Area Forecast Discussion
Issued by NWS Flagstaff, AZ

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FXUS65 KFGZ 221607

Area Forecast Discussion
National Weather Service Flagstaff AZ
907 AM MST Mon Jul 22 2019

.SYNOPSIS...Scattered showers and thunderstorms, along with the
best chances for rain, are expected east of a Payson to Window
Rock line today. West of this line, expect a few isolated high-
based showers or storms. Increasing monsoon moisture will lead to
a more typical monsoonal pattern with daily chances for showers
and thunderstorms from Tuesday through much of the coming week.


.UPDATE...Satellite and radar indicate the remnants from the
Sonora, Mexico MCS last night kicked off a few light showers
across Mohave and western Yavapai Counties this morning. Bumped
the probabilities of precipitation up a little and adjusted the
associated grids to cover these showers for the next hour or two.
Otherwise, the forecast is on track with moisture moving into the
area today and transitioning to a monsoonal weather pattern.


.PREV DISCUSSION /357 AM MST/...Water vapor satellite imagery this
morning finally shows the upper level high pressure circulation
nearing the Four Corners region. This will allow southerly flow on
along the lower quadrant of the high pressure center to draw
moisture north and west across Arizona. Overnight convection in
Sonora, Mexico has spread debris clouds across southern Arizona,
extending into Yavapai county this morning. In addition, a 5 to 10
degree increase in surface dew points is being observed across
southern and central Arizona. All of these factors lead to
greater confidence in the long awaited arrival of monsoon
moisture this week.

Today will be more of a transition day as moisture slowly creeps
northward. Expect the best coverage of showers and storms, along
with the best chances for measurable rain, to extend east of a
Payson to Window Rock line. West of this line, convection will be
more isolated with lightning and strong outflow winds of 40 to 50
mph being the primary concerns. With moisture increasing through
the overnight hours tonight, a chance for showers will continue
overnight primarily south of the I-40 corridor.

Tuesday will see the arrival of deeper moisture leading to better
coverage of showers and thunderstorms. Many areas along and south
of the Mogollon Rim will see measurable rainfall, though it will
still be scattered in nature (which is typical of the monsoon
season). Monsoon moisture will remain over the region through the
week underneath the subtropical high pressure. Scattered showers
and thunderstorms will develop each day and will be capable of
producing areas of heavy rain and hail. Accompanying the moisture
and showers will also be cooler daytime temperatures.

There are some indications of possible drying Friday or next
weekend, but we would like to see more subsequent model runs
suggesting this before making any big changes to the forecast. For
now in the extended forecast, we will continue with daily chances
for showers and storms favoring the mountainous areas.


.AVIATION...For the 18Z package...Expect VFR conditions across
northern Arizona for the next 24 hours. Isolated generally high-
based showers and thunderstorms developing this afternoon with
more numerous storms along and southeast of a KSOW-KRQE line. A
slight chance of showers and storms continues overnight
along/south of a KFLG- KRQE line. Wind gusts in excess of 35kt in
the vicinity of storms. Otherwise, winds generally south to
southwest at less than 15 kts. Aviation discussion not updated
for TAF amendments.


.FIRE WEATHER...The chance for high-based thunderstorms increases
this afternoon with the highest chances along and south of a Payson
to Window Rock line. These storms will produce strong outflow winds,
along with the potential for new lightning starts and low chances of
wetting rain. Tuesday, deeper moisture arrives with the chance for
thunderstorms increasing. The potential for strong outflow winds
will persist, but the chance for wetting rain and flash flooding
over sensitive areas, such as burn scars, will increase.

Wednesday through Friday...Active monsoon weather will continue.






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