Flash Flood Warning 111, NWS Flagstaff, AZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
144 PM MST Wed Aug 12 2026

.SYNOPSIS...An active monsoon pattern extends across northern
Arizona with scattered to numerous showers and thunderstorms
developing across the region. The main threat will be flash
flooding, but gusty winds and hail will be possible with the
strongest storms. A Flash Flood Watch remains in effect through
this evening. Monsoon conditions are expected to continue
Thursday, with a downtrend in Monsoon activity possible by the
weekend, as drier air moves into the region.

&&

.DISCUSSION...Plenty of Monsoon moisture extends across northern
Arizona as the high pressure system as moved eastward into the
southern plains and southerly flow and transported moisture
northward. Right now a trough at 850 mb is supporting the showers
and thunderstorms in northwestern Arizona, with showers and
thunderstorms also developing along the rim and higher terrain
down to the White Mountains. The UA WRF model shows this active
pattern continuing through 6 PM MST/7PM MDT, and then decreasing
as the potential area of development shifts southward. However,
due to the north-northeast storm motion, it is possible for rain
to move into areas near and south of I-40 overnight and early
Thursday morning. The UA WRF model also shows and active monsoon
pattern for Thursday afternoon and evening, though the 12 and 15Z
runs show a slight decrease in overall coverage. The Flash Flood
Watch may need to be extended into Thursday if shower and
thunderstorm coverage is still expected to be extensive enough to
warrant a watch.

A mid-level trough is currently sitting off of the west coast and
will attempt to move inland. This could bring drier, mid-level
area over northern Arizona and reduce shower and thunderstorm
activity across the region. However, if this trough fails to move
inland or moves farther north, then the active monsoon pattern may
continue into the weekend. Right now forecast trends does support
the trough moving inland and an overall decrease in monsoon
activity this weekend, but these trends will be monitored.

&&

.AVIATION...Wednesday 12/18Z through Thursday 13/18Z...Mainly VFR
conditions away from thunderstorms. SCT-NMRS SHRA/TSRA and ISO +TS
through the period, especially between 18Z-03Z. Stronger storms may
produce brief MVFR/IFR and wind gusts to 45 kts. Outside of storms,
W-SW winds 10-15 kts, becoming light and VRB overnight.

OUTLOOK...Thursday 13/18Z through Saturday 15/18Z...Mainly VFR
conditions away from thunderstorms. SCT SHRA/TSRA and ISO +TS
through the period, especially between 18Z-03Z. Storm trends shift
eastward on Friday. Stronger storms may produce brief MVFR/IFR
and wind gusts to 45 kts. Outside of storms, W-SW winds 10-15 kts
becoming light and VRB overnight.

&&

.FIRE WEATHER...This afternoon through Friday...Cooler temperatures
with active Monsoon conditions expected each day. Numerous showers
and thunderstorms through Thursday with an eastward push in activity
on Friday. Outside of thunderstorms, expect southwest winds around
10-15 mph.

Saturday through Monday...Eastward shift in monsoon activity through
the weekend with some drier conditions expected. Temperatures will
gradually warm to near normal by early next week. Expect
southwesterly winds at 10-15 mph each afternoon.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...
Flood Watch until midnight MST /1 AM MDT/ tonight for AZZ004>018-
037>040.

&&

PUBLIC...Schank
AVIATION...Meola
FIRE WEATHER...Meola

For Northern Arizona weather information visit
weather.gov/flagstaff