Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 170915

Area Forecast Discussion
National Weather Service Pocatello ID
215 AM MST Tue Jan 17 2017

.SHORT TERM...Today through Thursday night. We should have just
one more day under the influence of upper ridging. The ridge
shifts eastward tomorrow, as flow aloft becomes westerly. Moisture
transport increases late Wednesday morning across the Central
Mountains. Moderate snowfall amounts will be seen over the
Sawtooth range starting around this time. By Wednesday night,
precipitation will advance into the Eastern Magic Valley and South
Central Highlands. Ptype diagnostics continue to support freezing
rain potential for Cassia, Minidoka, and possibly Lincoln counties
until snow levels lower once again early Thursday morning.
Upper trough will swing across the area Thursday night. As it
does, precipitation should shift to the Eastern Highlands. Total
snow amounts of 10 to 12 inches can be expected over the Sawtooth
Range throughout the period. Amounts in the Eastern Magic Valley
should be inhibited by the presence of rain/freezing rain.

LONG TERM...Friday through Tuesday. Models in good agreement early
in the period. East Idaho remains under influence of broad western
US trough. Main center of low remains off PacNW coast with multiple
spokes dropping south and cutting into the intermountain west. Some
minor differences in precipitation timing early between GFS and
ECMWF but both generally agree on split flow crossing the region
through Friday night with weak diffluent ridge aloft for Saturday
into Saturday night thus have gone with slightly drier conditions
across the area. Next significant feature arrives Sunday, but
timing differences begin to multiply from here on out. GFS shifts
bulk of main trough inland through Monday while ECMWF continues
trend of previous days with shortwave spokes rotating around the
low and into the intermountain west. By Tuesday, GFS has Idaho
under the influence of dirty northwest flow but ECMWF maintains
broad somewhat cut off upper low across the central Rockies. GFS
ensemble mean favors a compromise solution, so that`s how the
forecast was played out this morning with a blend toward wetter
conditions early in the week. Overall guidance temps remain in
relative agreement. DMH


.AVIATION...Low stratus/fog somewhat obscured this morning with
passage of cirrus shield aloft. Observations however show a few
pockets across the lower elevation areas with conditions spread
between LIFR and MVFR. Once again expect each of the terminals other
than KSUN to flirt with low ceilings, and ice crystals again a
possibility though much less than previous night. Should see daytime
improvement to VFR all locations, as in previous days. Profiles
drier overnight tonight, so less potential for stratus/fog. Next
system pushing through PacNW, so could see cloud cover start to
increase by 12Z, mainly for KSUN. DMH


Winter Storm Watch from Wednesday morning through Thursday
afternoon for IDZ017-018-022-031.


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