Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 211500

Area Forecast Discussion
National Weather Service Boise ID
900 AM MDT Sat Oct 21 2017

.DISCUSSION...Leading edge of warm-frontal precipitation was
advancing steadily across eastern Oregon this morning, and will
get into western Idaho late morning through afternoon.  Pcpn
started as snow in Harney County and will start as snow in
western Idaho above 3500 feet MSL north to 5000 feet MSL south.
Snow will change to rain in Oregon this afternoon and Idaho
late today or tonight.  Lower elevations will have rain
throughout.  By sunrise Sunday the snow level will be 7500 to
8500 feet in western Idaho and 8000 to 9000 feet in eastern
Oregon, rising further to 8000 to 10000 feet late Sunday.
QPF through Sunday will be heavy in Baker County and Idaho
north of the Snake River Basin, and lighter in the south.
No advisories for snow are planned with this storm.  Current
forecast looks on track.


.AVIATION...Widespread precipitation and mountain obscuration in
southeast Oregon spreading into southwest Idaho and the central
Idaho mountains 16z-18z and south central Idaho 21z-23z. Snow levels
3500-4000 ft this morning rising to around 9000 ft by 00z/Sun.
Surface winds SE-SW 10-20 kt. Winds aloft at 10k ft MSL NW-W 25-35
kt this morning increasing to 35-50kt this afternoon.

Sunday outlook...Mainly VFR. Precipitation continuing over the
mountains of Baker County Oregon and west central Idaho, with local
MVFR conditions and areas of mountain obscuration. Snow levels 7500-
9000 ft MSL in the morning rising to 8000-10000 ft MSL in the
afternoon, highest in southeast Oregon and along the Nevada border.
Surface winds SE-SW 5-15kt.


SHORT TERM...Today through Sunday...A deep moisture plume and
strong westerly flow will push a warm front across the interior NW
today. Precipitation starts as snow this morning across much of
southeast Oregon with snow levels around 4000 feet. The front and
accompanying rain/snow advances into southwest Idaho late this
morning, pushing into central Idaho by evening. Snow levels will
range from around 4500 feet over the central Idaho mountains to
5500 feet along the ID/NV border through this afternoon.
Mountains of east-central Oregon and west-central Idaho will see
steady precipitation continue into Sunday under moist westerly
flow. Drier conditions develop across southeast Oregon and areas
from the Snake Plain to the NV border on Sunday. Snow levels rise
overnight and into Sunday, ranging from 8000 feet across the
central Idaho mountains to 10000 feet along OR/NV and ID/NV
border by Sunday afternoon. Temperatures 10-15 degrees below
normal today will warm to within 5 degrees of normal on Sunday.

LONG TERM...Sunday night through Friday...Showers will end across
the NE Oregon mountains and the west central Idaho mountains on
Monday morning as an upper level ridge begins to build into the
region and the moisture tap from the aforementioned system shuts
off. Temperatures will warm to slightly above normal values,
although northwest flow will keep temperatures at bay, compared to
SW Oregon. A trough will dig south along the Canadian Rockies into
Montana on Thursday, as a strong blocking ridge builds across the
Gulf of Alaska. A cold front will move through the region on
Thursday morning with showers focused across the higher terrain.
Forecast confidence remains low on the strength of the cold front
and temperature forecasts with this system. Northwest flow continues
into the extended period with dry conditions, as a blocking ridge
continues in the Gulf of Alaska.





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