Flash Flood Warning 231, NWS Flagstaff, AZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
946 AM MST Wed Aug 17 2022

.SYNOPSIS...An active monsoon pattern will continue across
northern and central Arizona through the remainder of the week.
Heavy rainfall leading to flash flooding will continue to remain a
threat, especially Thursday through Sunday. Cooler temperatures
are expected through the weekend.

&&

.UPDATE...An inverted trough currently over Chihuahua will
continue to retrograde westward today. This feature should
provide a little subsidence across eastern Arizona this afternoon,
subduing afternoon convection over Navajo and Apache counties.
However, mean northeasterly flow should allow thunderstorms to
develop primarily over the western Mogollon Rim (Flagstaff to
Heber-Overgaard), then advect into northern Gila and Yavapai
Counties later this afternoon and evening. The latest SPC HREF
3-hr QPF has neighborhood probabilities of exceeding 1" of
rainfall around 70 percent centered over Yavapai County later
this afternoon. As a result, think flash flooding will be the
primary threat over Yavapai County later this afternoon. Isolated
flash flooding will be possible elsewhere.

&&

.PREV DISCUSSION /236 AM MST/...Another day with scattered showers
and thunderstorms across the region is expected today. While we
won't be completely storm free, we will see less coverage of
storms than we have seen the past week or so. This brief
reduction in widespread storms will only last through today as we
will see an uptick in activity starting Thursday and increasing
across the region through the end of the week. Even with less
coverage today, any storms that do develop will still have heavy
rainfall and the potential for flash flooding will remain a
concern.

The monsoon will really start to pick up again on Thursday as
moisture increases across the forecast area in response to a
system moving across northern Mexico. This disturbance is
bringing in some tropical moisture and with it we will see PWATs
rise between 1.25"- 2" across the region. This influx of deep
moisture will result in an increased potential for heavy rainfall
resulting in flash flooding as we head through the weekend,
starting Friday where parts of the forecast area have been moved
into a moderate risk for excessive rainfall by the WPC. The best
forcing and instability may be off to our south but some of the
model guidance is indicating that we will see a very active day.
Whether in slight or moderate, the risk is there for widespread
1-2" rainfall amounts which combined with our already wet
antecedent conditions may lead to flash flooding. There remains
some limiting factors as cloud cover and lingering convection
will affect what areas may see the greatest impacts. As a
reminder, be sure to avoid flood prone areas (recent burn scars,
slot canyons, and low-water crossings) and never cross flooded
roadways.

With troughing across the region, temperatures are expected to be
much cooler through Saturday and generally 10-15 degrees below
normal for this time of year.

The active monsoon looks to continue into early next week but with
ridging situated across the area, we actually start to see some
drying out of the atmosphere. We still expect some storms to
develop each day but coverage may be more isolated to scattered
storms versus the numerous storms we anticipate over the weekend.
Temperatures will also start to rebound and rise back to near or
just below normal through the start of the week.

&&

.AVIATION...For the 18z TAF package...Primarily VFR conditions
are expected outside of thunderstorms over the next 24 hours.
Scattered showers and thunderstorms will develop from KGCN-KFLG
around midday, then will move westward into KSEZ-KPRC later this
afternoon/evening. Surface winds will generally be light away from
storms. Aviation discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Scattered showers and thunderstorms will develop
along the Mogollon Rim this afternoon, then move into Gila and
Yavapai Counties later this afternoon and evening. An uptick in
activity is expected Thursday. Gusty, erratic winds, and flash
flooding will be likely.

Friday through Sunday...Widespread shower and thunderstorm activity
is expected Friday into the weekend. Risk of flash flooding will
increase, especially on Friday.

&&

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...NONE.

&&

PUBLIC...TM/Meola
AVIATION...TM
FIRE WEATHER...TM/ET

For Northern Arizona weather information visit
weather.gov/flagstaff