880 
FXUS65 KBOI 060349
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
849 PM MST Fri Jan 5 2018

.DISCUSSION...Showers associated with an upper trough have been
increasing in coverage in southeast Oregon during the past hour. 
The showers will continue to shift east into southwest Idaho 
overnight as the trough moves into Oregon. Snow levels will remain
high - from around 5000 feet in the far north to 7500 feet near 
the Nevada border. Cold air remains trapped in the valleys due the
the inversion, although temperatures are currently running in the
30s. There is a slight chance of light freezing rain from west of
Boise to Baker City where temperatures could lower to near or
slightly below 32F in some locations overnight. The showers will 
diminish in southeast Oregon but will continue in southwest Idaho 
Saturday morning as the trough moves further east. Showers will 
end most areas by late Saturday afternoon as the trough moves into
eastern Idaho.

&&

.AVIATION...Mostly VFR. Increased shower activity throughout the 
night and early morning. Freezing rain threat remains around KONO 
and KEUL for early Saturday morning. Surface winds, light and 
variable. Winds aloft to 10k feet MSL, southwest-west 20-40 kts 
through 18z then 10-25 kts. 

Sunday outlook...Lingering showers around KMYL will die off by 
06Z. Light and variable winds.

&&

.PREV DISCUSSION...
SHORT TERM...Tonight through Sunday...The major focus of the 
period is the incoming trough tonight/tomorrow. Precipitation will
move into the area this evening, with threats for rain, snow, 
rain-snow mix, or freezing rain moving with the trough tonight. 
The most favorable location for the freezing rain threat is across
the Lower Treasure Valley during the late evening/early morning 
hours. Ice accumulations are expected to be light. The system is 
generally anticipated to impact the area through Saturday morning,
with building northwest flow expected Saturday afternoon. Some 
lingering snow will be possible as the trough axis moves east of 
the area, with widespread dry conditions anticipated by Sunday 
morning. Numerical models attempt to show some straggling moisture
over Baker County, Oregon and into the West Central Mountains of 
Idaho on Sunday afternoon. Current forecast mentions the 
potential, though confidence in development remains low. 
Temperatures to remain around normal values, with above normal 
possible across southeastern Oregon and southwestern Idaho. 

LONG TERM...Sunday night through Wednesday...The pattern will be 
unsettled as Pacific weather systems move inland across the 
northern Intermountain Region. A high pressure ridge will maintain
dry weather Sunday night and Monday, while an upper level trough 
and deep surface low pressure system bring widespread rain to the 
West Coast. Precipitation will reach eastern Oregon Monday night 
and spread across Idaho on Tuesday, with snow levels around 5500 
feet. The main trough will continue east over California and the 
Desert Southwest on Wednesday, while moist northwest flow aloft 
brings more showers to our area. Showers will decrease to isolated
Wednesday night and Thursday under a weak high pressure ridge. 
Temperatures will average a few degrees above normal.

Wednesday night through Saturday Morning. Cloudy, windy, and wet 
for the first two days as residual moisture associated with the 
exiting system slowly trails/follows behind combined with an 
influx of new moisture associated with an incoming system expected
to move in during the middle time frame. Anticipate rain along 
most valley floors and other lower elevations with snow 
predominant at higher elevations and mountains. Snow potential 
higher in the northern half the CWA as snow levels are much lower.
Windy conditions prevail in the beginning periods slowly tapering
off as the pressure gradient loosens. Wind direction mostly 
Westerly. By day three, looking for warmer and drier condition as 
a relatively drier high pressure ridge builds in. Temperatures 
throughout the period a little above normal.

&&

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

&&

$$

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DISCUSSION...BW
AVIATION.....JC
PREV SHORT TERM...KB
PREV LONG TERM....JT/WH