Heat in Arizona, August 18, 2024

Area Forecast Discussion
National Weather Service Tucson AZ
1000 AM MST Sun Aug 18 2024

.SYNOPSIS...There will be a daily chance of mainly afternoon and
evening showers and thunderstorms through the week across southeast
Arizona. The thunderstorms will be accompanied by the typical
monsoon threats of strong wind gusts, localized heavy rainfall and
flash flooding, and blowing dust. High temperatures will be several
degrees above normal into at least the middle of the week.

&&

.UPDATE...Decent moisture still in place, but large areas from
near Tucson westward have been worked over in the past 12 hours.
Remnant MCV drifting north of the area with another drifting up
from Sonora. We'll have some storms around but likely less than
yesterday. Eastern areas should be favored, but it's a little
drier over there too. Current forecast reflects this well with
lower chances out west and easy mountain initiation and slightly
less favorable valley support. No updates. Please see the previous
discussion below for additional details.

&&

.PREV DISCUSSION... /issued 224 AM MST Sun Aug 18 2024/
An MCS across Sonora extended into Arizona and resulted in the
development of late night convection that continues into the early
morning hours to the north and west of Tucson. This activity will
generally diminish over the next few hours with debris clouds
through the early morning hours for most locales. The combination
of the MCS which likely at least partially worked over the
atmosphere and the expectation of being on the backside of an MCV
later today will tend to result in considerably less convective
activity. The HREF/CAMs are rather tepid with storm intensity and
for those scattered storms that do form, it will mainly be from
Sells eastward. Some drier air is moving into far eastern areas
where PWAT values will drop down to near 1 inch.

High pressure aloft will remain centered over New Mexico on Monday
with our flow becoming a bit more easterly. Monday should see a bit
of an uptick in storm coverage compared to today. Again, eastern
areas are on the dry side so most of the storms should be west of a
line from Safford to Bisbee.

Ensembles are showing an inverted trough across Sonora on Tuesday.
Confidence is low on just how much that will impact us on our side
of the border but nonetheless a continuation in scattered showers
and thunderstorms with the best chances south of Tucson.

For the mid to late week period, troughiness will move into the west
coast with the mid/upper level high to our east gradually shifting
into Texas. This will result in a more southerly flow for our area
and still a decent moisture plume between these systems. Therefore,
a continuation of daily chances for showers and thunderstorms is
expected through the end of the week.

Temperatures will be about 3 to 6 degrees above normal through
Tuesday then gradually lower to just a few degrees above normal
through the end of the week.

&&

.AVIATION...Valid through 19/12Z.
BKN-OVC clouds AOA 15K ft AGL will diminish aft 18/12Z. SCT
SHRA/TSRA W/NW of KTUS will also taper off through the early morning
hours. Otherwise, SCT-BKN clouds at 6k-9k ft AGL redevelop aft
18/18Z along with ISOLD-SCT SHRA/TSRA thru 19/03Z before tapering
off tonight.  Expect MVFR conditions near TSRA, with VSBY
restrictions, wind gusts to 45+ kts, heavy rain and mountain
obscurations. Outside of thunderstorm wind gusts, wind speeds will
be 12 kts or less, favoring a SWLY through 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 a daily chance of mainly afternoon and
evening showers and thunderstorms across southeast Arizona through
this week. High temperatures will be 3 to 7 degrees above normal
through the Tuesday, then lowering to a few degrees above normal.
Min RH values will be in the 20-30 percent range in most valleys
locations (lowering to near 15 percent in eastern Cochise and the
upper Gila River valley) through the middle of this week. Outside of
any thunderstorm outflow winds, 20-foot winds will generally be 15
mph or less, with afternoon/early evening gusts to 20-25 mph and
light winds overnight.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
None.
&&

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