661
FXUS65 KTWC 132145
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
245 PM MST Thu Jun 13 2024

.SYNOPSIS...

Partly cloudy to mostly cloudy skies continue through this
evening. Temperatures remain above normal through the weekend,
with an Excessive Heat Watch in effect for portions of
southeastern Arizona Saturday and Sunday. Mostly dry conditions
through the forecast period with just a slight chance of a
sprinkle or light shower in areas west and north of Tucson this
this evening.

&&

.DISCUSSION...

In the upper levels, a low was circulating just off the far
southern California coast, slowly shifting northeast this
afternoon. An associated southerly push of modest mid-level
moisture was associated with this low, currently evident on water
vapor imagery from northern Mexico through Arizona. The increase
in precipitable water overlapping with an ejecting jet streak
through the base of the upper low was creating extensive cloud
cover as well as some isolated weak convection. This convection
was tied to the center of the overlap between the two features, as
of 230 PM located over far western Pima county in a north-south
orientation. Forecast soundings show a shallow moisture depth in
the mid-levels with little instability and subsequently lightning
coverage has been limited and as of this early afternoon, non-
existent so far in western Pima. With the ongoing cloud cover,
temperatures outside of Graham and Cochise counties have been
somewhat muted, or have come down a bit as cloud coverage
increased. Due to the persistence of this cloud cover this
afternoon and the effect on temperatures, the portions of the
Excessive Heat Warning west of the Graham-Cochise zones have been
cancelled. The remainder of the warning is in effect until 8 PM.

As the upper level jet streak nudges northeast, the lift
associated with the current convection in western Arizona may
avoid the southeastern Arizona areas through this evening (with
low chances remaining in northern areas through the White
Mountains overnight). A dry lightning strike or two can`t be ruled
out, especially in northern areas. But chances for this also
remain very low at any one point.

Through Friday, the upper low is expected to continue northeast
and open, becoming weaker in the process. Lingering stronger mid-
level flow should still be present over eastern zones, which
should translate to a modestly tightened pressure gradient and
breezy winds. As moisture will be on the way out during this
northeastward push aloft, fire weather concerns remain in place.
The Red Flag Warning for Friday remains in effect. Temperatures
will remain above normal on Friday, though not quite at excessive
heat levels with heat risk nudging down.

Broad ridging then sets up in the wake of the exiting low this
weekend. As a weak subtropical jet will be overhead or just to the
north, the rising temperatures will be moderated somewhat. This
brings afternoon highs this weekend to marginal heat risk levels,
which is supported by the current Excessive Heat Watch.

Going into early next week, broad troughing is expected to develop
over southern Arizona on the southern periphery of a western CONUS
low. This will bring forecast temperatures down a few degrees as
well as delivering afternoon breeziness. There continue to be
signs of better mid-level moisture arriving late next week with
reorientation of the upper high and a southeasterly push of
moisture. Many details remain to be seen on timing and moisture
characteristics, but non-zero precipitation chances in the NBM and
a wetter signal from the CPC in the 6-10 day period highlight this
potential pattern transition.

&&

.AVIATION...Valid through 15/00Z.

SCT-BKN clouds around 13k-20k feet AGL this afternoon and evening
with gradually clearing skies from west to east through tomorrow
morning. Slight chances for virga/light sprinkles west of Tucson
this afternoon before shifting into Graham/Greenlee Counties tonight
into tomorrow morning. SFC winds WLY/NWLY 10 to 20 kts with higher
gusts through 14/03Z. Winds then subside aft 14/03Z to generally
less than 12 kts. Tomorrow, surface winds SWLY/WLY after 14/16Z with
speeds of 10-20 kts and gusts to around 30 kts. Aviation discussion
not updated for TAF amendments.

&&

.FIRE WEATHER...

An increase in limited mid-level moisture this afternoon has
created increased cloud cover, though non-zero chances for any
rain or even dry lightning strikes remain low. The isolated chance
of a lightning strike will be highest west then north of Tucson
through this early evening, then into higher terrain northeast of
Tucson late tonight and early 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. Winds will increase a bit tomorrow,
especially in areas near the Arizona / New Mexico border, where a
Red Flag Warning remains in effect. Near critical fire weather
conditions elsewhere on Friday, but with winds below critical
levels. Another chance of increased winds may arrive on Monday.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
Excessive Heat Watch from Saturday morning through Sunday
evening for AZZ501-502-504>506-509.

Excessive Heat Warning until 8 PM MST this evening for
AZZ507>509.

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

&&

$$

Public...Edwards
Aviation...Van Stratten
Fire Weather....Edwards

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