Area Forecast Discussion
Issued by NWS Flagstaff, AZ

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FXUS65 KFGZ 281646

Area Forecast Discussion
National Weather Service Flagstaff AZ
946 AM MST WED SEP 28 2016

.SYNOPSIS...Weak low pressure will affect northern Arizona for the
next few days. Expect showers and thunderstorms across northern
Arizona today and Thursday, then decreasing on Friday. Drier air
is expected this weekend. Near normal temperatures will continue.


.DISCUSSION...Current radar indicates isolated showers mostly
along and south of the Mogollon Rim. These showers are resulting
from an upper-level low over southern California and an
associated shortwave trough rotating through northern Arizona.
This morning`s upper air sounding only measured around 0.5 inches
of precipitable water, but southerly flow is expected to draw
better moisture into the region from the lower deserts throughout
the day.

The forecast continues to call for chances of showers and
thunderstorms for most areas, with the greatest activity from
Flagstaff northwestward. While cloud cover may limit instability,
deep layer bulk shear around 30 to 35 knots could result in a few
severe storms, primarily north of the Mogollon Rim. Storm motion
will be from south to north at around 25 knots.


.PREV DISCUSSION /429 AM MST/...By Thursday, the low moves north
of the state and a second low moves toward southern California.
Even deeper moisture is forecast to be pulled northward in advance
of this system, some of it associated with a decaying tropical
system off the Baja coast. Showers and thunderstorms are likely
for most areas from Flagstaff eastward, with a chance of storms
farther west. Locally heavy rainfall possible in some isolated
spots where training storms develop, though flood threat is not
anticipated to be widespread. Enough low level moisture remains
Friday for a chance of showers and thunderstorms, mainly from the
Mogollon Rim northward as what is left of the second low moves

The weekend will be dry with increasing westerly flow, ahead of a
developing trough over the west coast. Models are trending toward
the western US low passing by to our north Monday, bringing gusty
winds and pushing a cold front through. Introduced some low PoPs
but right now the system looks fairly dry this far south.


.AVIATION...For the 18Z package...Scattered SHRA/isolated TSRA
remain possible through the morning hrs. SHRA/TSRA will increase
in coverage this afternoon especially from KFLG northwest. Local
MVFR possible in showers throughout the day. Aviation discussion
not updated for TAF amendments.






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