PM PDT this evening ORZ670. Flash Flood Watch until 9 PM MDT /8 PM PDT/ this evening ORZ061>063. && $$ www.weather.gov/Boise Interact with us via social media: www.facebook.com/NWSBoise www.x.com/NWSBoise DISCUSSION...BW AVIATION.....NF SHORT TERM...SP LONG TERM....JY