Area Forecast Discussion
Issued by NWS Flagstaff, AZ

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FXUS65 KFGZ 240448

Area Forecast Discussion
National Weather Service Flagstaff AZ
948 PM MST Sun Jul 23 2017

.SYNOPSIS...A Flash Flood Watch continues across northern Arizona
through midnight. Heavy rainfall with flash flooding is possible
from stronger storms. Active monsoon conditions are expected to
continue Tuesday. A decrease in storm coverage should develop
starting Wednesday, especially across western and central


.DISCUSSION...The flash flood watch covering the entire area
remains in effect through midnight. The bulk of the action this
evening has been over Yavapai County where a flash flood warning
remains in effect until 11:15pm tonight. Area creeks, streams and
rivers are running high and rises are currently being observed on
the Agua Fria River. This water could make it as far south as
Black Canyon City by late tonight. Otherwise, additional scattered
shower and thunderstorm activity is ongoing across a large
portion of the area. Latest model guidance indicates this will
likely continue through the overnight hours with an inverted
trough positioned to the south and west.

How widespread convection will be on Monday still remains in
question. Model soundings show a nearly saturated column which
would promote more in the way of cloud cover, cooler temperatures,
and light to moderate rainfall. However, overnight trends will
have to monitored as any breaks in the cloud cover and heating
would result in the development of more widespread storms across
northern Arizona on Monday. The next shift will fine-tune this
portion of the forecast for the morning package.


.PREV DISCUSSION /249 PM MST/...A flash flood watch continues
for all of Apache, Coconino, Navajo, Yavapai, and northern Gila
Counties until midnight tonight. We have already issued several
Flash flood Warnings and Flood Advisories for southern Coconino
County. Storms have been very slow moving, and observed rainfall
has been over 1.5 inches with some of the stronger storms. Radar
indicates outflow boundaries are moving southward and westward
into northeast Yavapai county now, and an active period of weather
is expected there through mid evening.

For tonight and Monday...Progs continue to show an inverted
trough feature moving from southeast AZ through western AZ, with
abundant moisture persisting. Storms could persist into the
overnight tonight with the help of the feature. The storm steering
flow to switch from southeasterly tonight to southerly Monday. 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 daytime storms to shut
down completely, but coverage should be isolated to scattered at

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 06Z package...A line of showers and
thunderstorms extending from Holbrook to Pinon are decreasing as
they move to the west-northwest. Light rain primarily west of I-17
and south of I-40 will continue into the early morning hours.
Scattered to numerous showers and a few thunderstorms will
develop again Monday after 18z-20z, with activity along the
Mogollon Rim extending from Flagstaff to the Grand Canyon and west
to the boarder. MVFR/IFR conditions in the stronger storms.
Aviation discussion not updated for TAF amendments.


.FIRE WEATHER...Expect above normal storm activity and high relative
humidity through Monday. Slightly drier and more stable conditions
arrive Tuesday, bringing activity back down to normal levels.

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


.FGZ WATCHES/WARNINGS/ADVISORIES...Flash Flood Watch until midnight
MST tonight FOR AZZ004>018- 037>040.




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