Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 031518

Area Forecast Discussion
National Weather Service Boise ID
916 AM MDT Fri Apr 3 2020

.DISCUSSION...Webcam showed patchy dense fog in/near Baker, OR
at 7AM PDT.  Otherwise, only scattered clouds around our CWA
this morning.  Not quite as cold this morning as it was yesterday
with lows 25-32 in the Treasure valley, mid 20s in the Magic
Valley, near 20 in eastern Oregon, and near 15 at McCall and
Fairfield.  Stanley was 8 below this morning.  It was 9 below
there yesterday morning.  Satellite this morning showed an
upper low in the Pacific 45N/139W and a developing upper trough
in the northern Gulf of Alaska.  The trough will come down the BC
coast today and tonight, then close off a low near 45/130 Saturday.
The first Pacific low will weaken as it moves onshore in Oregon
Saturday and spreads pcpn across eastern Oregon to the Idaho border
late Saturday.  Models show marginal instability in eastern Oregon
late Saturday, getting into Baker County Saturday evening and
possibly McCall by midnight.  Our forecast has a slight chance
of thunder Saturday afternoon only in Harney County but we may
also add a slight chance Saturday afternoon in northern Malheur,
Baker, and Adams Counties Saturday evening depending on what 12Z
models say.  Overall, pcpn Saturday and Sunday will be light, with
at most a tenth of an inch of rain in the valleys, and up to about
3 inches of snow in the Idaho mountains.


.AVIATION...Mainly VFR. Patchy fog in the KBKE area this morning.
Scattered snow showers over the west central Idaho and Baker County
mountains before 04/03z. Mostly clear tonight. Surface winds mainly
southeast to southwest 5-10 kts. Winds aloft at 10k ft MSL west 15-
25 kt increasing to 20-35 kt after 04/00z.

Weekend Outlook...Mainly VFR Saturday. Widespread rain and snow
spreading into eastern Oregon Saturday afternoon and central and
southwest Idaho Saturday evening, becoming showery and mainly over
the mountains late Saturday night and Sunday.


SHORT TERM...Today through Sunday night...Lowered ceilings
observed across portions of eastern Oregon this morning. Patchy
fog may linger through the morning hours. Another push of moisture
will bring a few showers across the West Central and Boise
Mountains, along with Baker County in Oregon this afternoon and
evening. Any snow accumulation with these showers should be light
at generally around 1 to 3 inches above 3000-4000 ft. Snowfall
will weaken after midnight. An area of low pressure approaching
the Pacific Coast will open into a trough as it spreads moisture
into eastern Oregon beginning Saturday late morning. As the trough
advances eastward, its organization falls apart, with another
area of low pressure off the northwest coast pushing its moisture
over the forecast area. Many areas are expected to see
precipitation with this system. Snow levels are anticipated to be
between 4000 and 5500 ft through Sunday, bringing mountain snow
and valley rain. With fairly mild temperatures and increased snow
levels, snow accumulation should remain between 2 and 5 inches
through Sunday evening, with some portions of southern Oregon
seeing up to 8 inches locally. Models continue to indicate
instability with the system`s progression so the forecast package
includes a slight chance of thunderstorms for both Saturday and
Sunday afternoons. Moisture will weaken late Sunday night. The
next area of low pressure begins to impact California and western
Oregon late Sunday. Temperatures will start off around 10 degrees
below normal today, but will warm to within 5 degrees of normal
by Sunday.

LONG TERM...Monday through Friday...A trough will move south
along the West Coast toward Southern CA by Tuesday. Wrap-around
moisture will bring showers to the region, mainly during the
afternoon on Monday and Tuesday. Temperatures will be near normal.
By Wednesday, the trough will become completely cut off from the
jet stream with upper level ridging bringing warm temperatures to
southwest ID and southeast Oregon. Temperatures will be around
5-8 degrees above normal on Wednesday and Thursday.





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