Area Forecast Discussion
Issued by NWS Pocatello, ID

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270
FXUS65 KPIH 182039
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
239 PM MDT Wed Oct 18 2017

.SHORT TERM...Today Through Saturday Evening.
SE ID will remain under the back side of a departing ridge of
high pressure through Thurs, providing high confidence in two
days of dry weather, mostly sunny skies, breezy conditions, and
continued mild fall temps reaching the upper 60s/lower 70s across
the Snake Plain and many valley locales. High temps were nudged
upward 1-3 degrees above guidance both this afternoon and Thurs
to better fit expected trends from current observations.

A wave of low pressure is progged to move onshore across the Pacific
NW Thurs night, pushing W to E across ID Fri and early Sat. This
will bring a period of widespread rain/snow showers to the
region. For 2 consecutive days, all model guidance except the
often overdone SREF has held initial precip off until after 06Z
Fri. With good model agreement, we have removed PoPs from the
Central Mntns prior to 06Z. This will spell out a dry Thurs eve
and early night for everyone, and in fact, best chance for initial
showers may not come until after 3 AM Fri morning. Other then
delaying precip onset, made only minor adjustments to the ongoing
forecast. Showers will start in the Central Mntns Fri AM,
overspreading the region during the day, and winding down from W
to E Fri night, except for lingering activity into Sat in the
Central Mntns, Upper Snake Highlands, and Teton Valley. Snow
levels start at 5,500 to 6,500 feet, falling to 4,500 to 5,500
feet by Fri eve. With this in mind, our latest forecast carries
accumulations of 4-7 inches in the higher elevations of the
Central Mntns, especially near/west of Stanley and Ketchum, and
1-3 inches in the higher elevations of the Upper Snake Highlands
and Caribou Highlands. This will definitely create some impacts
for roads and passes in these areas. At this time, snow
accumulations are not expected for the Snake Plain or most valley
floors. Fri afternoon will be breezy region-wide and especially
windy in the Snake Plain, where winds of 25-35 MPH with gusts to
45 MPH will be possible. Overall forecast confidence for this
system is moderate. Stay tuned for updates! Sat looks dry and
breezy in the Snake Plain with isolated lingering rain and snow
showers possible in the Central Mntns, Upper Snake Highlands, and
Teton Valley. - KSmith/DMH

.LONG TERM...Saturday Night Through Wednesday.
Long term trend looks to contain very mild temperatures with
mainly dry conditions expected. A weak Pacific wave is expected to
produce mainly mountain showers Saturday night through Sunday
night with snow levels rising from around 6,500 feet Saturday
evening to 10,000 feet Sunday night. System should push rapidly
east with an upper level ridge building to the west. After some
lingering showers in far east Monday...expect dry conditions
everywhere Tuesday and Wednesday with high temperatures rising to
10 degrees or so above normal. - GK

&&

.AVIATION...
TAF period continues VFR across the region. Winds have increased
slightly, especially through northern portions of the Snake Plain,
with a few places seeing gusts approach 25 knots. This activity
is expected to decrease around sunset with the loss of daytime
mixing. - DMH

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$



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