Area Forecast Discussion
Issued by NWS Flagstaff, AZ

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FXUS65 KFGZ 280452

Area Forecast Discussion
National Weather Service Flagstaff AZ
952 PM MST WED JUL 27 2016

.SYNOPSIS... The high pressure ridge is building westward and
drier air will block Monsoon moisture moving up into
northern Arizona. Expect drier conditions over Northern
Arizona through Friday. Isolated to scattered showers will
develop across the higher terrain of central Arizona each day.
Drier and warmer air under the ridge will lead to hot temperatures
in the Grand Canyon and Page regions through at least Thursday.
Another Monsoon moisture surge is forecast to start this weekend
with increasing chances for showers and thunderstorms with storm
activity lasting into next week.


.DISCUSSION...The subtropical ridge remains in an unfavorable
position to advect Monsoon moisture northward into Arizona. Rather
the east to west flow will push moisture westward out of Mexico
and into the Pacific with drier air moving into Arizona from the
north. Additionally downward moving air or subsidence under the
ridge will cap convective development and produce warmer
temperatures over the northern third of the state. Hot
temperatures are forecast for the Grand Canyon region with an
Excessive Heat Warning still in effect for elevations below 4000
feet. Dry and warm weather with isolated to widely scattered
showers and thunderstorms through Friday.

On Friday, a low pressure system will cross the mouth of the Gulf
of California. The passage of this low center will likely send a
pressure wave northward helping to push deeper Monsoon moisture
surging northward into Arizona over the weekend. Higher moisture
levels and instability will lead to increasing chances and
coverage of showers and storms through Sunday.

Long range forecast guidance next week continues to show deep
Monsoon moisture across Arizona with precipitable water levels in
the 1.2 to 1.5 inch range across much of the northland through
Wednesday. These climatologically high moisture amounts will
likely produce good shower coverage, however the extensive cloud
cover in the morning and afternoon hours may reduce the
convective heating trigger and limit thunderstorm coverage.


.AVIATION...Expect mostly VFR conditions with isolated to
widely scattered shower and thunderstorm coverage over central
Arizona. Aviation discussion not updated for TAF amendments.


.FGZ WATCHES/WARNINGS/ADVISORIES...Excessive Heat Warning until 11 PM MST
Thursday for the Grand Canyon and Page regions below 4000 feet




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