543
FXUS65 KTWC 172149
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
249 PM MST Mon Jun 17 2024

.SYNOPSIS...

After a mild decrease in temperatures today and Tuesday, high
temperatures heat back up again Thursday and Friday. Moisture
should begin to increase late this week which would bring the
potential for thunderstorms late in the week into the weekend.

&&

.DISCUSSION...

In the upper levels, dry west to southwest flow remained as
western CONUS troughing was sitting to the north. This
unidirectional flow through the lower levels was also creating
southwesterly surface breezes, with observed gusts of 15 to around
30 mph observed across southeastern Arizona at time of discussion.

The story this week will be the reorientation of a southeastern
CONUS high back towards the southwest CONUS by this weekend. This
will act to bring heat risk back into the moderate to major
categories Thursday and Friday, as well as turning mid to low
level flow to the southeast. Anomalously warm Gulf of Mexico
waters and a tropical disturbance should give a boost in moisture
to the southeasterly air flow towards southeastern Arizona.
Precipitable water values may begin to exceed 1 inches as early
as Thursday (around a 30% chance around Tucson and 40-60% near the
Arizona / New Mexico border) but becomes much more likely Friday
into the weekend. The westward surge of moisture will also depend
on daily convective activity from further east, so model run to
run consistency is fairly low in precipitation chances each day.
By Saturday, probabilities from the global ensembles for
precipitable water values reaching 1.5 inches reach 15 to 35%
across southeastern Arizona, indicative of impressive moisture for
this time in June. The probabilities for surface dew points
exceeding 55 degrees follow roughly the same trajectory. All this
to say, probabilities for precipitation follow the trajectory of
richer moisture, with highest chances following diurnal trends in
the afternoon and evening hours.

Going into the weekend, there isn`t a huge temperature change in
the low level air mass but the forecast high temperatures become
more uncertain due to the likelihood of convective activity. With
the likelihood of excessive heat peaking Thursday and Friday, an
Excessive Heat Watch has been issued with this shift.


&&

.AVIATION...Valid through 19/00Z.

SKC through the forecast period. Surface winds gusting 25 to 30
kts this afternoon become around 10 kts after 02Z then light after
06Z. Aviation discussion not updated for TAF amendments.

&&

.FIRE WEATHER...

Temperatures are expected to heat back up by Thursday and Friday
after the brief few degrees of cooling today and tomorrow. Through
Wednesday expect minimum relative humidities of 5 to 9 percent in
the lower elevations and 8 to 15 percent in the mountains, along
with overnight recoveries between 25 to 40 percent. Afternoon
breeziness out of the southwest can be expected through Wednesday
with gusts to around 20 to 25 mph. Starting Thursday, surface
winds turn to the south to southeast, which also begins to open
the door for increasing mid-level moisture. Chances for mainly
dry thunderstorms east of Tucson arrive on Thursday and then as
far west as Tucson by Friday.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
Excessive Heat Watch from Thursday morning through Friday
evening for AZZ501>506.

&&

$$

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