Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 190509

Area Forecast Discussion
National Weather Service Pocatello ID
1009 PM MST Thu Jan 18 2018

.UPDATE...This Evening`s update incorporated edits along the
`downslope corridor` following Interstates 84/86 from Burley to
Pocatello. These changes including boosting wind speeds and
Temperatures, as well as delaying the start of Precipitation along
this corridor -- as has been the trend with this incoming system.
Expect Snow and Rain (below about 6,500 feet) showers to persist
across the Sawtooths and adjacent ranges and valleys through the
night, with a secondary area of more persistent Precipitation
developing across the Island Park region after 2 AM. Expect most
widespread Precipitation across the Snake Plain to hold off until
closer to Sunrise Friday morning. Until that time, isolated
Showers are expected. Some of these Showers may contain some gusty
winds. Road surface temperatures across the Arco Desert (Highways
20/26) from Tom Cat Summit to Arco to Blackfoot and Idaho Falls
are below freezing, so any Rain falling on these surfaces may
create a few slick spots overnight. AD/Hinsberger


.PREV DISCUSSION... /issued 113 PM MST Thu Jan 18 2018/

SHORT TERM...Expect a strong cold front to arrive tonight. This
will bring a good chance for low elevation rain with snow likely
above 6000 feet. Precipitation associated with this system will be
somewhat slow to progress through the region. By Friday morning,
precipitation will slowly moving past the I 15 area and may linger
into the afternoon. Light rain or snow will persist across the
southeast highlands through much of the day Friday and will
probably not clear the region until Friday evening. There`s an
outside chance that enough cold air could work into the system
that some light snow could fall from Idaho Falls to Pocatello and
Burley, but amounts would be light, probably less than half an
inch. The more impressive snow totals are found above 6500 feet
where 4 to 10 inches is likely from Galena Summit to Banner
Summit. Areas around Island Park could pick up close to 6 inches.
Areas in the 5500 feet to 6500 feet range will most likely see 1
to 3 inches. Models are now trying to develop a weak convergence
event, well after the main system has left the region late Friday
night into Saturday morning. Am continuing snow chances during
this time along the 15 corridor from Pocatello through Idaho Falls
to Rexburg to account for this possible convergence. Highly
unsure of additional snow amounts, if any, associated with the
convergence at this time. Elsewhere, Saturday into Saturday night
looks relatively quiet with colder, closer to normal temps.


LONG TERM...Sunday through Thursday. The latter half of the
weekend looks relatively dry with near normal temperatures. The next
chance for precipitation comes in early Monday though this should be
a quickly moving system. It is a bit early to tell how much snow
will fall with this system; right now this system not look very
potent. Forecast models become in disarray by the middle of the
week with disagreement in the next approaching low. The GFS model
is very moist with this system while the European model is less-
so. Additionally the positioning of the low pressure trough are
not in line. Confidence in our forecast Wednesday and Thursday is
low at this time. NP/Valle

AVIATION...Lowered ceilings and visibilities expected with
approaching snow showers at SUN first overnight, followed by the
remainder TAF sites early morning. LLWS is expected at PIH and IDA
in the late evening hours before stronger winds reach the surface
thereafter. NP/Valle


Winter Weather Advisory until 11 AM MST Friday for IDZ018.


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