990
FXUS65 KTWC 271617
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
917 AM MST Fri Jun 27 2025

.SYNOPSIS...Afternoon and evening chances for showers and
thunderstorms are possible today south and east of Tucson, mainly
along the International border east of Nogales and closer to the New
Mexico border. Temperatures become hotter this weekend as conditions
dry out. Monsoonal moisture is expected to increase next week with
increasing precipitation chances, especially the second half of the
week including around Independence Day.

&&

.Key Messages...

-Temperatures will be on the increase this weekend, peaking Monday
with highs of 107 to 112 degrees in the deserts including Tucson and
Upper Gila River Valley. An Extreme Heat Warning is in effect Monday
for these locales.

-A few thunderstorms today mainly in Cochise County then drier
conditions return this weekend with only a slight chance of
thunderstorms along the Int`l border in Cochise County.

-Monsoon 2025 will swing into full gear next week. The heat will be
on the downward trend by midweek as moisture will be on the
increase. Initial monsoon storm threats will be focused more on
gusty winds, but will quickly transition more towards heavy rain and
flash flooding threats as the week progresses. This includes
Independence Day.

&&

.UPDATE...Higher pressure is gradually returning to the Desert
Southwest. The higher pressure building in will generally result in
subsiding air aloft, continued drying of the low and mid levels with
decreasing precipitation chances until deeper moisture returns.
However, to the east and south of Tucson, yesterday`s convective
activity near and east of the NM border has aided in providing some
additional boundary layer moisture to spill into the Upper Gila, San
Simon, and San Bernardino valleys of Graham, Greenlee, and
eastern Cochise counties. Similar to yesterday, GOES-19
precipitable water imagery showed values between 0.8" and 1" out
east along the AZ/NM border this morning. High resolution
convective allowing models depict perhaps a slight uptick in
convective activity this afternoon across Cochise, Graham, and
Greenlee counties compared to yesterday. Overall, this afternoon
there are slight chances (15-30%) for isolated shower and
thunderstorm activity this afternoon with the best chances
consolidated to near and along the AZ/NM and International
borders. Can`t rule out a heavier downpour and/or brief gusty
outflow or two with winds to around 45 mph in any stronger storm.

&&

.PREV DISCUSSION... /issued 213 AM MST Fri Jun 27 2025/

This forecast period will encompass our typical early monsoon
transition from extreme heat to increased moisture resulting in a
dramatic uptick in shower and thunderstorm chances as next week
progresses.

In the near term, the main focus will continue to be on hotter
temperatures this weekend as high pressure aloft builds over the
area. There is still ample moisture south and east of Tucson for
isolated to scattered showers and thunderstorms, mainly in Eastern
and SE Cochise County, though slight chances extend northward along
the NM border and westward to Nogales. Main concern for today will
be gusty outflow winds and brief downpours.

As the aforementioned high pressure strengthens this weekend,
increased subsidence and drying aloft will result in a drying trend
with generally dry conditions across our forecast area as any deeper
moisture to support showers and thunderstorms chances should remain
to our south and east. With that said, temperatures will be on the
rise this weekend and peak Monday. In coordination with WFO Phoenix,
we`ve gone ahead and upgraded to an Extreme Heat Warning on Monday
for the deserts of SE Arizona and Upper Gila River Valley with highs
107 to 112 degrees. The event is a bit borderline in terms of high
HeatRisk coverage but based on thickness regression, the NBM might
be underestimating high temperatures a degree or two. Expect a bit
of an uptick in thunderstorm chances Monday afternoon and evening,
mainly from Tucson eastward. Gusty outflow winds would be the
primary threat.

As the rest of next week progresses, a steady increase in moisture
from the south and east is expected as the subtropical high
positions itself more towards the Four Corners with troughing near
the southern California coast. This scenario will open the door to
well above normal moisture values by mid to late next week with a
quick transition from our typical early season monsoon threats
including gusty winds and blowing dust to more of a heavy rain/flash
flood threat with wind potential as well by around next Thursday and
Independence Day. With the increased moisture, temperatures will
drop back down to near normal by Wednesday and then below normal
late next week. Monsoon 2025 will certainly kick into full gear.
Stay tuned!

&&

.AVIATION...Valid through 28/12Z.
Mainly SKC this morning, then SCT to lcl BKN clouds at around 10-13k
ft AGL developing aft 27/19Z mainly along the Int`l border from KOLS
eastward and along the AZ/NM border. For these areas, expect isold -
SHRA/TS this afternoon, diminishing after 28/03z. Isold gusts up to
40 kts nr -TSRA otherwise winds light and under 12 kts with an ocnl
aftn gust up to 20 kts. Aviation discussion not updated for TAF
amendments.

&&

.FIRE WEATHER...Isolated showers and thunderstorms this afternoon
mainly along the AZ/NM border and Int`l border from Nogales
eastward. Minimum relative humidities from 10 to 20 percent today,
with a drying and warming trend this weekend. Winds generally light
and under 15 mph with isolated gusts up to 45 mph under any
thunderstorms Moisture will be on the rise next week with widespread
rain chances by mid to late next week. Initially, the main threats
will be gusty winds early in the week, but that will transition to
both a wind and rain/flooding threat late next week.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
Extreme Heat Warning from 10 AM to 8 PM MST Monday for AZZ501-502-
504>506-509.

&&

$$

Update...DVS

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