867
FXUS65 KFGZ 202036
AFDFGZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
136 PM MST Fri Sep 20 2024

.SYNOPSIS...A low pressure system moving across Arizona will
bring cooler temperatures, breezy winds, and chances for showers
and thunderstorms tonight through Saturday. Warmer and drier
weather is expected to return for much of the upcoming week.

&&

.DISCUSSION...An upper level closed low is near San Diego this
afternoon with showers and thunderstorms developing across
southern California and Nevada. The low will gradually move east
into Arizona tonight, and then northeast across the state on
Saturday before exiting Saturday evening. We still expect
scattered showers and thunderstorms to develop, mostly from late
tonight through midday Saturday. Although a few isolated showers
or storms are possible across western Arizona this afternoon, the
bulk of the activity is expected to develop late tonight (after 10
pm MST). High resolution models are in pretty good agreement with
a band of convection developing over Mohave/Yavapai Counties and
spreading northeastward through the overnight hours. The best
wind shear profiles still look to proceed the convection, so we
expect only a minimal threat for a few isolated strong/severe
storms. Light precipitation amounts are expected, from a few
hundredths of an inch up to ~0.25 inches. Isolated heavy rain is
possible, but any flood threat is low.

On Saturday, the low is expected to be centered over central
Arizona in the morning and track northeast through the day. Most
shower/thunderstorm activity is expected to occur along and north
of the Mogollon Rim. Overall, we`ve seen a continued slight increase
in precipitation chances with chances extending a bit longer on
Saturday along the Mogollon Rim. Another result of the trough will
be colder temperatures Saturday, which have continued to trend a
bit cooler and will be the coldest yet this season. Also notable
is the possibility of some very light snow above 10,000 ft over
the San Francisco Peaks. Dry conditions return Saturday evening
when the low and trough axis move east of Arizona.

A generally warmer and dry pattern is forecast from Sunday through
next week while strong high pressure builds from the Pacific into
the western states. The caveat is potential shortwave activity
early/mid week. There is some ensemble support (about 30-40% of
members), as well as previous operational model run support for a
shortwave passing through the Rockies to drop as far west as
Arizona and bring additional showers to the area. The majority of
the guidance favors continued dry conditions, but something to
keep an eye on for next week.

&&

.AVIATION...Friday 20/18Z through Saturday 21/18Z...VFR conditions
will prevail for most areas through 06Z. Expect south to
southwest winds at 10-20 kts gusting to 20-30 kts through 01Z
then diminishing. After 06Z, scattered -SHRA/-TSRA and MVFR
conditions west of a KPRC-KPGA line after 06Z with chances
gradually increasing and spreading eastward through 18Z.

OUTLOOK...Saturday 21/18Z through Monday 23/18Z...Scattered
-SHRA/-TSRA and MVFR conditions will continue during the day
 Saturday. Greatest chances will be along and east of a KPRC-KFLG-
 KPGA line. VFR conditions with clear skies return later Saturday
 night into Sunday. West-northwest winds at 10-20 kts on
 Saturday, then variable winds mostly 10 kts or less for Sunday
 and Monday.

&&

.FIRE WEATHER...Saturday and Sunday...An area of low pressure
will deliver chances for showers and thunderstorms on Saturday. Dry
and warmer weather will move in on Sunday. Look for west-northwest
winds at 10 to 20 mph on Saturday followed by northerly winds at 5
to 10 mph on Sunday.

Monday through Wednesday...Warm and dry conditions will continue
through Wednesday. Light and variable winds under 10 mph are
forecast for Monday with northerly winds at 10-20 mph expected to
develop on Tuesday and Wednesday.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...None.

&&

$$

PUBLIC...MCT
AVIATION...McCollum
FIRE WEATHER...McCollum

For Northern Arizona weather information visit
weather.gov/flagstaff