Area Forecast Discussion
Issued by NWS Pocatello, ID

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000
FXUS65 KPIH 230857
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
257 AM MDT Sat Mar 23 2024

.SHORT TERM...Today through Sunday night.
Upper level ridge moves east today ahead of a Pacific upper level
trof which will move through eastern Idaho Sunday. Will have
periods of rain showers as the system works through in several
waves of energy. Snow levels start out at 7 to 8 thousand feet
today will drop to 5 to 6 thousand feet by late afternoon in the
central mountains and Snake Plain and by Sunday morning to 3500 to
4500 feet or near valley floors. Will see another rise to 5
thousand feet Sunday afternoon then drop to valley floors again
overnight. So most of precipitation in the Magic Valley and Snake
Plain will be rain with any snow accumulation in the mountains.
Elevations of 6 thousand feet to 7500 feet will see about a 50
percent chance of 2 to 4 inches with above 8 thousand feet locally
6 inches may fall. So could see some travel impacts mainly going
over mountain passes late Saturday and Sunday. Will not issue
highlights as will see several breaks in the precipitation the
next two days and accumulations are for 48 hours and expect most
24 hour totals under 4 inches. Will see a cool down today with
clouds and precipitation and highs in the 40s mountains and 50s
valleys with lows tonight in the 20s and 30s and highs Sunday back
to below normal with mountain highs mainly in the 30s and valleys
in the 40s. Will have breezy conditions today with 10 to 20 mph
sustained winds in the Snake Plain with strongest winds Sunday in
the Magic Valley and southern hills with gusts 25 to 35 mph behind
the cold frontal passage.
GK

.LONG TERM...Monday through next Saturday.
By Monday morning the upper-level low pressure center will have
fully translated to the four-corners region of the southwest opening
up to a broad trough fueling a downstream Colorado low. Lingering
moisture and weak ascent through the west and specifically through
our area will continue to feed areas of showers Monday and Tuesday,
but the absence of more organized ascent will keep precipitation
totals rather light and terrain-enhanced. Temperatures will have
been suppressed back down to below seasonal averages, dropping snow
levels to near or below valley floors, even during daylight hours.
Still snow totals will be rather light, with accumulations mostly
contained to the high country Monday and Tuesday.

Wednesday still looks to be the relative dry day of the week as a
transient short-wave ridge quickly passes through the mean flow.
Clusters 1 and 2 (67 percent of the ensembles) are now solidly drier
than the ensemble mean. It should be noted that the GEFS mean is
solidly deeper and slower with the arrival of the next coastal low
late Weds and 100 percent of the GEFS members are in the drier
clusters 1 and 2. Regardless, it looks like Wednesday should be
drier and thus warmer than the previous three days.

By late week, that next system will arrive into the PacNW bringing
additional precipitation chances that will likely last through next
weekend. Reinforcing shots of low pressure from the Gulf of Alaska
is causing subtle differences across the three ensemble suites to
increase through Saturday. Currently during that late-week
timeframe, the wettest period looks to be late Wednesday night
through Thursday. Southerly flow ahead of this system will advance
warmer air northward to the point where snow levels will raise to at
least 5k and perhaps even nearing 6k feet, supporting rain and rain
snow mix in the lower elevations and limiting winter-related impacts
to the higher elevations. Although it`s a little too early to talk
specific amounts, with this fetch of moisture streaming in, the
Sawtooths, Smokys, White Clouds, Boulders, Pioneer, Lost River
Range, Centennial, Big Hole, and northern Wasatch Mountains stand to
see moderate snow accumulations (>50 percent of 6" of snow or more
Thur-Fri).

With the recent spate of warmer weather, we`ve begun to see feeder
creeks and streams begin to swell and tick upward on streamflow. As
we advance through this next week of wet weather we`ll continue to
monitor these smaller creeks and streams closely as some may flirt
with bankful status. Larger rivers should continue to behave as the
mid and high-elevation snowpack remains largely untapped.
TAX



&&

.AVIATION...
VFR conditions prevail across eastern Idaho ports early Saturday
morning. Looking upstream on satellite we see moisture beginning to
increase through western Idaho as the parent low churns off the
PacNW coast. Still some significant differences in timing the
precipitation into BYI, SUN, and PIH this morning with the HREF
favoring dry conditions through around midday. Timing of SHRA may
push a few hours later, but largely VFR conditions should remain
throughout. Still looking at the potential for convection with the
primary shower activity this afternoon for all ports except SUN.
That said, lightning activity is not expected to be widespread, so
limiting to VCTS. The focus of precipitation shifts east after 00z
tonight, lingering longest in DIJ and perhaps IDA. Temps should drop
enough to be primarily snow in any remaining precipitation for DIJ
through the remainder of the current TAF period.
TAX


&&

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

$$


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