Flash Flood Warning 109, NWS Flagstaff, AZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
832 PM MST Fri Jul 29 2022

.SYNOPSIS...An active monsoon pattern will continue through the
weekend with scattered to widespread showers and thunderstorms
expected. Beginning next week, a slight downward trend in
thunderstorm coverage is expected. Flash flooding will remain the
main threat during this time.

&&

.UPDATE...Thunderstorm activity is winding down Friday evening,
although the threat of flash flooding remains. Normally-dry washes
and slot canyons are most vulnerable. Isolated spots across
northern Arizona could still pick up additional heavy rainfall
tonight.

&&

.PREV DISCUSSION /237 PM MST/...Storms have begun to ramp up along
I-40 near Flagstaff and throughout Yavapai County. Flash flooding
is expected for areas in and around the Pipeline and Museum burn
scar for the few hours. Widespread activity is expected to
continue throughout the afternoon and evening hours. According to
our 12Z sounding this morning, our PW values were just shy of an
inch, so we still have plenty of moisture to tap into throughout
the afternoon. Flooding and flash flooding will remain the biggest
concerns for today. Be sure to have a way to check updates on
current weather information, and check recent forecasts before
traveling.

Widespread thunderstorm activity is expected to continue on
Saturday, thanks to the ridge remaining in place over the Pacific
Northwest. This placement is allowing moisture to funnel up from
the Gulf of California, which has been the primary source of
moisture the last several days. Strongest storm development is
forecast to begin after 11 AM MST and continue well into the
afternoon/evening hours. Very similar to what has occurred
throughout our CWA over the last several days. Aside from
rainfall, temperatures will be slightly cooler than average for
this time of year.

Beginning late Sunday/early Monday, the high pressure system
aforementioned will shift north of us toward the Plains. With the
movement of this system, we're expecting a slight downward trend
in monsoon activity. This downward trend will result in storm
coverage becoming isolated to scattered across northern Arizona.
Depending on where the high pressure system positions itself later
next week (models currently are showing discrepancies in
placement), we could see an increase in moisture into northern
Arizona.

&&

AVIATION...For the 06Z TAF package...Scattered showers
and thunderstorms through 08Z, decreasing through the Saturday
morning. Thunderstorms will increase in coverage after 16Z.
Otherwise, mainly VFR conditions expected with light winds. Gusty,
erratic winds and MVFR or lower conditions possible in and near
thunderstorms. Aviation discussion not updated for TAF amendments.

&&

FIRE WEATHER...Scattered to numerous storms Saturday and Sunday
with flash flooding the main threat. Light winds, seasonally cool
temperatures, and humid both days with gusty, erratic winds in and
near storms.

Monday through Wednesday...Daily showers and thunderstorms will
continue with flash flooding as the main threat.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...
Flood Watch until 5 AM MST Saturday for AZZ004>018-037>040-
104>118-137>140.

&&

PUBLIC...McCollum/BAJ
AVIATION...Meola
FIRE WEATHER...Meola

For Northern Arizona weather information visit
weather.gov/flagstaff