Area Forecast Discussion
Issued by NWS Pocatello, ID

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000
FXUS65 KPIH 181035
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
335 AM MST Sat Nov 18 2017

.SHORT TERM...Tonight through Monday Night.
High pressure will produce dry weather through the weekend. Today
and tonight will be the coldest periods of the weekend. Could see
some very cold temps tonight with many locations dropping into
the single digits or teens except that we are expecting a
considerable amount of high clouds to arrive this evening. This
should help insulate us. Low temps tonight will largely depend on
how fast those clouds arrive. So, we could see a free fall early
in the evening if the clouds are slow to arrive. We will see some
light precipitation arrive in the central Idaho mountains late
Sunday night and quickly overspread the region on Monday. Models
continue to bounce around with this system which is leading to a
high degree of uncertainty of how strong snowfall amounts will be
and how widespread precipitation will be. Previous solutions
looked much more widespread and more intense. The 00Z solutions
all have this system as a ridge is trying to develop across the
area. So, coverage is much less and snowfall amounts are much
less. Amounts in the central Idaho mountains look to be around 2
to 4 inches and generally from Galena northward. Eastern Idaho
highland amounts are 1 to 3 inches and mainly above 5000 feet. The
bulk of the precipitation will move through during the day on
Monday with some light upslope flow moisture possible for westward
facing slopes of the central Idaho mountains and Teton range.

Valle

.LONG TERM...Tuesday Through Saturday.
Significant forecast uncertainty continues in the long-term due to
persistent model discrepancies and poor run-to-run consistency.
Generally an active pattern is expected to continue, and with the
busy holiday travel week, everyone is encouraged to continue
monitoring the latest forecast updates. GFS/EC continue to struggle
on how quickly moisture pulls out following Monday`s system (if at
all), so a low chance of rain/snow showers continues into Tues
night. Some ridging is noted on the GFS/EC/Canadian Wed, but the
models continue to advertise low-level moisture, and again here we
continue to broad-brush low PoPs everywhere. Ridging continues into
Thurs with perhaps less moisture. We trended PoPs lower, but with
poor model performance not quite yet ready to advertise dry weather
for Thanksgiving. All models swing through a quick trough Fri-Sat
morning, and have nudged PoPs up for this time frame. There is some
indication Fri afternoon/eve could be quite windy across the Snake
Plain. This was not reflected at all in the guidance 24 hours ago,
and is likely tied to the evolution of the trough. Undercut guidance
for wind speeds in the forecast and will continue to monitor trends
as changes seem likely. Finally, a more pronounced ridge builds in
Sat with potentially dry weather aside from a few isolated showers
in the Central Mntns and along the WY border. Still not currently
seeing strong indications toward heavy precip/significant weather
Tues-Sat, aside from possible wind Fri. - KSmith/Valle

&&

.AVIATION...A ridge of high pressure has built across SE ID with
clear skies currently reported at all TAF sites. We continue to
closely monitor for fog/low stratus following 2 days of precip.
However, winds remain elevated early this morning at 8-12 kts, and
temp/dew point depressions remain fairly significant. Model
guidance is also not showing strong indications of problems, so
while some patchy fog cannot be ruled out, we are not currently
expecting fog/stratus at the terminals. Greatest chance for
especially low stratus if it does develop will be at KIDA/KDIJ.
Otherwise, moderate to high confidence in solid VFR conditions and
partly cloudy skies at all terminals both today and Sun, with no
aviation concerns. - KSmith/Valle


&&

.PIH WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$


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