Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 221047

Area Forecast Discussion
National Weather Service Pocatello ID
347 AM MST Wed Nov 22 2017

.SHORT TERM...Today through Saturday. Expect lingering light
rain today as a weak, moist trough exits the area and high
pressure continues to build into the area. With snow levels at
10000 feet, there are no travel concerns from snow. There is some
patchy fog lowering visibilities this morning. Temperatures will
be well above normal through the period, 10 to 20 degrees above
normal. Areas that break out of cloud cover today and Thanksgiving
day will likely see record temperatures. Thanksgiving day will
start out with partly cloudy skies but will have increasing
clouds and breezy winds by the afternoon ahead of the next system.
Thursday evening into Friday morning a weak system briefly breaks
down the the high pressure ridge bringing light valley rain and
mountain snow along with breezy winds. Only around 1 to 2 inches
of snow is expected mainly for the Western Central mountains and
Upper Snake Highlands, mainly above 7000 feet. Expect dry
conditions on Saturday as the high pressure ridge quickly rebuilds
across the area. Wyatt

.LONG TERM...Saturday night through Wednesday night. Primary impact
period during the long term portion of the forecast period will
center around Monday as a seasonably-strong trough quickly saunters
East across the forecast area. The leading edge of the Precipitation
is forecast to begin on Sunday across the Sawtooths/Pashimeroi, with
Precipitation expected to overspread the majority of SE Idaho Monday
morning. Ahead of the trough, Snow levels will remain fairly high in
the presence of moist, mild southwest flow. However, a strong cold
front will sweep Eastward across the state on Monday in association
with the trough. Snow levels Monday morning range from 4,500 to
5,000 feet elevation across the Central Mountains to 6,000-6,500 feet
along the Wyoming border. By late Monday afternoon, Snow Levels are
forecast to drop to Valley floors all areas, bringing a quick
transition from Rain to Snow. There is some question to how much
Precipitation will remain after cold air rushes into the region,
which will ultimately determine Snowfall amounts. Currently, the
Eastern Highlands are favored for the highest amounts from this
system, as well across the Sawtooths, with 6-12" possible. These
amounts are certainly not out of the ordinary, but the rapid
transition from Rain to Snow is where the primary impacts may lie
with this system. Will also have to watch for the development of a
convergence band late Monday. Plenty of Wind expected to accompany
the trough passage as well, with SW wind gusts of 30-40 mph possible
across the Snake Plain after the cold frontal passage Monday
afternoon, with stronger gusts at Pass level. Perhaps a fine day to
browse the latest `Cyber Monday` deals. Despite the strength of the
cold front, temperatures are forecast to drop to around
climatological normals for this time of the year for Tuesday and
Wednesday -- from around 20 degrees above normal on Sunday.


.AVIATION...Copious low-level moisture in place across SE Idaho
currently, with MVFR Stratus in place from KIDA northward. Breaks in
the high clouds have allowed occasional MVFR/IFR fog to develop at
PIH. These issues will persist at least through the morning hours.
Stratus is much more plentiful than depicted on most forecast
models, and increasing mid/high cloud cover may limit incoming solar
radiation on Wednesday, likely leading to low clouds persisting
longer than forecast. Will therefore hang onto low clouds through
the morning at KIDA, mention Fog at PIH. Elsewhere, conditions
should remain VFR. Some gustiness off of the deck with 20-30kt winds
developing in the 3kft AGL layer. Will carry VCSH at all TAF sites
through the morning. AD/Wyatt



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