Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 130836

Area Forecast Discussion
National Weather Service Pocatello ID
236 AM MDT Tue Mar 13 2018

.SHORT TERM...Today through Thursday night. We remain under the
influence of upper ridging today and tonight. WV imagery shows
some energy is beginning to lift out of the Pacific trough, and is
beginning to make landfall. Ridging should shift eastward tonight,
allowing the shortwave to push into Idaho. Models show onset of
precipitation between 06Z and 12Z Wednesday for the Central
Mountains, and quickly overspreading the rest of the forecast area
after sunrise. Warm temperatures will keep snow levels fairly
high, but the higher Central Mountain peaks may see a quick 3 to 4
inches, and tapering off after 12Z. Weather will remain unsettled
while the initial Pacific wave rotates through the Great Basin
into UT/WY by Thursday night. Heaviest precip looks like it will
accompany the surface cold front, which should work its way
through southeast Idaho Wednesday afternoon. Convection may
develop along the cold front around this time, so kept thunder
mention. Hinsberger.

.LONG TERM...Friday through Tuesday. Overall forecast trends
remain similar to previous solution with models coming into better
agreement early in the period. Pacific low in place with main center
along CA/OR coastal border, and secondary shortwave/low wrapped
around East Idaho to low center in central Plains. East Idaho
between these two features but still under moist flow with difluence
aloft. So despite guidance/model solutions indicating lack of QPF
across the region, maintained some mention of showers most areas,
but mainly focused toward the southwest half in closer proximity to
main low. Second main shortwave generally associated with some
semblance of main trough axis, shifts across the region on
Saturday. This should be a fairly active period and have
maintained higher PoP most areas, shifting focus to along WY
border overnight into early Sunday. Model consensus degrades from
there. General idea is that low redevelops into the Pacific, but
this leaves much of East Idaho under the influence of weak
shortwaves trying to shift/meander through strengthening ridge
over the Great Basin. Hard to drop all precipitation under this
scenario, but overall trend should be drier than earlier in the
period, at least until next amplified low pushes inland later in
the week. DMH


.AVIATION...So far this morning there is no sign of developing fog,
and surface dew point depressions are a little bit higher than
yesterday morning. Will likely leave BCFG around sunrise, but
confidence is quite low. Higher cloud cover trying to push into
ridge axis from the west, but conditions will remain VFR into
tonight most areas. Exception will be KSUN as band of precipitation
associated with next system begins to shift into the central
mountains after 06Z. Will likely see ceilings there drop to IFR with
-SHRASN after 09Z. This precip band is expected to shift toward the
remainder of the sites during the day Wed. DMH



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