965
FXUS65 KBOI 171546
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
946 AM MDT Tue Sep 17 2024

.DISCUSSION...Forecast is right on track and no updates are
planned this morning. The latest WSR-88D radar as of 9:45 am MDT
this morning shows areas of showers and isolated thunderstorms
rotating around a closed upper low centered over southern Idaho.
An area of showers in eastern Oregon is moving south around the
western side of the low and will likely affect the area around
Burns later this morning. The area of showers in the Boise
Mountains is moving toward the southwest and will likely move
into the treasure valley before noon brining some more rain to
Boise, Meridian, Nampa, Caldwell and surrounding areas before
noon.


&&

.AVIATION...Mostly VFR. Areas of MVFR in showers and isolated
thunderstorms, mainly in southwest Idaho after 17/21Z. Gusts up
to 40 kt with the stronger storms. Surface winds: W-NW 5-10 kt
gusts to 25 kt in SE Oregon, becoming generally variable 5-10
kt overnight. Winds at 10kft: NE 10-20 kt becoming W-NW 20-30 kt
after 18/00Z.

KBOI...VFR. A 90 percent chance of showers today, diminishing
to about a 30 percent chance this evening...then dry after
18/04Z. Additionally...there is about a 20 percent chance of
thunderstorms with gusty winds in the vicinity of KBOI this
afternoon. Surface winds: Generally NW 5 to 10 kts.

&&

.PREV DISCUSSION...
SHORT TERM...Today through Thursday night...Showers and
thunderstorms continue to rotate around a closed upper low
centered over southwest Idaho this morning. The low will
gradually lift to the northeast today with wrap-around shower
and thunderstorm development keeping at least a 60% chance of
precipitation in the forecast across most sites through this
afternoon. Showers and thunderstorms today will bring locally
heavy rainfall which will continue to pose a threat for flooding
and debris flows on recent burn scars. Storm motion and speed
will vary as individual cells follow the upper low circulation.
This could lead to slower movement and training of storms near
the upper low center over SW Idaho. Shower and thunderstorm
coverage will diminish this evening as the low exits into MT,
but wraparound moisture and instability will keep a low chance
of showers in the w-central Idaho mountains through Wednesday. A
second low dropping down the coast will track further west and
south than the current system. This will allow much of the
region to dry out while areas near the northern NV border keep a
20-30% chance of showers through Thursday. Today is the coolest
day of the week with high temperatures about 15 degrees below
normal. Wednesday and Thursday will warm about 5 degrees each
day bringing lower elevations back into the mid-70s by Thursday.

LONG TERM...Friday through Tuesday...Widespread model agreement
amongst deterministic solutions exists in the position of an
upper level low pressure system on Friday. This will continue to
bring below normal temperatures and a slight chance of showers
to the region through Sunday morning. Northwest flow will then
return as the low center moves East on Sunday. Temperatures will
climb slightly and conditions will be mostly dry. The GFS/ECMWF
runs then hint at a shortwave trough moving through northern
and eastern Idaho, which would bring another chance of
precipitation to the Central ID Mountains on Monday night into
Tuesday. A weak ridge will then likely build in according to
ensemble clusters, bringing a return to normal temperatures and
dry conditions for Tuesday.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...None.
OR...None.

&&

$$

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DISCUSSION...JB
AVIATION.....JB
SHORT TERM...DG
LONG TERM....SA