731
FXUS65 KFGZ 212254
AFDFGZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
354 PM MST Mon Sep 21 2026

.SYNOPSIS...Increasing moisture will bring chances for showers
and thunderstorms in northwest Arizona late this afternoon and
evening, and across eastern Arizona on Tuesday. Precipitation
becomes more widespread Wednesday and Thursday as deeper moisture
and a low pressure system impact the area. Unsettled weather may
continue into the weekend.

&&

.DISCUSSION...Current satellite and upper-air data show that a 500
mb low is moving inland into central California. This system has
begun advecting moisture into northern Arizona. Precipitable Water
values, a measure of atmospheric moisture, range from 0.50-0.85
inches this morning. For comparison, values ranged from 0.25-0.50
inches yesterday morning. Surface dew points have also increased
and are generally 5-15 degrees above what was observed yesterday.
That said, even with the increase in moisture, model soundings
indicate thunderstorm development will be hindered by a stable
layer around 550mb. The best chances for precipitation (20-30%)
are forecast across Grand Canyon Country later this afternoon and
overnight, with only a 10-20% chance over higher terrain
elsewhere. Only light rainfall is expected. Otherwise, expect
breezy southerly winds and near-normal daytime temperatures.

On Tuesday, the low lifts to the northeast, drawing moisture
primarily into eastern Arizona. The current forecast calls for a
40-60% chance for showers and thunderstorms across Navajo and
Apache counties, with decreasing chances farther west. In
addition, southerly wind speeds are forecast to increase, with
gusts in the 20-30 mph range. There is only a marginal risk of
flash flooding over eastern Arizona, as the band of heaviest
precipitation is expected to occur farther eastward into New
Mexico.

On Wednesday, interaction between a high centered over Texas and
a cut-off low off the west coast of Northern Baja turns the flow
more southerly resulting in further increases in atmospheric
moisture and cooler daytime temperatures. In addition,
precipitation should be enhanced by a disturbance moving northward
out of Mexico. As a result, chances for precipitation and a
marginal risk of flash flooding spread farther west to include
portions of Yavapai County.

An active weather pattern is expected to remain in place through
the remainder of the workweek. On Thursday, the cut-off low is
forecast to move northeastward in response to a deepening West
Coast trough. This will likely lead to the most widespread shower
and thunderstorm activity of the week, with chances for showers
and thunderstorms continuing into Friday. High uncertainty exists
regarding the chances for precipitation over the weekend due to
uncertain interactions among another West Coast trough, and
Hurricane Polo/Tropical Storm Odalys currently located in the
eastern tropical Pacific.

&&

.AVIATION...Tuesday 22/00Z through Wednesday 23/00Z...Mainly VFR
conditions. ISOLD -SHRA/-TSRA INVOF KGCN through 03Z, then again
after 19Z mainly east of KINW. Brief MVFR conditions and gusty winds
possible in and around TS. Winds VRB 5-10 kts, becoming S 10-20 kts
with gusts 20-25 kts after 18Z.

OUTLOOK...Wednesday 23/00Z through Friday 25/00Z...Mainly VFR
conditions. ISO-SCT SHRA/TSRA possible Wednesday afternoon east of
KINW, spreading westward along the higher terrain on Thursday. Brief
periods of MVFR and gusty winds possible in and around TS. Daytime
winds E/SE 4-8 kts, becoming light and variable overnight.

&&

.FIRE WEATHER...Tonight through Wednesday...Shower and thunderstorm
chances return starting this evening. Best chances are across
northwest AZ tonight, then across eastern AZ on Tuesday through
Wednesday. Stronger storms will bring heavy rainfall and
gusty/erratic winds. Outside of storms, winds are south through
southwest 10-20 mph gusting to 25 mph on Tuesday, then generally
easterly at 10 mph or less on Wednesday

Thursday through Saturday...Chances for showers and thunderstorms
continue Thursday, potentially trending downward on Friday and
Saturday. The best chances will be seen across eastern Arizona each
day. Outside of storms, winds will be generally light and variable
at 10 mph or less.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...None.

&&

$$

PUBLIC...RR
AVIATION...Humphreys
FIRE WEATHER...Lewandowski

For Northern Arizona weather information visit
weather.gov/flagstaff