Severe Thunderstorm Warning 37, NWS Tucson, AZ

Area Forecast Discussion
National Weather Service Tucson AZ
104 PM MST Thu Jul 31 2025

.SYNOPSIS...Scattered thunderstorms are expected this afternoon
and evening across much of southeastern Arizona. Periods of heavy
rain, isolated strong wind gusts, and blowing dust will be
hazards with any thunderstorm today. An isolated flash flood
threat accompanies today's thunderstorm activity. Thunderstorm
chances begin to decrease Friday as dry air moves in through the
weekend. Extreme heat is expected Friday through the weekend as
high temperatures become 7 to near 10 degrees above normal.
Temperatures remain above normal through next week.

&&

.KEY MESSAGES...
-Scattered thunderstorms are expected this afternoon and evening
 across much of southeastern Arizona. Chances begin to decrease
 Friday as dry air moves in through the weekend.

-Periods of heavy rain, isolated strong wind gusts, and blowing
 dust will be hazards with any thunderstorm today. An isolated
 flash flood threat accompanies today's thunderstorm activity.

-Extreme heat is expected Friday through the weekend as high
 temperatures become 7 to near 10 degrees above normal.
 Temperatures remain above normal through next week.

&&

.DISCUSSION...There are currently isolated thunderstorms in areas
south and east of Tucson in the mountains. There have been a few
lightning strikes so far, with some gusty winds in the 20-30 mph
so far. The storms have been struggling to get tall updrafts
thanks the the very dry layer aloft shown very well in the 18Z
sounding. Overall, the main threats continue to be strong gusty
outflow winds, possible blowing dust, and locally heavy rainfall.
The threat for isolated areas of flash flooding continues as the
storm motion is light at 5-10 kts, making the storms nearly
stationary and rain on the same area in a short period of time.
The push of moisture from the Gulf of California and Sonora,
Mexico continues with current surface dew points in Western Pima
County is in the low to mid 60s and satellite estimated PWs in
the 1.3 to 1.4 inch range. This moisture may be able to work its
way eastward through the NE flow aloft and/or outflows from
thunderstorms this afternoon. The 18Z sounding showed 1.27 inches
of PW, which is a tad more than yesterday, so storm activity in
Tucson is certainly possible this afternoon and evening. In terms
of wind, the HREF model is showing wind gusts of 30-40 mph with
thunderstorms, however that may be a tad underdone as the RAP
model is showing 1400-2000 J/kg of DCAPE allowing for dropping
thunderstorm cores to evaporate, cool, then accelerate the overall
collapse. This is shown by the 18Z sounding where there is
roughly 1800 J/kg of DCAPE in Tucson.

After today, a drying and warming trend begins Friday into the
weekend, thanks to the high pressure system will build to our
west. Temperatures will be 7 to 10 degrees above normal during
this time, with an Extreme Heat Warning in effect those days.
Major HeatRisk is expected for much of the valley locations, so
much of the population and those without adequate hydration and
air conditioning should prepare. Be sure to know where cooling
centers are, move outdoor plans to the morning or evening, and
keeping hydrated Friday into the weekend.

Forecast models are still in disagreement with how much moisture
can make it into the area early next week as the high pressure
shifts back to the east. This will determine how hot the area
will get mid to late next week. Some heat headlines may be needed
during this timeframe, so stay tuned.

&&

.AVIATION...Valid through 02/00Z.
Isolated to scattered thunderstorms thru 01/05Z. Brief periods of
heavy rainfall and gusty erratic winds possible with any
thunderstorm. Winds generally below 12 kts away from thunderstorm
activity, with occasional afternoon gusts to 20 kts. Aviation
discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Minimum relative humidities mainly above 20
percent today across southeastern Arizona. Scattered
thunderstorms are expected this afternoon and evening. Overall
winds are expected to remain under 15 mph with occasional
afternoon gustiness, however strong erratic winds are possible
with any thunderstorm. A drying trend is expected through the
weekend with high temperatures bumping up.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
Extreme Heat Warning from 10 AM Friday to 8 PM MST Sunday for
AZZ501>507-509-515.

&&

Tetrault

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