065
FXUS65 KTWC 112047
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
147 PM MST Tue Jun 11 2024

.SYNOPSIS...Excessive heat this afternoon through Thursday as
high pressure results in very hot temperatures. Slight cooling
Friday but temperatures still a few degrees above normal. Temperatures
then nudge upward again this weekend into early next week. Generally
dry conditions through the forecast period with a slight chance
of mainly dry thunderstorms in the eastern mountains late in the
week.

&&

.DISCUSSION...The main weather impact this week will continue to
be the very hot temperatures for the lower elevations of Southeast
Arizona through Thursday. Its the kind of heat that you wouldn`t
want to store your egg-salad sandwich outside for an hour before
deciding to bite into it. Of course I say this in jest, but in
reality this is the kind of heat that is both dangerous and
potentially deadly if proper accommodations for its impact are
not made. We currently have an Excessive Heat Warning in effect
for the lower elevations of Southeast Arizona through Thursday. We
will continue to prioritize heat safety messaging to the public
and our partners, but can always use the help to encourage people
to check in on those friends and loved ones who are vulnerable to
heat related illness. The NBM probabilities of meeting or
exceeding 108F at the Tucson International Airport (KTUS) is 63%
Wednesday and 56% Thursday.

Expect a brief respite Friday as a closed upper-low (seen on the
latest water vapor satellite imagery spinning off the northern
Baja near 28.6N/120.7W) begins to eject NE across the NW half of
Arizona. This should cool afternoon temps down 3 to 6 degrees
across the board. The main impact of this upper-low will be the
breezy west to southwest winds across the eastern portions of the
forecast area Friday afternoon. The most recent Hot Dry and Windy
Index (HWDI) running off the GEFS members suggests values above
the 95th percentile Friday across Cochise county which usually
means critical fire weather conditions will be met. Therefore, we
have decided to hoist a Fire Weather Watch for fire weather zone
152, which includes portions of Cochise, Graham and Greenlee
counties from 11 AM MST Friday morning thru 8 PM MST Friday
evening. This matches up well with the area defined by the 70%
probability on the SPC Day 5 Dry T/Low RH/Wind graphic.

As we move into the extended, ensemble members of both the GEFS
and ECMWF are showing a trough developing along the West Coast
next week. I know what you are thinking...wouldn`t this give us a
dry SW flow aloft? Yes...but it also supports a moistening up of
Sonora Mexico to our south as any easterly wiggle in the broad
high pressure to the south will result in a northerly intrusion
of deeper moisture. It`s what has to happen before we can start to
see moisture make it this far north. The extended ensemble
members depict this solution with QPF across SE AZ the last week
of June. This is supported by the fastest CPC 8-14 day
precipitation Outlook. So...it won`t be too long until those
crayons stop spontaneously melting on your back-patio and we see
Monsoon moisture make its way into the area...thus cooling us back
to normal.

&&

.AVIATION...Valid through 13/12Z. SKC thru the forecast period.
SFC wind generally less than 12 kts thru this forecast cycle,
favoring a WLY/NWLY direction during the afternoon/early evening
hours and variable in direction at other times. Some afternoon
gusts to around 20 kts. Aviation discussion not updated for TAF
amendments.

&&

.FIRE WEATHER...Hot temperatures this week, with high temperatures
7-10 degrees above normal through Thursday and then 3-6 degrees
above normal Friday through the weekend. Limited mid-level
moisture will result in a slight chance of mainly dry
thunderstorms in the higher terrain northeast of Tucson late
Thursday and Friday. These storms may produce gusty and erratic
winds, along with occasional lightning. 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. Outside of any
thunderstorm outflows, 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 through Wednesday, with elevated winds at 15-22
mph and gusts to around 35-40 mph along the Arizona/New Mexico
border Friday. This will result in critical fire weather
conditions. Therefore, A Fire Weather Watch is in effect Friday for
Fire Weather Zone 152 (including Cochsie, Graham and Greenlee
counties).

&&

.TWC WATCHES/WARNINGS/ADVISORIES...

Excessive Heat Warning until 8 PM MST Thursday for AZZ501>509.

Fire Weather Watch from Friday morning through Friday evening
for AZZ152.

&&

$$

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