Area Forecast Discussion
Issued by NWS Flagstaff, AZ

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FXUS65 KFGZ 131722

Area Forecast Discussion
National Weather Service Flagstaff AZ
1022 AM MST Thu Jul 13 2017

.SYNOPSIS...Expect a warming trend with a slight downturn in
activity heading to the early portions of the weekend. A shift in
the high position will then bring an increase in activity by late
in the weekend and into early next week.


.UPDATE...No major changes were made to the ongoing forecast. The
latest high-res models indicate isolated/scattered thunderstorms
developing over the higher terrain of Coconino and Yavapai
counties this afternoon, and not so much over Gila, Navajo, and
Apache counties. Still expect the greatest concentration of
thunderstorm initiation over the White Mountains. However, storms
should quickly move south into Greenlee and Graham counties after

The main hazards will be lightning and localized flash flooding
this afternoon, mainly over Yavapai County. Confidence is low, but
not zero.


.PREV DISCUSSION /520 AM MST/...The middle and upper levels of the
airmass over the CWA will continue to become a bit drier and more
stable each day through Friday or Saturday. Complicating this is
the fact the Gulf of California surged overnight, the northward
extent and depth of this surge may bring a bit more activity to
our southern zones than what the models are indicating.

Overall, trends the next few days will be for warming and less
convective activity, especially over the northern zones. The ridge
will peak over the weekend and will move back westward, placing
our CWA back into northeasterly/easterly steering flow.
Increasing convective activity south of the border each day,
especially over the weekend as an easterly wave moves through,
will enhance surge and outflow activity. This will eventually
make central Arizona a battleground between warm, stable and dry
air to the north and the moist and unstable boundary layer over
the southern zones.

By early next week, the ridge weakens and slides east again, this
should open the door for all the moisture waiting to the south of
the Mogollon Rim and we will launch into a few days of high-grade


.AVIATION...For the 18Z package...Another round of scattered
thunderstorms is expected to develop aft 18Z and last through around
sunset this evening. These storms are expected to reduce flight
categories briefly to MVFR or IFR. A few isolated strong
thunderstorms could produce hail and gusty outflow winds in excess
of 35 knots. Otherwise VFR conditions are expected. Aviation
discussion not updated for TAF amendments.


.FIRE WEATHER...Expect a medium grade monsoon pattern through the
week with isolated to scattered thunderstorms developing each day.
The greatest concern will be gusty and erratic thunderstorm winds
along with any new lightning-started fires.

Saturday through Monday...Increasing moisture will lead to greater
thunderstorm coverage and intensity over the weekend into next week.
The chance for widespread rainfall will increase. Daytime
temperatures will trend cooler while afternoon humidities increase.






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