Area Forecast Discussion
Issued by NWS Flagstaff, AZ

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FXUS65 KFGZ 281650

Area Forecast Discussion
National Weather Service Flagstaff AZ
950 AM MST Fri Jul 28 2017

.SYNOPSIS...Expect daily chance for showers and thunderstorms as
an active monsoon pattern remains in place across northern Arizona
into next week.


.DISCUSSION...Satellite and radar imagery shows extensive cloud
cover across much of area, and a line of light showers across
eastern Coconino and western Gila counties. Short-term model
guidance suggests this band will weaken and continue it`s
westward push through the morning hours.

Surface observations reveal dew points are up a bit from
yesterday morning, with values ranging from the mid 50`s to mid
60`s across the region. However, this mornings upper-air sounding
from near Flagstaff shows slight warming between 500 and 400 mb.
As a result, mixed layer instability remains on the low side,
roughly 700 J/kg or less across the area.

Most hi-res model guidance indicates convective initiation over
higher terrain beginning first for locations from Flagstaff
eastward. This makes sense given the presence of a strengthening
inverted trough in this area. Subsequent outflow boundaries then
initiate new convection further west, with a line of storms
propagating through Yavapai County by the mid afternoon.

The 0-6 km mean wind is forecast to be light and from the north,
roughly 5 knots or less. Deep layer bulk shear remains light,
which is typical for this time of year. Although, the GFS predicts
bulk shear values approaching 20 - 25 knots in far northeast
Arizona. With that said, slow storm movement, modest instability
and relatively light wind shear should combine to make flash
flooding the primary hazard from today`s storms.


.PREV DISCUSSION /407 AM MST/...Over the weekend and into early
next week, a developing inverted trough across the southern
portion of the state will turn the flow aloft to the southeast.
This will advect more moisture-rich air northward with continued
chances for showers and thunderstorms each afternoon and evening.
There are some indications of a bit of drier air making its way
into the region the middle of next week with decreasing storm
chances. This will continue to be monitored over the coming days.


.AVIATION...For the 12Z package...Scattered SHRA/TSRA expected
again from around 18Z to 02Z with MVFR to IFR conditions in the
heavier storms. Aviation discussion not updated for TAF amendments.


.FIRE WEATHER...Expect daily rounds of showers and thunderstorms
across the fire district this weekend and into early next week.
Winds to be generally light except in the vicinity of thunderstorms.






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