139
FXUS65 KTWC 191025
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
325 AM MST Wed Jun 19 2024

.SYNOPSIS...High temperatures a few degrees warmer today becoming
noticeably hotter Thursday. Moisture will increase Thursday
resulting in the potential for thunderstorms through the weekend.
The added moisture will help suppress high temperatures on Friday.

&&

.DISCUSSION...The upper air pattern this morning is characterized by
broad troughing over the western CONUS and an upper level ridge over
the eastern CONUS. Smooshed between these two features is Potential
Tropical Cyclone One currently located over the western Gulf of
Mexico.

Today: Broad troughing continues over the western CONUS, though
heights/thickness values nudge upward locally. Consequently, high
temperatures will be a few degrees warmer today across southeast
Arizona.

Thursday: A unique weather pattern begins to unfold. While heights
remain elevated with a ridge axis just to our southeast, a strong
low level east push, at least partially attributed to what is now
the Potential Tropical Cyclone One in the western Gulf of Mexico,
will move into Arizona from the east. A very tight surface pressure
gradient will ramp up winds considerably, but most notably near the
NM border and in the Upper Gila River Valley. A Wind Advisory has
been issued from Thursday morning through Friday morning for Eastern
Cochise County below 5000 feet and the Upper Gila River Valley.
Southeast winds of 30 to 40 mph with gusts 40 to 50 mph are expected
which may result in areas of blowing dust at times.

The strong east push will bring with it increased moisture
as PWAT values jump to the 1" to 1.25" range Thursday. The western
edge of this east push will make it to around the Tucson area
Thursday afternoon with a pseudo dry-line/convergence setting up.
Still some differences in the ensembles with the GEFS/GEPS pushing
the moisture farther west than the ECMWF EPS. This boundary may help
to initiate a few mainly dry thunderstorms with little rain but
strong and gusty outflow winds. Patchy blowing dust may arise from
thunderstorm outflows combined with the background synoptically
scale gusty winds, especially between Tucson and Phoenix.
Temperatures have trended up in the latest NBM guidance giving
Tucson a 65 percent chance for yet another run at our first 110 on
Thursday. An Excessive Heat Warning has been issued from Tucson
westward Thursday as high heat risk is anticipated for those
areas.

Friday: The moisture and east push will have made it all the way to
the western deserts with ensemble mean PW values ranging from about
1 inch to 1.5 inches across the forecast area. The wind speeds and
gradient will remain strong on Friday with continued breezy to windy
across the forecast area. Even with the increased moisture, as the
high aloft will be nearly overhead with warm mid level temperatures,
that will help to limit widespread convection. With that said, still
expect at least isolated mainly dry thunderstorms. Decided to cancel
the Excessive Heat Watch for Friday as the added moisture will help
suppress afternoon high temperatures below high heat risk levels,
especially for areas near Tucson. Hotter temperatures will be more
likely west of Tucson where drier air remains in place.

Saturday into next week: Once the moisture comes in, it doesn`t
appear to be going anywhere per ensemble guidance. That means from a
moisture perspective, we are in the monsoon. However, with the
mid/upper level high nearby, that will certainly be a mitigating
factor. Depending on the strength/location of the high each day,
that will drive convective trends but at least a low grade monsoon
pattern is expected during this time frame with temperatures a few
degrees above normal.

&&

.AVIATION...Valid through 20/12Z.
SKC through the forecast period. SFC winds terrain driven becoming
SWLY after 19/17Z at 10-15 kts with gusts to 25 kts. After 20/06Z,
winds increase and become SELY at 15-20 kts with gusts to 30 kts.
Winds will remain elevated and increase beyond the valid period with
the highest speeds anticipated near KSAD and KDUG. Aviation
discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Temperatures are expected to heat up a few degrees
today with an even greater increase by Thursday from Tucson
westward. Minimum relative humidity values today will be 8 to 15
percent with overnight recoveries between 25 to 40 percent.
Afternoon breeziness out of the southwest can be expected with gusts
to around 20 to 25 mph. Starting Thursday, surface winds turn to the
east to southeast and become stronger, especially across
Graham/Greenlee/Cochise Counties where sustained 20-ft winds of 20
to 35 mph are expected with stronger gusts. The strongest of these
winds will be in the Upper Gila River Valley near Safford as well
as near Douglas along the International and NM borders. With
these east to southeast winds, there will be increased moisture
with min RH values in these locales around 20 percent Thursday. So
while the winds are at critical levels, RH values will remain
just above critical levels but certainly still elevated fire
weather conditions due to the strong winds and dry fuels Thursday.
Breezy to windy conditions continue Friday, though increased
moisture will have overspread more of the forecast area. Some
isolated mainly dry thunderstorms are expected starting Thursday
from Tucson eastward and then to include the remainder of
southeast Arizona Friday. As moisture remains this weekend,
isolated thunderstorms will continue each day through the weekend
into early next week with a low grade monsoon pattern in place.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
Excessive Heat Warning from 10 AM to 8 PM MST Thursday for
AZZ501>506.

Wind Advisory from 5 AM Thursday to 5 AM MST Friday for AZZ508-
509.

&&

$$

DVS

Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson