288
FXUS65 KTWC 060903
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
202 AM MST Sat Jul 6 2024

.SYNOPSIS...Excessive heat and hot temperatures through at least
Tuesday, with high temperatures expected to approach record levels
in some locations. Shower and thunderstorm chances will mainly be
confined to south and east of Tucson through early next week as
drier air overspreads Arizona from the north.

&&

.DISCUSSION...Very little change in the forecast pattern and
thinking versus 24 hours ago. A strong ridge of high pressure was
currently centered over the northern California coast. This ridge
will build slowly southeast through early next week, when it will be
centered along the AZ/CA/NV borders. The models then show the high
lifting northeast into Utah mid to late next week. This pattern will
result in hot daytime temperatures and a low grade monsoon through
early next week, with deeper moisture moving back into the region
mid to late next week.

The main story continues to be the EXCESSIVE HEAT and HOT daytime
temperatures across southeast Arizona, with near record to record
high temperatures. Have decided to extend the Excessive Heat (EH)
Warning out through 8 pm MST Tuesday of next week. It may still need
to go out even further depending upon how quickly moisture moves
back into southern Arizona. At this time, the Excessive Heat Warning
is in effect for all but Santa Cruz and Cochise counties and the
mountain zones of southeast Arizona.

During this time frame monsoon activity will be limited to mainly
south/southeast of Tucson, across Santa Cruz and Cochise counties as
the deeper moisture gets pushed south into northern Mexico and high
pressure builds in from the northwest. GOES-16 Total Precipitable
Water (PW) Imagery shows values currently around 0.67 inches in
Tucson (0.81 inches on the KWTC 240706/00Z sounding), with 1.0-1.2
inches along the International Border and a very dry 0.20 inches in
the White Mountains. The ensemble models indicate PW values will
continue to lower through the weekend into early next week, when PW
values will range from around 0.25 inches in the White Mountains to
0.5-0.7 inches across the rest of southeast Arizona and even much of
northern Mexico.

As the high shifts north and then northeast of the region mid to
late next week, a more favorable moisture pattern returns to
southeast Arizona and expect shower and thunderstorm chances to
increase, as well as high temperatures to slowly decrease (but still
remaining several degrees above normal levels). Model PW`s rebound
to around 1" late next week. By next weekend, the models have the
high centered over Colorado, with deep south/southeast flow across
Arizona and PW`s increasing to 1.25-1.50" across southeast Arizona.

&&

.AVIATION...Valid through 07/12Z.
FEW-SCT clouds at 13k-15K ft AGL and BKN-OVC clouds AOA 20k ft AGL
southeast of a Sells to KTUS to KSAD line thru 06/15Z, then
diminishing cloud cover. Clear skies elsewhere. Between 06/18Z and
07/05Z, SCT-BKN clouds at 7k-10k ft AGL and ISOLD-SCT TSRA/SHRA
mainly south and east of KTUS. MVFR conditions near TSRA, with
mountain obscurations, VSBY restrictions and gusts to 40+ kts. Aft
07/05Z, gradual clearing thru the remainder of the forecast period.
Outside of TSRA outflows, SFC wind 12 kts or less favoring a
WLY/NWLY direction during the afternoon/early evening hours and
variable in direction at other times. Aviation discussion not
updated for TAF amendments.

&&

.FIRE WEATHER...There will be the daily chance for isolated to
scattered showers and thunderstorms mainly from Tucson south and
east into early next week. High pressure aloft will build to our
northwest through the weekend into early next week, which will
result in hot conditions. With the hotter temperatures and some of
the deeper moisture getting pushed to the south and east of the
region, min RH values will lower into the 10-17% range across the
lower elevations and 14-25% in the higher elevations into the middle
of next week. Hot high temperature are expected through at least
Tuesday, with highs 106-113 degrees from Tucson westward and in the
Gila River Valley, and in the upper 90s to 105 degrees across Santa
Cruz and Cochise counties. Excessive Heat will be an issue during
this time frame. Outside of any thunderstorm outflow winds, 20-foot
winds will generally be 15 mph or less each afternoon with
occasional gusts to 20-25 mph through the weekend. The exception
will be in the upper Gila Rover valley near Safford on Sunday where
northwest winds of 20-25 mph and higher gusts are expected. Early
next week elevated wind speeds in the 15-20 mph range will be
possible mainly to the east of Tucson.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
Excessive Heat Warning until 8 PM MST Tuesday for AZZ501-502-504>506-
509.

&&

$$

Zell

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