Severe Thunderstorm Warning 239, NWS Tucson, AZ

Area Forecast Discussion
National Weather Service Tucson AZ
148 PM MST Mon Jul 29 2024

.SYNOPSIS...

Daily chances for thunderstorms continue this week. Heavy rainfall
may cause localized flash flooding. Isolated strong wind gusts
will also be possible. High temperatures should rise a few degrees
by late this week.

&&

.DISCUSSION...

Isolated to scattered convection is expected to develop this
afternoon, with greater coverage likelier further south. RAP
guidance indicates richer low level moisture remains in areas
closer to the International Border with higher mixing ratio values
boosting instability across these areas. This is where coverage of
convection today will also be greatest, with the potential for
very heavy rainfall rates. Convective layer wind under 10 knots
will lead to very slow moving thunderstorms again, while the
seasonably moist atmosphere should lead to the very heavy
rainfall rates. While coverage will decrease this evening with
sunset, convective chances may linger through the night as a mid
level low approaches from the Gulf of California. Guidance
indicates an additional draw of mid-level moisture from this low
into southeastern Arizona, which along with the added ascent may
produce additional showers and thunderstorms even through Tuesday
morning.

By Tuesday afternoon, southeastern Arizona is forecast to be on
the wrong side of an impulse ejected through this closed low,
which should create a "lower" grade monsoon day. Continued active
flow from the lingering low however may produce additional
convection overnight into early Wednesday. At this point forecast
slight chances past midnight Tuesday night were kept to Santa Cruz
and Cochise counties, but these may need to be expanded.

Daily chances for thunderstorms continue through the forecast
period this week. The other part of the story will be the building
of a western CONUS ridge, which will warm up high temperatures
across the region. This should bring high temperatures 5 to 7
degrees above normal with moderate Heat Risk levels.

&&

.AVIATION...Valid through 31/00Z.

Isolated to scattered TSRA through 30/02Z. Very heavy rainfall
with isolated strong wind gusts to near 45 kts expected with any
thunderstorm today. An isolated shower can't be ruled out tonight
or early Tuesday morning as well. Otherwise winds generally light
this morning and under 12kts this afternoon. Aviation discussion
not updated for TAF amendments.

&&

.FIRE WEATHER...

Elevated moisture will continue with scattered afternoon and
evening showers and thunderstorms. Each day has the threat of
heavy rain, localized flash flooding and strong gusty outflow
winds. 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. As high pressure builds late this week,
high temperatures should rise a bit and minimum relative
humidities should fall by a few percentage points.

&&

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

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Preliminary Local Storm Report
National Weather Service Tucson AZ
601 PM MST Mon Jul 29 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0543 PM     Tstm Wnd Gst     8 NNW Pirtleville       31.47N 109.60W
07/29/2024  M56 MPH          Cochise            AZ   ASOS

            KDUG ASOS reported 56 mph wind gust.

&&

JVT