Area Forecast Discussion
Issued by NWS Pocatello, ID

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000
FXUS65 KPIH 190856
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
256 AM MDT Thu Oct 19 2017

.SHORT TERM...Today and Friday...Today will be another lovely warm
weather day with some breezy conditions across the Highlands and
Central Mountains of 15 to 25 mph. Tomorrow though, weather
conditions will certainly change. An approaching broad upper
trough will track a cold front across Idaho by days end, before
dropping temperatures 20 degrees, bringing rain, snow and very
strong winds. Snow showers will begin along Banner Summit and in
the western/northern portions of the Central Mountains in the
overnight hours tonight before quickly spreading southeast and
eastwards during the early morning hours. Snow levels Friday
morning will be dropping quickly from 6500 ft in the early morning
to approximately 5000 ft by the afternoon hours. This may bring a
mixture of rain and snow to portions of Snake Plain briefly
Friday; otherwise these areas can expect rain. For snow totals
Friday in the Central Mountains, 3 to 5 inches of new accumulation
is forecast at pass level with upwards of 8 inches over 8000 ft.
One to 2 inches are forecast above 6000 ft in the Highland areas.
Of concern Friday will be increasing wind speeds of 30 to 40 mph
with gusts to 50 mph across the Snake Plain and 25 to 35 mph gusts
to 45 mph in the mountains. As a result of these winds combined
where snow is forecast, blowing snow will be a risk for those
driving on Galena Summit and along state highways. NP/RS

&&

.LONG TERM...Saturday through next Thursday...Chances for snow
showers will remain across the higher terrains of the Central
Mountains and Eastern Idaho areas Saturday as additional troughs
of energy track through Idaho and Montana. Much of the snow will
hug the western facing slopes as our flow will shift more
northwesterly through Sunday. Additional snow amounts of 1 to 2
inches are forecast. We are not expecting much, or any, precip
across the Snake Plain areas over the weekend. Temperatures
Saturday versus Sunday will be comparatively different with low
50s on Saturday and low to mid 60s Sunday. Looking toward next
week, expect mid 60s for high temperatures and dry conditions with
a mild weather pattern as high pressure builds into our area.
NP/RS

&&

.AVIATION...TAF period continues VFR across the region today. Winds
increase slightly again today, especially through northern portions
of the Snake Plain, KIDA may gust to 25kts. Much different on Friday
with the trough moving inland. Expect rain and possible MVFR
ceilings at KSUN early Friday morning, maybe 13-14Z. Scattered
showers develop quickly across SE Idaho and a Wind Advisory has been
issued for the Upper and Lower Snake Plain 20/17Z to 21/02Z. We are
keeping watch for wind gusts reaching or exceeding 50 KTS in the
Arco Desert, GFS MOS has been flirting with 35-37 KTS of wind at
KIDA and KPIH. Snow levels will be lowering to 6000-5500 feet by
early evening. RS

&&

.FIRE WEATHER...A low pressure disturbance will be entering the
Washington and Oregon Coast today. Southwesterly winds will increase
over the exposed upper elevations of the mountains in all areas,
gusts to 30 mph pretty common, 35 for the Lemhi and Bitterroot
Ranges. Minimum humidity in the middle and upper teens will also be
common in this warm SW flow. The trough has been stretching a little
more north and south with time, resulting in timing of precipitation
moving into the Central Mountains a couple of hours slower, could be
3 or 4 in the morning for Stanley area. Showers will spread to the
Wyoming border by noon Friday. A Wind Advisory will be issued for
the Snake Plain from about Richfield to Hamer for Friday afternoon.
Southwest winds of 30 to 40 mph with gusts up to 55 mph possible.
Through about midnight Friday night, the west slopes of the Central
Mountains, including Stanley and Galena Summit area could see .10 to
.30 inch liquid equivalent of precipitation, a few west facing
slopes possibly up to a half inch. Temperatures drop back to the 40s
in the mountains and around 50F valleys Friday. Snow levels after
rising to near 10000 feet elevation on Thursday, come back down to
around 5500-6000 feet Friday afternoon and continue to fall to the
valley floors by Saturday morning. Scattered showers will diminish
Friday night and early Saturday before the next round of moisture
advances across the Central mountains and Eastern Highlands Saturday
night and Sunday. Then a gradual return to dry high pressure ridge
follows Monday and Tuesday. Models continue to show disagreement by
Wednesday of next week, one favoring a chance of showers and another
favoring nothing but a warm and dry high pressure ridge over this
area. RS

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Wind Advisory from 10 AM to 8 PM MDT Friday for IDZ017-020-021.

&&

$$



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