textproduct: Boise

DISCUSSION

Moderate to locally heavy rain and mountain snow all day today, then decreasing tonight. Pcpn will be heaviest in the Boise Mountains and West Central Idaho Mountains. Accumulating snow was reported as low as 4500-5000 feet MSL early this morning, lower than expected. McCall (elev 5050) had an inch at 7 AM MST. Snow levels should still gradually rise until this evening when a cold front arrives from the WNW. Therefore, most of the snow below 6000 feet has already occurred. We are also tracking forecast wind gusts in south- central Idaho Wednesday afternoon. The trend is slightly lower speeds so a Wind Advisory for Wednesday is not planned at this time.

AVIATION

Widespread precipitation and mountain obscuration. Snow levels generally 5-7kft rising to 7-8kft MSL this afternoon, except steady around 8kft MSL near the NV border. Surface winds: SW- SE 5-15kt except SW 20-30kt with gusts to 40kt near the OR/NV border. Areas of LLWS this morning. Winds aloft at 10kft MSL: W 35-50 kt.

KBOI...Rain. Low VFR with MVFR ceilings at times. 20% chance of IFR conditions late afternoon/early evening. SE winds 10 kt.

PREV DISCUSSION

SHORT TERM...Today through Thursday night...Widespread rain and high elevation snow today as a plume of subtropical moisture moves overhead. Precipitable water values will reach the 99th percentile, or near record highs for this time of year, resulting in moderate to locally heavy precipitation. Steady rain and snow will become showery tonight and focused in the mountains as the moisture plume sags south. Strong westerly flow through the event will enhance precipitation totals in the mountains with 1-2" rain or snow water equivalent. Most lower elevations will see 0.25-0.75" rain, locally up to 1". This system will be mild, with snow levels rising from 5-7kft MSL this morning to 6500-8500 feet by late afternoon (lowest across the north). Light snow accumulations are expected in higher mountain communities, such as McCall, this morning before turning to rain this afternoon. Rain and melting snow in the mountains below the snow line will increase the risk for rock and mud slides below steep slopes. Above 6-7kft, 8-16" snow will be common, with totals approaching 2 feet on the highest peaks. High temperatures today will be around 5 degrees cooler than Monday due to widespread precipitation. Winds in the higher terrain will be gusty, especially near the Nevada border with gusts 30-45 mph.

Showers will gradually taper off Wednesday as a cold front moves south. Snow levels will lower to 4-5kft behind the front with a dusting of snow possible in mountain valleys. Despite cooling aloft, less precipitation will mean high temperatures Wednesday will be similar or a couple degrees warmer than today, or slightly above normal. Winds Wednesday will be gusty across the area, strongest across south-central ID and the higher terrain where gusts will reach 35-45 mph. Dry conditions will return Wednesday night into Thursday under northwest flow aloft. Temperatures will be similar with locally breezy winds.

LONG TERM...Friday through Tuesday...A stationary front will remain along the Canadian border on Friday, with dry and mild west- northwest flow and precipitation remaining north. A weak system off the West Coast will move inland on Sunday with a 30-50 percent chance of precipitation. Snow levels will range from 5000-7000 ft MSL, but precipitation amounts will be light. This system will move south into the Four Corners region by Tuesday, with an upper level ridge building over the area. This will bring Spring-like temperatures with valleys reaching the low to mid 60s on Tuesday and Wednesday, or around 10-15 degrees above normal.

BOI WATCHES/WARNINGS/ADVISORIES

ID...None. OR...None.