Area Forecast Discussion
Issued by NWS Boise, ID
FXUS65 KBOI 201009
Area Forecast Discussion
National Weather Service Boise ID
309 AM MST Fri Jan 20 2017
.SHORT TERM...Today through Saturday...Areas of dense fog (with
visibilities of a quarter mile or less) will continue this
morning from west of Boise to Ontario and northeast into the
Upper Weiser Basin. The fog is expected to dissipate by late
morning. An upper trough near the coast will direct precipitation
into SE Oregon this morning and SW Idaho late this afternoon and
evening. Latest models continue with the trend of slightly warmer
temperatures and slightly higher snow levels through Saturday.
Therefore, will adjust both of these weather parameters
accordingly. The net result, however, doesn`t change the Winter
Weather Advisories for portions of SE Oregon. Northern Harney and
northern Malhuer Counties are still on track to receive 2-5 inches
of snowfall today through this evening, and the Lower Treasure
Valley around Ontario is also on track for 1-3 inches late this
morning through this evening. The slightly warmer temps and higher
snow levels will lead to the possibility of rain with the snow in
Upper Treasure Valley, where snow levels will average 2500-3000
feet tonight through Sunday. Snow accumulations are possible in
the Upper Treasure and Western Magic Valleys, but total amounts
are expected to be less than an inch.
.LONG TERM...Saturday night through Thursday...Active weather
pattern still on track through Tuesday. An upper level low off the
Pacific Northwest coast Saturday night will slowly shift east
through Monday night. Best chance of precipitation will be Sunday
as a moist southwesterly flow develops over the area ahead of the
approaching upper level low. As with the previous weather systems,
snow level will be tricky, but still looking like most locations
will see snow, but there could be a change to at least a rain/snow
mix in the lower valleys by Sunday afternoon. As the upper level
low gets closer to the region, snow levels will once again fall to
valley floors. Models do not seem to have a good handle on how
much precipitation we will see with this latest storm but still
thinking 2-4" in the valleys and 4-6" in the mountains. Upper
level low will move over the forecast area Tuesday with decreasing
precipitation. Wednesday and Thursday an upper level ridge
develops over the area with a cold northerly flow and increasing
chance of valley inversion developing.
.AVIATION...LIFR conditions in low stratus and fog from KEUL-
KONO will persist through 19Z. Otherwise mostly VFR conditions
with thickening and lowering clouds and local MVFR/IFR conditions
in valley low stratus and fog through 19Z. Snow will spread over
southeast Oregon after 12Z for mountain obscuration and widespread
MVFR and areas of VFR conditions. Surface winds east to south
10-20 knots with gusts of 25-30 knots. Winds aloft southwesterly
20-30 knots up through 10K feet MSL.
Weekend Outlook...Mountains will be obscured. Deteriorating
conditions over southwest Idaho Friday evening as snow spreads over
the region. Light snow showers will remain over the area Saturday
and Saturday night with MVFR conditions and areas of IFR
conditions. Next round of heavier snow will move over the area
Sunday for widespread MVFR and areas of IFR conditions.
ID...Dense Fog Advisory until 11 AM MST this morning IDZ012-033.
OR...Dense Fog Advisory until 11 AM MST this morning ORZ064.
Winter Weather Advisory until 11 PM MST /10 PM PST/ this evening
Winter Weather Advisory from 11 AM this morning to 11 PM MST
this evening ORZ064.