Area Forecast Discussion
Issued by NWS Flagstaff, AZ
FXUS65 KFGZ 240536 CCA
Area Forecast Discussion...CORRECTED
National Weather Service Flagstaff AZ
1036 PM MST SAT JUL 23 2016
.SYNOPSIS...After a brief downturn in precipitation chances this
weekend we continue to see positive signs of a return to deeper
Monsoon moisture through Tuesday. By Wednesday the high pressure
ridge moves over California bringing much drier air into
northeastern Arizona. Expect good chances for showers along and
south of the Mogollon Rim region each day from Wednesday onward,
with low grade Monsoon activity and only isolated storms across
the northern third of the state.
.DISCUSSION...A slight downturn in shower development was noted
today along with 40 to 60 degree dewpoint depressions as drier air
filtered in from the west. However the drying trend was not enough
to stop scattered thunderstorm development mainly along and south
of the Mogollon Rim region. National Weather Service Doppler Radar
precipitation estimates indicated between 0.5 to 1.5 inches of
rainfall reached the ground in the strongest thunderstorms. The
precipitation amounts were also a bit lower today than previous
On the afternoon GOES satellite imagery we see a broad trough
moving through the western states along the U.S. Canada border.
The subtropical ridge axis extending from New Mexico to Southern
California and the Tropical Upper Tropospheric Trough over
northern Mexico. A low developing in this trough over the Gulf of
California will likely enhance mesoscale convection in the Sierra
Madre mountains of northern Mexico. These Mesoscale Convective
Systems are the heartbeat of the Summer Monsoon moisture surges.
The latest American GFS weather model predictions indicate one of
these MCS `systems` may develop tonight and again on Sunday
night, helping to pump up moisture levels into Arizona for the
first half of next week. Evening GOES satellite imagery is already
showing early signs of this convective system roughly 200 miles
south of Douglas on the Arizona Mexico border.
On Sunday deeper moisture lingers across the Mogollon Rim region
from Flagstaff to the White Mountains with precipitable water (PW)
values around 1 inch. PW values around 0.75 inch to 1.25 inch typically
indicates favorable moisture levels for Summer season convective
development. Expect good chances for showers and thunderstorms to
develop around noon from the Mogollon Rim region southward into
Yavapai and northern Gila counties. Northward of the Rim country
only a few showers can be anticipated with the best chances near
Window Rock and the Chuska Mountains zone.
Monday through Tuesday...Forecast guidance continues to show
deeper moisture marching northward into Arizona with precipitable
water amounts reaching 1 inch along the Utah border by Monday
Wednesday through Friday...The mid level high moves into Nevada
and Utah in a position to bring dry northerly flow into the
northern third of Arizona. This shift will result in a downturn in
thunderstorm activity in our northern forecast zones north of the
interstate 40 corridor where only low grade Monsoon convection is
forecast. Enough moisture will linger along the Mogollon Rim
region for good chances of storm activity through the rest of the
week. Slightly drier moisture level will elevate the risk for
strong gusty outflow winds during this period along with an upper
level northeast to southwest wind pattern.
.AVIATION...For the 06Z package...Shower activity has diminished
this evening with only isolated coverage across northern Arizona.
Showers and thunderstorms will redevelop around 19Z Sunday.
Mostly VFR conditions will prevail with scattered MVFR and
isolated IFR in strong showers and thunderstorms. Expect erratic
and gusty winds up to 35kts near heavy showers and storms.
Aviation discussion not updated for TAF amendments.
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