677
FXUS65 KPIH 171944
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
144 PM MDT Tue Sep 17 2024

.DISCUSSION...
An upper low in place over the region is bringing waves of
showers/storms throughout eastern Idaho this afternoon. Widespread
clouds and precip have kept temperatures in 40s and 50s throughout
the area and the cooler than normal temperatures look to stick
around through the forecast period, although they will slowly
moderate over the days ahead. Today will be the coolest and
wettest day though as the low continues to pivot overhead on its
way to Montana by tomorrow morning. PoPs will slowly diminish from
SW to NE over the next 24 hours or as the low departs to the
east. That being said, most of the precipitation will be today but
we could see a few additional hundredths across the upper Snake
and up towards Island Park during the first part of the day
Wednesday.

A second low will move into the Pacific NW tomorrow and traverse
through the Great Basin throughout the remainder of the work week.
As has been the case for the past few days, looks as if the bulk
of the moisture will stay to our south. In fact, models have
continued to trend drier and we`ve seen the PoPs for Thu and Fri
get trimmed back for most spots although we could still squeeze
out an isolated shower or two. The cooler air will be reinforced
though with the upper flow aloft remaining predominantly out of
the north. Temperatures will slowly moderate into the weekend but
will remain on the cooler side of normal. Later this weekend and
into next week, there remains disagreement amongst model ensembles
on the upper level pattern over the region but clusters are
slowly trending towards more of a ridge solution. This would keep
us on the warmer side and dry but for now, will maintain NBM blend
since things certainly aren`t set in stone just yet. If the
trends hold, I`d imagine forecast temps creeping up a few degrees
from their current values. Something to keep an eye on over the
days ahead. McKaughan


&&

.AVIATION...For the 18Z TAFS through 18Z Wednesday
A mix of VFR/MVFR conditions are expected this afternoon through
Wednesday morning as a wet Pacific system shifts directly
overhead. Scattered to widespread showers and thunderstorms will
continue to shift NE into tonight, bringing progressively drier
conditions in from the SW through the overnight hours. Where there
are some clearer skies and drier conditions building in, low
stratus and fog will be possible and will allow for further
MVFR/IFR CIGS/VIS at times, particularly Wednesday morning.
Isolated to scattered showers and thunderstorms will continue for
Wednesday with best chances around KIDA, KSUN, and KDIJ. MacKay

&&

.FIRE WEATHER...
A wet Pacific low pressure system working directly overhead today
will support continued scattered to widespread showers and
thunderstorms with wetting rains expected regionwide. Cooler
temperatures will accompany this system with highs across our
lower elevations in the 50s/60s and 30s/40s in the higher terrain,
bringing accumulating mountain snow generally above 8500-9000
feet. As this system departs NE into Montana Tuesday night into
Wednesday, best precipitation chances will also shift NE as drier
conditions build in from the SW. Flash flooding potential will
exist on burn scars given locally heavier rain from more organized
showers and thunderstorms.

Precipitation will trend more isolated to scattered starting
Wednesday and shift northeast before becoming much more isolated
in nature starting Thursday through the weekend. As a generally
weak unsettled pattern persists over our region, a secondary
Pacific low will moves onshore to California and tracks east
across the Great Basin. Given this southerly track in comparison
to our system earlier in the week, little to no precipitation is
expected but it will keep temperatures seasonably cool courtesy of
zonal/NW flow with sufficient lift and moisture to at least
support isolated showers and storms each day, primarily in the
mountains. Starting late this week into the weekend, a ridge of
high pressure remains favored to build into the NE Pacific which
will allow for a shift in the H5 jet, turning the bulk of moisture
north as warmer and drier conditions prevail. Our next chances
for precipitation will depend on this ridge feature and how it
responds to several H5 troughs that look to move onshore for next
week starting midweek. MacKay

&&

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

$$