Area Forecast Discussion
Issued by NWS Boise, ID
Issued by NWS Boise, ID
994 FXUS65 KBOI 250250 AFDBOI Area Forecast Discussion National Weather Service Boise ID 850 PM MDT Wed Apr 24 2024 .DISCUSSION...This evening, scattered showers persist in the Southwest Highlands and Southern Twin Falls County, though much of the activity has tapered off. Earlier, a few outflow boundaries were observed from stronger storms, but there haven`t been any additional boundaries sighted in the past hour. A dry cold front is advancing southeastward this evening, accompanied by brief gusty winds. As of 8:30 PM MDT, the front was positioned south of a Burns-Baker City line and will continue its southeastward trajectory. It`s expected to reach Ontario by approximately 9:30 PM MDT, Boise by 10:30 PM, and eventually Twin Falls and Jerome around 4 AM MDT. Wind gusts of up to 30 MPH are anticipated with the passage of this front. Dry conditions are forecasted to persist through early Thursday afternoon until the arrival of the next cold frontal system, which will bring widespread showers Thursday night into Friday morning. The current forecast appears comprehensive, requiring no updates at this time. && .AVIATION...Generally VFR. Isolated rain showers in south-central Idaho. Gusty outflow winds up to 30 kt. Surface winds: SW to NW 5-15 kt, with gusts to 20-30 kt from KBKE/KONO to KMUO with cold front overnight. Winds aloft at 10kft MSL: W-NW 10-20 kt. KBOI...VFR under mid to high level clouds. Surface winds: NW 5-15 kt. Cold front arrives around Thu/04-05Z, with the potential to bring gusts to around 20 kt overnight. Light rain showers arrive Thursday night after Fri/03Z, lowering ceilings to 5000-7000 ft AGL. Thunderstorm chances less than 15% Thursday night. && .PREV DISCUSSION... SHORT TERM...Tonight through Friday night...A broad upper low lifting out of the Desert SW will keep a chance of showers over far southern zones overnight, mostly along the ID/NV border. The thunderstorm potential with this activity will diminish with sunset. As that system moves eastward a cold front will push through the region tonight in advance of the next upper wave. The frontal passage will be dry, bringing gusty winds to SE Oregon and portions of the Snake Plain in Idaho. Thursday will see breezy, dry and cooler conditions to start, with showers developing over higher terrain in the afternoon. Precipitation fills in Thursday night as an upper low provides dynamical support. Valleys will see a 30-50% chance of measurable precipitation with a 70-90% chance of rain and high elevation snow in the mountains through the day Friday. Afternoon instability will support a 15-20% chance of thunderstorms Friday across SE Oregon and higher terrain of SW Idaho. Snow levels will range between 5500-6500 feet Thursday night into Friday with 3-6 inches possible above 6500 feet. Breezy northwest winds will be strongest across open terrain, especially through the Snake Plain east of Boise where gusts of 40 mph are possible each afternoon/evening. The gusty winds will carry into Friday morning as the low begins to exit eastward. Temperatures will trend 5-8 degrees cooler each day through Friday. LONG TERM...Saturday through Wednesday...As an upper level trough exits our area to the east on Saturday, surface gradient forcing will support very windy conditions in the Snake Plain. Winds gusts of up to 40-50 mph in the Middle Snake Plain meet Wind Advisory criteria, although it is still too far in the future for a product at this time. Gusts in the Lower Snake Plain will generally be 30-40 mph. Some lingering precipitation potential exists on Saturday, 20- 50% chances, mostly along our eastern boundary and in the Central Mtns of Idaho. At the same time our next upper low pressure system begins tracking south from the Gulf of Alaska, putting us under southwest flow from Monday morning through at least Tuesday. Models are split on where the low sets up exactly, which is resulting is some pretty varied forecasts as all of them show the low slowing down. Most of the ensembles keep the low offshore, with a cold front stalled over our area, and it is the position of the front that is resulting in the uncertainty. Temps may be 10 degrees above normal if we remain east of the front, or 10 degrees below normal if we are west of the front. The range of precipitation chances is roughly 10- 50%, with best chances over higher terrain. There is a slight warming trend, a degree or two each day, through the period and winds are set to be somewhat breezy each afternoon. && .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.....SH SHORT TERM...DG LONG TERM....JM