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367
FXUS65 KFGZ 231114
AFDFGZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
414 AM MST Sun Jul 23 2017

.SYNOPSIS...Active monsoon conditions will return today and
continue through Tuesday. Heavy rainfall with flash flooding
remains possible from stronger storms. A decrease in storm
coverage should develop starting Wednesday, especially across
western and central Arizona.

&&

.DISCUSSION...Expecting an active day as abundant monsoon moisture
is present over central and northern Arizona. Model forecast soundings
indicate fairly high levels of instability along and south of the
Mogollon Rim this afternoon, with steering flow generally pushing
storms slowly toward the west/northwest. This setup would allow
for a few strong to marginally severe thunderstorms developing
along the Mogollon Rim/White Mtns and pushing slowly into northern
Gila and portions of Yavapai County later in the afternoon and
evening. Also, with the stronger storms (and/or areas with cell
training), there will be a risk of heavy rain and localized flash
flooding. One thing that could limit this possibility is ongoing
cloud cover, acting to inhibit instability and storm strength. If
these clouds show a decreasing trend later this morning, there
could be a need for a Flash Flood Watch for this
afternoon/evening from the Mogollon Rim southward - we will
monitor through the morning. Later tonight and Monday...an
inverted trough feature over southeast AZ is forecast to move up
into northern Arizona, with abundant moisture persisting. This
will turn the steering flow from the southeast tonight and then
southerly Monday. Storms could persist into the overnight hours
tonight with the help of the feature. On Monday, forecast
soundings show a nearly saturated atmosphere through a deep layer.
Rain chances are high, but the amount of cloud cover could act to hold
down instability and decrease storm intensity, rainfall rates and
flash flood potential. Stay tuned as this part of the forecast
remains uncertain and could change.

Tuesday - the inverted trough is forecast to move north of the
state, with slightly lower precipitable water values over the
region. Looking for a more typical monsoon pattern, with scattered
afternoon storms moving SW to NE.

Wednesday & Thursday - models indicating a drier air mass and
some warming in the mid levels. Not expecting storms to shut down
completely, but coverage should be isolated to scattered at best.

Friday onward - high pressure forecast to shift to our north,
allowing for easterly flow and gradual moistening. Storm chances
return to typical monsoon levels.

&&

AVIATION...For the 12Z package...Expect scattered to numerous
showers and thunderstorms after 18z-20z Sunday. Storms will
generally be moving from the southeast to northwest, with new
storms forming along outflow boundaries moving through Yavapai
County and the Little Colorado River Valley by mid-afternoon.
MVFR/IFR visibilities, along with gusty winds, will be possible in
the vicinity of storms. Shower activity may continue through the
overnight hours. Aviation discussion not updated for TAF
amendments.

&&

.FIRE WEATHER...Expect above normal storm activity and high relative
humidity values Sunday and Monday, as moisture continues to stream
into the district. Wetting rain chances will remain high.

Tuesday through Thursday...Chances for showers and thunderstorms
will continue, but coverage and frequency should decrease. Slightly
drier conditions near the surface will enhance the threat for gusty
outflow winds, associated with thunderstorms.

&&

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

&&

$$

PUBLIC...JJ
AVIATION...RR
FIRE WEATHER...RR

For Northern Arizona weather information visit
weather.gov/flagstaff