textproduct: Boise

LONG TERM...Sunday through Thursday

Precipitation will continue on Sunday as an upper level trough approaches the coast. As the trough approaches, a warm front will lift north through the area Sunday morning with snow levels climbing to 5500-7000 feet. This will result in strong southwesterly flow aloft with a brief shadowing/drying trend in the Snake Plain, but the mountains especially in central Idaho will continue to see heavy precipitation. A cold front will push through late Sunday and the upper level trough axis will pass overhead by Monday morning. Precipitation will continue along and behind the front, then decrease by Monday morning as the trough axis moves east of our area. Snow levels will fall to valley floors by Monday, but showers will be mostly confined to the mountains. Precipitation amounts on Sunday will vary greatly, ranging from around 0.10-0.25 inch of rain in the lower elevations to 0.50-1.50 inch of liquid water equivalent in the mountains. Additional snow amounts of 8-16 inches are possible above 6000 feet on Sunday, with a couple inches of snow in mountain valleys as snow levels fall.

Temperatures will cool from 5-15 degrees above normal on Sunday to up to 5 degrees above normal on Monday. The trough will bring gusty winds Sunday into early Monday, then subside by late Monday. A ridge will start to build overhead on Tuesday bringing dry conditions and light winds, with temperatures near normal. For Wednesday and Thursday, ensembles depict a trough moving over the ridge, but uncertainty exists about whether the trough will move far enough south to bring precipitation to our area. For now, this uncertainty results in a 20-50% chance of precipitation, with snow levels near valley floors.

AVIATION

Widespread rain/snow decreasing from W to E this morning. Periods of MVFR/IFR in rain, IFR/LIFR in snow. Mountains obscured. Snow levels 3k-4k feet. Then, numerous convective showers along a cold front will move across SE Oregon this morning and SW Idaho this afternoon with the highest coverage over the mountains. Moderate to heavy precipitation rates possible in showers, and lightning cannot be ruled out. Brief break in widespread precipitation this evening before the next round of rain and snow moves in from the west late tonight into Friday morning. Surface winds: SE-SW 10-20 kt with 20-35 kt gusts for most areas this morning. Winds briefly becoming W-NW behind a cold front this afternoon. Winds aloft at 10kft MSL: W-SW 40-65 kt, decreasing to 20-40 kt by 00Z/Fri. Areas of low level wind shear this morning.

KBOI...Rain, mixing with snow at times, will continue through 13Z/Thu. Little to no snow accumulation expected as temperatures should remain in mid-30s. Lower confidence in the visibility forecast as it will depend heavily on precip type, but MVFR/brief IFR is likely with precip. Conditions improving after Thu/13Z, except in periodic rain showers late this morning through early this afternoon. Surface winds: SE 10-20 kt with gusts to 20-30 kt, becoming W 8-15 kt around 19Z/Thu along a cold front.

Weekend Outlook...Widespread rain and snow Friday morning. Rain and snow will continue Friday afternoon in the central Idaho mountains while decreasing elsewhere. More rain and snow will arrive Friday night and continue through Sunday, heavy at times in the mountains. MVFR/IFR conditions and mountain obscuration in rain and snow. Snow levels rising from 3500-5500 ft MSL on Friday to 4500-6500 ft Saturday and Sunday. Surface winds SE-SW 10-20 kt with gusts 25-40 kt Friday morning, becoming W-NW behind a cold front Friday afternoon. Winds switching back to SE-SW 5-15 kt Friday night through Sunday morning, then W-NW 10-20 kt with gusts 20-35 kt late Sunday. Areas of low level wind shear.

BOI WATCHES/WARNINGS/ADVISORIES

ID...Winter Weather Advisory until 5 PM MST Friday IDZ011-013-028. Winter Weather Advisory until 11 AM MST this morning IDZ014-016-033. OR...Winter Weather Advisory until 10 AM PST this morning ORZ062.