Severe Thunderstorm Warning 162, NWS Tucson, AZ

Area Forecast Discussion
National Weather Service Tucson AZ
228 PM MST Sun Jul 21 2024

.SYNOPSIS...Temperatures will remain 1-4 degrees above normal for
the next 7 days. Storms today will move off the rim and move
through lower elevation this afternoon and evening producing
strong winds and heavy rainfall. After today there will be daily
chances for afternoon and evening thunderstorms with the normal
threats of heavy rainfall and strong outflow winds.

&&

.DISCUSSION...Isolated storms have begun to form over the rim and
a couple of the sky islands. Mid-level flow is out of the
north/northwest around 15-25 kts which should be sufficient to
move storms off the rim and into the lower deserts. CAPE values
are around 1000-1500 J/kg with 0-6 km shear of 15-25 kts which
should help sustain storms as they move southwestward this
afternoon and evening. Hi-res models are in fairly good agreement
with the above scenario. Storms will begin to propagate off the
rim in the next hour or two, making it to Tucson between 4-6 pm,
then the international border by 7-8 PM. Storms will be capable of
strong to severe wind gusts aided by 1000 J/kg of DCAPE and a small
dry layer at 400 mb measured by the 21/12Z KTWC sounding. A Severe
Thunderstorm Watch is in place for Pinal County. Blowing dust may
become an issue in Pinal County later this afternoon. Heavy
rainfall will be another threat with PWAT values around the NAEFS
90th percentile. Storms will be capable of rainfall rates of 1"-2"
per hour which could cause flash flooding issues especially over
areas that received rainfall yesterday. Also, WPC has most of the
CWA in a slight risk for excessive rainfall.

Monday the high moves a little further north keeping southeast
Arizona under northeast flow aloft. PWAT also decreases by 0.2"
east of Tucson as well. 500 mb wind speeds look to be a little
weaker, but another rim shot will be possible. Hi-res guidance
shows this with storms again forming along the rim and moving
southwestward into the lower deserts. Coverage looks to be
slightly reduced compared to today but storms will again be
capable of strong outflow winds and heavy rainfall.

The upper level ridge stays centered over southern Nevada until
around the Thursday timeframe. PWAT values hover around or just
below normal for areas east of Tucson and slightly above normal
from Tucson west. This will lead to continued daily afternoon and
evening scattered thunderstorms with the normal monsoon threats of
strong winds and locally heavy rainfall. This coming weekend
ensembles still show the high moving south thanks to troughing in
the Pacific Northwest. This doesn't seem to affect moisture in
southeast Arizona, but with the high being closer overhead this
could lead to less vigorous storms.

&&

.AVIATION...Valid through 23/00Z.
SCT-BKN clouds at 8k-12k ft AGL thru tonight then gradual clearing
after midnight. Thunderstorms have formed along the Mogollon Rim
and are expected to move southwestward this afternoon. KTUS is
expected to be impacted by TSRA between 21/23Z-22/02Z and
KOLS/KDUG 22/00Z-22/04Z. MVFR conditions in TSRA with wind gusts
in excess of 45 knots. Outside of TSRA, SFC winds at most
locations 12 knots or less favoring NWLY direction during the
afternoon/early evening hours and variable in direction at other
times. Aviation discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Scattered afternoon and evening showers and
thunderstorms for the next 7 days with day-to-day variability on
which areas will see the best chance of rainfall. Each day will
have the threat of heavy rain, localized flash flooding and strong
gusty winds. Minimum relative humidity values will be 20-30
percent in most lower elevation locations and 25-40 percent in
mountain areas. Away from thunderstorms, 20-foot winds will
generally be 15 mph or less, with afternoon/early evening gusts to
20-25 mph and light winds overnight. Wind direction during the
afternoon hours will primarily be west to northwest through the
weekend, especially from Tucson westward and in the upper Gila
River Valley.

&&

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

Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson