595 
FXUS65 KBOI 290333
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
833 PM MST Sat Dec 28 2019

.DISCUSSION...A broad swath of mid level moisture remains on track
to impact the area mid/late Sunday. There is good agreement that
although the area will see accumulating snowfall, amounts will be
on the lower end. No updates planned this evening.

&&

.AVIATION...Areas of MVFR/IFR stratus in the Magic Valley and Upper 
Treasure Valley. Otherwise, VFR with increasing high clouds tonight. 
Surface winds variable 10 kts or less. Winds aloft at 10K ft MSL 
north 20-30 kt.

Sunday Outlook...Snow becoming widespread by 18z Sunday with areas 
of MVFR/IFR through Sunday night. Mountains obscured. Snow ending by 
12z/Monday.

&&

.PREV DISCUSSION...
SHORT TERM...Tonight through Monday...A Pacific frontal boundary
will be impacting the region late tonight into Sunday. There is a 
consensus among models of total snow accumulations of less than 1
inch during this time period for most locations, however which 
locations and timing are still a struggle. Temperatures will be 
below freezing for all locations throughout the period in question
which means any and all snow that falls will stick to surfaces 
including roadways. Motorists should expect for slick conditions 
and allow themselves extra time even with the minimal snowfall 
expected. A stronger frontal system absorbs the weaker system late
Sunday and drops south of our area which will allow for drier 
conditions come Monday afternoon. 

LONG TERM...Monday night through Thursday...Weather systems moving 
around the northern periphery of an offshore high pressure ridge 
will bring more precipitation to southeast Oregon and southwest 
Idaho. Snow will start over our northern zones Tuesday afternoon and 
spread across the rest of our area Tuesday night. Precipitation will 
continue on Wednesday, with snow levels rising to around 4500 feet. 
Valley rain and mountain snow showers will continue through 
Thursday. Temperature will be near normal on Tuesday, around 5 
degrees above normal on Wednesday, and 5-10 degrees above normal on 
Thursday. 

Thursday night through Saturday night...Showery, and windy are the 
expected conditions as a moist, active, and progressive pattern 
dominates the region. On Thursday, as snow levels are lifted some 
associated with an exiting of a shortwave ridge, expect rainfall 
across major valleys, snow in the mountains, and mixed along the 
foothills. Breezy westerly winds are expected to persist (throughout 
the period) as the pressure gradient tightens. Starting Saturday 
morning, snow levels will begin dropping (ultimately to valley 
floors) as a cold frontal system begins to rapidly push through. 
This will turn (change) all falling precipitation to snow. High and 
low temperatures are expected to register in around 10 degrees above 
normal (at the start) and abruptly drop down to around 2 to 3 
degrees above normal by Saturday.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...None.
OR...None.

&&

$$

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DISCUSSION...MC
AVIATION.....JS
PREV SHORT TERM...JC
PREV LONG TERM....JT/WH