344
FXUS65 KTWC 041627
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
927 AM MST Tue Aug 4 2026

.UPDATE...The atmosphere is primed for another day of scattered
strong to severe thunderstorms this afternoon and evening. An
elongated ridge is in place with modest mid-level flow of 20-30
kts at 500 mb. This will lead to 0-6 km shear of 25-35 kts with
CAPE values 1000-1500 J/kg and seasonal PWAT values. Hi-res
guidance shows initial development over the White Mountains and
Sky Islands east of Tucson by mid-afternoon. Storms then
progress westward into the lower elevations of Santa Cruz,
Cochise, and eastern Pima Counties late afternoon into the
evening. Heavy rainfall will be a threat in Cochise and Santa
Cruz Counties with HREF one inch in one hour probabilities
within 25 km of a point 20-50 percent between 4 PM - 9 PM.
Areas that received heavy rain yesterday will also be more
likely to see runoff and flash flooding. Because of this a Flood
Watch has been issued for these areas from 3 PM - 11 PM. With
the aforementioned shear some storms could be rotating, which
could lead to an isolated hail threat and a more widespread
severe wind threat. Model soundings also show a nose of dry air
around 400 mb which would act to enhance downdrafts through
entrainment. Because of all of these factors some storms may be
capable of wind gusts 70-80 mph. There is also a small tornado
threat as well with 0-3 km helicity values 150-250 m^2/s^2. The
best environment for a tornado looks to be along the
international border, but confidence is low in any tornado
developing.

&&

.SYNOPSIS...Chances for thunderstorms will develop each
afternoon and evening this week with day to day variability.
Thunderstorms may produce severe outflow winds with areas of
blowing dust, as well as locally heavy rainfall with a flash
flooding risk. High temperatures will remain a few degrees above
normal through the week.

&&

.DISCUSSION...Yesterday was an active monsoon day across
Southeastern Arizona with recorded wind gusts of 58-88 mph, with
a 74 mph wind gust recorded at Tucson International Airport.
Along with the strong outflow winds, there was dust storms
bringing near zero visibilities.

A weak outflow from mexico is currently triggering
weak showers/thunderstorms for areas south of Tucson in southern
Cochise and Santa Cruz counties. With this lingering overnight activity
and the needed time for the atmosphere to recover, leading to a
later start time for storm initiation this afternoon/evening.
This is showing up with the CAMs having initiation in the White
Mountains around noon/1 PM then more widespread initiation 2 to
3 PM. Storms will begin in the NE then slowly move SW/W over the
course of the afternoon and evening. Tucson will begin to have
storm chances beginning after 5/6 PM and moving westward into
the evening. Main impacts for storms today follow the
wind/blowing dust threat area wide, then an added flash flooding
threat areas south of Tucson along the International Border in
southern Cochise and Santa Cruz Counties. The 04/00Z HREF once
again is showing a large area of 10% probability of 50 kts (and
a small 30% probability as well). With this, the threat for
blowing dust continues with the storm outflows, so a Blowing
Dust has been issued for the portions of Graham and Cochise
counties. As for the flash flooding component, the 04/00Z HREF
is once again highlighting Cochise and Santa Cruz counties with
the 3 hour probability matched mean introducing a 10%
probability for 3 inches of accumulation in these areas.

Wednesday looks like a downtick in coverage and intensity,
however the moisture and favorable flow continues, so chances
for afternoon and evening thunderstorms remain.

Favorable flow for monsoon activity continues through the week
with the upper high drifting north towards the Four Corners with
day to day variability. Forecast high temperatures will fall to
2-4 degrees above normal, with some variability due to
thunderstorm activity and cloud cover.

&&

.AVIATION...Valid through 05/12Z.
Isolated to scattered thunderstorms expected to develop this
afternoon mainly between 04/21Z to 05/03Z with lingering
isolated activity through 04/06Z for areas east of KTUS.
Coverage around KTUS more likely 05/02Z-05/08Z and KOLS
05/02Z-05/08Z. Gusty erratic winds of 35-45 kts possible with
any thunderstorm with potentially blowing dust. Otherwise SFC
winds WLY/NWLY at 8-12 kts with occasional afternoon gusts to 20
kts. SFC winds light and terrain driven after 05/06Z. Scattered
thunderstorm chances return Wednesday afternoon and evening.
Aviation discussion not updated for TAF amendments.

&&

.FIRE WEATHER...An active monsoon period looks favorable this
week with daily chances for showers and thunderstorms each
afternoon and evening, with day to day variability. Minimum
relative humidity values will likely remain above 25-40 percent
through the week with temperatures 2-4 degrees above normal.
Outside of thunderstorms, winds terrain driven to around 10 mph
with occasional afternoon gusts to 25 mph.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
Flood Watch from 3 PM MST this afternoon through 11 PM this
evening for AZZ503-504-507-508-511>513.
Blowing Dust Advisory from 2 PM this afternoon to 8 PM MST this
evening for AZZ507>509-511>513.

&&

$$

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