Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 241019

Area Forecast Discussion
National Weather Service Pocatello ID
319 AM MST Fri Nov 24 2017

.SHORT TERM...Today through Sunday.
A wave sliding through today will bring mainly rain showers to the
region with snow levels around 7500 to 8 thousand feet dropping
to around 6 to 7 thousand feet by late afternoon while the
precipitation ends persisting only in the southern and eastern
mountains by 4 pm this afternoon. All precipitation ends this
evening. Will have cooler conditions both today and Saturday with
windy conditions today in the Snake River Plain with 20 to 25 mph
sustained winds expected. Should remain slightly below advisory
level winds however. High temperatures today and Saturday should
be about 10 degrees cooler than Thursday but remaining well above
late November normals with temperatures rising again Sunday ahead
of the next Pacific system and record highs again a possibility.
Expect dry conditions Saturday with the potential for showers
Saturday night and Sunday with the best chance in the central
mountains. GK

.LONG TERM...Sunday night through next Friday night. Trough of Low
Pressure remains on track to bring a round of Rain, Snow and Wind to
the region Monday into early Tuesday, but there have been some
changes, most notably with timing as this system is now trending
slower. Precipitation is now forecast to develop across the
Sawtooths and adjacent valleys Sunday night, with Precipitation
developing across the Upper Snake Highlands/Island Park region
Monday morning, with a more consolidated, heavier NE-SW oriented
band developing from the Eastern Magic Valley NE to Island Park
Monday morning, meandering Eastward across SE Idaho during the
afternoon reaching the Wyoming border region Monday evening, with
still some possibility for a convergence band Monday night across
the Snake Plain. Colder air will quickly filter into the region
behind the strong Cold Front that will accompany the main
Precipitation band, with any lingering low-elevation Rain changing
to Snow Monday evening. Current thinking places 1-3" of Snow in the
Wood River Valley, with 6-10" for the Sawtooths and higher elevation
areas along the Wyoming border. Up to 1" with locally higher amounts
possible along and especially just east of the I-15 corridor along
the benches. Monday is also expected to be a breezy/windy day with
SW wind gusts around 35 mph possible for the Snake Plain, which
would result in some difficult travel for I-15 and I-84 Burley to
the Utah border. Temperatures will plummet to climatological
averages in the wake of the cold front Tuesday. Any lingering Snow
Showers across the Wyoming border region are expected to end
Tuesday morning.

Another fairly significant change to the forecast revolves around
the Wednesday timeframe, as Canadian and GFS solutions have come
around to the ECMWF idea of swinging a Low Pressure trough across SE
Idaho on Wednesday. Given this new-found model agreement, have
increased Snow Shower chances for Wednesday along with winds. This
trough would bring a round of light Snow Showers to higher terrain
areas, with lesser chances for the Snake Plain. A reinforcing Cold
Front swings through the region in the wake of the trough. Snow
Shower activity with this trough should end Wednesday night with dry
conditions for Thursday and Friday. A warming trend is slated to
emerge Friday within developing SW flow in advance of a
strengthening East Pacific trough. AD/GK

.AVIATION...Low Pressure trough forecast to bring a round of showers
to terminals this morning along with the potential for MVFR CIGS.
Window for showers goes as follows: KSUN:09-15Z, KBYI: 10-17Z,
KPIH/KIDA/KDIJ 12-18Z. Mainly RA expected with low-end chance for SN
to mix in at the tail-end of Precipitation at KSUN and KDIJ. Breezy
conditions expected in advance of the trough at KPIH, KIDA and KDIJ
in particular, with SW winds 15-25KTs at times through about 18-21Z.
Period of low Stratus depicted on model cross-sections at KIDA, KPIH
and KBYI from roughly 15-21Z with potential for CIGS to dip into the
IFR range. Conditions should improve after 21Z. Some MVFR/IFR
Stratus may re-develop across the Snake Plain sites (KBYI, KIDA,
KPIH) Friday night into Saturday morning. AD/GK



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