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 16
000
FXUS65 KPIH 232035
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
235 PM MDT Sat Mar 23 2024

.SHORT TERM...Tonight through Sunday night. Satellite imagery
shows shortwave axis shifting into Western Idaho early this
afternoon. Diffluent flow aloft, advancing cold front, and weak
instability across the northeast corner have already allowed for a
couple isolated thunderstorms to form near Rexburg and further
southwest near Atomic City. Gusty winds around 45 mph and small
hail the most likely threats as frontal boundary shifts northeast
into early evening. Elsewhere, expect showers to continue. Snow
levels ranging from around 7500 ft to 5500 ft east to west this
afternoon, falling to 5500 ft in the east and 4000 ft in the west
by midnight, sufficient to be at valley floors in many locations.
Area of secondary precipitation sliding south behind the frontal
boundary generally depicted as a low to medium confidence
convergence zone event, but GFS hanging on to a wider batch of
precipitation across the region. QPF forecast a terrain-influenced
blend between NBM mean and NBM 90 percentile look, which focuses
light snow along the I-15 corridor around/just after sunrise.
Upper trough axis shifts east into Wyoming through the day Sunday,
but secondary shortwave currently over central BC Canada enough to
help fire another round of snow showers across the region Sunday
through Sunday night. Snow totals remain below thresholds of
concern for Advisory, especially given 36-48 hour time frame, but
convective influence could certainly over-achieve in a few
locations through tonight. DMH


.LONG TERM...MONDAY THROUGH NEXT SATURDAY...
Little change in the long-term, which will be characterized by a
train of multiple shortwave troughs and low pressure systems working
in off the Pacific resulting in daily chances of rain and snow along
with cooler overall temps. Overnight low temps will generally
support snow to valley floors assuming precip is ongoing (although
accumulations should remain quite limited outside of some mntn
valleys), while snow levels rise as high as 4,500 to 5,500 feet some
afternoons, allowing rain to mix in especially in the Snake Plain
corridor and some of the adjacent srn highland valleys. Highs will
generally be in the upper 30s and 40s for most population centers,
occasionally touching 50 especially at lower elevations west of
Pocatello. Deterministic models and 500mb height cluster analysis
continue to show some increasing hope in a break in precip on Wed,
before perhaps our wettest system of the week arrives Wed night and
Thu. The Sawtooths, Smokys, White Clouds, Boulders, Pioneers, Lost
River Range, Centennials, Big Holes, and northern Wasatch Mountains
stand to see moderate snow accumulations (>50 percent of 6" of snow
or more Wed night through 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
approach bankful status. Larger rivers should continue to behave as
the mid and high-elevation snowpack remains largely untapped, and
the cooler temps will also help slow melting. 01/TAX


&&

.AVIATION...
Minor tweaks made to start/end time of -SHRA and VCTS at the
terminals this afternoon/eve based on fresh HRRR and HREF data, with
activity generally ending by 01-02z/7-8pm everywhere except KDIJ.
Regional winds have been verifying a bit stronger than expected this
afternoon, resulting in a recent round of amendments to nudge speeds
slightly higher (blending NBM/MOS forecast data toward recent obs),
generally 13-20kts gusting 20-30kts out of the W-SW at the Snake
Plain terminals. We`re also seeing cigs drop solidly into MVFR
territory directly under organized showers and storms, but
confidence remains low on occurrence and timing of direct hits to any
particular airport. Will continue to monitor radar, obs, and trends
closely. Winds and showers wind down this eve with just VCSH and mid-
level VFR clouds expected for the overnight and Sun AM. At KDIJ,
snow shower activity may continue for much of this period. A couple
high-res models (especially the HRRR) are also trying to generate
some convergence-induced snow Sun AM affecting KIDA and KPIH (09-
17z/3-11am window), but agreement across the model suite is poor
including on whether or not this activity will develop at all,
lending to low confidence. We`ve continued VCSH but have not
introduced impacts at this time. Expect another round of rain and
snow showers Sun afternoon across the region, along with moderate
and gusty westerly winds at KBYI. 01

&&

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

$$


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