Area Forecast Discussion
Issued by NWS Flagstaff, AZ

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FXUS65 KFGZ 201608

Area Forecast Discussion
National Weather Service Flagstaff AZ
908 AM MST WED JUL 20 2016

.SYNOPSIS...Monsoon moisture will continue to keep showers and
thunderstorms in the forecast through at least Thursday. Friday
and into the weekend, a drier westerly flow will decrease shower
coverage across northwestern Arizona with decent chances for
thunderstorms across southern Navajo and Apache counties.


.UPDATE...Clouds cleared out nicely in many locations this
morning, which will allow for ample surface heating. Look for
storms to develop between 10 and 11 AM MST, first across Yavapai
County and the Mogollon Rim, then spreading elsewhere across
northern Arizona. Slow storm motion today from south to north will
make for a flash flood threat. The stronger storms may also
contain small hail and gusty winds. The previous forecast looks
good and no significant changes were made.


.PREV DISCUSSION /335 AM MST/...Deep southerly flow continues to
import plentiful moisture into the state this morning. A few light
showers and an occasional lightning strike were noted at 3 am from
around Williams into western Yavapai county and also southern
Apache county. Later this morning through the afternoon, expecting
another round of showers and thunderstorms, most numerous along
the higher terrain though some storms will push northward into
some lower terrain areas. Morning cloud cover could play a role in
where storms develop first and how strong they become. A mid and
upper level disturbance rotating northward across our region today
could also act to enhance storm coverage. The main threats today
will be locally heavy rainfall and flooding, with some hail and
gusty winds with stronger storms as well. Similar conditions are
expected Thursday, then a downward trend in moisture and storm
activity is forecast starting Friday in the northern part of the
state as the ridge axis sinks southward. However, due to the
forecast position of the ridge axis, a tight moisture gradient is
likely to set up across the area, with higher values of moisture
in the southern portion of the forecast area. So we kept a chance
of thunderstorms each day into early next week across the Mogollon
Rim and White Mountains with generally slight chances elsewhere.
There is still some uncertainty with where this moisture gradient
sets up, so watch for updated forecasts as the pattern evolves.


.AVIATION...For the 18Z package...Scattered to numerous SHRA/TSRA
will redevelop between 18z-02z today. Brief MVFR/IFR conditions
in the stronger storms with locally heavy rain, small hail, and
gusty winds. Aviation discussion not updated for TAF amendments.


.FIRE WEATHER...Scattered to numerous showers and thunderstorms can
be expected today and again on Thursday. Storms will generally be
moving slowly from south to north.

Friday through Sunday...Drier air will start to filter in from the
west, which will bring a decrease in thunderstorm activity,
especially across the western portion of the state. Minimum RH
values will drop back into the teens generally from Flagstaff north.






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