Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 191010

Area Forecast Discussion
National Weather Service Pocatello ID
410 AM MDT Sat Oct 19 2019

The winter storm that has been advertised for days will arrive
today impacting SE Idaho with a wide range of weather hazards-
rain (perhaps thunderstorms), wind and heavy snow are all expected
across the area today. Pacific moisture will stream across the
region today along with a strong shortwave trough. That being
said, expecting the first wave of moisture to impact the Central
Mountains beginning in the next few hours with higher PoPs
gradually moving into the remainder of the forecast area by the
afternoon. Snow levels early this morning will run around 5000
feet across the Central Mountains so snow is expected from the
onset of precip beginning. Across lower elevations, light rain
showers can be expected as moisture streams into the area.

During the afternoon hours, as the aforementioned shortwave energy
swings through the area, it appears we may have enough instability
to support a few thunderstorms especially across the eastern Magic
Valley and southern Snake Plain. Numerous Hi-res model guidance
members support this solution so will keep mention of thunder in
the forecast. In addition to the storm potential, Saturday will be
another windy day across the region as Wind Advisories continue
for the Upper/Lower Snake Plain, Eastern Magic Valley and the Arco
Desert. 700 mb winds support the potential for 40-45 kt wind
gusts to mix down to the surface this afternoon and into the
evening and this would appear even more likely if any convective
activity transpires later this afternoon.

Across the higher elevations, this will be an all-snow event with
winter storm warnings and winter weather advisories in place. Made
no changes to the existing hazards and the forecast still
supports winter storm conditions being met across the Sawtooths/Stanley
Basin and Sun Valley area, and Winter Weather Advisory conditions
for all of the eastern highlands, Teton Valley and Island Park
area as well. Snow amounts could approach or exceed 12 inches in
the Galena and Banner summit areas, with 6-10 inches across the
eastern highlands, with locally higher amounts for favored
westerly upslope flow regions.

The majority of the precipitation will be over with by Saturday
night, except across the eastern Highlands where upslope flow
will likely promote additional snow showers. An additional wave
of moisture will enter the central Idaho mountains late Sunday,
with moisture spilling over into the eastern highlands late Sunday
night, falling in the form of snow showers. Some lingering
moisture will remain in place on Sunday and with snow levels
dropping to valley floors still cant rule out some isolated snow
showers in the valleys but generally the majority of snowfall for
this event is expected across the higher elevations. McKaughan

The upcoming week continues to look cool and low-impact, with moist
NW flow keeping a chance of light rain/snow showers in the forecast
across our nrn/ern mntn ranges through Wed. Model agreement remains
poor on whether any weak waves/disturbances in this flow will
enhance that shower activity or spread it into the Snake Plain/srn
highlands. Forecast confidence increases a bit in a transient lobe
of high pressure ridging providing dry/sunny wx Thurs/Fri.


Widespread RA/SN is expected today at all terminals as a low
pressure system/attendant cold front push through, solidly dropping
everyone into MVFR cigs, and pushing IFR limits at KSUN/KIDA/KDIJ.
Vsbys should generally remain VFR, but will likely drop to IFR at
times at KSUN/KDIJ due to cooler temps supporting SN or RASN mix.
We`ll also have to contend with strong SW winds that may last
uncharacteristically late into tonight, and the potential for a
convective line of heavy showers/thunder this afternoon just ahead
of the front. Will try to time all of these impacts out as best as
possible in the TAFs, handling the line with TEMPO groups based on
HREF ensemble timing. Showers generally wind down this eve post-
front, but may continue into Sun at KDIJ with IFR cigs/vsbys.


Winter Weather Advisory until noon MDT Sunday for IDZ060-062>066.

Wind Advisory from noon today to 9 PM MDT this evening for

Winter Storm Warning until noon MDT Sunday for IDZ072-073.


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