Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 171616
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
916 AM MST Sun Dec 17 2017

.DISCUSSION...Fog was minimal last night and this morning, but it
did get quite cold in eastern Oregon.  Burns dropped to zero and
Rome had 7F.  Mid and high clouds prevented even further cooling.
More clouds will come in from the northwest today in warm-advection
aloft.  Weak warm front will bring a slight chance of snow to
northern mountains tonight and especially Monday.  Min temps will
be milder tonight, and max temps Monday will be near normal.
Faster warming aloft will result in a weak inversion in the
valleys tonight through Tuesday, but Wednesday`s expected storm
will end it.  Current forecast is on track.

&&

.AVIATION...VFR under increasing mid-upper level clouds ahead of a
warm front. MVFR snow showers anticipated across Baker County OR and
the central Idaho mountains beginning around 17/18Z, continuing
through the night. IFR fog/stratus in sheltered mountain valleys to
develop toward 18/12Z. Mountain obscuration is expected. Surface
winds: variable, 10 kts or less. Winds aloft at 10 KFT MSL: NW 20-30
kts, turning W around 18/03Z.

&&

.PREV DISCUSSION...
SHORT TERM...Today through Monday...The departure of the trough
this morning left clearing skies through tonight. The combination
of mostly clear skies and recent precipitation will provide
favorable conditions for fog development. Patchy fog is
anticipated across the valleys, which should lift by the late
morning hours. Moisture riding along the ridge will bring the
potential for some shower activity to Baker County OR and into the
West Central and Boise Mountains of Idaho this evening, which
will continue through at least Monday afternoon. Impacts with this
precipitation will be limited with most snow remaining over
higher terrain. Cold temperatures this morning will set the stage
for cooler temperatures today, with warming conditions anticipated
on Monday.

LONG TERM...Monday night through Saturday...After relatively mild
temperatures, models have been consistently forecasting a transition
to a colder pattern starting Wednesday. Precipitation will be mainly
confined to our northern mountains through Tuesday, ahead of a deep
low pressure trough approaching from the Gulf of Alaska. Showers
will spread south and east across all of southeast Oregon and
southwest Idaho Tuesday night as the trough moves inland. Snow
levels will be near 5000 feet through Wednesday morning, then drop
to the valley floors by Wednesday evening as the cold core of the
trough moves over our area. Snow showers will end by Thursday
morning as the trough exits to the southeast, and an upper level
high pressure ridge builds offshore. This will result in colder
northwesterly flow aloft over the Intermountain Region. Models are
showing a chance of more snow showers over the central Idaho
mountains Friday and Friday night as a weak disturbance moves south
out of Canada, but most of our area is expected to stay dry through
Saturday. Temperatures will be 5 to 10 degrees above normal through
Tuesday night, then gradually lower to around 10 degrees below
normal on Saturday.

&&

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

&&

$$

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DISCUSSION...LC
AVIATION.....AB
PREV SHORT TERM...KB
PREV LONG TERM....JT



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