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388
FXUS65 KPIH 180826
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
226 AM MDT Tue Jun 18 2024

.SHORT TERM...
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Today through Wednesday night. Satellite imagery
shows main shortwave axis/cold front has swept well east of the
region. Secondary shortwave axis sliding through the Idaho
panhandle today will bring a few showers and thunderstorms to
northern zones, mainly central mountains and along the Divide.
Locally breezy winds are possible. Temperatures remain cool,
though slightly warmer than yesterday. Another cool night is
anticipated tonight, with hopefully the last Frost Advisory of
the season expected for the Arco Desert/Upper Snake Plain zones.
Low elevation areas outside the Snake Plain, such as Teton Valley,
Gem Valley, and all lower elevations from Blackfoot Reservoir
south to Bear Lake will also see near or just sub- freezing
temperatures. Though these areas are outside the region for
Frost/Freeze headlines, most people will want to cover sensitive
plants tonight as well. Upper flow turns southwest for Wednesday
and Wednesday night in response to amplified trough developing
along the Pacific coast. This is expected to usher in a period of
dry conditions and warming temperatures headed into the latter
half of the week. DMH

.LONG TERM...Thursday through next Tuesday. The main story in the
long term portion of the forecast continues to be warming
temperatures and predominantly dry conditions. Ensemble means from
the GEFS and EPS, along with WPC ensemble clusters, continue to show
fairly strong agreement with the pattern evolution during this
timeframe, lending increased confidence to the forecast. The Gem
State will be under a weak southwest flow aloft on Thursday, in
between weak troughing along the West Coast and the dominant ridge
over the Eastern CONUS. This weak western trough lifts east across
the region on Friday, bringing low chances (20-30%) of showers and
thunderstorms to the Lost River area east along the Divide into the
Eastern Highlands. This looks to be the extent of any precip chances
through the period. Shortwave ridging amplifies over the area on
Saturday ahead of an upper low sliding into western BC, with
resultant rising heights helping to further the warming trend.
Portions of the Eastern Magic Valley, Lower Snake Plain, and
Southern Highland valleys will climb back into the 90s on Saturday,
with these 90s expanding into the Upper Snake Plain on Sunday as
southwest flow aloft strengthens ahead of the slowly eastward-
advancing BC upper low. Most higher mountain valleys will climb well
into the 80s by Sunday and southern portions of the Wood River
Valley including Hailey and Bellevue look to flirt with the 90
degree mark (30-45% chance of hitting 90F around Hailey/Bellevue on
Sunday). Sunday currently looks like the warmest day of the next
seven, with a slight cool down arriving early next week as the upper
low passes to our north, ushering in slightly cooler (although still
well above normal) temperatures. Winds will also strengthen Sunday
into early next week as the pressure gradient tightens south of this
low, leading to some breezy days. KB
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.AVIATION...
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A low pressure system centered over Montana early this
morning will continue to slowly work east through the day. We`ll see
some wraparound clouds and showers on the backside of this system,
although the showers will primarily be focused north and east of the
terminals today. Cannot rule out an afternoon shower near KDIJ but
chances currently appear too low (less than 15%) to mention in the
TAF. Lingering lower CIGS at KDIJ this morning are expected to
remain VFR, with VFR conditions also anticipated at the other
terminals today. Winds will be much lighter than yesterday. KB
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.FIRE WEATHER...
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Wraparound moisture on the backside of a low pressure
system working east across Montana today will bring rain and
mountain snow showers to the Central Mountains east along the
Montana Divide into the Northeast Highlands. A slight chance of
thunderstorms (20%) will also exist in these same areas this
afternoon. Precipitation amounts today will be light, with most
areas expected to see less than a tenth of an inch of liquid
precipitation and only very low chances (10-15%) for a few isolated
spots to pick up over a quarter inch of precipitation under heavier
showers. Any snowfall accumulations will be around 1 inch or less.
Showers will dissipate this evening. Following a cold start this
morning, a gradual warming trend will begin today, although high
temps today will still be 10-15 degrees below normal. One more cold
night is on tap tonight with most areas falling into the 20s and 30s
for lows. The steady warming trend will then continue into the
weekend, with most lower elevations seeing highs back in the 90s by
Sunday. Aside from a 20-30% chance of showers and thunderstorms for
portions of the Central Mountains and Eastern Highlands on Friday,
dry conditions are forecast into early next week. Fairly light winds
are expected the next few days, but it looks like we`ll get back
into a windier period Sunday into early next week. KB
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.HYDROLOGY...
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Water levels for the Teton River near Driggs remain
high with continued lowland flooding. Will continue the river
flood warning for the Teton River near Driggs until flooding drops
off. Water levels are forecasted to drop even more, down to 3-6
feet, by Wednesday. Much cooler temperatures and a diminishing
snowpack are causing river flows to drop off. TW/DMH
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.PIH WATCHES/WARNINGS/ADVISORIES...
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Frost Advisory until 9 AM MDT this morning for IDZ051>055.
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