Area Forecast Discussion
Issued by NWS Flagstaff, AZ

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FXUS65 KFGZ 201027

Area Forecast Discussion
National Weather Service Flagstaff AZ
327 AM MST Thu Jul 20 2017

.SYNOPSIS...Expect very active monsoon conditions for the next
several days. Local heavy rainfall capable of producing flash
flooding remains possible from stronger storms.


.DISCUSSION....Monsoon moisture will remain entrenched across
northern Arizona today. The primary change over the past 24 hours
is that high pressure in the mid-levels has shifted further to the
east. The result over Arizona will be for the steering flow to
point from south to north. Such a flow pattern favors an increase
in shower thunderstorm activity across northeast Arizona as storms
that form in the mountains and along the Mogollon Rim send outflow
boundaries across the Little Colorado River Valley, as well as
the Navajo and Hopi Nations. The northeast is a bit drier so
storms could produce wind gusts in excess of 50 mph. Otherwise,
local downpours of up to an inch will be possible. South of the
Mogollon Rim, under this steering flow, there likely will be a
downturn in activity with storms more isolated and tending to
remain over and near the mountains. We have adjusted the forecast
grids to account for this tendency. Still saturated soils across
the broad area encompassing Prescott and Payson with isolated 2+
inch downpours and flooding possible.

From Friday onward...The steering flow remains south to north on
Friday with similar results as described above. A center of high
pressure then moves in from over the eastern Pacific for Saturday
and Sunday with the steering flow becoming northeast to
southwest. We will have to see how the moisture hangs in across
central Arizona but under this steering flow typically it is quite
active from the Mogollon Rim southward (similar pattern to that of
the past few days). Beyond the weekend, monsoon moisture remains
entrenched across Arizona with daily thunderstorms continuing.


.AVIATION...For the 06Z package...Isolated showers will continue
through the early morning hours with locally heavy rain capable of
producing MVFR conditions through the morning. Scattered to
numerous showers and thunderstorms are expected to develop along
and North of the Mogollon Rim again today, with scattered showers
and thunderstorms possible south of the rim. Most of this activity
should begin to develop around 17z-19z. MVFR/IFR in the strongest
storms. Aviation discussion not updated for TAF amendments.


.FIRE WEATHER...The active monsoon conditions will continue with
scattered to numerous showers and thunderstorms each day. Heavy rain
and gusty winds will remain the primary impact. Expect near average
temperatures across the area.

Saturday through Monday....Expect daily chances for showers and
thunderstorms. No significant changes in the weather pattern are






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