591
FXUS65 KFGZ 200959
AFDFGZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
259 AM MST Fri Sep 20 2024

.SYNOPSIS...A low pressure system will bring cooler temperatures,
gusty 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 low pressure system continues to spin
across southern California early this morning. As we move through
the day the low will start to track to the east to northeast and
will cross through Arizona tonight through Saturday. Models continue
to support precipitation, mainly along and north of a Prescott to
Window Rock line. The low is not moving particularly fast as it is
cut off in both the mid and upper levels. The slow movement of the
low will mean the precipitation will linger into Saturday, likely
ending during the afternoon. It is still looking like a meager event
with most areas seeing less than 0.25" of rain. There is some
instability available along with some shear so thunderstorms are
possible as the low makes its way across the region. However, the
best shear/instability is offset from the onset of the precipitation
and while there may be a few stronger storms that develop, it is not
looking like we will see much in the way of strong/severe storms and
any that do develop will be fairly isolated. Additionally, there is
the possibility that some snow may fall across the San Francisco
peaks but with snow levels generally above 10,000 ft, any
accumulation will be light. A couple more facets of this low will be
the cooler temperatures across the region along with some gusty
winds. Saturday will be the coolest of the the next couple of days
with temperatures averaging 5-10 degrees below normal across the
entire forecast area.

The low moves off to the northeast by late Saturday and we see
things starting to clear out as a ridge starts to build across the
west. Temperatures will warm and conditions dry out once again
heading into the new week. A couple of kinks in the forecast come in
the shape of cut off lows and shortwave troughs. A trough looks to
drop down from the north, crossing through the Four Corners area on
Tuesday. This may bring a chance for some isolated showers and gusty
winds. A second cut off low may also develop along the California
coast but the strength and depth of the approaching Four Corners
trough early in the week looks like it may keep this low off to our
west before deflecting the low off to the north as the ridge builds
over the southwest during the middle of the week. Lots of moving
parts in this forecast with plenty to grab our attention over the
coming days.

&&

.AVIATION...Friday 20/06Z through Saturday 21/06Z...VFR conditions
prevail for most areas. Expect variable winds under 10 kts
overnight. South- southwest winds increase again after 18Z Friday
with speeds 10-20 kts and gusts 20-30 kts. There is a slight
chance of a light shower west of a KPRC-KPGA line after 22Z with
chances gradually increasing through the evening.

OUTLOOK...Saturday 21/06Z through Monday 23/06Z...Cloud cover
increases from west to east Friday night through mid day
Saturday, with chances for -SHRA and an isolated -TSRA. Greatest
chances will be along and west of a KPRC-KFLG-KPGA line. Showers
could linger throughout Saturday near the AZ/UT border before
ending by sunset. Localized/brief MVFR conditions in
precipitation. VFR conditions with SKC return on Sunday. West-
northwest winds 10-20 kts on Saturday, then variable winds mostly
10 kts or less for Sunday.

&&

.FIRE WEATHER...Today and Saturday...An area of low pressure
approaching from the west will bring increasing chances for showers
and thunderstorms today through Saturday. South winds 15-25 mph this
afternoon, followed by west-northwest winds 10-20 mph Saturday.

Sunday through Tuesday...Warmer and drier Sunday and Monday with
afternoon humidity in the 10-20% range. Humidity increases slightly
Tuesday with a 10-15% chance of rain. Light west to north winds
under 15 mph are likely Sunday and Monday, with northerly winds 10-
20 mph Tuesday.

&&

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

&&

$$

PUBLIC...Meola
AVIATION...JJ
FIRE WEATHER...MAS

For Northern Arizona weather information visit
weather.gov/flagstaff