Weather Service Report


103 
FXUS65 KBOI 240406
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
906 PM MST Fri Feb 23 2018

.DISCUSSION...Latest model runs continue to support current winter
weather headlines for Saturday. Snow will begin across the far
north late tonight and spread across most of southeast Oregon and
southwest Idaho Saturday morning. The widespread snow will become
showery in the afternoon behind a cold front. It will also become
windy, especially in southeast Oregon and behind the cold front 
in southwest Idaho Saturday afternoon with west-northwest winds of
15 to 25 mph with higher gusts. Some locations, mainly in the
morning and at higher elevations, could see some blowing snow.
Another winter storm is expected to impact mainly the mountain
areas Sunday through Monday morning. No updates for now.

&&

.AVIATION...VFR tonight under increasing clouds. Isolated snow 
showers over the mountains will begin as early as 24/09Z, becoming
widespread between 24/15Z-21Z. Expect mountain obscuration and 
areas of MVFR/IFR conditions in snow and blowing snow. Surface 
winds: generally southeast to southwest 12 kts or less overnight,
increasing across southeast Oregon and along the ID/NV border to 
about 15 kts with gusts to 25 kts. Surface winds turn west-
northwest by 24/18Z with gusts ranging between 20-30 kts in most 
areas south of the west central Idaho mountains. Winds decrease 
after 25/03Z. Winds aloft at 10kft MSL: NW 25-35 kts, becoming W 
by 24/09Z, and increasing to 35-50 by 24/15Z.

Outlook for Saturday night and Sunday...Scattered snow showers at
higher elevations Saturday night, becoming widespread Sunday over
higher terrain with mountain obscuration.

&&

.PREV DISCUSSION...
SHORT TERM...Tonight through Sunday...A quick moving storm system
will drop through the Intermountain Northwest late tonight and
Saturday bringing widespread snow to the region. Snow will  
develop in Baker county and the west-central Idaho mountains by 
midnight, spreading south and east through Saturday morning. All
elevations will see snow with this storm. The upper dynamics 
and stiff mid-level winds will enhance snowfall across mountains
(especially south and west facing slopes). Could also get an
isolated lightning strike or two Saturday afternoon as the trough
axis passes. Have changed over the Winter Storm Watch to mostly
Advisories with a Warning in the Owyhee mountains. Could see some
blowing snow to start, but precipitation is scattering out in most
locations by the time the strongest winds develop on Saturday
afternoon. Precipitation tapers off Saturday night before another
upper wave drops into the area on Sunday. This system will be more
orographically driven, focusing snowfall across the mountains of
east-central Oregon and west-central Idaho on Sunday. Snowfall
amounts are such, that more highlights may be needed for the
mountains by late Sunday. Winds will be gusty Saturday and Sunday
afternoon, especially across the open rangeland in southeast
Oregon. Temperatures are around 10 degrees below normal through
the weekend.

LONG TERM...Sunday night through Friday...The unsettled and 
unseasonably cold pattern will continue. The next upper level
trough will move inland Sunday night and Monday. Most of its 
energy will head south over California, so storm total snowfalls 
are expected to be relatively light in the valleys of southeast 
Oregon and southwest Idaho. Monday night and Tuesday will be dry 
across most of our area, but chances of snow will increase Tuesday
night and Wednesday under moist westerly flow aloft. Temperatures
will average 10 to 15 degrees below normal.

Wednesday evening through Saturday morning. A very active and wet 
troughing pattern to take hold and dominate the weather across the  
CWA. Expect a major storm system to arrive by Thursday morning and
continue to push through eastward, bringing with it colder 
temperatures, gusty winds and widespread snow across most of the 
region. Mountainous areas will receive the lion's share of the 
snowfall. On the heals of this major system will be more periodic 
minor systems that will propagate though and continue, on a lesser
scale, with wet, gusty conditions; however, temperatures will 
begin to gradually warm, raising the snow levels and surface 
temperatures, especially in the Treasure and Magic valleys. This 
will allow for mixed precipitation to occur there. High 
temperatures will be 5 - 10 degrees below normal, and low 
temperatures just a few degrees below normal.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Winter Weather Advisory from 5 AM to 5 PM MST Saturday 
     IDZ011-013-016-033.
     Winter Storm Warning from 5 AM to 5 PM MST Saturday IDZ029.
     Winter Weather Advisory from 11 AM to 8 PM MST Saturday 
     IDZ015-030.
     Winter Weather Advisory from 5 AM to 11 AM MST Saturday 
     IDZ012-014.
OR...Winter Weather Advisory from 4 AM to 4 PM PST Saturday 
     ORZ061-062.

&&

$$

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DISCUSSION...BW
AVIATION.....AB
PREV SHORT TERM...DG
PREV LONG TERM....JT/WH

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Western Regional Climate Center, wrcc@dri.edu