Sleet in Idaho, April 5, 2019

Area Forecast Discussion
National Weather Service Pocatello ID
214 PM MDT Fri Apr 5 2019

.SHORT TERM...Tonight through Sunday. We are still expecting an
increase in showers with some late afternoon/evening
thunderstorms. This is ahead of our weakening storm and cold
front. By sunrise, the front should be generally paralleling
I-15 and out of the state before noon. Snow levels by roughly the
same time should be around 5000-6000ft in the central mountains
and closer to 7000ft ahead of the front, then leveling off around
6000-7000ft for the rest of your Saturday. We definitely could see
them lower with heavier showers. Any snow that we see in the next
24 hours will be on the light side, but a heavier snow showers
could create brief slushy/slick conditions. Rain/melted snow
numbers should be on the order 0.10" or less for the Snake Plain
and Central Mountains. Across the southern and eastern highlands,
the general range should be 0.15-0.35". In any given area, heavier
showers or bands of showers could easily produce locally higher
amounts that predicted. Along and behind the front, the wind will
definitely be blowing. At their peak tomorrow afternoon, winds of
20-40mph...including gusts are forecast over most of our side of
the state. At the moment, we may briefly hit low end thresholds
for a Wind Advisory across the Arco Desert, Craters and Upper
Snake Plain. Since it would be brief, we will not put out any
headlines right now.

We should see a break in most areas, before the next wave moves
in for Sunday. All of the models are showing the Sawtooths, Sun
Valley area, Frank Church Wilderness and from Island Park south to
Palisades seeing most of the precipitation. Some of the models
keep the rest of eastern Idaho fairly dry, while others show a
quick but better shot of during the day Sunday. The Blend of
Models, since it is a blend, seemed to capture the best of both
worlds. That shows isolated showers across the Magic Valley and
Snake Plain, with scattered showers across the southern highlands.
Snow levels quickly rebound and rise to 7500-8500ft later Sunday.
Keyes

.LONG TERM...Monday through next Friday Highlights:
Expect a wet period with the return of another atmospheric river
event.  Moisture returns in a warmer than normal southwest flow late
Monday with an upper level low moving over the area on Tuesday.  The
GFS model takes this low across our southern forecast area while the
ECMWF model shows a wetter solution with the low moving over our
entire area. Temperatures will drop below normal on Tuesday with
snow levels around 6000 to 6500 feet and even cooler Wednesday and
Thursday with snow levels around 4500 feet before rising to normal
on Friday. Thursday the models vary even more. The GFS starts to
develop another low over our area for Thursday and Friday while the
ECMWF drops this low south of our area warming temperatures and
bringing drier conditions. The greater impacts will be Tuesday day
into Wednesday morning for mountain passes with moderate snow. Also,
with warmer temperatures on Monday and then moderate rain for lower
elevations on Tuesday, there will be some hydro concerns. Mainly the
concerns are for the Portneuf river and perhaps some sheet flooding
in the Sun Valley/Island Park areas. There will also windy
conditions Wednesday bringing impacts across the area as well. Wyatt

&&

.AVIATION...Expect isolated to scattered rain showers this afternoon
into the the morning as a storm/weak cold front moves through the
area. Expect vicinity thunderstorms this afternoon which will bring
brief gusty, erratic winds. Most terminals will remain VFR. However
with showers on station expect MVFR/IFR conditions, particularly
during the morning tomorrow. KDIJ,KIDA, and KPIH, to a lesser extent
are expected to see showers on station by early tomorrow morning
into the mid morning. KDIJ showers will last through late morning
into the early afternoon tomorrow and will likely become snow
showers as temperatures drop. Wyatt

&&

.HYDROLOGY...Hydrologic Outlook continues for most of the area as
local creeks and some rivers are starting to rise due to recent snow
melt and light rain. Small streams and the Portneuf river as well as
ponding concerns will increase the next 24 hours with a passing
system. Most of the precipitation looks to be across our Eastern
areas with the NOHRSC modeled snow melt being around 0.50 to 0.75
for the Portneuf drainage and around Montpelier, Driggs and Ashton.
Lesser snow melt of 0.25 to 0.50 is expected elsewhere for lower
areas with snow to include Hailey, Little Wood drainage, Mackay and
Soda Springs areas. Snow melt will back off this weekend with cooler
temperatures and drier conditions. Expect more snow melt by Monday
with warmer temperatures ahead of the next system. An upper level
low is moving across the area with the potential to bring moderate
to heavy rainfall for lower elevations. This system could push the
Portneuf river to minor flood stage. Snow levels are uncertain at
this point, but may be high enough for minor ponding in cities with
remaining snow. Temperatures quickly drop Tuesday afternoon into
Wednesday, which will help slow down snowmelt. Wyatt

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
None.
&&