St. Anthony, Idaho 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

970
FXUS65 KPIH 231035
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
335 AM MST Sat Nov 23 2024

.SHORT TERM...Today through Mon night. Peak snowfall rates are
expected this morning as the latest short wave passes through the
forecast area. The precipitation will start decreasing during the
afternoon and evening. It should end from west to east during the
late night hours tonight in the west to Sun afternoon in the ID-WY
border region. Thus have kept the current timing for all zones and
the same level of highlight for the zones affected. Light
precipitation begins again Mon morning in the central Idaho
mountains, then spreads to the ID-WY border region during the late
night hours Mon night. Would not expect any highlights for the
Mon/Mon night period, unless combined with what develops Tue/Tue
night in the extended period.

Cloud cover and the influx of cooler air will mean afternoon highs
should be down 3 to 10 deg F from yesterday highs. The thinning of
clouds late tonight should mean a cooling trend developing in the
morning lows, again a 3 to 11 deg F or so drop. As precipitation
ends from west to east on Sun and clouds continue to clear out,
the highs and lows continue the downward trend, with afternoon
highs struggling to get above 40 degrees F and single digit
overnight lows by Sun night in the central Idaho mountain basins.
Mon will see more sunshine and thus a warming trend returns, and
the increase in cloud cover overnight on Mon night will keep
temperatures much warmer compared to the previous night.

Some windy conditions this afternoon and evening in the Arco
Desert and Mud Lake region are the only significant winds; at most
15 to 25 mph with higher gusts. Otherwise, wind is fairly light
except on ridges. This should allow some late night and morning
fog, and limited areas of blowing and drifting snow.

Messick

.LONG TERM...Tue through Fri night. The Tue trough appears to be
weak in all the clusters and with a strong positive tilt in the
upper levels means a light precipitation event, which is also
developed in the NBM guidance. Currently is appears to affect
areas south and east of the Snake River the most, with the
highlands getting more snow than the Snake River plain. Only the
Bear River Range looks to threaten an Advisory-level snow, while
the Snake River plain appears to accumulate an inch or less. The
accumulation may linger on Wed as afternoon highs at Pocatello
barely get above freezing. The trend has been for less
precipitation than the previous forecast for this Tue-Wed period.
Temperatures bottom out Thanksgiving night with single digits
expected in the Arco Desert and teens for the Snake River plain.
Afternoon highs just do not warm up under a north to northwest
upper level air flow, keeping highs even in the Snake River plain
in the lower to middle 30s. The flow is cold, but the air is
fairly dry and see no threat to the holiday return travel at this
time. Only 15 percent of cluster solutions has any upper level
"troughiness" over the Gem State; the majority indicates an upper
level ridge axis over the Pacific Northwest, producing that NWly
upper level flow.

Messick

&&

.AVIATION...
Challenging aviation forecast today as a cold front tracks across
southeast Idaho bringing a period of rain and snow to all TAF
terminals, especially with regard to precip type.

KBYI, KPIH, and KIDA are just warm enough that VFR conditions will
likely manage to prevail, with the period of most organized precip
and attendant thicker/lower cigs timed out for 13-19z/6am-12pm at
KBYI, 14-21z/7am-2pm at KPIH, and 15-21z/8am-2pm at KIDA based on
the 00z HREF suite of CAMs, 06z NAMNest, and 07z HRRR. No
significant trends noted here in the guidance compared to the
previous forecast. If things decide to get freaky at any of these
terminals, it`s going to be KIDA where marginal temps COULD allow
for a brief changeover to snow with a hit to vsbys (maybe 2 SM
briefly) IF precip rates get heavy enough...and we do note that
current temps there are running several degrees colder than forecast
to kick off the early morning. That said, the probability of this
occurring is only about 10% and it would be brief, and we will not
be carrying these impacts in the forecast at this time. Winds will
ramp up with the front (somewhere in the middle of the precip
windows mentioned above) and then remain breeziest through sunset
generally out of the SW at all 3 terminals, on the order of roughly
10-15kts with gusts to 20kts. Overall forecast confidence is
moderate, but definitely higher here compared to KSUN and KDIJ.

For KSUN and KDIJ, slightly colder marginal temperature profiles
will ride the line between rain and snow, which could mean the
difference between VFR conditions and the terminals approaching
closure thresholds. Period of most organized precip and attendant
MVFR to IFR cigs is timed out for 13-18z/6-11am at KSUN and 16-
22z/9am-3pm at KDIJ. Our confidence in KSUN holding below airfield
minimums isn`t solid, and thus we will be backing off from the
previously advertised 1SM in the 12z TAF. However, both terminals
will still have the potential to drop to 1SM vsbys during periods
with the heaviest precip rates (which will favor snow), as hinted at
in NBM vsby probabilities showing as high as a 30% chance of this
occurring at KSUN and a 20% chance at KDIJ. This potential impact
will lag the start times of the precip periods mentioned above by an
hour or two, and will be covered by TEMPO groups. We do have several
models that are hinting at the potential for lingering snow showers
overnight into Sunday morning at KDIJ, but not every model agrees
and for now we will back both sites off to VCSH tonight. Stay tuned.

Broadly speaking, all terminals should trend back into higher
confidence VFR/low-impact conditions Sunday as the system pulls away
from the region. - KSmith

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 11 AM this morning to 5 PM MST
Sunday for IDZ060.

Winter Weather Advisory from 5 AM early this morning to 5 PM MST
Sunday for IDZ066.

Winter Weather Advisory until 11 PM MST this evening for IDZ069-
071.

Winter Storm Warning until 11 PM MST this evening for IDZ072>074.

&&

$$