Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 282045

Area Forecast Discussion
National Weather Service Pocatello ID
145 PM MST Tue Jan 28 2020

.SHORT TERM...Tonight through Thursday night.
First round of precipitation has occurred across all of southeast
Idaho this morning and early afternoon. Warm air has changed rain
to snow from Burley through Pocatello and up to Blackfoot while
Idaho Falls through Rexburg has received snow as well as the
mountains. Models indicating convergence zone a possibility
tonight from Idaho Falls south through Pocatello and upped snow
amounts in Snake Plain a bit. Went with 1 to 3 inches of snow
tonight and Wednesday morning for Snake Plain and eastern
mountains in that period. Passage of a cold front will allow snow
levels to reach valley floors by midnight and even though not 100
percent sure will play for the convergence development in the
grids. Will dry out Wednesday afternoon with only lingering snow
in the eastern mountains. Then a fast moving wave will drop south
on the east side of the ridge Wednesday night with widespread
light snow overnight and Thursday morning with 1 to 2 inches in
the eastern mountains and less than an inch elsewhere expected.
Expect dry conditions Thursday afternoon and evening. Temperatures
are expected to remain slightly above normal through Thursday.

.LONG TERM...Friday through next Tuesday. We will see a brief period
of upper ridging and mostly settled weather Friday night into
Saturday night. Just prior to this on Friday, expect to see some
lingering remnants of a shortwave over the area as it pushes through
the ridge. The upper ridge will flatten Saturday night as an
upstream trough pushes into the PAC NW. Will likely see snowfall
begin sometime late Saturday night into Sunday morning in the
Central Mountains. The 12Z GFS shows some significantly enhanced
snowfall behind the surface front. GFS numerical guidance shows 6 to
8 inches at Pocatello/Idaho Falls on Monday, though the ECMWF has
similar amounts pushed further to the south and east over the
mountains. Both models are showing upslope-enhancements in the low-
levels along with the potential for a post-frontal convergence band
underneath broad synoptic scale forcing, setting the stage for a
significant winter storm. Tweaked extended PoPs above the blended
model, but forecast well below the 12Z GFS. Temperatures will
plummet after the cold front passes with lows back into the single
digits. This was not reflected well in the blend, so made some
downward adjustments for Monday/Tuesday. Hinsberger


.AVIATION...A cold front will sweep through southeast Idaho today,
bringing rain and snow to the terminals. Flight categories will
fluctuate from MVFR to LIFR due to both ceiling and visibility as
the system progresses through this afternoon and evening. Some
temporary VFR conditions will be possible for KBYI this afternoon.
Models are indicating a second round of snow after the front passes
with timing consistent with the 500mb trough passage early tomorrow
morning. This feature will mainly impact KIDA, KDIJ and possibly
KPIH. Hinsberger



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