700
FXUS65 KTWC 092130
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
230 PM MST Sun Jun 9 2024

.SYNOPSIS...Seasonable heat within a few degrees of normal
through Monday before high pressure allows very hot temperatures
to return Tuesday through Thursday. Dry conditions are expected
this week.

&&

.DISCUSSION...Fairly quiet afternoon across Southeast Arizona this
afternoon, despite the weak upper disturbance moving up along the
Arizona/New Mexico border. This beautiful swirl (aka the residual
vort max from the closed upper-low that has been impacting our
neck of the woods the past few days) can be seen on the mid and
upper water vapor satellite imagery near the extreme SE corner of
Cochise county. Initial thinking given the cooler temps between
550-450 mb on the 09/12Z KTUS sounding was there may be enough
instability and mid-level moisture near this feature to support a
weak dry thunderstorm...but current observations have suggested
otherwise. I still wouldn`t rule out the possibility of a
lightning strike or two across Northern Graham and Greenlee
counties into the early evening as the area of best lift
associated with this feature moves north.

In any event, the most impactful aspect of this forecast package
will be the excessive heat that is anticipated as we move into the
middle of the week. This is setup as the upper pattern begins to
amplify with the trough of low pressure along the west coast
digging south and becoming a closed low off the northern Baja by
Monday afternoon. This allows for an amplified ridge to develop
across Arizona and New Mexico by the middle of the week. Latest
deterministic GFS and ECMWF runs suggest an 850-700 mb thickness
between 1690 and 1700m Wednesday and Thursday, which empirically
supports afternoon high temperatures in Tucson between 107-111
degrees. The latest NBM probabilities of meeting or exceeding 108F
in Tucson are 26% Tuesday, 54% Wednesday and 53% Thursday. We
currently have an Excessive Heat Watch in effect for the lower
elevations of Southeast Arizona Tuesday thru Thursday. Although
the hottest days are expected to be Wed/Thu, we will still be very
hot on Tue as well.

There is good temporal and spatial agreement between the GEFS and
ECMWF ensemble members ejecting the closed low across NW AZ on
Friday. Although my own pattern recognition and experience makes
me wonder how there is consensus amongst the members because there
appears to be a lack of a significant kicker system that is
necessary to eject a low like this. In any event, I will defer to
the model solution at this juncture. This solution would
marginally cool us down beginning Friday and into the weekend but
would also be responsible for some gusty winds east of Tucson
Friday. The latest HDWI indicates values mostly above the 95th
percentile Fri to the east of Tucson, suggesting that we may near
critical fire weather thresholds. TIn addition, there may be a
weak intrusion of mid-level moisture to support a slight chance
of a mainly dry thunderstorm Thu/Fri along the Arizona/New Mexico
border but I have low confidence in that at this time due to my
lack in confidence in the timing and track of the ejecting closed
low.

The main weather story will be the Excessive Heat.

&&

.AVIATION...Valid through 11/00Z.
FEW-SCT clouds at 10k-14k ft AGL and SCT-BKN clouds AOA 20K ft AGL
east of KTUS thru 10/04Z, otherwise clear skies to SCT clouds AOA
20k ft AGL areawide thru the remainder forecast period. There will
be a slight chance of -SHRA/-TSRA mainly east of a KALK to KSOW line
thru 10/03Z. SFC wind SLY/SWLY at 11-16 kts and gusts to 18-26 kts
thru 10/02Z, then between 10/02Z and 10/18Z SFC wind will be less
than 10 kts and variable in direction. Aft 10/18Z, WLY/NWLY SFC wind
at 8-13 kts, with some gusts to around 20 kts. Aviation discussion
not updated for TAF amendments.

&&

.FIRE WEATHER...Limited mid level moisture will result in a slight
chance of mainly dry thunderstorms east of Tucson through the early
evening hours tonight and then again Thursday and Friday of this
week. These storms may produce gusty and erratic winds, along with
lightning. High temperatures will be 1-3 degrees above normal
through Monday, warming to 7 to 10 degrees above normal Tuesday
through Thursday, lowering back to 2-5 degrees above normal late in
the week and next weekend. Expect min RH values of 3-9 percent in
the lower elevations and 8-15 percent in the mountains this week,
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 Monday through Wednesday,
with elevated winds at 15-20 mph and gusts to around 30 mph to the
east/southeast of Tucson Thursday through next weekend. The
strongest 20-foot winds at this time appear to be Friday, with wind
speeds near critical levels to the east of Tucson.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...

Excessive Heat Watch from Tuesday morning through Thursday
evening for AZZ501>509.

&&

$$

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