289
FXUS65 KTWC 062108
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
208 PM MST Sat Jul 6 2024

.SYNOPSIS...Excessive heat and hot temperatures through 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. Thunderstorm activity will
begin to ramp back-up the middle of next week.

&&

.DISCUSSION...The main weather story/impact for Southeast Arizona
the next several days reminds me of the time I ordered some hot
wings...hot with a side of hot sauce. Not a pleasant experience to
say the least. Unfortunately, that is what we have to deal with
today as excessive heat continues to have a stronghold on the
area. Yesterday, the Tucson International Airport was able to tie
a daily max temperature record of 111 degrees and we can expect
more of the same today. I guess the good news is that across the
region, we are running 0-2 degrees cooler compared to this time
24 hours ago...which matches up well with our forecast high today
of 109 degrees. The 06/13Z NBM probability for KTUS to meet or
exceed 110 degrees is 20% today, increasing to 50%/55%/45% for
Monday/Tuesday/Wednesday. Yuck.

With regards to storm coverage today, things are shaping up to be
fairly quiet for the forecast area. The upper pattern is dominated
by a strong ridge of high pressure aloft centered over northern
California, with the extreme SE periphery of this feature extending
into SE AZ. The generalized warming that will occur today at 500
mb as this feature moves slowly SE has warmed/eroded away some of
the CAPE available to us on the 06/12Z KTWC upper air
sounding, limiting the potential for thunderstorms across the
majority of our neck of the woods. However, an area of very weak
diffluence aloft is noted in the White Mountains and along the
Arizona/New Mexico border extending WSW into northern Sonora. As
of 2 PM MST, the White Mountains have seen some weak thunderstorm
development but are struggling to develop into anything
significant due to the drier airmass. The best location for storm
development will be along the southern Arizona/New Mexico border
and across the southeast half of Cochise. Given the hot and
relatively dry sub-cloud layer, the main threat from these storms
will be strong and gusty outflow winds. This matches up well with
the 06/12Z HREF area of 50-70% likelihood for outflows in excess
of 30 kts along the southern Arizona/New Mexico border and even a
near 10% chance of outflow winds in excess of 50 kts in NM
bordering our CWA. However, organized outflows that do develop
will generally push SSW into NE Sonora/NW Chihuahua Mexico this
afternoon, just clipping southeast Cochise county.

As the upper high drifts slowly SE the next few days this will
further stabilize the atmosphere aloft significantly limiting the
chance of pcpn across SE AZ. The H5 center makes its way into SE
CA Monday afternoon then begins to positively tilt and move
toward NW AZ by the middle of next week. This will increase our
thunderstorm activity as we not only start to import deeper
moisture from the east/northeast but it as also a favorable flow
for storms to move storms off the higher terrain near the Mogollon
Rim downhill toward the lower elevations/Tucson Metro in the late
afternoon/evening. Although ensemble members suggest a bigger
dayto occur Wednesday, experience suggests that it is the
transition days (Tuesday) that are the most active days as we
will be experiencing the excessive heat during the day followed by
strong storms moving down off the rim in the evening.

Given this pattern change, I am very hesitant to extend the
Excessive Heat Warning into Wednesday and Thursday even though the
NBM probabilities for KTUS reaching 110 degrees is 45% both days.
There is just too much change going on and with deeper moisture
within arms-reach, it will make it that much more difficult to
get that hot. In any event, HOT conditions will be around well
into the upcoming work week.

&&

.AVIATION...Valid through 08/00Z. SKC-SCT clouds at 8k-12K ft AGL
becoming SCT-BKN clouds at 7k-10k ft AGL and ISOLD-SCT TSRA/SHRA
along the Arizona/New Mexico State line in the mid-late afternoon.
MVFR conditions near TSRA, with mountain obscurations, VSBY
restrictions and gusts to 40+ kts. Aft 07/05Z, gradual clearing
thru the Sunday morning. 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...Hot with a daily chance for isolated to scattered
showers and thunderstorms south and east of Tucson into early
next week. Excessive heat will be an issue during this time
frame 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. With hot temperatures and deeper
moisture getting pushed to the south 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.
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 River valley near Safford on Sunday where northwest
winds of 20-25 mph and higher gusts are expected.

&&

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

&&

$$

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