Sunrise 6:37 AM   Sunset 8:46 PM Moonrise 1:14 AM   Moonset 9:29 AM

  Print   HELP   Reset   Save   Recall

FXUS65 KBOI 292046 AFDBOI

Area Forecast Discussion National Weather Service Boise ID 246 PM MDT Mon Apr 29 2024

SHORT TERM
Tonight through Wednesday night...An unseasonably cool upper level trough is moving across the Pacific NW today.
This system is bringing a cold front through the area, and has reached Ontario, OR as of 2pm MDT. This front will continue to track southeast through the afternoon, and temperatures will slowly fall behind the front, with rain, snow and graupel showers mainly north of a line from Burns OR to Boise ID.
Isolated thunderstorms possible too. The front is forecast to generate windy conditions in the upper Treasure and Magic Valleys and Camas Prairie through this evening where a wind advisory remains in effect. The upper level trough will remain over the area on Tuesday, keeping temperatures around 10 to 15 degrees below normal. The coldest air aloft will reach -30C at 500mb and extend from a line north of Burns to Boise on Tuesday.
Slightly warmer 500mb temperatures near the NV border will lessen the chance of showers. Scattered showers will redevelop on Tuesday afternoon with a slight chance of thunderstorms, where the coldest air aloft is. Another shortwave moves south into the upper level trough on Wednesday morning, enhancing the threat of snow showers over the area. 500mb temperatures reach -33C on Wednesday morning, which is near record cold for this time of year. Light snow possible down to the valley floors, but precipitation will be showery in nature, so some places may see snow, while others will not. Snow showers will linger over the mountains on Wednesday afternoon, but warmer air aloft and ridging will bring drier and more stable conditions by Wednesday evening.

LONG TERM
Thursday through Monday...Long-term models are showing poor agreement that gets worse with time. As a result, most aspects of the forecast have a high degree of uncertainty.
A compact low will move in from the northwest on Thursday, bringing precipitation through Thursday night with breezy afternoon winds. Chance of precip is fairly low, 25-35% in higher terrain and ~10% in lower valleys. Most precipitation will be rain, but above 5000 ft MSL snow becomes possible since some colder air lingers from the low earlier in the week.
Instability in central Oregon will support a slight chance of thunderstorms. The track of this low varies a little model to model, but most of the disagreement is in the coverage of the precipitation, hence the mediocre precipitation chances.

A brief calm period persists Friday into Saturday morning thanks to a ridge of high pressure. At the same time, a deep closed low from the Gulf of Alaska tracks southeast along the Canadian west coast. While models are beginning to show more agreement with each run, they are still not quite there. The GFS continues to the low making landfall in California, and then putting us under a deformation zone as it moves east. While the 12z EC now shows the core of the low moving directly overhead, putting us under the coldest part of the airmass. This is a fairly big change from the 06z EC, that showed the low becoming a longwave trough leading to still unsettled but a notably weaker weather pattern. The National Blend consensus is area- wide 30-50% precip chances beginning Saturday afternoon, dropping to 20-40% Sunday afternoon through the rest of the long-term. Saturday onwards each afternoon will have a chance of thunderstorms and breeziness. The spread in maximum temperature forecast is 10-20 degrees each day, with the consensus being normal temps.

AVIATION
VFR. Widespread rain/snow showers in the north and isolated to scattered elsewhere. Instances of graupel and lightning are possible in the north as the chance of thunderstorms is just below 30%. Mountains obscured. Snow levels 4000-5000 ft MSL, lowering to 2500-3500 ft MSL by Tue/06Z.
Surface winds: W 15-25 kt with gusts to 30 kt this afternoon, peak gusts of up to 40 kt. Winds aloft at 10kft MSL: W 20-30 kt.

KBOI...VFR with increasing clouds. Slight chance (less than 20 percent) of -SHRA between Mon/18Z and Tue/00Z. Surface winds: NW 12- 15 kt increasing to 15-20 kt with gusts to 23-28 kt this afternoon.
Winds decrease to 8-12 kt around Tue/05z and switch to SE around Tue/11z.

BOI WATCHES/WARNINGS/ADVISORIES
ID...Wind Advisory until 7 PM MDT this evening IDZ014-016-028.
OR...None.

Full Color Weather Map

Link to Loop


Other links: GEOS-West     Contential US     Full GOES-East

Boise, ID,