Area Forecast Discussion
Issued by NWS Pocatello, ID

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000
FXUS65 KPIH 231101
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
401 AM MST Thu Nov 23 2017

.SHORT TERM...Thanksgiving day through Monday. Thanksgiving day
will start out with partly cloudy skies under strong high pressure
ridging. Expect areas of fog this morning across the Snake River
plain and patchy fog elsewhere. A dense fog advisory is in effect
this morning for the Upper Snake plain. As the high pressure
ridge moves east today, look for increasing clouds and winds of 15
to 25 mph by this afternoon ahead of the next system. This
evening into Friday morning a weak system briefly breaks down the
the high pressure ridge bringing light valley rain and mountain
snow along with winds to 20 to 30 mph. Only around 1 to 2 inches
of snow with 3 inches for higher peaks is expected. Snow will
occur mainly across the Western Central mountains and Upper Snake
Highlands, primarily above 7000 to 7500 feet. Expect dry
conditions on Saturday as the high pressure ridge quickly rebuilds
across the area. Expect temperatures 20 to 25 degrees above
normal today with high temperature records likely. Temperatures
moderate some Friday but jump 15 to 20 degrees above normal for
Saturday and Sunday.

For Sunday, both models start to bring moisture across the the
Western Central mountains ahead of the next system. The GFS model
continues to be faster with this system bringing more widespread
precipitation across the area by Sunday afternoon and continuing
through Monday. Snow levels will start out around 8000 feet Sunday
afternoon dropping to around 5000 to 5500 feet on Monday
morning and around 4500 feet by Monday afternoon. In general
expect 3 to 7 inches of snow for the mountains. The Central
mountains will likely see 6 to 12 inches of snow particularly for
Western slopes. For bench areas, 1 to 3 inches is likely with a
trace to 1 inch for the valley floors for late Monday afternoon
into the evening. Expect gusty winds with a crosswind component
for I-84 and I-15 Monday afternoon as well when the cold front
moves through. Wyatt

.LONG TERM...Monday night through Friday night. A fast-moving robust
through is seen exiting to the East Monday night, however there will
be some lingering impacts in the trough`s wake, including lingering
Snow Showers along the Wyoming border Highlands, at least a decent
chance for convergence band development, and strong winds.
Anticipate Snow Showers to continue across the Central Mountains and
Eastern Wyoming border Highlands into Tuesday morning before
diminishing, and a convergence band whose eventual location will
need to be monitored. Snowfall of generally 1-4 inches with locally
higher amounts is currently forecast across the Eastern Highlands
towards the Wyoming border Monday night. West winds of 25 to 35 mph
are expected, and will produce strong crosswinds along I-15 and I-84
from Burley to the Utah border. These winds will continue into
Tuesday while slowly diminishing. Temperatures will fall
considerably behind the trough. Despite the significant temperature
drop, readings will be around climatological averages for this time
of year, a testament to just how mild it is currently. For Wednesday
and beyond, gone is yesterday`s excellent model agreement in the
depiction of a high pressure ridge building across the region late
Tuesday through the rest of the week. European allows a weak ridge to
build into the area before another trough passes by to the North on
Wednesday, bringing a renewed round of light Snow Showers to the
Montana border region followed by a ridge for late week. Said trough
is much weaker on the Canadian and non-existent on the GFS.
Therefore, confidence from Tuesday and beyond is diminished. One
thing for certain is temperatures will be back to around or just
above climatological averages through the remainder of the week.
AD/Wyatt

&&

.AVIATION...Primary aviation issues this morning revolve around
LIFR/IFR Fog/Stratus at PIH and IDA, and CIGS and VIS are expected
to fluctuate around these thresholds through around 15Z before
improving. This afternoon, a VFR high cloud deck will transition to
a mid deck ahead of an approaching trough. Rain showers are forecast
develop first around KSUN after 00Z with a window of IFR CIGS
possible between 00-06Z. Rain showers are then expected to
overspread the remainder of SE Idaho Friday night, with the most
widespread precipitation expected at DIG. Showers are expected to
sag southward across the region Friday morning and exit to the South
by afternoon. In the wake of the trough, model time-heights indicate
good potential for MVFR/IFR Stratus to develop across the Snake
Plain after 12Z Friday and possibly linger through the day. Gusty SW
winds with gusts possibly approaching 30kts across the Snake Plain
Friday, especially during the morning. AD/Wyatt

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 9 AM MST this morning for IDZ020.

&&

$$



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