529
FXUS65 KPIH 042112
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
212 PM MST Wed Dec 4 2024

.SHORT TERM...TODAY THROUGH THURSDAY NIGHT...
High pressure and attendant quiet, low-impact weather continue.
While most guidance does not advertise fog Thursday morning, we did
see development in a few areas this past morning, and max RH values
look very similar tonight in this stagnant, stable pattern. Thus,
leaned on some hints of development in the HRRR (especially in the
lower and upper Snake Plain areas) and broadbrushed slightly to add
just patchy morning freezing fog to the forecast.

.LONG TERM...Friday through Wednesday. Models remain consistent
with portrayal of shortwave feature moving through for the
weekend. Weak dry shortwave on Friday helps to lead the way for
stronger trough to break down the blocking high Saturday into
Sunday. Models have slowed down onset of precipitation slightly,
trending later in the day Saturday, and ensemble blends reflect
this slower timing. Bulk of the precipitation falls Saturday night
through Sunday before decreasing over the eastern highlands Sunday
night or Monday morning at the latest per current GFS/ECMWF
timing. Moisture remains limited for the event, so 72-hr ensemble
means through mid-day Monday carry a meager 2-5" for higher
elevations mainly Sawtooths and Big Hole/Teton areas and a
trace-1" for the Snake Plain from American Falls north. Low end
25% probabilities (3 in 4 chance of exceedance) are far more
limited, only an inch or two for the higher elevations of the
central mountains and eastern highlands. High end 90th percentile
(1 in 10 chance of exceedance) are more generous with some of the
higher elevation mountain ranges, with 4-around 7" of snow. The
higher end probabilities also carry about an inch of snow for the
I-15 corridor from Pocatello to Idaho Falls. All that to say, this
is not expected to be an impactful event for East Idaho. Ridge
of high pressure returns for Monday/Tuesday. This should be a
colder pattern on the northerly flow side of the ridge. Model
blends support highs around freezing, some 10-15 degrees colder
than recent days. DMH

&&

.AVIATION...
High pressure and attendant quiet, low-impact weather continue, with
NBM and MOS guidance supporting some of the lightest winds you can
get in Idaho. Have kept all sites at 4kts or less in the TAFs,
except slightly higher at KSUN with their usual diurnal wind
evolution. While most guidance does not advertise fog Thursday
morning, we did see development in a few areas this past morning
(briefly affecting KPIH), and max RH values look very similar
tonight in this stagnant, stable pattern. Thus, leaned on some hints
of development in the HRRR and broadbrushed slightly to add just
patchy morning freezing fog to the forecast. Best chance for impacts
will be 11-18z/4-11am at KPIH similar to this morning, but
confidence in direct LIFR impacts at the airport is low for now
given a holistic look at our guidance sources. Will hint at this,
at least nearby potential for now via 6 SM BR VCFG with SCT002.

&&

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

$$