Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 222022

Area Forecast Discussion
National Weather Service Pocatello ID
222 PM MDT Sat Apr 22 2017

.SHORT TERM...Weather wise, a very busy week ahead. We begin with
a disturbance moving through Oregon this afternoon that will begin
to affect Southeast Idaho later tonight in increasing
southwesterly flow. showers will develop in the Eastern Magic
Valley after midnight and progress towards Island Park by early
Sunday morning. Portions of the forecast area will see some sun
late morning and early afternoon that will help destabilize the
airmass. Additional moisture will approach from the west by
afternoon with scattered showers over all of the mountains areas
and a slight chance of thunderstorms during the afternoon and
early evening. Rainfall potential from this round of showers is
limited to around .10 to .15 inch. Snow levels tonight 8000 to
9000 feet, will lower through the day sunday to around 7800 over
the Central Mountains and about 8500 feet towards Bear lake. The
second round of moisture comes in on Monday and persists through
Tuesday and further into mid week. Rain fall increases across the
area, the South Central and Caribou Highlands likely seeing the
most with around a half inch possible through Tuesday afternoon.
Snow levels drop to around 6000 feet elevation during the early
morning hours, and rise to about 6500 feet in the afternoon both
Monday and Tuesday. Areas above 7000 feet may see 3 to 6 inches of
snow. A cold front should come through Monday afternoon, followed
by breezy 20 to 30 mph winds Monday night in the Snake Plain and
South Central Highlands. The increased rain fall this week will
bring increased risk of rising streams and water ponding in
fields. RS

.LONG TERM...Tuesday night through Saturday. For those looking for
warm, dry Spring weather, this will not be the week. Energetic,
moisture-laden Pacific Jet will be oriented from west-east through
much of the week, sending several disturbances through the region.
The strongest disturbance of the region is forecast to slide through
the region Tuesday night through Wednesday with precipitation
amounts possibly exceeding totals that are only only observed about
once per 10 years for the date. At this time, the heaviest
precipitation is expected across the Southern Highlands, with
precipitation amounts possibly exceeding 0.30" for the day. Snow
levels expected to hover around 6,000-6,500 feet elevation before
falling to 5,000-5,500 feet through the day Wednesday and remaining
there through the week. This will mean some significant higher
elevation snows -- adding to the already record or near record
amounts of Snow Water Equivalent across our mountains and
potentially causing difficult travel for passes. Showers linger
Wednesday night into Thursday. By Thursday, the GFS closes off an
area of low pressure over the Great Basin, which focuses
precipitation across the Eastern Highland Thu-Fri, while the ECMWF
maintains a transition to more of a broad trough over the Northern
Rockies during the Thu-Fri timeframe. By next weekend, both models
indicate drier NW flow across the region. Expect temperatures to
remain below average through the week, with persistent breezy W-SW
winds across the Snake Plain/Eastern Magic Valley. AD/RS

.AVIATION...VFR conditions in place at all TAF sites through this
evening. Some breezy southerly winds of 10-20 kts have developed at
PIH, IDA and DIJ and expect those to persist through sunset. A
somewhat robust wave moves SW to NE through the region tonight into
Sunday morning, and has medium potential to bring CIGS down to MVFR
(w/ low-end potential for IFR) at all TAF sites in SHRA followed by
low stratus trailing the precipitation. At PIH and IDA the best
window for reduced CIGS appears to be from about 10-15Z Sunday,
perhaps lingering a bit longer for BYI. At SUN, models hint at some
potential for moist upslope, which may cause lower CIGS to linger
into the early afternoon there. Best potential for reduced CIGS is
at DIJ from about 12-18Z where SHRA likely turn to SHSN and persist
to nearly 18Z. AD/RS




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