000
FXUS65 KPIH 232023
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
223 PM MDT Tue Apr 23 2024

.SHORT TERM...Today and Wednesday.
Looking at satellite imagery our area is under weak high pressure
with a weak ridge axis over southeast Idaho currently. Expect dry
conditions, slightly warmer than normal temperatures, and
slightly breezy winds today. Wind gusts will range from 15 to 25
mph this afternoon. Look for southwesterly flow to set up by later
this afternoon as the ridge axis weakens and moves east this
afternoon. Temperatures will run about 4 to 8 degrees above normal
today and 8 to 12 degrees above normal on Wednesday. Moisture
ahead of an upper level low off the coast of California will start
to make its way into our southern areas late today. There is a 10
to 20 percent chance of showers along the Utah border late this
afternoon into the evening. By Wednesday more moisture makes its
way into our area in southwest flow as the upper level low moves
over central California. Look for more widespread showers and
thunderstorms Wednesday afternoon into the evening. The best
chance for thunderstorms on Wednesday, around a 40 to 60 percent
chance, is in our Southern and Southeastern Highlands. Look for a
20 to 40 percent chance of thunderstorms for the Eastern Magic
Valley, Snake Plain, and Upper Snake Highlands. Expect just a 10
to 20 percent chance of thunderstorms for our northern areas,
including the Central mountains. This is just the start of our
return to a more active pattern. Look for temperatures to drop
after Wednesday as well.
Wyatt

.LONG TERM...Thursday through next Tuesday.
Beginning Thursday, upper flow will turn westerly as another Pacific
Northwest trough moves onshore. Precipitation chances will become
increasingly widespread and increase through Friday as the trough
axis shifts over Idaho, with chances for isolated to scattered
thunderstorms again Thursday afternoon. Temperatures will run at
least 5 degrees cooler than Wednesday`s highs, although still
remaining slightly above climatological norms. Daytime temps will
decrease by another 5 to 10 degrees on Friday following a cold front
passage. After that, temperatures look to remain fairly stable for
Saturday before they begin to trend slightly warmer again. EPS 72-
hour QPF through end of day Saturday is around a tenth of an inch to
0.20 inch across the eastern Magic Valley and Shoshone area, 0.25 to
0.40 inch across the upper Snake Plain and mid-elevations, and 0.60
to 1.15 inches in the central and eastern highlands/mountains.
National Blend probabilities for half an inch total for this same
period run 30% to 50% for the corridor from Pocatello north through
Rexburg. It carries at least a 35% probability of 0.60 inch across
much of the E/SE Highlands and central mountains. 500 mb ensemble
clusters continue to feature differences in the depth of the trough
as it shifts east. For early next week, even more discrepancies
exist amongst ensembles regarding the timing and depth of the next
low working into the PNW and a ridge building in from the
west/southwest. It is clear that models are struggling with whether
ridging or troughing will be the dominant synoptic pattern from
early to middle of next week and therefore confidence in forecast
temperatures and precipitation remains low during this timeframe. At
this time, the deterministic NBM carries widespread PoPs up to 30%
through this period along with fairly stable daytime highs just
above normal.
Cropp

&&

.AVIATION...
VFR and mostly dry conditions forecast areawide under SCT to BKN
high clouds. Slight chances exist for rain showers to lift north
near KBYI late this evening and overnight and therefore have
forecast VCSH beginning at 02z. Winds will remain light through the
period, generally 7 kts or less and variable at times. Cloud cover
and precipitation chances will increase early Wednesday through the
weekend.
Cropp

&&

.HYDROLOGY...
No major changes in the hydro forecasts at this time. Water
levels on the Portneuf river continue to run high, just below
moderate flood stage for the Portneuf river in Pocatello. The
river forecast for the Portneuf river in Pocatello shows the river
running above flood stage for the foreseeable future and likely
climbing back to moderate flood stage by Thursday and peaking
Saturday at around 10.5 feet or midway through moderate flood
stage. At Topaz on the Portneuf, current levels are slightly above
minor flood stage. Water levels are forecast to slowly rise
toward the end of the week with warming temperatures through
Wednesday and the return of precipitation chances in the second
half of the week into the weekend.
Wyatt

&&

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

$$