115
FXUS65 KFGZ 170850
AFDFGZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
150 AM MST Tue Sep 17 2024

.SYNOPSIS...Showers and thunderstorms will continue over eastern
Arizona through the early afternoon. Below normal temperatures
and breezy conditions continue through the rest of the week.
Mostly dry conditions are also expected, with only a slight chance
of showers late Thursday and Friday over far northern Arizona.

&&

.DISCUSSION...this morning...Current meso analysis early this
morning shows a pocket of instability over Apache and Navajo
counties this morning, with around 500-1000 J/Kg of MUCAPE. A
sharp moisture gradient is also in place across central Arizona,
with dewpoints in the upper 20s F to mid 30s F near and west of
the I-17/US-89 corridor and upper 40s F to mid 50s F to the east.
Given this, the precipitation chances for the overnight and into
the morning hours will largely be limited to Apache and Navajo
counties. As the trough axis approaches, upward motion will
increase over the area which should lead to storms developing over
eastern Arizona this morning. While much of this activity should
be minimal, the added upper-level dynamics could lead to a few
stronger (and potentially severe) storms around day break, however
widespread severe weather is not expected.

This afternoon through Wednesday...Mainly dry, cool, and breezy
conditions are expected today as the trough axis sweeps through
Arizona and departs to the east. A couple of isolated showers can
not be entirely ruled over the Chuska and White Mountains this
afternoon, but the vast majority of the area will remain dry.

Afternoon highs today are expected to be around 8 to 14 degrees F
below normal for this time of year. Overnight lows will similarly be
below normal, with near-freezing to event some sub-freezing
temperatures expected across the High Country.

Thursday and Friday...A second trough drops southward on Thursday,
and ejects off the Pacific into southern California. While the
system will move into Arizona with favorable dynamics and flow, the
system overall looks to be moisture starved. There is some uncertainty
into exactly how much moisture can be advected northward as the
trough moves through, and this will play a critical role in
determining the impacts from this system. A drier, solution will
result in another mainly wind event. If sufficient moisture can be
advected northward, there will be the possibility for showers and
thunderstorms to develop over Arizona, along with a non-zero
chance for a few strong to severe thunderstorms. Current ensemble
guidance favors the drier solution, but time will tell as model
solutions evolve.

Regardless of the moisture, below normal and breezy conditions will
continue through Friday.

Saturday through Monday...Heights rise behind the trough as an upper-
level ridge builds over the southwest. Dry conditions, lighter
winds, and more seasonable temperatures look to return for the
weekend and start of next week as a result.

&&

.AVIATION...Tuesday 17/06Z through Wednesday 18/06Z...Isolated to
scattered SHRA/TSRA are forecast to persist across portions of
Navajo and Apache counties through around 15Z. MVFR conditions
and hail are possible with any stronger storms that develop. In
addition, there is a 30%-50% chance that some localized MVFR cigs
will develop over high terrain areas including KGCN/KFLG between
06Z and 15Z. Breezy overnight winds will increase in speed after
15Z, becoming southwest 15-25 kts gusting 25-35 kts through 02Z
Wednesday.

OUTLOOK...Wednesday 18/06Z through Friday 20/06Z...VFR conditions
expected. On Wednesday and Thursday, southwest winds at 10-20 kts
gusting 20-30 kts. A few showers are possible in northwest
Arizona late Thursday.

&&

.FIRE WEATHER...Today through Wednesday...Scattered showers and
thunderstorms are expected through this morning, mainly east of a
Payson to Four Corners line. Dry weather will arrive by this
afternoon. Today look for south to southwest winds at 10 to 25 mph
with gusts of 25 to 35 mph. Wednesday will see afternoon southwest
winds at 10 to 15 mph with gusts to 25 mph.

Thursday through Saturday...Remaining cool, breezy and mostly dry.
Another low pressure system could bring a few showers to northwest
Arizona late Thursday into Friday. Look for southwest winds at 10 to
20 mph gusting to 30 mph Thursday and Friday, becoming light
northerly by Saturday for most areas.

&&

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

&&

$$

PUBLIC...Humphreys
AVIATION...RR
FIRE WEATHER...McCollum

For Northern Arizona weather information visit
weather.gov/flagstaff