634
FXUS65 KTWC 042118
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
218 PM MST Fri Jul 4 2025

.SYNOPSIS...A drying trend is expected today into this weekend
with mainly isolated storm coverage focused on locales south of
Tucson. Temperatures will remain below normal this afternoon
before warming back up to above normal levels by Sunday and
continuing through much of next week. Very hot conditions may
return Wednesday.

&&

.DISCUSSION...Independence Day is one of those perfect holidays
to get together with family and friends, enjoy your time in the
moment and also reflect on the past. I guess we do the same type
of thing with meteorology. Southeast Arizona has successfully
made its move into the 2025 Monsoon this past week with plenty of
thunderstorm activity the past several days already under our
belt. Not all Monsoon seasons are like that. Some storm activity
kinda trickles into the area over the first half of July.

In any event, we have been advertising a decrease in thunderstorm
activity today into this weekend and it looks like that will hold
tight. The upper pattern is defined by the 500 mb high center
building into Southeast Arizona from the WSW, in the wake of a
departing trough which is currently moving through the Rockies.
The latest GOES PWAT imagery indicated slightly over an inch of
precipitable water across the southern half of Arizona. This
matches up well with the 04/18Z KTWC sounding that has a PWAT
value of 1.13 inches. Surface dewpoints have mixed out into the
upper 40s to mid 50s. There is a weak 850-700 mb Theta-E ridge
axis that extends across Sonora Mexico into Santa Cruz county.
Normally, this should be enough moisture for storms to feed off of
today...but the position of the upper high should hinder deep
convection across the area. In fact, you can see it on the KTWC
sounding AOA 550 mb. This warm layer will essentially choke off
the storms as they get going. You can see this in the real world by
looking at the storms that have shot-up real quick. The convective
plume goes vertical into a thin tower, then it seemingly loses its
base base and the tops then become a long plume of cirrus that
extends NE due to the strong flow aloft. In any event, expect
isolated to low-end scattered convection to develop across Santa
Cruz and SW half of Cochise this afternoon. There is ample
moisture to work with...so the storms will be capable of producing
locally heavy rainfall. In fact, the 04/12Z HREF indicates on
their 3-hr ensemble probability matched mean QPF a 30-50 percent
chance of 1+ inch of rainfall. This matches up with reality since
in several of the gages in the Huachuca mountains have received
between 0.75 and 1.00 inch.

We will see a reinforcement of lower level moisture across our
neck of the woods overnight tonight into Saturday as a weak gulf
surge spill into the lower deserts of SW Arizona. Despite the
increase in moisture across the Western portions of the forecast
area, The coverage of thunderstorms Saturday will also be limited,
with the focus for storms shifting a little farther west into
Santa Cruz county into the Tohono O`odham Nation.

The 500 mb high is expected to slowly drift northward into NE AZ
Sunday into the first half of next week. Although this seems like
a subtle shift, this does change the direction of the flow from
the SW to a more divergent NE flow, which is more conducive for
thunderstorm activity Monday thru Wednesday. The only downside is
that this will also lift the 300 mb high into WRN AZ. This will
not only limit thunderstorms coverage across the western portions
of thew forecast area, but will also warm us up. The 04/20Z NBM
probabilities of reaching 110 degrees at the Tucson International
Airport (KTUS) are now 14% Tuesday, 35% Wednesday and 18%
Thursday. Nobody is a fan of that. For now, the warm celebrations
with a quiet-ish holiday weekend will have to suffice.

&&

.AVIATION...Valid through 06/00Z. SCT-BKN 7-12k ft AGL until
05/05Z...then SCT 12-15k ft AGL thru 05/19Z...then SCT-BKN 7-12k
ft AGL again Saturday afternoon. ISOLD- SCT SHRA/TSRA are expected
through 04/04Z with CIGS BKN 5-8k ft AGL and gusty outflow winds
up to 40 kts. Surface winds generally WLY 8-13 kts, becoming SLY
less than 10 kts overnight. Aviation discussion not updated for
TAF amendments.

&&

.FIRE WEATHER...Slightly below normal temperatures this afternoon,
then warming back this weekend into next week with the potential
for very hot temperatures to return the middle of next week.
Expect isolated to scattered showers and thunderstorms this
afternoon into this evening mainly south and southeast of Tucson.
A decrease in thunderstorm activity is expected this weekend as
the area transitions into a low grade monsoon pattern. An eventual
uptick in monsoon activity is possible the middle of next week
but will be dependent on how quick the high pressure aloft shifts
north. Winds generally light and under 15 mph with the exception
of gusty and erratic winds up to 35-45 mph near any thunderstorms.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...None.

&&

$$

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