601
FXUS65 KTWC 131517
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
817 AM MST Sun Jul 13 2025

.SYNOPSIS...Above normal temperatures will continue through
Monday. Increasing monsoon activity is expected in to begin
today in areas east and south of Tucson. These chances increase
across southeastern Arizona through the work week. As moisture and
storm chances increase, temperatures will drop back down to
seasonable levels Tuesday onwards.

&&

.UPDATE... Mostly sunny skies this morning with some dissipating
clouds over northern Graham and Greenlee counties. Minor to
Moderate HeatRisk today as the high temperatures will be around
100 to 105 degrees this afternoon. Today is still looking to be an
active monsoon day. Satellite derived PWATs this morning are
around 1 to 1.15 inches and expected to persist throughout the
day. More moisture may be advected into the area from convection
later this afternoon into the evening. Several convective
allowing models are showing two convective systems developing, one
in Graham and Greenlee counties and the other in Cochise and
Santa Cruz counties. The Graham and Greenlee counties system has
storms starting early this afternoon around 1 to 2 PM moving
south-southwest off the Whites. The other system in Cochise and
Santa Cruz counties has storms developing around 2 to 3 PM moving
west-southwest. Both systems have the potential for strong, gusty
outflows, locally heavy rainfall and blowing dust. There is a
Blowing Dust Advisory for these counties (with the exception of
Santa Cruz) this afternoon from 2 to 8 PM. With blowing dust
expect visibilities to be between 1/4 to 3 miles. There is a
lower chance (20-30 percent) for storms to impact the Tucson area
however there is still the potential for blowing dust to move
into the area from storms to the west or south. There is also the
potential for a strong storm to push moisture and lift into the
Tucson area that could initiate storms to develop. If that does
happen, storms in the Tucson ares would be later this afternoon
into the early evening hours.

&&

.PREV DISCUSSION... /issued 341 AM MST Sun Jul 13 2025/

.DISCUSSION...After a bit of a respite from Monsoon thunderstorm
activity the past several days with the quiet and hot conditions
we have experienced across Southeast Arizona, it looks like we are
getting back into the mix starting today. The upper pattern this
morning is defined by a stacked ridge of high pressure aligned
with a neutral N-S orientation off the southern California coast,
a weak secondary high center at 500 mb positioned across northern
Arizona, a weak shortwave in between these two features from
Southeast Arizona into west-central Arizona, and a baggy trough
at 300 mb extending from the Upper Midwest into southern New
Mexico.

As the day progresses today, expect the stacked ridge to drift
west becoming positively tilted into the Great Basin. As this
occurs, we will see several things that will assist the overall
lift east of Tucson this afternoon/evening. First at 500 mb, a
divergent northwest flow begins to develop near the Arizona/New
Mexico border with a larger scale area of deformation/stretching
developing as the upper ridge is re-orienting itself and pulling
away. At 300 mb, the baggy upper trough is brought west into SE
AZ/NE Sonora Mexico resulting in a stacked area of deformation
aloft across the eastern portions of the forecast area.

The moisture profile across the region is defined by an 850-700 mb
theta-e ridge extending from central Sonora into south central
Arizona. The latest GOES PWAT imagery indicated drier values of
precipitable water (0.85-0.95 inches) east of Tucson in
Cochise/Graham/Greenlee counties, even drier air (0.65-0.75
inches) across western Pima county and values between 1.10 and
1.20 inches extending along the International Border east of
Sasabe with the highest values extending from central Sonora into
south central Arizona and between Tucson and Phoenix. The drier
airmass aloft as well as the dry sub-cloud layer to the east of
Tucson today will enhance evaporation within thunderstorm
downdrafts today...increasing the potential for damaging outflow
winds winds. The 13/03Z SREF indicates a 50-90% chance of DCAPE
values of 1500 J/kg across southern Graham county into extreme SW
NM at 00Z this afternoon. The 13/00Z HREF has been consistent
depicting a 50-90% neighborhood (40-km) probability for wind gusts
in excess of 30 kts across Graham/Cochise/Santa Cruz counties
Sunday afternoon with a 10-30% neighborhood probability of 50+ kts
across eastern Graham/Cochise and Santa Cruz counties. The big
concern with these wind gusts to 45-55 mph will be the potential
for dense blowing dust, especially originating from the Lordsburg
Playa and impacting the San Simon Valley and the areas along
Interstate 10 between Willcox and the NM state line in northeast
Cochise county. We currently have a blowing Dust Advisory for the
areas east of Tucson from 2 pm to 8 pm MST today and this still
looks on track.

My only concern is that storms look like they will develop in two
distinct areas. The first near the Gila National Forest in west
central New Mexico early this afternoon and a second area a few
hours later developing across southern Cochise and Santa Cruz
counties. The storms moving into the area from NM wont be as
strong as the other area, but the dry-air/DCAPE will result in a
higher potential for severe/damaging thunderstorm outflow
winds/blowing dust. The stronger storms across southern Cochise
and Santa Cruz county will have that theta-e ridge to feast upon
and there will be an equal threat for gusty outflow winds and
heavy rainfall resulting in the risk for localized flash flooding.
I considered expanding the area of the Blowing Dust Advisory to
cover the lower elevations of Santa Cruz and central/eastern Pima
county but held off because they may not have a strong enough
organized outflow and may only see localized patchy blowing dust.

In any event, these transition days from quiet to active are
usually busy and severe in nature for our neck of the woods. The
SPC is trending this direction as well, and they have put the
eastern half of our forecast area into the Marginal risk for
severe thunderstorms on their Day 1 Convective Outlook for today.

Otherwise, the ensemble members (especially the ECMWF) are still
excited about increasing precipitable water values 1-2 standard
deviations above normal the second half of the week into next
weekend. With an upper low wobbling around over the northern Gulf
of California, this should result in a better chance for
precipitation across Southeast Arizona. The primary threat will
transition away from damaging winds the next few days to a risk of
heavy rainfall/flash flooding by the end of the week.

&&

.AVIATION...Valid through 14/12Z. SFC wind from the southeast
less than 10 kts this morning thru 13/19Z, then west to
northwest 10-15 kts, with 15-20 kts and gusts to 30 kts at KSAD.
Skies SKC thru 13/20Z, then SCT-BKN clouds 8k-11k ft AGL with SCT
-TSRA/-SHRA with areas of 1-3SM BLDU possible east and south of
Tucson between 13/20Z and 14/04Z, including both KDUG and KOLS.
Aviation discussion not updated for TAF amendments.

&&

.FIRE WEATHER...An uptick in monsoon activity is expected to begin
today and persist into next week as the upper high shifts to a
more favorable location aloft. Temperatures will remain above
normal through Monday, then drop back down to near or slightly
below normal by mid to late next week. Winds will remain westerly
from 10-15 mph, with occasional gusts at or above 25 mph.
Afternoon RH values in the low lying areas will be between 10-15%
through Monday, then 20-30% through the remainder of the week.

&&

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
Blowing Dust Advisory from 2 PM this afternoon to 8 PM MST this
evening for AZZ507>509.

&&

$$

Malarkey

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