Area Forecast Discussion
Issued by NWS Boise, ID
Issued by NWS Boise, ID
606 FXUS65 KBOI 020942 AFDBOI Area Forecast Discussion National Weather Service Boise ID 342 AM MDT Thu May 2 2024 .SHORT TERM...Today through Saturday night...Precipitation will expand across the area today as a compact low tracks from the Oregon coast into SW Idaho. An initial shield of rain/snow will focus oriented along a NW-SE warm front that lines up over SE Oregon and far SW Idaho this morning. This area of more stratiform precipitation isn`t expected to extend beyond the I-84 corridor this morning before dissipating. Snow levels this morning will range between 3500-4500 feet and accumulations of of to 2 inches above 4500 feet are possible through this morning. Showers will become more widespread this afternoon as the upper low center passes overhead. Snow levels will rise to between 4500-6000 feet and any accumulation will be limited to the higher mtn peaks. While the probability of a thunderstorm isn`t zero, instability parameters are marginal, and less impressive than yesterday, so have opted to keep mention of thunder out of the forecast. Flow aloft will bring wind gusts to 30 mph across open and elevated terrain near the northern NV border this afternoon otherwise we`ll see lighter winds than yesterday. Friday brings a break in the active weather as dry and mild conditions accompany a transiting shortwave ridge. The next storm will take the form of a deep closed that will push into SW Oregon by Saturday night. Precipitation will form along the cold front at the leading edge of the low, spreading across SE Oregon early Saturday and into SW Idaho through the evening. There is good agreement among the deterministic models on the track of the low and development of precipitation along the cold front. While differences in amounts are notable they are all fairly robust and support a 70-90% chance of 0.10" or more of liquid across much of the area. Winds will ramp up on Saturday as well, first out of the east as air is pulled into the deep surface low, then shifting to the NW Saturday night behind the cold front. This will bring sustained winds of 20-30 and gusts of 30-40 ahead of the front on Saturday along the I-84 corridor from Twin Falls to Baker City as well as the over higher open terrain of SE Oregon. Warmer air ahead of the low will raise snow levels to 7-9kft MSL for the bulk of the precipitation through Saturday evening. .LONG TERM...Sunday through Thursday...A quick moving upper level low will move inland on Sunday, bringing a very cold air mass along with widespread precipitation to the region. Temperatures will be about 10-20 degrees below normal through Monday as the low center moves to our southwest and then lifts out of the southeast by late Monday. Cold northwest flow will build in over the region, keeping similar weather for the area through Tuesday. High terrain will see the heaviest precipitation, with anywhere from 10-12 inches of snow anticipated above about 7000 feet by Tuesday morning. Mountain valleys are currently forecast to see about 1-2 inches by Tuesday morning, but there is a chance that forecast snowfall totals will increase as we get closer to the day. Current model blends show about a 5% chance of the Snake River Valley seeing snowfall. However, based on the depth of the upper level low and the forecast trend from the past few nights, there is medium confidence from this forecaster (50% chance) in at least a trace of snowfall in most locations on Monday and Tuesday morning. Snow levels will be around 4000-5000 feet through Monday, with the potential for lowering to valley floors each night through Tuesday. As this low tracks to our east, cold northwest flow will keep temperatures below normal and a chance for showers each day through the long term period. The best chance for precipitation will continue to be over high terrain (40-50% chance) on Wednesday and Thursday, with low chances over the Snake River Valley (10-20% chance). Model agreement remains high through Wednesday with regards to the storm track, but after Thursday, there`s differences in the deterministic solutions, but better agreement in the ensemble clusters. A few members show another deepening low over the region on Thursday, although not quite as strong as the low this weekend. The majority of members show agreement in a ridge building in by the end of the week. Therefore, forecast uncertainty is high after Wednesday. && .AVIATION...Mainly VFR. Scattered rain and snow showers will move into the region by Thurs./12Z and SW ID by Thurs./15z creating MVFR/IFR conditions. Mountains obscuration in precipitation and low clouds. There`s also a slight chance of thunderstorms near the ID-NV border after Thurs./22Z. Showers will dissipate by Fri./04Z. Surface winds: W-NW 10-20 kt with gusts to 35 kt in terrain west of the Owyhee Mtns, otherwise S-SE 10-15 kt in the Snake River Valley, becoming W-NW 5-10 kts after Fri./06Z. Winds aloft at 10kft MSL: W- NW 25-35 kt south of the Treasure Valley, NE-E 10-20 kt northeast of the Treasure Valley. KBOI...VFR with scattered/broken clouds 6000-9000 ft AGL. Showers will develop this morning near KBOI, with a 30% chance of rain showers hitting terminal between Thu/16Z-Thu/23Z, and again Fri/06Z-08Z. There`s also a low chance (<10% chance) in a thunderstorm near the terminal Thursday afternoon. Surface winds: SE 5-15 kt overnight, shifting to NW 5-15 kt around Thu/22Z. && .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 SHORT TERM...DG LONG TERM....SA AVIATION.....SA