979
FXUS65 KPIH 141902
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
102 PM MDT Sat Sep 14 2024

.DISCUSSION...
Things are rather pleasant this afternoon across eastern Idaho as
temperatures are comfortable and skies mostly clear aside from a
few high clouds streaking across the region. Upper level flow is
zonal over the region which will keep things quiet today. Temps
will warm into the mid to upper 70s this afternoon across the
valleys with maybe a few spots reaching 80. Sunday will be another
warm day as the upper level flow becomes more southwesterly ahead
of a potent upper low moving into the Pacific NW. This feature
will bring a drastic change to the weather across the region for
much of the remainder of the week but more on that shortly. Winds
will be a touch breezy Sunday but should stay below any headline
levels but nevertheless could gust upwards of 20-25 kts during the
afternoon. After sunset Sunday, precip chances ramp up
significantly as we start to see a surge in moisture ahead of the
aforementioned low.

Throughout the day Monday, the low will move across the northern
extent of the Great Basin before settling overhead by Tuesday AM.
Confidence is high in a prolonged period of cloudy, wet and
eventually cool weather, the latter of which should last into next
weekend. The wettest period looks to be late Monday and
throughout Tuesday where chances for precip are basically 100%
regionwide, a rare occurrence for these parts. Forecast QPF from
late Sunday through the day Tuesday shows a high likelihood of
1/2-1" in the valleys, trending towards the higher side, with
1-1.5" in the higher terrain of the central mountains and eastern
highlands. Increased cloud cover on Monday should drop temps 5-10
degrees of their Sunday highs but as the low moves overhead on
Tuesday, we`re expecting a drop of some 15-20 degrees off of
Monday`s highs which will keep everyone in the 40s and 50s on
Tuesday. With the cooler air moving in, snow levels will drop to
around 9kft so higher peaks will likely see a bit of snow
accumulation.

The low will move into Montana and Saskatchewan on Wednesday while
to the west, a second upper low moves into central California and
eventually the Great Basin. This feature looks like it`ll track a
bit further south than the first one keeping the bulk of the
moisture to our south. Nevertheless, we`ll still likely have
enough lift and moisture to support PoPs at any time really from
Wed-Fri but QPF looks low outside of the far SE corner of the Gem
State and even here, QPF looks around a quarter of an inch or so.
The one certainty with the second low is that the upper level
pattern will support a continued intrusion of cooler air which
should keep highs in the 50s and 60s throughout much of the week
with more clouds than sun expected.

By the weekend, models start to show differing opinions on the
upper level pattern so not nearly as much confidence during this
time period but this is still 7-8 days out so much can still
change. The main takeaway is that things will certainly feel very
fall-like for the week ahead; almost as if the autumnal equinox
was right around the corner...McKaughan


&&

.AVIATION...
No impacts expected through 6 PM MDT on Sunday.  Widespread VFR
conditions with only high cloud cover and mainly light winds with
afternoon upslope winds around 10 knots today at PIH, BYI and IDA
and 10 to 15 knots on Sunday.

&&

.FIRE WEATHER...
Dry and warm conditions will continue through Sunday with
temperatures well above seasonal normal. Will undergo a
significant change early next week as an upper low drops
southeast into central California tomorrow night then tracks
northeast through Idaho on Tuesday. Expect rain to overspread the
region Sunday night and continue off and on through Tuesday
evening. Significant rain amounts are expected everywhere with
lower elevations in the 0.50 to one inch range with many high
mountain locations expected to go over 1 inch of rainfall. Lighter
precipitation may linger through the remainder of the week. After
the very warm conditions this weekend it will be significantly
cooler with elevated humidity next week beginning Tuesday.

&&

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

$$