570
FXUS65 KBOI 210245
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
845 PM MDT Mon May 20 2024

.DISCUSSION...An upper level trough that brought scattered
showers, isolated thunderstorms, and gusty winds to the area
today will move east tonight, leaving clearing skies and
decreasing winds in its wake. Showers will continue to decrease
this evening and end by midnight MDT. A weak upper level ridge
will move overhead on Tuesday, bringing temperatures around 5
degrees warmer than today, lighter (but still breezy) winds, and
mostly sunny skies. Clouds will increase late in the day as a
deep upper low approaches the area. Current forecast is on track
and no updates anticipated this evening.

&&

.AVIATION...VFR. Isolated showers ending by 06Z. Snow levels
5500-6500 ft MSL. Surface winds: W-NW 10-20 kt with gusts to 30
kt, diminishing to 5-15 kt by 06Z. Winds aloft at 10k ft MSL:
N-NW 10-20 kt.

KBOI...VFR under mostly clear skies. NW winds 10-15 kt with
gusts to 25 kt diminishing to less than 10 kt by 04Z.

&&

.PREV DISCUSSION...
SHORT TERM...Tonight through Wednesday night...An active and
unsettled pattern is on deck for the short term period as
successive upper level lows move through the region. The first
upper level trough will continue to dig through the region
today, bringing sufficient instability for thunderstorms and
showers. As of 1:00pm MDT, there is one weak thunderstorms just
north of Gooding, ID, bringing strong winds and brief rain.
Winds are gusting quite a bit throughout the region with KBOI
sustained at 18 mph with gusts to 33 mph. This is mainly due to
downsloping and gradient winds, but additional outflows could
strengthen local gusts to 40-50 mph. Radar indicates showers
developing and satellite visible imagery shows widespread
cumulus development throughout the region. Therefore, have
increased chance of precipitation and coverage of showers and
thunderstorms to further west over portions of southeast Oregon.
Hi-res model guidance continues to show pulsing showers-
thunderstorms over much of southwest Idaho through the early
evening.

Tuesday should be somewhat mild, with a weak upper level ridge
building ahead of a much colder and wetter cut off low late
Wednesday into Thursday. Winds will be mostly light, with
Tuesday likely being the warmest day of the week. By Tuesday
evening, valley rain and snow above 6000 feet should begin in
southeast Oregon. Precipitation will come in a line with the
initial cold frontal passage late Tuesday night. By early
Wednesday morning, precipitation will spread into southwest
Idaho. Most of this precipitation should be stratiform with the
initial line on Wednesday morning, but convective showers with
a stray thunderstorm could form over the Central ID mountains.
Snow levels will be right around 6500 feet during the day,
lowering to 5000 feet overnight. Therefore, light snow is
possible early Wednesday and late Wednesday night. Temperatures
will be below normal after Tuesday.

LONG TERM...Thursday through Monday...Moisture wrapping around the
exiting closed low will keep rain and snow over the mtns of Baker
County and w-central Idaho Thursday. Liquid amounts will be less
than a tenth of an inch (0.10) limiting additional snow totals to less
than an inch. Snow level forecasts remain between 4500-5000 feet
Thursday morning rising to 6-7kft MSL by afternoon. Otherwise most
of SE Oregon and SW Idaho are dry on Thursday and the drying trend
will extend into the mountains Thursday night as the low exits
eastward. Friday will be mostly dry though the Baker County and w-
central Idaho mtns will keep a 20% chance of light afternoon showers
fueled by increasing instability and moisture ahead of the next cold-
core low. Precipitation accompanying this next low will arrive
Friday night, carrying through Saturday night as the it tracks from
WA into eastern ID. Among the deterministic models the best overlap
for precipitation remains across e-central Oregon and w-central
Idaho where probability for rain/snow remains 30-60%. Areas from the
I-84 corridor and points to the south and east will see lesser
probabilities generally below 25%. Sunday and Monday will trend drier
as a shortwave ridge moves into the area. Thursday will be the
coolest day, warming closer to normal Friday through Sunday, warming
above normal on Monday.

&&

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

&&

$$

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DISCUSSION...ST
AVIATION.....BW
SHORT TERM...SA
LONG TERM....DG