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fxus65 kpih 222053 

Area forecast discussion
National Weather Service Pocatello Idaho
153 PM MST Fri Nov 22 2019

Short term...tonight through Sunday. High pressure still in
control over east Idaho. Broad area of stratus still in place over
much of the eastern and southeast Highlands per satellite imagery
and area web cams. Imagery shows cloud cover slowly thinning and
eroding from the western edge but believe that much of this area
likely to stay covered through tonight. In addition, have added
patchy fog to a few low lying areas overnight where moisture
likely to stay trapped, though the stratus could mitigate the
potential due to lack of strong radiational cooling. Otherwise
northwest flow strengthens aloft ahead of shortwave trough
Saturday night. Deeper moisture starts to push close to the
central mountains late Sunday, but overall impact for now is
expected to be increased cloud cover for the latter half of the
day, and a beginning to the big pattern change for the
Thanksgiving Holiday week. Winds do start to pick up for the snake
plain as well, but hold just below 20 mph so no headlines expected
yet so far. Dmh

Long term...Sunday night through Friday. Leading shortwave drops
southeast across east Idaho Sunday night, focusing precipitation
over the higher elevation regions. Feature moves quick, and is not
carrying much moisture so early precipitation totals are expected
to be fairly light particularly in lower elevations. Ensemble
spreads generally keep snowfall less than an inch for lower
elevation areas, and a top end range of 3-5 inches at Ridgetop
level for this first shot of snowfall. Winds remain a concern for
the snake plain, which may approach at least the lower bounds of
advisory criteria during the day Monday. Temperatures drop
significantly behind this first front, with daytime temperatures
remaining cold enough to support snow through the rest of the
week. Upper trough deepens over the intermountain west, with
second more significant shortwave feature helping to carve out the
low over northern California along the pacnw coast. This feature
and the associated southerly diffluent flow looks to be much more
significant with snowfall potential across east Idaho, though
there is still a lot of uncertainty regarding the moisture
amounts. Have stayed with the blended solution which produces
enough precipitation and cold enough temps to support enough
snowfall across the region to make Thanksgiving Holiday travel
hazardous. Low continues to deepen and sag south along the
California coast through Thanksgiving day. Moisture stream still
points directly at east Idaho so expect light to moderate snowfall
to continue through Friday as low begins to migrate east through
the Great Basin. Overall messaging will remain centered over the
potential for hazardous to dangerous travel especially right
before the Thanksgiving Holiday. Again, there is a lot of
uncertainty in the details, and significant ensemble spread
regarding how much precipitation is expected to fall, but the
message is the same: be prepared. Dmh


Aviation...stratus lingers over the eastern and southeast
Highlands this afternoon, despite slow erosion from the west
through the snake plain and some thinning of the region per
satellite imagery. Kdij remains MVFR this afternoon with all other
sites improving to VFR. Have been optimistically forecasting kdij
to break out as well but this may have to be adjusted with the 00z
taf issuance depending on the satellite and observational trends
for the remainder of the afternoon. Models hold on to a little bit
of moisture overnight, so where the stratus can stay cleared out
there is a low confidence threat of some MVFR/IFR fog at kida/kpih
and possibly even as far southwest as kbyi. Again, given the trend
at kdij today, keeping the forecast VFR overnight may be too
optimistic. Dmh


Pih watches/warnings/advisories...

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