046
FXUS65 KBOI 220250
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
850 PM MDT Sat Sep 21 2024

.DISCUSSION...A few clouds will continue to move across the
area this evening associated with a weak frontal passage. The
clouds will have no impact on temperatures tonight, which are
expected to drop to the mid-40s in the Western Snake River Plain
and the mid-30s in the mountains. Late Sunday, high clouds will
increase in the northern zones, with southern zones seeing more
cloud cover by Sunday night as another weak dry cold front
moves in. The clouds and post-frontal northwest winds will
prevent the typical nighttime inversion, resulting in slightly
warmer low temperatures Monday morning.

Monday night, lighter winds and fewer clouds will allow for the
inversion, but low temperatures will only be marginally cooler
due to a warming Pacific upper ridge moving inland. High
temperatures for both Sunday and Monday are expected to remain
close to normal, similar to today.

Additionally, the autumnal equinox will occur at 6:44 AM MDT on
Sunday. No updates are needed at this time.

&&

.AVIATION...VFR. A few clouds this evening becoming clear after
midnight. Increasing high clouds north in the afternoon.
Surface winds: Variable less than 10kt. Winds at 10kft:
Variable around 10 kt.

KBOI...VFR. Light and variable wind.

&&

.PREV DISCUSSION...
SHORT TERM...Tonight through Monday night...Little change
through Sunday under dry northwest flow aloft. A band of high
clouds passing through tonight will have little effect on low
temperatures. High clouds will increase again in northern areas
late Sunday and southern zones Sunday night as a weak, dry cold
front passes through. The clouds and post-frontal northwest
winds will inhibit the usual nighttime inversion and low temps
Monday morning will be several degrees warmer. Lighter winds and
fewer clouds Monday night will allow the inversion but low temps
will be only slightly cooler as a warming Pacific upper ridge
will also be coming inland. High temps Sunday and Monday will
be close to normal, much like today. The autumnal equinox occurs
at 644 AM MDT Sunday.

LONG TERM...An upper level ridge will be centered over the area
Tuesday, and will bring dry and warmer weather. As it rapidly
moves to the southeast Tue night and Wed, we will become even
warmer as southwest to southeast winds increase. A weak
shortwave trough is forecast to move by to our north Wed into
early Wed night, with excellent ensemble agreement on the
timing and strength. Dry west to southwest flow aloft should
then remain over the PacNW through Saturday, and precipitation
chances are low (a small part of northeast Valley County gets
up to 15% Fri-Sat, but otherwise the chance of precipitation is
too small to mention in the forecast). Temperatures will cool
after a very warm Wed (around 10 degrees above normal), with
readings falling back down to near normal by Saturday.

&&

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

&&

$$

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DISCUSSION...JDS
AVIATION.....JDS
SHORT TERM...LC
LONG TERM....SP