Severe Thunderstorm Warning 242, NWS Tucson, AZ

Area Forecast Discussion
National Weather Service Tucson AZ
135 PM MST Thu Aug 1 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...

Ridge of high pressure is currently centered across northern New
Mexico, allowing for weak southeasterly flow to remain over
southeastern AZ today and tomorrow. With moisture remaining in
place today and tomorrow, expect typical daily scattered showers
and thunderstorms to develop in the afternoon-evenings. HREF 24
hr probabilities for 1" or more both today and tomorrow only show
30-50%, so a few heavy rain producers may cause flooding issues,
especially if they fall over already saturated grounds from
yesterdays storms. The wind threat today and tomorrow looks
unimpressive, with the HREF only showing 20-30% probabilities of
getting 45 mph with any storms. This is also supported by DCAPE
values of 800-1200 J/kg. Timing of showers and storms developing
today looks like initiating around 1-2pm along the higher terrain,
with Tucson potentially seeing some isolated to scattered
activity between 7-11pm this evening. Tomorrow, storms will begin
to initiate around 1-2pm along the higher terrain, moving from
southeast to northwest across much of southeast AZ.

As the ridge center shifts more toward the Four Corners region
over the weekend, it will amplify a bit, which will increase
temperatures over the weekend and bring in drier air aloft. The
added drier air will help suppress storms over the weekend. Even
so, enough moisture will still be in the mid levels, so isolated
showers and thunderstorms will still be possible, mainly along the
higher terrain where enough lift will be able to overcome the
inhibition.

By Monday, the ridge will weak enough to drop temperatures a bit
and open the door for easterly waves to influence southeastern AZ.
Both the ECMWF and GEFS ensembles show an easterly wave moving
into the region sometime Monday night-Tuesday, likely leading to
increased activity Tuesday and/or Wednesday depending on timing of
the easterly wave.

Looking beyond mid week, cluster analysis indicates the Four
Corners ridge may get shifted/suppressed next weekend with an
upper trough digging into the PacNW. With that shift of the ridge
to the east, the flow would return to becoming east-southeasterly,
potentially bringing in drier air from the east.

&&

.FIRE WEATHER...
Isolated to scattered thunderstorms and showers expected today.
Thunderstorm chances will trend downward slightly this weekend and
into the start of the new week. There will be a slight chance (20%-
30%) each afternoon with higher chances over the mountains. 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.

&&

.FIRE WEATHER...
Isolated to scattered thunderstorms and showers expected today.
Thunderstorm chances will trend downward slightly this weekend and
into the start of the new week. There will be a slight chance (20%-
30%) each afternoon with higher chances over the mountains. 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.
&&

DISCUSSION...Peters
AVIATION/FIRE WEATHER...Strongman

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