Wildfire in Arizona, August 19 to 31, 2025

Area Forecast Discussion
National Weather Service Tucson AZ
911 AM MST Tue Aug 19 2025

.SYNOPSIS...Isolated to scattered thunderstorms this week across
Southeast Arizona, with day to day variability in intensity and
chances. The big story for Southeast Arizona will be the extreme
heat returning the second half of the week. An Extreme Heat
Warning is in effect Wednesday morning through Friday evening.

&&

.KEY MESSAGES...

- Main story will be the increase in temperatures through the week
  and into the weekend, especially the abnormally warm low
  temperatures, resulting in areas of Major HeatRisk.

- Extreme Heat Warning in effect 10 am Wednesday to 8pm Friday for
  all lower desert areas in southeast AZ, including Pinal and Pima
  counties, the Upper Gila River Valley and the Upper San Pedro
  River Vally.

- Daily monsoon chances through the upcoming week, mainly bringing
  Minor Risk of strong, gusty winds and localized flash flooding
  with any strong thunderstorms.

&&

.UPDATE...

Based on satellite and radar data, the large swath of mid-level
clouds and mostly virga showers moving across Pima and Cochise
counties are continuing to dissipate and shift westward this
morning. The mostly cloud-free areas are across Graham/Greenlee
counties, where the better instability will develop this
afternoon. Latest models/meso analysis suggest the White Mountains
and just south of the Sierra Vista/International Border are the
primary areas for strong storms today, with mostly
isolated/scattered showers and low-end thunderstorms for other
areas east and south of Tucson. Even the two areas that see
'strong' storms today will likely see sub-severe winds with a
30-50% of winds over 35-40 mph today. Mean wind is fairly light
(5-10 knots), but with marginal instability (500-1000 J/kg), only
a minor risk for localized flash flooding today, primarily for the
strong storms that move over vulnerable/flash flood-prone areas.
Isolated showers are possible in the Tucson Metro today, mainly
focused on the eastern edges of the Valley, bringing little if any
impacts.

&&

.PREV DISCUSSION... /issued 230 AM MST Tue Aug 19 2025/

.DISCUSSION...At this writing, very light showers are passing
through the Graham County and southwestern portion of Cochise
County. Very light accumulations were observed at the rain gauges,
generally 0.05 to 0.1 inches. Showers will pass northwest and
dissipate by 4AM. A high pressure center is hovering around the
Four Corners which will bring two forecast points for the rest of
the week: chances for thunderstorms and heat.

The influx of moisture has already arrived over the region. This
will provide chances for thunderstorms and rain showers each day.
The high center will push the moisture around...from the
southeasterly to easterly...the area. This will be the constant
theme of variability of coverage and intensity through the week.
Today's highest chances will be Tucson and east as the PWATS will
be around the 75th percentile per the 00Z HREF. The White
Mountains has one of best chances for storms and a 50% gust
potential for 30 kts or more, whereas the other locations have at
least a 10% chance for 30 kt gusts. Tomorrow, the chances will
expand as far west as Why, AZ.

High pressure brings one of the good 'old Arizona summer
classics...heat. Temperatures will continue to trend warmer each
day and staying above normal through majority of the work week.
Our overnight lows will also be elevated and near daily low highs
records, resulting in Major HeatRisk in the lower elevations.
There is an Extreme Heat Warning starting on Wednesday through
Friday.

Looking beyond this week, the upper pattern is poised to bring a
change in the flow. The ensemble models are showing a troughing in
the Pacific Ocean and the high breaking down a bit, resulting in
southerly flow. That leads to tapping into moisture sources from
the south which brings high chances for rain showers and
thunderstorms. That being said, it is over a week out and it
depends on how close the troughing and the high position is by the
weekend. This scenario will also bring temperatures down to near
normal.

Otherwise, stay cool this week.

&&

.AVIATION...Valid through 20/12Z.

SCT-BKN clouds 10-14k AGL ft through the forecast period. Isolated
light -SHRA this morning near KSAD and along the International
Border until 19/11Z. Increased chances for scattered -SHRA/-TSRA
after 19/18Z for terminals from KTUS east. Light and terrain
driven winds through the forecast period with afternoon gusts up
to 20kt. Gusts up to 40kts are possible with any -TSRA. Aviation
discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Expect daily chances for thunderstorms and
wetting rain showers into next week. Min RHs will generally be
15-20 percent in the lower elevations and 20-30 in the mountains.
Winds will generally be less than 15 mph with typical afternoon
gusts up to 20 mph into next week. Temperatures will be above
normal this week, with an Extreme Heat Warning in the lower
elevations of Southeast Arizona Wednesday through Friday.

&&

&&

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

&&

UPDATE/KEY MESSAGES...Peters
DISCUSSION...Strongman

Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson