Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 211549
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
949 AM MDT Thu Sep 21 2017

.UPDATE...Quick update this morning for current radar and
satellite trends. Light to moderate rainfall continues in a
consolidated band at the southeast edge of the Snake Plain. Bright
banding visible on radar has decreased through the morning but
estimates are that light snow could be falling as low as 6000
feet. Accumulations more likely above 7000 feet. Have also
continued flood advisory for Powerline burn scar with light to
moderate rain continuing over that area through the remainder of
the morning. DMH



&&

.PREV DISCUSSION... /issued 330 AM MDT Thu Sep 21 2017/

DISCUSSION...Radar imagery early this morning depicting a wide
band of precipitation across a line extending from Driggs through
Idaho Falls and Pocatello and exiting Idaho near Almo. Varying
intensities of rain is noted within the nearly stationary line
this morning. As the day advances, expect very little movement
within the line, however a gradual shift to the southeast is
expected by the evening hours. Additional showers are expected to
fill into other parts of Idaho today as well. Snow is forecast to
fall between 6500 and 7500 ft (and above) across the Central
Mountains today with the majority of it falling above 8500 ft. An
estimated 2 to 6 inches is forecast to fall today alone with
totals in the 7 to 11 inch range through tomorrow. From the
Upper Snake Highlands southwards along the Wyoming and Utah
borders (east of the interstate corridor) the majority of snow is
expected to fall above 6500 ft this later this evening through
Friday. As a result of this first significant snowfall event,
Winter Weather Advisories have been posted starting this evening. The
feature responsible for all this activity is an upper low,
currently located to our west. This low will generally meander to
out west through the end of the week, and bring us all this rain
and snow. Forecast models are in pretty good agreement regarding
its position this week and subsequent weakening and exit this
weekend. A slight chance for additional showers will lie in the
Bear Lake area Saturday otherwise look for clearing conditions for
all areas Sunday. Next week will bring warming, dry weather
conditions. NP/KB

AVIATION...A strong upper-level low pressure system will continue
to impact the region today and Friday, leading to deteriorated
flight conditions. Rain expected to continue most of the day at
KPIH, KIDA, KBYI, and KDIJ before becoming more showery tonight.
Could see some snow mix in with the rain at KDIJ this morning. Some
showers are possible at KSUN this morning, but better chances hold
off until this afternoon and then continue into Friday morning. Will
see fluctuating conditions at all sites based on precipitation
timing/intensity, but overall MVFR conditions look to be most common
through the period. Will however likely see conditions improve at
times to low end VFR during breaks in the precipitation, and
possibly drop to IFR during times of heavier precipitation. KB

FIRE WEATHER...Cool and wet conditions will continue today and
Friday as the region remains under the dominance of a strong upper-
level low pressure system. A persistent band of precipitation
stretching across much of the Southern and Eastern Highlands and
Snake Plain has produced widespread wetting rainfall overnight (snow
levels generally around 8,000 ft MSL currently), and this band will
persist through much of the day although its overall intensity is
expected to ease during the day. The bulk of the precipitation has
remained southeast of the Central Mountains overnight, but this will
change this afternoon as wraparound precipitation develops over the
Central Mountains east into the Upper Snake Highlands amid lowering
snow levels. Should see some decent early season snow accumulations
above roughly 6500 ft MSL in these areas by the time the
precipitation winds down late Friday afternoon or early evening.
We`ll see a drying trend this weekend as the low opens and begins to
shift east, leaving just some lingering rain/snow shower activity
over the Central Mountains and Eastern Highlands, becoming confined
to the Eastern Highlands by Sunday. Temperatures will gradually
rebound this weekend and next week as high pressure amplifies along
the West Coast, with readings climbing back closer to normal by
mid week. KB

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 3 PM this afternoon to 6 PM MDT
Friday for IDZ018-019-031-032.

&&

$$



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