318
FXUS65 KTWC 130938
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
238 AM MST Thu Jun 13 2024

.SYNOPSIS...Excessive heat continues today as high pressure results
in very hot temperatures. Slight cooling Friday but temperatures
still a few degrees above normal. Temperatures nudge upward again
this weekend with an Excessive Heat Watch in effect for portions of
southeast Arizona. Generally dry conditions through the forecast
period with a just a slight chance for a sprinkle or light shower
west of Tucson today, then shifting to Graham and Greenlee County
tonight into Friday.

&&

.DISCUSSION...Latest WV/IR satellite imagery shows partly cloudy
skies across much of southeast Arizona with the region in southerly
flow aloft between an upper ridge centered just to our east and a
mid/upper low centered near 32N/120W off the southern
California/northern Baja coast. This southerly flow will continue
through the day and with the increased mid level moisture, there
will be a continuation of mid level cloudiness streaming northward.
PWAT values increase to around 0.8" but with a very dry sub-cloud
layer it will be hard to get much more than some virga/sprinkles
mainly west of Tucson during the day today. Convective parameters
are pretty abysmal with MLCAPE values less than 100 J/KG so will be
hard pressed to get lightning. Meanwhile, with more cloudiness today
than was previously expected, that could temper down high
temperatures a couple of degrees. For continuity sake and with some
uncertainty on the clouds and its impact on temperatures, we
continued the Excessive Heat Warning for today. Otherwise, expect
some afternoon breeziness to go along with the hot temperatures
today.

As the mid/upper low moves into AZ late tonight into Friday, the
modest mid level moisture plume will be shunted more towards locales
to the north to northeast of Tucson, mainly in the higher terrain
Graham/Greenlee Counties where a slight chance of sprinkles/light
showers is expected.

With the mid/upper low to our north Friday lowering
heights/thicknesses, temperatures will cool just enough to be out of
excessive heat criteria. However, with the slight cooling will come
an uptick in winds which will be enough for fire weather concerns
near the NM border. A Red Flag Warning has been issued for these
locales. See fire weather discussion below for additional
information.

The mid/upper level pattern will reorient itself this weekend into
next week and dominated by a strong subtropical ridge centered
across northern Mexico, with southeast Arizona under dry westerly
flow as broad troughing dominates much of the western US. Even
though the ridge is centered to our south, height/thickness values
support borderline excessive heat levels this weekend. Decided to
hoist an Excessive Heat Watch for Saturday and Sunday for the
deserts and up into Graham County to include the Safford area.
Temperatures and heat risk is marginal, so later shifts can monitor
trends and evaluate the need for upgrading to a warning.

As the troughing to our north nudges heights down early next week,
that will lower temperatures a few degrees. Expect afternoon breezes
each day through the forecast period. Otherwise, the high will
reorient itself a bit more to our east which could help introduce a
bit more mid level moisture again by late next week.

Otherwise, expect breezy afternoon winds for most days of the
forecast period from the weekend through much of next week.

&&

.AVIATION...Valid through 14/12Z. SCT-BKN clouds around 13k-20k feet
AGL through much of the forecast period. Slight chances for
virga/light sprinkles west of Tucson today, then shifting into
Graham/Greenlee Counties tonight and Friday. SFC winds generally
less than 12 kts early this morning, becoming WLY/NWLY 10 to 20 kts
with higher gusts aft 13/18Z. The strongest winds will be near KSAD.
Winds then subside aft 14/03Z to generally less than 12 kts.
Aviation discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Hot temperatures through the weekend, generally
5-10 degrees above normal. Limited mid-level moisture will result in
a slight chance of sprinkles/virga or very light isolated shower
activity mainly west of Tucson today, then shifting to the higher
terrain northeast of Tucson tonight and Friday. Expect min RH values
of 3-9 percent in the lower elevations and 7-15 percent in the
mountains through this weekend, along with poor overnight recoveries
between 20-35 percent in most locations. 20-foot winds will follow
typical diurnal patterns, with afternoon/early evening gustiness due
to strong surface heating. Sustained 20-foot wind speeds will
generally be 15 mph or less today, though locally higher in the
upper Gila River valley near Safford where near critical fire
weather conditions are expected. Winds will increase a bit more
Friday, focused on locales near the Arizona/New Mexico border. A Red
Flag Warning has been issued for Zone 152 Friday where winds of 15
to 25 mph are expected and gusts up to 35-40 mph are possible.
Elsewhere, expect elevated fire weather conditions Friday but winds
below critical levels. Thereafter, breezes continue each day into
next week with  some afternoon gustiness Saturday, then perhaps
another uptick with Monday having potential for wind speeds near
critical levels.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
Excessive Heat Warning until 8 PM MST this evening for AZZ501>509.

Excessive Heat Watch from Saturday morning through Sunday evening
for AZZ501-502-504>506-509.

Red Flag Warning from 11 AM to 8 PM MST Friday for AZZ152.

&&

$$


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