Area Forecast Discussion
Issued by NWS Pocatello, ID

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
000
FXUS65 KPIH 230828
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
228 AM MDT Thu Mar 23 2017

.SHORT TERM...Today through Saturday...A fairly quiet day is
expected with a weak high pressure ridge in place. A chance for
rain and snow showers will exist in the eastern Highlands this
morning before the ridge builds over this area later this evening.
The ridge will be in place through Friday evening when an
approaching upper trough arrives late Friday into Saturday
morning. This trough will increase rain and snow potentials
substantially. Elevations above 6500 ft are expected to receive 4
to 8 inches of new snow across the Sawtooth Mountains and Salmon-
Challis National Forests. Elevations between 6000 and 6500 ft are
expected to see closer to 1 to 2 inches of snowfall with rain
falling below 6000 ft for the rest of the Central Mountain region.
Upper Snake, Caribou and Eastern Highland locations may also see
some snowfall with 2 to 4 inch average amounts forecast during
this period. For locations expected to experience rainfall, below
6000 ft, rainfall amounts of 1/10 to 1/4 inch totals are possible
over a 30 hour period Friday evening through Saturday.

The precipitation potentials for late Saturday into Sunday morning
have been cut in half across the Central Mountains as through
responsible for the expected activity looks to bring heaviest
activity to the north of this region. A split flow pattern looks
to set up during this period with heavier activity in the Idaho
Panhandle and activity over Utah and southern Idaho. The Snake
Plain and most of Southeast Idaho is looking more dry for Saturday
into Sunday at this time. This is not to say all areas will be
precip-free and areas like Bear Lake and the Southern Highlands
are currently forecast to experience some showery activity.
NP/Keyes

&&

.LONG TERM...Sunday through next Thursday. Models continue to
advertise split flow across the western U.S. next week. Right now,
Monday and Thursday look to be the wettest days. However, the
degree of split flow has been swinging back and forth a bit which
would affect timing and/or precipitation amounts. If we end up in
between the northern and southern branches, we can end up fairly
dry. If the southern stream doesn`t head south far enough and/or
the northern stream hits eastern Idaho, then we could end up with
quite a bit of lower elevation rain and mountain snowfall. Less
splitting means the current timing pattern would be a bit slow.
Being out west, sometimes the models struggle with this pattern
until these storms are almost ashore. Either way, the current
pattern should shave a few degrees off temperatures, but nothing
that would help slow down any snowmelt and flooding problems
except at night in some places. Keyes

&&

.AVIATION...Showers continue across the southeast corner of Idaho
extending northward along the Wyoming border toward Driggs. That
pattern is expected through the rest of the day, although the trend
will slowly downward. Right now, KDIJ is MVFR (flirting with IFR
actually).  They are the most likely candidate for occasional
showers and/or ceilings other than VFR through the day and into
tonight. Cross sections indicate that we COULD see a brief period of
MVFR/IFR at KIDA, KPIH or KBYI early on. With rain in the past 24
hours, it`s certainly possible so we aren`t going to say no but not
necessarily go full blast in that direction. It should remain dry at
those sites it appears however. Stronger west winds are expected at
KBYI and KPIH, 15-25kts including gusts. KSUN appears as the winner
when it comes to confidently remaining VFR throughout the day.
Keyes

&&

.Hydrology...Additional rainfall is expected late Friday into
Saturday morning with 1/10 to 1/4 inch amounts forecast. Some
areas may received up to 1/2 inch over a 36 hour period,
including areas along the Continental Divide including Island
Park, the Bear Lake region and Cache Valley of Idaho. This rain
will add to flooding risk in these areas. Because overnight
temperatures are cooler now and will continue tonight and Saturday
morning, at or below freezing, a possible slow down to the
snowmelt flooding may occur. Areal flood watches will persist
until further notice for all areas previously until the watch.

The Portneuf and Bear Rivers continue to run high. The Portneuf
remains under a flood warning with latest forecasts still solidly
pushing into Moderate flood category Saturday night and staying
there into the beginning of April. The Bear is currently in action
stage and expected to reach Minor Flooding this evening through
Saturday. NP/Keyes

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Flood Watch until noon MDT today for IDZ017>019-022>025-031-032.

&&

$$



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.