az discuss
Office: PSR
FXUS65 KPSR 140006
AFDPSR
Area Forecast Discussion
National Weather Service Phoenix AZ
506 PM MST Sun Sep 13 2026
.UPDATE...00Z Aviation Discussion.
&&
.KEY MESSAGES...
- Abundant moisture will remain situated across the eastern half
of Arizona providing enhanced chances for showers and
thunderstorms through the middle portion of the week, especially
over the mountain locations.
- Although uncertainty remains, there will be potential for some
storms to produce strong gusty and heavy rainfall leading to
localized flash flooding over the next several days.
- Near to slightly above normal temperatures are expected
throughout the upcoming week.
&&
.SHORT TERM /Today through Monday/...
Latest objective analysis depicts the subtropical ridge of high
pressure situated over Texas while a robust upper-trough is
situated over the northwestern CONUS. The ridge of high pressure
is forecast to reposition over the southeastern states while broad
troughing will remain situated to the northwest of the region
through much of the upcoming week. This overall pattern
configuration will continue to result in south to south-southwest
flow over the area, aiding with periodic moisture influxes and
thus an elevated potential of shower and thunderstorm activity,
mainly across central and eastern AZ.
The 12z KPHX sounding from early this morning depicted a very moist
airmass in place with a low-level mixing ratio of 14 g/kg and PWATs
in excess of 1.9". The abundant moisture already in place combined
with strong daytime heating will result in MLCAPE values this
afternoon between 1500-2000 J/KG across much of south-central AZ
with near zero convective inhibition. Even though the thermodynamics
look very favorable for thunderstorms, the main limiting factor
for widespread coverage continues to be lack of good upper-level
forcing for ascent given that most of the jet dynamics associated
with the troughing pattern over the northwestern states will
remain to the north of the region. Therefore, thunderstorm
activity this afternoon through early this evening will be
orographically induced, with the latest hi-res guidance showing
isolated to widely scattered activity across the eastern and
southeast third of AZ this afternoon. However, even though the hi-
res guidance shows little to no activity further west into Pinal
and Maricopa Counties, given the lack of convective inhibition in
place, it will not take much to get storms to pop up in the
smaller terrain features such as the Table Top Mountains and the
Estrellas, with potential outflows potentially instigating new
storm development in the lower elevations, including into portions
of the Phoenix area. With these storms that do develop, given the
very moist environment in place, heavy rainfall leading to
localized flash flooding will be the primary threat with a
secondary threat being strong downburst wind gusts given that
DCAPE values are expected to range between 1000-1200 J/KG. With
the loss of daytime heating, storm activity should diminish by
early this evening.
Heading into the overnight and early morning hours on Monday,
several of the hi-res guidance indicate a round of elevated
showers and storms materializing across portions of south-central
AZ, including the Phoenix area. This is likely due to a northern
Sonora storm complex that is being depicted by guidance to develop
later this evening and is likely to send a gravity wave/outflow
northward and aid as the triggering mechanism for convective
development. Latest NBM is honing in on this potential, showing
PoPs between 30-50% from central Phoenix eastward into Gila
County. Heading into Monday afternoon, there is a greater signal
for better storm coverage across southeast AZ with activity
impacting the higher terrain areas east of Phoenix. However, given
that the convective inhibition will once again be nearly absent
due to abundant moisture in place with low-level mixing ratios of
12-14 g/kg and at least 1500 J/KG of MLCAPE assuming the morning
activity does not disrupt the daytime heating significantly, a
modest outflow is likely to be sufficient to trigger additional
storm activity across the lower deserts of south-central AZ.
Similar to today, heavy rainfall leading to localized flash
flooding will be the primary threat.
Temperatures during the next couple of days will be near to slightly
above normal levels with afternoon highs ranging between 100-107
degrees, with the warmest readings across the western deserts,
along with above normal early morning lows in the low to mid 80s.
This will maintain the overall HeatRisk level in the moderate
category.
&&
.LONG TERM /Tuesday through Saturday/...
The weather pattern through at least the middle of the week will
continue to support good moisture levels over at least the eastern
half of Arizona and likely improved upper level ascent for Tuesday-
Thursday. Tuesday may involve a brief period of drier air moving
into south-central Arizona from the southwest and this shows up in
the fairly limited PoPs Tuesday afternoon/evening. However, NBM
guidance shows a resurgence of moisture and rain chances during the
overnight hours Tuesday night/Wednesday morning. Chances Wednesday
into Thursday are also looking better with a potential disturbance
tracking northward into central/eastern Arizona at some point.
Needless to say, the model differences call into question the best
timing for rain chances and the exact areas, but as long as the
upper level support and good moisture remain present chances will
remain elevated.
WPC has added a slight risk on the Days 2-4 (Monday- Wednesday)
Excessive Rainfall Outlooks over the eastern Arizona high terrain.
It would not be surprising for subsequent issuance's of the EROs to
extend the risk through Thursday or even Friday depending on the
forecast available moisture. Although the risk for heavy rainfall
and flooding will be present through at least the middle of the
week, the risk for strong downdraft/outflow winds is likely to
decrease with guidance showing decreasing forecast DCAPEs. Models
are still trending toward drier air finally moving eastward through
most of Arizona by Friday or Saturday. This should mostly shut down
rain chances over the lower deserts and decrease chances over higher
terrain areas.
Temperatures throughout the entire week are expected to remain
fairly close to seasonal normals with the lowest forecast highs
occurring on Tuesday and Wednesday. As long as models are correct
with the drying trend late in the week into next weekend,
temperatures are favored to drift back to above normal with highs
more in a 103-108 degree range by Friday or Saturday.
&&
.AVIATION...Updated at 0000Z.
South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
The main aviation concerns this forecast period will be the
potential for SHRA/TSRA developing over the Phoenix Metro early
Monday morning around sunrise. There is still a good amount of
uncertainty as to which terminals see any direct impacts.
Currently chances for TS are highest (20-30%) at KIWA and KPHX.
The main impacts from any storms that do develop will be gusty
S-SE winds and potential brief reductions in vsby due to heavy
rainfall. High-res guidance indicates the initial batch of
SHRA/TSRA clearing east of the TAF sites by 16Z-17Z. There could
also be a second round which develops by the late afternoon/early
evening, and a PROB30 group has been added to KPHX to reflect this
possibility. The wind forecast will not be a straight forward
tomorrow with most models showing southerly flow prevailing
through much of the day before returning out of the southeast by
the early evening. Clouds will remain few through this evening,
becoming SCT to BKN by early Monday morning with bases hovering
around 8-9 kft.
Southeast California/Southwest Arizona including KIPL and KBLH:
No aviation weather concerns will exist through the TAF period
under mostly clear skies. Confidence is high that winds will
behave similar to the past 24 hours varying between southeasterly
and southwesterly at KIPL and southerly to southwesterly at KBLH
with periods of calm and vrb conditions anticipated early Monday.
&&
.FIRE WEATHER...
Chances for scattered showers and isolated storms will continue
today before increasing and becoming more widespread into the south-
central Arizona lower deserts beginning Monday. Moisture levels will
remain high enough to support localized heavy rainfall with any
storms. Minimum humidity levels over the next several days will only
fall into a 15-25% range in western districts and 25-40% in eastern
districts. This will follow fair to good overnight recovery of 40-
70%. Outside of thunderstorms, winds will generally remain light
with a south to southwest heading though nearly calm conditions
will be common in the morning hours.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&
$$
SHORT TERM...Lojero
LONG TERM...Kuhlman
AVIATION...Salerno
FIRE WEATHER...Kuhlman
Office: TWC
FXUS65 KTWC 131933
AFDTWC
Area Forecast Discussion
National Weather Service Tucson AZ
1233 PM MST Sun Sep 13 2026
.SYNOPSIS...An active week ahead with daily chances of showers
and thunderstorms. Elevated precipitation chances Monday with a
Flash Flood Watch for portions of southeast Arizona. Daily
high temperatures will fluctuate between near normal and a few
degrees below normal.
&&
.DISCUSSION...The calendar shows mid September but still no
transition to drier non monsoonal weather for the upcoming work week
as deep layer southerly flow continues. Moisture levels remain quite
elevated today with PWAT values ranging from 1.3 to 1.7 inches
(lowest near the NM border and highest west of Tucson). These values
are about 150 to 200 percent of normal and with the southerly flow
remaining this week, the above normal moisture isn't going anywhere.
Now with the abundant moisture in place, we start looking for other
atmospheric signals for more active days. The sun angle in September
certainly isn't as good now compared to July or August so it's
really helpful to have other upper level support for better storm
chances. Not much upper level support for today, though isolated to
scattered showers and thunderstorms will continue through the
afternoon into early evening mainly from Sells eastward. Heavy rain
will be the main threat.
Monday is shaping up to be a more active day. While we can't rule
out a bit of morning convection, HREF/REFS/UofA WRF-HRRR are leaning
to a more active afternoon into evening as the combination of a
ample instability (MLCAPE 1000-2000+ J/KG) and some modest
mid/upper level support result in more widespread shower and
thunderstorm chances. Given the anomalously high moisture and broad
wetter antecedent conditions over the past few days it won't take as
much rain for to get notable responses in our washes and rivers. The
HREF has a large 50 to 90 percent area of 1 inch or greater of rain
(40-km neighborhood probability) from Tucson eastward with about 10
percent for 2 inches of more. Given the increasing confidence for
scattered to numerous thunderstorms Monday and heavy rain potential
along with previously mentioned wet antecedent conditions, decided
to hoist a Flash Flood Watch from late Monday morning through Monday
evening on a line from Sasabe-Eloy eastward but excluding the White
Mountains where the setup isn't as favorable up there.
Beyond Monday, it's looking like an active week. Tuesday will likely
be a bit more down compared to Monday, though still will have
isolated to scattered showers and thunderstorms. Wednesday into
Thursday are looking like another up period with some enhancement of
a disturbance coming in from the south. Westerly flow aloft tries to
establish itself Friday into next weekend which should result in
decreasing precipitation chances especially from Tucson westward but
still plenty of time to sort out those details.
Temperatures this week will range from near normal to up to a few
degrees below normal.
&&
.AVIATION...Valid thru 15/00Z.
SCT-BKN clouds 8k-10k ft AGL with ISOLD-SCT SHRA/TSRA thru 14/04Z.
Can't rule out ISOLD SHRA/TSRA overnight into Monday morning but
confidence low. Scattered to locally numerous SHRA/TSRA expected to
develop aft 14/18Z and continue thru end of valid pd. SFC winds
SWLY/WLY 5-10 kts thru 14/04Z then terrain driven less than 10 kts
thru 13/16z. SLY/SWLY SFC winds 6-12 kts resume aft 13/16Z thru end
of valid pd. Aviation discussion not updated for TAF amendments.
&&
.FIRE WEATHER...An active week ahead with daily chances of
showers and thunderstorms. High temperatures will fluctuate
between near normal and a few degrees below normal. Min RH
values mainly 20 to 45 percent in the valleys and 35 to 65
percent in the mountains over the next week. RH recoveries will
continue to be excellent overnight. Winds will generally remain
less than 15 mph and terrain driven. Gusty and erratic winds
will accompany thunderstorms.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...
Flood Watch from Monday morning through Monday evening for
AZZ503>509-511>514.
&&
$$
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Office: FGZ
FXUS65 KFGZ 132307
AFDFGZ
Area Forecast Discussion
National Weather Service Flagstaff AZ
407 PM MST Sun Sep 13 2026
.SYNOPSIS...An active pattern will remain in place through the end
of the week. Greatest coverage for showers/storms look to be
during the afternoon/early evening hours each day, but we cannot
rule out the potential for overnight activity. Otherwise, expect
seasonable daytime highs and breezy southwest winds.
&&
.DISCUSSION...Storms have fired up across portions of our CWA,
especially in Yavapai and Coconino Counties where model guidance
suggests the strongest instability is. Sufficient moisture remains
in place across the state as shown in our above normal PW values.
Another shortwave is the main culprit for today's activity. The
sounding from this afternoon does show a decent cap, so storms
aren't very severe in nature, but that could change through the
rest of the afternoon. For now, training storms leading to flash
flooding seems to be the main concern.
A broad trough across the West Coast will lead way to a handful of
embedded shortwaves pushing through the state this week. This will
keep us in a rather activity pattern each day. Although guidance
suggests convection being rather widespread/heaviest during the
afternoon periods, overnight activity could quickly downplay how
each day turns out. Between the atmosphere being worked over and
likelihood of debris clouds, we could see quieter days than
models are depicting at this time. As always, we'll do our best,
but in environments like this taking it day-by-day is usually the
best plan of attack.
By next weekend overall precipitation chances look to diminish,
but a few isolated showers across eastern Arizona may still
remain in the forecast. More details on that later.
&&
.AVIATION...Monday 14/00Z through Tuesday 15/00Z...Expect patchy
ceilings 4-7 kft AGL over the next 24 hours. Mainly isolated
SHRA/TSRA overnight and scattered-numerous SHRA/TSRA between
18Z-00Z producing occasional MVFR conditions. Daytime winds
outside of gusty thunderstorms/outflows, south to southwest at
10-20 kts.
OUTLOOK...Tuesday 15/00Z through Thursday 17/00Z...Expect patchy
ceilings at 5-8 kft AGL. Mainly scattered-numerous SHRA/TSRA
between 18Z-03Z with isolated SHRA/TSRA otherwise. Occasional
MVFR conditions anticipated. Daytime winds outside of
thunderstorms/outflows, south to southwest at 10-20 kts.
&&
.FIRE WEATHER...Monday and Tuesday...Scattered showers and
thunderstorms will persist into Sunday evening, especially over
Yavapai and Coconino counties. Gradual clearing overnight, but
redevelopment may occur early Monday morning as outflows approach
from the south. The chances for showers and thunderstorms continue
Monday and Tuesday, but the focus shifts eastward, due to a trough
passing to our north. Mainly daytime south through southwest winds
from 10 to 20 mph, with gusts to 25 mph, can be expected each day.
Temperatures will remain right around normal.
Wednesday through Friday...Chances for showers and thunderstorms
continue, possibly becoming more widespread during this time frame.
Daytime southwest winds from 10 to 20 mph.
&&
.FGZ WATCHES/WARNINGS/ADVISORIES...None.
&&
$$
PUBLIC...Konieczny
AVIATION...McCollum
FIRE WEATHER...Peterson
For Northern Arizona weather information visit
weather.gov/flagstaff
