Severe Thunderstorm Warning 249, NWS Tucson, AZ

Area Forecast Discussion
National Weather Service Tucson AZ
158 PM MST Fri Aug 2 2024

.SYNOPSIS...

Daily chances for thunderstorms continue through next
week, with more limited coverage over the weekend. Some storms will
generate heavy rain and strong gusty winds. Temperatures will
increase over the weekend, peaking Sunday, subtly trending down a
few degrees early to middle of next week.

&&

.DISCUSSION...

Convection has started to fire in western New Mexico the past few
hours, and this activity will spread in coverage and intensity
westward into AZ between 1-3pm this afternoon.

The 12Z TWC sounding reported 1.86 inches of precipitable water,
surprisingly juicy compared to the previous morning's sounding
that had 1.61 inches which is more on par with what would be
expected climatologically.

Thus, we tossed up an 18 UTC Sounding to get another look at the
low level moisture profile, and it came back a little bit less
moist than the 12 UTC run (1.6in vs. 1.86in). The well mixed
layer below 700mb remained, and surface CAPE values rose to above
1600J/kg, which means there is enough energy to help initiate and
sustain storms through the afternoon hours.

Drier air has already begun to move in aloft which will be
available to entrain into any afternoon thunderstorms and perhaps
enhance the wind threat a bit. The HREF gives a 70 percent chance
of winds at least 30 kts (35 mph) from the Tucson Metro west and
a 10 percent chance of winds of 50 kts (58 mph) in this area as
well. There was 17 kts of effective shear reported in the 18 UTC
sounding which is also enough to sustain a stronger storm or two.

CAMs show isolated to scattered thunderstorms forming mainly
south and east of Tucson and over mountainous terrain around 20Z
(1 pm MST) before propagating through the Tucson Metro from around
22Z to 02Z (3 pm to 7 pm MST). With the loss of daytime heating,
expect thunderstorm organization to diminish a bit after sunset.

Also of note, WPC issued an MPD for portions of eastern and
southern Arizona for this afternoon and evening to highlight the
potential for flash flooding.

Overall, looking like an average to perhaps a slightly above
average Monsoon day with southeasterly flow helping propagate
storms to the northwest into the afternoon hours. A couple storms
may produce strong to severe wind gusts and very heavy rainfall.

After this afternoon/evening round of storms, The heat becomes
the story once again, as portions of the CWA will be well above
normal with highs in in the 106-111F range across portions of
Western Pima County and in the Tucson Metro Area. HeatRisk values
in the major category will pose risks to vulnerable populations.

Chances for stronger thunderstorm activity will trend downward on
Saturday and Sunday before a more favorable monsoon pattern
returns on Monday and Tuesday.

&&

.AVIATION...

Valid through 04/00Z. SCT -SHRA/-TSRA after 02/22z thru 03/04z,
then ISOLD -SHRA/TS thru end of valid pd. MVFR conditions and wind
gusts to 45 kts near thunderstorms. Outside of thunderstorms
expect wind speeds less than 12 kts and following typical diurnal
trends. Aviation discussion not updated for TAF amendments.

&&

.FIRE WEATHER...

Daily chances of thunderstorms can be expected across the region
this afternoon and evening. Thunderstorms that develop today could
have the potential to be heavy rainers, which would help suppress
active fires. Dryer air will move into the region this weekend
that will keep min RHs in the upper teens to lower twenties in the
lower locations and thirties in the higher elevations. Min RHs
will trend upward by next week due to thunderstorm influences.
Outside of thunderstorm 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.
&&

Public...Singer/DVS
Aviation...Singer/DVS
Fire Weather....Singer/DVS

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