Flash Flood Warning 98, NWS Tucson, AZ

Area Forecast Discussion
National Weather Service Tucson AZ
115 PM MST Fri Aug 23 2024

.SYNOPSIS...

Daily chances for thunderstorms continue. Localized flash
flooding, strong winds, and small hail will be possible with any
thunderstorm over the coming days. High temperatures are expected
to remain near normal.

&&

.DISCUSSION...

Amid relatively active southerly to southwesterly flow aloft,
thunderstorm activity is expected to expand this afternoon across
much of southeastern Arizona. A Pacific northwest trough has
brought some dry air aloft in from the west, which has trimmed up
precipitation chances today over western Pima, with best chances
mainly near and east of Tucson-Nogales. Increased shear due to the
proximity of the Pacific trough will allow for a few thunderstorms
to produce potentially severe hail, along with heavy rainfall
rates despite the modest decrease in atmospheric moisture aloft.
Downdraft CAPE isn't terribly high, though the increased shear
should allow for an isolated severe wind threat. Finally, storm
motions should preclude a more widespread flash flooding threat,
however storm mergers or storms over locations vulnerable to
flooding will still provide a flash flooding threat.

Tomorrow, as the PNW trough moves inland towards the Great Basin,
divergence aloft over southeastern Arizona increases under the
right exit region of an ejecting jet streak. This added ascent may
act to increase thunderstorm coverage in a case where today's
activity would otherwise bring a "down" day. Either way, chances
remain but will still partly depend on how widespread today's
activity becomes. Sunday remains under a similar synoptic pattern
and will see thunderstorm chances in the afternoon and evening as
well. Highest chances generally remain east of Tucson-Nogales.

Daily monsoon activity will continue with some day to day
variation through next week. Though ensemble mean precipitable
water and CAPE guidance shows potentially some drying early next
week (especially from the ECMWF members), there remains enough
moisture and background support to continue daily forecast chances.

&&

.AVIATION...

Scattered thunderstorms this afternoon through 24/03Z, with
isolated late this evening, mainly near and east of KTUS-KOLS. Outside
of thunderstorm wind gusts, winds generally 15 kts or less with a
south to southwest direction. Scattered thunderstorms again
Saturday afternoon. Aviation discussion not updated for TAF
amendments.

&&

.FIRE WEATHER...

Scattered thunderstorms this afternoon and evening, mainly near
and east of Tucson to Nogales as drier air nudges in from the
west. Scattered thunderstorms are forecast again each day through
the weekend. High temperatures remain near normal. The drier air
pushing in will act in lowering minimum relative humidities to
around 18-28 percent through the weekend, though areas east of
Tucson to Nogales should keep higher values. 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.
&&

Public...Edwards
Aviation...Edwards
Fire Weather....Edwards

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