283
FXUS65 KFGZ 171553
AFDFGZ

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

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

&&

.UPDATE...Scattered showers and thunderstorms across eastern
Arizona continue to diminish this morning as drier air moves in
from the west. Expect cooler temperatures for this afternoon with
breezy to gusty southwest winds, 20-35 mph. Widespread dry
conditions are forecast through Wednesday. The weather pattern
remains unsettled through Friday, however, precipitation chances
will be minimal. Besides for cleaning about the POP forecast over
the next few hours, the remainder of the forecast is on track with
no changes needed at this time.

&&

.PREV DISCUSSION /353 AM MST/...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 17/12Z through Wednesday 18/12Z...Isolated to
scattered SHRA/TSRA are forecast to persist east of a Payson to
Four Corners line through around 16Z. MVFR conditions and hail
are possible with any stronger storms that develop. In addition,
there is a 30%-50% chance that some localized MVFR ceilings will
develop over high terrain areas including KGCN/KFLG until 15Z.
Winds will increase in speed after 15Z, becoming southwest 15-25
kts gusting 25-35 kts through 02Z then diminishing.

OUTLOOK...Wednesday 18/12Z through Friday 20/12Z...VFR conditions
are forecast. Wednesday and Thursday will see southwest winds at
10-20 kts gusting 20-30 kts. A few showers are possible across
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...LaGuardia/Humphreys
AVIATION...McCollum
FIRE WEATHER...McCollum

For Northern Arizona weather information visit
weather.gov/flagstaff