Severe Thunderstorm Warning 321, NWS Tucson, AZ

Area Forecast Discussion
National Weather Service Tucson AZ
222 PM MST Sat Aug 17 2024

.SYNOPSIS...There will be a daily chance of mainly afternoon and
evening showers and thunderstorms through next 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 next
week.

&&

.DISCUSSION...Things are starting off as expected this afternoon.
The 12Z KTWC sounding shows plenty of moisture with a working
subcloud region that should allow insolation to overcome the
convective inhibition present. Very modest shear with decent
steering level flow out of the south/southeast. HREF ensembles
suggest initiation over the higher terrain of eastern Pima, Santa
Cruz and western Cochise counties in the early afternoon with
solid support for outflow initiated valley storms by mid to late
afternoon. Storms will tend to be strong with isolated severe
possible under wet microbursts. Storm movement will be decent, but
may or may not be brisk enough to avoid localized flooding
issues. Still could see some activity in the overnight hours.

For the coming week, high pressure will initially nudge back
overhead into a blocking position. Mid level warming and modest
drying in eastern areas will likely bring overall down days to
start the new week, at least by Monday and Tuesday (with the
exception of areas south to southwest of Tucson).

An interesting development later in the week. Ensemble means
suggest the ridge building back east with a high center
consolidating over northern Texas. Meanwhile a very early
transition season type trough for much of the west. These patterns
create interesting dynamics and moisture couplets that can lead
to severe weather the day before more drying overwhelms the
pattern. You also keep a close eye on the tropics when the western
region troughs start.

&&

.AVIATION...Valid through 19/00Z.
FEW-SCT clouds at 6K-9k ft AGL becoming SCT-BKN clouds at 6k-9k ft
AGL and BKN-OVC clouds AOA 15k ft AGL by 17/23Z, along with ISOLD-
SCT SHRA/TSRA thru 18/06Z. Slowly clearing skies between 18/06Z and
18/18Z. Aft 18/18Z, SCT-BKN clouds at 6k-9k ft AGL and ISOLD-SCT
SHRA/TSRA thru the end of the forecast period. 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
next week. Today looks to be the most active day in terms of storm
coverage and strength and Monday the least active. High temperatures
will be 3 to 7 degrees above normal through the middle of next week.
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 next 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.
&&

Meyer/Zell

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