059
FXUS65 KBOI 161609
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
1009 AM MDT Mon Sep 16 2024

.DISCUSSION...A trough of low pressure will influence the region
today through Tuesday with below normal temperatures and the
threat of precipitation. There will be a brief period this
evening where storms could generate wind gusts of 30-50 mph
across both SE Oregon and southwest Idaho. Current projections
indicate a 20-40% of wind gusts of 30 mph or greater. The
current forecast looks like it handles the scenario well and no
updates are planned this morning.

&&

.AVIATION...Generally VFR, with MVFR possible in/around showers
later this afternoon and evening. Gusts to 40kt with the
strongest storms, with the best chance near KJER/KTWF after 22Z.
Surface winds: N to NW 5-15 with gusts to 25 kt in SE Oregon,
and generally variable 5-10 kt in SW Idaho. Winds at 10kft: NE-
SE 10-20 kt.

KBOI...VFR. A 30-50 percent chance of showers, after 21Z. A 30
percent chance of thunderstorms after 21Z, with wind gusts up to
35 kt possible. Surface winds: variable mainly NW to 10 kt.


&&

.PREV DISCUSSION...
SHORT TERM...Today through Wednesday night...

KEY POINTS

*Isolated to scattered thunderstorms this afternoon will bring
 the risk for wind gusts in excess of 40-50 mph with locally
 heavy rain.

*Temperatures will cool through Wednesday, with daytime highs
 about 10-20 degrees below normal.

*Unsettled conditions with rain and cool temperatures will
 continue through the middle of the week with a slight warming
 and drying trend beginning early next week.

The upper level low will continue to dive down over central
California this morning, with a few showers and thunderstorms
over the region as of 2 am MDT. Most of the thunder has been
centralized over the Magic Valley and eastern Idaho. Showers
will continue through the day, with an uptick in stronger
thunderstorms across the region around 2 pm MDT this afternoon.
Current high resolution guidance shows the storms moving from
south to north near the Nevada border and east to west over the
Central ID Mountains with outflow winds in the 40-50 mph range.

Current QPF totals range from 0.4-0.7 inches of rain across
much of the forecast area valleys for today through Tuesday
night. Ridgetops could see anywhere from 0.8-1.0 inches of rain.
Current hi- res probability guidance indicates a low chance
(<10%) of reaching flash flood precipitation amount thresholds
(0.50" in one hour), with the best chance over steep ridges in
the Central ID Mountains and higher elevations in southeast
Oregon. This low risk of reaching higher QPF lands us again in a
marginal risk in the excessive rainfall outlook from the Weather
Prediction Center.

Weak showers and thunderstorms will continue through the
overnight hours on Tuesday, tapering off as the low continues
to move to the northeast early Wednesday. An extremely brief
ridge will build in on Wednesday, ahead of another trough
moving in late Wednesday in this double barrel low evolution.
This low will eventually dry up quite a bit later this week,
with below normal temperatures continuing through the short term
period.

LONG TERM...Thursday through Monday...Models generally agree on
the initial position of an upper low in Nevada on Thursday, but
differ with the timing of its eastward progression. Some of the
ensembles favor a slower solution, while the bulk of the members are
faster and show it moving into Utah on Friday. Forecast for our area
will indicate a 15-30 percent chance of showers in SW Idaho and
along the OR/NV border on Thursday, along with a slight chance (less
than 20 percent) of thunderstorms near the ID/NV border. Mostly dry
conditions follow on Friday, except for a slight chance (less than
20 percent) of showers near the ID/NV border south of Twin Falls.
The weather for next weekend is uncertain, although the guidance has
trended drier in the latest run. Previously, the models were
depicting an upper low moving southeast into the northern Rockies
and eastern Idaho, but the newer ones have favored a flatter and
drier northwest flow aloft. Forecast remains generally unchanged
until the models show consistency, so there is a 15-30 percent
chance of showers Saturday through Saturday night, trending drier
Sunday and Monday. Temperatures will depict little day-to-day
trends, averaging 5 degrees below normal.

&&

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

&&

$$

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