485
FXUS65 KFGZ 151938
AFDFGZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
1238 PM MST Tue Sep 15 2026

.SYNOPSIS...Northern Arizona will see an increase in shower and
thunderstorm activity from later tonight through Thursday, when a
Flash Flood Watch is in effect. Expect multiple rounds of rain
and thunderstorms, with a few stronger storms possible. We`ll see
a drying trend with less thunderstorm activity over the weekend.
Outside of precipitation, look for seasonable temperatures and
breezy southwest winds.

&&

.DISCUSSION...An active monsoon pattern continues across Arizona
as monsoonal moisture lingers across the state. Confidence
continues to increase today in an even more active period of rain
and thunderstorms developing from late tonight through early
Thursday morning and a Flash Flood Watch has been issued for all
of northern Arizona.

For today, we expect scattered showers and thunderstorms to
develop with prime daytime heating. Most of this activity looks to
favor the Mogollon Rim and areas north/east. Storm motion around
15 mph should limit the flash flood threat, though isolated heavy
rain leading to flooding cannot be ruled out. Thunderstorm
activity looks to increase substantially after midnight tonight
and through the day on Wednesday as increasing moisture interacts
with a shortwave feature that`s expected to move across northern
Mexico and through Arizona over the next 48 hours. This pattern is
favorable for multiple rounds of shower and thunderstorm
activity, and that`s very consistent with what the latest CAM
(convection allowing) model guidance suggests. The first round
will likely develop after midnight tonight and move north through
the morning hours, followed by multiple additional rounds on
Wednesday. Storms will be capable of producing heavy rain, and the
repeated nature of activity will increase the threat of flash
flooding, thus a Flash Flood Watch has been issued for all of
Apache, Navajo, Coconino, Yavapai and northern Gila counties. The
potential for the highest rainfall amounts are in-line with WPC`s
"Moderate" risk of excessive rainfall across eastern Yavapai and
Gila counties. The areas that see the more persistent bands of
rainfall could see amounts of 1-3+ inches over the next 48 hours.
The persistent trough across the Pac. Northwest is adding some
wind shear to the environment as well. Though flash flooding will
be the primary threat, there will be secondary threat of isolated
severe thunderstorms that could produce large hail and damaging
wind.

Storm coverage will decrease Thursday, but we still expect to see
at least scattered thunderstorm coverage. By Friday, the
aforementioned trough begins to progress through the western U.S.
and will begin to spread drier air across the state. Expect a
downturn in activity over the weekend with mostly isolated
showers/storms.

Forecast confidence decreases dramatically early next week as
additional troughs move into the southwest and the guidance is
split on potential interactions with additional moisture.


&&

.AVIATION...Tuesday 15/18Z through Wednesday 16/18Z...ISOLD-SCT
SHRA/TSRA through 02Z Wednesday, then ISOLD -SHRA/-TSRA or partial
clearing through 08Z-10Z. AFT 08Z-10Z, NMRS SHRA/TSRA and ISOLD
+TSRA moving south to north through the remainder of the period.
Areas MVFR CIGS due to low clouds and TSRA through the period.
Sfc winds S-SW5-15g20kts.

OUTLOOK...Wednesday 16/18Z through Friday 18/18Z...Expect SCT-NMRS
SHRA/TSRA and ISOLD +TSRA through the period. Areas MVFR CIGS due
to low clouds and TSRA through the period. Sfc winds outside of
stronger convection generally light.

&&

.FIRE WEATHER...Wednesday and Thursday...An increase in
shower/storm activity is expected from late tonight through
Thursday morning with widespread wetting rain likely. There is an
elevated risk of flash flooding, especially over recent burn
scars. A few isolated severe storms are also possible. Outside of
storm activity, expect near to below average temperatures and
south to southwest winds 10-15 mph gusting up to 25 mph. Expect
gusty and erratic winds in/near storms.

Friday through Sunday...A drying trend will lead to decreasing
storm coverage over the weekend. Temperatures will remain near
average with south to southwest winds around 10 mph during the
daytime hours, becoming light overnight.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...
Flood Watch from late tonight through late Wednesday night for
AZZ004>018-037>040.

&&

$$

PUBLIC...MCT
AVIATION...Peterson
FIRE WEATHER...Peterson

For Northern Arizona weather information visit
weather.gov/flagstaff