369
FXUS65 KBOI 281609
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
1009 AM MDT Sun Apr 28 2024

.DISCUSSION...Westerly flow aloft continues today as a trough
approaches the Pacific NW. Continued breezy westerly winds this
afternoon, with the strongest winds in the Magic Valley
(20-30mph). This trough will bring a cold front through the
area late tonight into Monday morning and bring scattered rain
and snow showers to the area. Snow levels will range around
5500-6500 feet MSL. The front will bring minimal precipitation
to the area, but strong westerly winds on Monday afternoon,
where a wind advisory remains in effect for the Camas Prairie,
Treasure and Magic Valleys. Thunderstorm potential is minimal
with the front as it passes through during the nighttime hours
this evening, but will address that in the afternoon forecast.
No updates to the forecast.

&&

.AVIATION...VFR. Isolated showers over the mountains north of KBKE-
KMYL, then becoming scattered showers over the mountains late
tonight into Monday, with mountain obscuration. Snow levels
5500-6500 ft MSL. Surface winds: W-NW 10-20 kt. Gusts to 30 kt
east of KMUO, including KTWF/KJER. Winds aloft at 10kft MSL:
W to NW 10-20 kt.

KBOI...VFR. Surface winds: NW 7-12 kt.

&&

.PREV DISCUSSION...
SHORT TERM...Today through Tuesday night...A deep upper level
trough will move into the Pacific Northwest today, bringing
slightly cooler temperatures and increased cloud cover to the
region. A cold front with strong winds will move through on
Monday, bringing slightly below normal temperatures and gusty
winds. The Magic Valley, Camas Prairie, and Upper Treasure
Valley will see the strongest winds, with sustained west winds
around 25-35 mph and gusts anywhere from 40 to 50 mph. High
terrain in south central ID could see gusts as high as 60 mph.
Therefore, a wind advisory has been issued for Monday afternoon-
evening for the Upper Treasure Valley, Camas Prairie, and Magic
Valley zones. This cold front looks to be mostly dry, but there
is a slight chance of showers for the northern most areas of
our CWA, in the West Central Mountains and Baker County, OR.
Instability during the day looks to be limited, mainly due to
cooler temperatures, but there is low confidence (10-20% chance)
in afternoon thunderstorms as the front moves through on
Monday.

A better chance of precipitation (70-80% chance) over the
mountains exists overnight on Monday night into Tuesday morning
as the trough moves to our north. Colder temperatures will mean
most of this will fall as snow over the higher terrain. Snow
levels look to be around 3000-4000 feet overnight throughout the
region, but weak moisture aloft (precipitable water values in
the 20th-30th percentiles) will limit snowfall accumulations for
those areas. This upper level trough will deepen into a closed
low as it moves east, keeping us in zonal flow. The pressure
gradient will remain tight over our region through Tuesday, so
breezy westerly winds, albeit lower than Monday, will persist
through the short term period for most of the region.

LONG TERM...Wednesday through Sunday...The models are in decent
agreement with regard to the large scale pattern through the end of
the week, but differ somewhat in the details. An upper trough over
Idaho on Wednesday will support a chance (mainly 15-40 percent) of
showers over the higher elevations of SW Idaho, but any precip
amounts will be light. A weak and short-lived upper ridge,
accompanied by dry conditions, moves through the region Wednesday
night through Thursday. A Pacific upper low is then progged to move
through the region late Thursday into Friday. Models agree on the
timing of the system, but differ in the track with some ensemble
members favoring a northern track which would maintain dry
conditions across most of our area, while other members depict a
track closer to our area resulting in a better chance of showers.
Latest forecast will show a 15-30 percent chance of showers over the
northern high terrain. An upper ridge returns on Saturday for dry
conditions. Confidence diminishes early next week due to significant
differences in the timing, strength, and track of the next Pacific
low pressure system, which has implications on the forecast for our
area. A blend of models results in precipitation chances generally
in the 15-30 percent range on Sunday. Wednesday will be the coolest
day through the period with below normal temperatures, warming to
near normal on Thursday and above normal by the end of the week.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Wind Advisory from noon Monday to midnight MDT Monday night
     IDZ014-016-028.
OR...None.

&&

$$

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DISCUSSION...KA
AVIATION.....KA
SHORT TERM...SA
LONG TERM....BW