Area Forecast Discussion
Issued by NWS Boise, ID
Issued by NWS Boise, ID
116 FXUS65 KBOI 032023 AFDBOI Area Forecast Discussion National Weather Service Boise ID 223 PM MDT Fri May 3 2024 .SHORT TERM...Tonight through Sunday night...Dry, warmer, and increasingly windy weather overnight and Saturday ahead of an approaching north Pacific cold front. Southeast through southwest winds will increase in southern CWA zones Saturday, reaching 30 mph with gusts to 45 mph, enough for a Wind Advisory in the Upper Treasure Valley and western Magic Valley, and the southern half of Harney County. These winds will help boost temps to near 70 degrees Saturday in the southern Idaho valleys, and 60s in the rest of Idaho, but only 50s and 60s in Oregon as rain will begin there around midday. A deep upper low in the north Pacific will come inland along the OR/CA border late Saturday then due east along the southern OR border Saturday night and southern Idaho border Sunday. This is an ideal track for pcpn in our CWA. The rain will be moderate to heavy late Saturday through Saturday night as the cold front moves eastward across our CWA. Totals will be .50 to 1.25 inch in the mountains, and .30 to .60 inch in the valleys. Snow level will drop sharply behind the cold front all the way to valley floors in Oregon, and 3500 to 4200 feet MSL in western Idaho Sunday morning. But by then most of the pcpn will be ending so snow totals will only be a couple inches, except above 7000 feet where a foot may fall. Behind the cold front Sunday`s high temps will be some 20 degrees lower than on Saturday, only in the 30s and 40s in the mountains and 40s to lower 50s in the valleys. Sunday will also be windy but not as windy as Saturday, and from the west or northwest. Lighter rain and snow showers will continue Sunday night as moisture wraps around the eastward-moving upper low. Thunderstorms were taken out of the forecast, except for a 15 to 20 percent chance in southern Twin Falls County Sunday afternoon. .LONG TERM...Monday through Friday...Northwest flow aloft will prevail as a deep low moves eastward out of the area. Embedded in the flow, another trough will move into the area late Monday and early Tuesday. As this trough moves into already moist and cold air, it will extend the chances (50-70%) of precip through the early parts of the long term. With snow levels still between 5000-6000 ft MSL, a chance for mtn valley mixed precip will exist, while mtns continue to favor snow. At the same time, Monday afternoon instability supports a slight chance of thunderstorms in the W-Central Mtns of Idaho and the ID/NV border. Precipitation chances will taper off between Tuesday and Wednesday as the trough exits the area, but a slight chance for showers will remain over central Idaho through Thursday morning. Models continue to agree on a period of calmer weather kicking off on Thursday, as a ridge of high pressure builds north of our area. The exact position of the high varies, but the forecast remains the same: warmer, drier, calmer by the end of next week. Temps will rise from 10-15 degrees below normal on Tuesday to near normal on Thursday/Friday. && .AVIATION...VFR with scattered mid and high level clouds through early Sat morning. Sat/12z a north-south oriented band of moderate precipitation begins to enter Harney county. Winds at 2000ft will increase significantly as it approaches, and as sfc winds lag behind a 6-10 hour LLWS threat exists at TAF sites NW of MUO and in SE OR. Surface winds: Becoming SE 10-20 kt, winds increasing Sat morning to SE 15-25 kt gusts to 25-35 kt. Winds aloft at 10kft MSL: S 15-25 kt. KBOI...VFR through the period, clouds generally building. LLWS threat exists Sat/06z through Sat/15z as surface winds struggle to keep up with rapidly increasing 2000ft winds. The timing of the LLWS threat may not be exact, but should cover the entire period of concern. Winds becoming SE 10-15 kt Friday afternoon. Winds are set to increase significantly early Sat morning to SE 15-25 kt with gusts to 25-35 kt. Weekend Outlook...A band of widespread precipitation will move into SE Oregon mid-morning Saturday, then into SW Idaho Saturday afternoon and will continue across the region through Sunday. High confidence (<100%) for rain at all sites as the precip band moves through. A 20% chance of thunderstorms Saturday afternoon in s-central Idaho. Snow levels 6000-7000 ft MSL, lowering to 4000-5000 ft Sunday. Lowered snow levels on Sunday means a switch to mixed precip in mtn valleys and snow in mtns. IFR and widespread mountain obscuration Saturday night through Sunday. Surface winds: SE 15-25 kt with gusts 30-40 kt Saturday afternoon, W 5-15 kt with gusts to 20-30 kt Sunday. && .BOI WATCHES/WARNINGS/ADVISORIES... ID...Wind Advisory from 9 AM to 6 PM MDT Saturday IDZ014-016. OR...Wind Advisory from 8 AM to 5 PM PDT Saturday ORZ061. && $$ www.weather.gov/Boise Interact with us via social media: www.facebook.com/NWSBoise www.twitter.com/NWSBoise SHORT TERM...LC LONG TERM....JM AVIATION.....JM