132
FXUS65 KPIH 041140
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
540 AM MDT Sat May 4 2024

...AVIATION UPDATED...

.SHORT TERM...TODAY THROUGH SUNDAY NIGHT...
FREEZE WARNINGS and FROST ADVISORIES remain in effect until 9 AM
this AM up the ern Magic Valley and Snake Plain corridor, but winds
will quickly turn into the south by this afternoon and allow high
temps to surge into the 60s to low 70s, significantly warmer than
what we`ve had to contend with over the last several days! As this
southerly flow increases ahead of our next approaching low pressure
storm system, a WIND ADVISORY remains in effect starting this
afternoon across the Raft River region and south hills/Albion Mntns,
and we have extended the advisory until 4 AM Sun AM as 700mb flow
strengthens further to 50+kts during the evening and first part of
the night. Hazardous driving for high profile vehicles is possible.
Precip is still expected to hold off until this eve (making today a
really nice day as a whole!), before overspreading the region from
west to east between sunset and after midnight. Sun we return to
much colder temps with widespread rain/rain showers, snow showers, t-
storms, and continued breezy conditions. Snow levels drop Sun night
and we`ll have to closely monitor whether or not snow will be able
to effectively accumulate at valley floors. 01

.LONG TERM...MONDAY THROUGH NEXT SATURDAY...
Under the influence of an organized H5 low directly overhead,
widespread precipitation, gusty winds, and colder temperatures will
remain in place Mon. The latest QPF/rainfall forecast continues to
show 0.50-1.25" across the region with locally lighter totals across
portions of the NRN Magic Valley and Arco/Mud Lake Desert through
Monday night. We will need to watch regional rivers closely as they
respond to this moderate precip event.

Given colder air associated with this system, a mix of rain and snow
in the valleys and predominant snow in the mountains continues to
remain favored. There also exists moderate to heavy snow potential
in the backcountry above 7000-8000` where 1-1.5 feet of snow will be
possible through Monday night. As we get colder air in place Sunday
night into Monday as the H5 low works NE into Wyoming and Montana,
this will be the best timeframe for widespread valley snow potential
especially south and east of the Snake Plain as snow levels fall to
valley floors. WINTER WEATHER ADVISORIES may be needed to capture
this event in the mountains with only light accumulations expected
at this time across the Snake Plain and Magic Valley. Taking a look
at winds, strong winds out of the W/SW are favored to continue into
Sunday and Monday aided by an enhanced PGF and 30-45 kt 700 mb winds
aloft. This will support additional WIND ADVISORY potential across
the Snake Plain and Magic Valley where wind gusts up to 40-60 mph
will exist.

As this system ultimately exits to our east onto the NRN Great
Plains for Tuesday and Wednesday, temperatures will remain
seasonably cool with isolated to scattered rain/snow showers.
Starting Thursday, around 75% of ensemble cluster solutions show a
return to a broad H% ridge over the PacNW and NRN Rockies which will
begin to shift east heading into the weekend. This will support
warmer and drier weather to round out the work week into the weekend
with highs back in the 50s/60s/70s as soon as Friday. The latest NBM
50th percentile high temperatures also show the potential for mid to
upper 70s across our lowest elevations by the weekend which could
mark the warmest airmass we have seen so far this year. Stay tuned
as we track the latest and plan ahead for wet and windy weather
Sunday and Monday with lingering showers through midweek. MacKay/01

&&

.AVIATION...
Main concern for the bulk of the day today will continue to be
increasing winds out of the SSE this afternoon and tonight, which
will be at least a partial crosswind at most of our TAF terminal
runways. Otherwise, expect gradually increasing high-level clouds
streaming in ahead of our next approaching low pressure system,
but otherwise high confidence in VFR conditions through early eve.
Tweaked start time of -SHRA this eve and then initiated
predominant -RA groups at 08-09z/2-3am at KBYI/KSUN/KPIH based on
the latest HREF suite as widespread rain moves in. Once rain
begins, MVFR cigs are likely with support from both the NBM and
HRRR. Confidence is low in exactly when snow may be able to mix in
at KSUN...temps will be very marginal. If snow becomes
predominant Sun AM (currently most possible after 11z/5am), vsbys
of 1-2 SM would be possible. This kicks off several days of
unsettled wx with multiple rounds of wind, rain/snow showers, and
low cigs across the region. 01

&&

.HYDROLOGY...
Moderate flooding remains ongoing at the Portneuf River at Pocatello
with rising levels late this weekend into early next week with the
latest river forecast reaching 10.9 inches very near major flood
stage on Tuesday. Minor flooding continues for the Portneuf River at
Topaz where the gauge remains above flood stage and will remain so
for several days with only a slight rise expected late this weekend
into early next week. Flood warnings also remain in effect for the
Blackfoot River near Shelley at Wolverine Canyon with the river
remaining at flood stage and also near Blackfoot where the river
remains in flood stage. With the potential for significant
precipitation this weekend into early next week, rivers will need to
be monitored closely. GK

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Frost Advisory until 9 AM MDT this morning for IDZ051-055.

Freeze Warning until 9 AM MDT this morning for IDZ052>054.

Wind Advisory from noon today to 4 AM MDT Sunday for IDZ056-057.

Winter Storm Watch from Sunday afternoon through late Monday
night for IDZ060.

&&

$$