Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 212039 CCA
AFDBOI

Area Forecast Discussion...corrected
National Weather Service Boise ID
233 PM MDT Sat Oct 21 2017

.SHORT TERM...Pcpn has been slow to spread east today but at
2 PM MDT the leading edge was across the OR/ID border, with
light snow at McCall, ID, and light rain at Ontario and Rome,
OR.  Radar shows echoes out ahead but this is virga.  Snow
fell all morning at Burns, OR, with temp near 32F.  Wet snow
accumulated a couple inches there but web cams showed melting
early this afternoon.

Models agree that warm-frontal rain and snow will move into
western Idaho this afternoon and evening, then retreat northward
in Idaho overnight.  Models look a little too heavy on QPF tonight.
Rain and snow will continue through the night and Sunday north of
the Snake Basin.  The Treasure Valley will be on the southern
fringe Sunday morning.  Snow level near 4000 feet MSL north to
5000 feet MSL south this evening will rise to 7500 feet north
and 9000 feet south by early Sunday morning.  Snow accumulation
will be light below 5000 feet MSL and roads should be wet or at
worst slushy.  Low temps will range from near 30 in the mountains
to near 40 in the lower valleys.  Sunday will be warmer than today
with highs 45 to 55 in the mountains and 55 to 65 in the lower
valleys, warmest in southern Malheur County.  Chance of light
rain will continue Sunday night in central Idaho, but other
areas will become drier.  Lows 30 to 40.  Monday looks mostly
sunny under dry northwesterly flow aloft, with high temps in
the 50s in the mountains, and 60 to 65 in the lower valleys.
Southwest winds tonight 15 to 25 mph in eastern Oregon and
southeast 10 to 15 mph in Idaho.  Light south or southwest winds
in all areas Sunday, and light west winds Monday.

.LONG TERM...Monday night through Saturday...A high amplitude upper
level ridge over the western U.S. will maintain mostly clear skies
Monday night through Tuesday night. The ridge will relocate off the
west coast on Wednesday. This will allow strong northwest flow aloft
to bring an upper level trough over north Idaho and Montana
Wednesday night, with scattered rain and snow showers as far west as
the mountains of central Idaho and Baker County Oregon. In Idaho
isolated showers are possible as far south as the Nevada border. The
system will be followed by clearing skies and cooler temperatures
Thursday and Friday. Temperatures will be slightly above normal
Monday night through Wednesday night, and around 5 degrees below
normal Thursday through Friday night. A slow warming trend will
begin on Saturday as the ridge shifts east over the coast.

&&

.AVIATION...Widespread precipitation across eastern Oregon and the
west central and Boise Mountains this afternoon, with local IFR/LIFR
conditions in snow above 4k ft MSL. Rain reaching KEUL and KBOI BY
21Z, KMUO by 22z, and the KTWF/KJER area around 01z, with areas of
MVFR ceilings. Snow levels rising to 6k-8k ft MSL this evening and
7k-9k ft MSL by Sunday morning. Conditions improving overnight with
precipitation mostly confined to the mountains of Baker County
Oregon and central Idaho after 06z. Surface winds southeast to
southwest 10-20 kts. Winds aloft at 10k ft MSL west 35-50 kts.

Sunday outlook...Mainly VFR. Precipitation continuing over the
mountains of Baker County Oregon and the west central Idaho and
Boise Mountains, with local MVFR conditions and areas of mountain
obscuration. Snow levels 7k-9k ft MSL in the morning rising to 8k-
10k ft MSL in the afternoon, highest in southeast Oregon and along
the Nevada border. Surface winds SE-SW 5-15kt.

&&

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

&&

$$

www.weather.gov/Boise
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AHORT TERM...LC
LONG TERM....JT/WH
AVIATION.....JT



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