260
FXUS65 KTWC 191700
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
1000 AM MST Wed Aug 19 2026

.SYNOPSIS...An uptick in afternoon showers and storms returns to
Southeast Arizona this afternoon and evening with the strongest
storms capable of producing isolated strong to severe wind gusts,
blowing dust, and heavy rainfall. Blowing dust could impact travel
along and near Interstate 10 and Interstate 19. Moderate to major
HeatRisk continues with forecast high temperatures 5 to 7 degrees
above normal.

&&

.UPDATE...High resolution guidance as of this writing depict
increasing confidence for storms capable of producing strong, gusty,
and erratic outflow winds, blowing dust, and locally heavy rainfall
this afternoon and evening.

The 19/12Z run of the HREF depicts a high chance (70-90%) for gusty
outflow winds exceeding 35 mph, with a slight chance (10-20%) for
gusts to exceed 55 mph. The Storm Prediction Center (SPC) has
upgraded most of southeast Arizona into a slight risk for
thunderstorms today capable of producing isolated severe wind gusts
which is consistent with the aforementioned wind exceedance
probabilities. Scattered showers and storms forming around Noon MST
will become more widespread and perhaps more organized later in the
afternoon as they propagate west and south toward the Tucson Metro
(most likely around the 5 pm to 7 pm MST timeframe) and
continuing into Central Pima County into the evening. Storms
will be supported by modest deep layer (0-6 km) shear of around
20-25 kts with mean storm motions of around 10-15 mph. As
always, blowing dust becomes an increasing concern with gusty
outflow winds from organized thunderstorm clusters. But with the
increasing probabilities for gusty winds from model guidance,
my confidence in organized thunderstorm outflows and potential
haboob formation for today are notably higher than they were at
this point yesterday. The night shift did coordinate with the
Phoenix WFO to hoist a Blowing Dust Advisory for portions of
Pima and Santa Cruz counties extending into Pinal and Maricopa
counties. That will be in effect from 3 pm to 10 pm today.
Motorists should use caution when driving this afternoon and
evening, especially along the Interstate 10 and 19 corridors.

Secondarily, we`ve seen a notable surge of moisture over the past 24
hours. The Weather Prediction Center has upgraded areas from Tucson
metro west from a marginal risk into a slight risk for excessive
rainfall with isolated instances of flash flooding. Surface
dewpoints across the area have surged into the mid/upper 60s over
the past 24 hours. Satellite estimated precipitable water ranges
from about 0.9 inches in the White Mountains and along the
international border in Cochise County to 1.4 inches in western Pima
and southeast Pinal counties with even higher amounts south of the
international border. HREF depicts likely chances (70-90%) for
precipitable water to exceed 1.5 inches this afternoon and evening
as even richer and deeper moisture moves into the area. The deeper
moisture has been a rapidly evolving situation over the last few
days, and in my opinion the guidance is looking a bit more
impressive than yesterday with a slight chance (10-20%) for hourly
rainfall rates exceeding an inch per hour.

&&

.PREV DISCUSSION... /issued 236 AM MST Wed Aug 19 2026/

The combination of ample moisture moving into Southeast Arizona
from the Gulf of California and a more favorable weather
pattern aloft will result in an active Monsoon thunderstorm day
across all of Southeast Arizona. Expect storms to initially
develop over the Gila National Forest of New Mexico and the
higher terrain of northern Graham and northern Greenlee counties
around mid- day, then drive southwest toward the valleys of
Southeast Arizona through the afternoon, then across central and
western Pima county this evening. The primary concern with
storms today is that they will be capable of producing organized
storm outflow winds to 45-55 mph, potentially producing
localized dense blowing dust. A Blowing Dust Advisory is in
effect from 3 PM MST this afternoon through 10 PM MST this
evening for the western portions of Southeast Arizona. Deep
moisture moving into the region from the Gulf of California
(gulf surge) will bring about a secondary concern of heavy
rainfall capable of producing isolated flash flooding,
especially across central and eastern Pima county.

The upper pattern this morning is defined by a 500 mb high center
over NW AZ, and a SW-NE tilted 500-300 mb ridge axis extending from
the NRN Baja Peninsula northeast into NW AZ. This ridge axis will
move into NRN Arizona today and become oriented along a W-E axis.
This will result in a modest area of deformation/lift aloft along a
general axis extending from Safford to Sells. In addition, the
latest GOES precipitable water imagery indicated a gulf surge was
making its way into SW AZ this morning, with PWAT values between
1.50 and 1.75 inches across central and western Pima/WRN Pinal and
Maricopa counties. Surface dewpoints have been on the increase west
of Tucson, with values ranging from the mid 60s to lower 70s. An
even  deeper area of moisture with PWATs values between 1.80 and
2.00 inches was currently in the NRN gulf of California, and should
advect into the lower deserts through the day today. With the strong
heating the past several days along with this deep moisture, MUCAPEs
between 1500-2000 J/kg will be available across the western half of
SE AZ this afternoon. The drier sub- cloud layer SE and S of Tucson
today will initially provide the opportunity for strong outflow
winds of 45-55 mph. These outflows will generally kick to the west
and northwest into the evening. Given the high CAPEs available,
these boundaries will initiate additional convection along them with
new development re-inforcing the outflows. This is supported by the
19/00Z HREF with 10-20% neighborhood probabilities of storms
outflows 50+ kts across Santa Cruz/central and ERN Pima and SE Pinal
counties between 3-10 PM MST. Given this, we thought it would be
necessary to hoist a Blowing Dust Advisory for dense blowing dust
and the potential for a haboob formation this afternoon impacting
mainly Pima and SE Pinal counties.

The NWLY/WLY flow in the lower-mid levels will push this deeper
moisture into the mid-levels of storms today, increasing the
potential for heavy rainfall across central and eastern Pima
counties (including the Tohono O`odham Nation and the Tucson Metro
Area). Coordinated with the WPC this morning to elevate these areas
into their SLGT category on their Day 1 Excessive Rainfall Outlook
(ERO) for today.

Otherwise, we will remain in an active weather pattern into the
weekend as the upper high center moves toward the Four Corners
Thursday and Friday, then into the Rockies by Saturday afternoon.
The Monsoon season rolls on.

&&

.AVIATION...Valid through 20/00Z.
FEW-SCT 12-15k ft AGL through 19/20Z, then SCT-BKN 7-11k ft AGL BKN-
OVC 12-15k ft AGL with scattered to numerous -SHRA/-TSRA through
20/05Z. Gusty and erratic outflow winds possible near TSRA with
gusts to 40-50 kts. Organized outflows may produce VSBY less than
1/2SM in BLDU, especially from KTUS west and northwest. Winds
outside of thunderstorms mainly light and terrain driven. Aviation
discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Strong thunderstorms will return to Southeast
Arizona today. The primary concern with storms today is that they
will be capable of producing organized storm outflow winds 45-55
mph, potentially producing localized dense blowing dust. Deep
moisture moving into the region from the Gulf of California will
bring about a secondary concern of heavy rainfall capable of
producing isolated flash flooding, especially across central and
eastern Pima county. Otherwise, an uptick in storm strength and
coverage into the upcoming weekend. Hot conditions will persist this
week with an Extreme Heat Warning in effect today through Friday for
portions of the Southeast Arizona. Winds mainly light and terrain
driven. Strong, gusty and erratic winds will accompany
thunderstorms. Minimum relative humidities 15-25 percent in lower
elevations with 25-35 percent in the higher terrain.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...

Extreme Heat Warning until 8 PM MST Friday for AZZ501-502-504>506-509.

Blowing Dust Advisory from 3 PM this afternoon to 10 PM MST
this evening for AZZ501>506.

&&

$$

DVS

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