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264
FXUS65 KPIH 201950
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
150 PM MDT Fri Sep 20 2024

.SHORT TERM...
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Tonight through Sunday Morning...
Cool, dry and mostly clear conditions are expected through the
short term period as we find ourselves in sandwiched but not
necessarily close to several areas of low pressure. Current
satellite imagery this afternoon showing some fair weather cumulus
clouds developing over higher terrain of the central mountains
and along the eastern highlands. Broad low pressure well north of
the area will drag a diffuse trough axis through central MT this
evening, which could develop an isolated shower or two near
Yellowstone NP and perhaps further west near Island Park, but
overall precipitation potential is quite low.

Quiet conditions will reign into Saturday with temperatures
knocked back down a few degrees off of today`s readings. Sunny
skies, breezy winds and temperatures about 5 degrees cooler than
average will make for nearly ideal conditions for any outdoor
activities that may be occurring. Clear skies and weakening
surface flow will lead to temperatures dropping a little further
for lows Sunday morning. The current NBM shows about 50% chance of
minimum temperatures below 36 degrees in the ag fields adjacent
to and just north of American Falls Reservoir as well as across
portions of the Mud Lake Desert. These probabilities really fall
off when the threshold is lowered to 32 degrees with only a 15-20%
chance. With this in mind, will opt for inclusion of patchy frost
in the forecast for Sunday morning, but not seeing widespread
enough potential for any headlines.
TAX


.LONG TERM...Sunday through next Friday. A stretch of rather benign,
low-impact weather looks to persist through the extended forecast
period. A progressive mid/upper-level shortwave trough embedded in a
northwest flow aloft is projected to clip the area Sunday
night/Monday, bringing increased clouds and a slight uptick in
winds, along with a 20-40% chance of showers to the MT Divide and
Eastern Highlands. Moisture is very limited with this system,
keeping any precip very light (65% or greater chance of remaining
less than 0.1"). High temperatures will cool a few degrees from
Sunday to Monday with this passing system, keeping most valley
locations in the 60s to near 70F on Monday and mountains in the 50s
to lower 60s. Beyond Monday, overall ensemble consensus is for
transient upper ridging to take hold Tuesday/Wednesday, before
giving way to a west/southwest flow Thursday and Friday as the ridge
slides east and an upper trough works into the PacNW and BC. However
there are some differences hiding among the ensemble members as to
exactly how this overall pattern evolution ultimately plays out. On
Tuesday, just under 50% of the ensemble clusters pivot some energy
around the upper ridge into the Great Basin vs. tracking it quickly
east. Either way, this shouldn`t have much of an impact locally. For
mid to late next week, the main differences revolve around how
quickly the upper ridging gives way to increased west/southwest flow
aloft. Roughly 60% of ensemble solutions are quicker to shift the
ridge axis east and transition to west/southwest flow ahead of the
PacNW/BC trough. The net effects will primarily be to daily
temperature modulations and degree of breeziness, but either way no
significant impacts are expected. Predominantly dry conditions look
to persist through late next week with temperatures rebounding from
a few degrees below normal early in the week to a few degrees above
normal by late week. Bottom line, looks like a pleasant stretch of
early Fall weather for any outdoor interests.
KB
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.AVIATION...
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A weak disturbance passing north of the region will
support breezy west/southwest winds this afternoon and evening,
gusting to around 20 kts. Winds will diminish after sunset, becoming
light overnight in wake of a weak cool front. VFR conditions to
persist through Saturday, with just some mid clouds this
afternoon/evening with the passing disturbance (particularly at KSUN
and KDIJ) and some high clouds late tonight and Saturday in
continued northwest flow aloft.
KB
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.FIRE WEATHER...
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Cool, dry and mostly clear conditions are expected through the
near term and likely through the weekend. A weak and diffuse
trough passing to the north this evening will increase winds
incrementally today and then to a lesser extent Saturday
afternoon, especially across the Snake Plain and upper Snake
Highlands. Cannot rule out an isolated shower along the MT/ID
divide country this evening, but any impacts should be extremely
limited. Drier air will move in for Saturday driving RH values a
little lower compared to today, but temperatures will be knocked
back a few degrees so that will help limit min RH values from
cratering lower.

The next real chance of precipitation comes with a passing system
Sunday night into Monday. The best chances for any precipitation
will again be from the divide area east through the WY border, but
totals look very light and not significantly impactful. A
transient high pressure ridge will then quickly build into the
area Monday and Tuesday but will shift east by Wednesday as
another broad low pressure system brings moisture back into the
PacNW late next week. Precipitation chances with that system
currently look very limited, but temperatures should be largely
held in check through the end of next week.
TAX
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.PIH WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$