Severe Thunderstorm Warning 63, NWS Tucson, AZ

Area Forecast Discussion
National Weather Service Tucson AZ
331 PM MST Sat Aug 22 2020

.SYNOPSIS...A chance of thunderstorms through the weekend, with
temperatures closer to average for late August. High pressure
building back through Arizona will tend to limit thunderstorm
coverage and push temperatures back up next week. Excessive heat
is possible with near record high temperatures Monday and Tuesday.

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.DISCUSSION...The mid morning discussion remains valid for the
rest of today regarding storm activity. For storms in the Tucson
Metro, a strong outflow will be needed to break the cap. Best
chance for that to happen would be in the evening. Elsewhere,
storms developing across the higher terrain will work south and
west through the evening, with the greatest coverage south and
east of Tucson.

Did not make any changes to the Excessive Heat Watch at this time.
There is just enough uncertainty in regards to moisture/storm
chances Monday into Tuesday, which could keep temperatures down a
degree or two from forecast. The way this Monsoon has gone, an
upgrade to a warning is probably coming.

Sunday remains on track for an active day across most of SE AZ,
including the Tucson Metro. Storms will once again fire off the
higher terrain north and east of Tucson and work into the lower
deserts to the south and west through the late afternoon and into
the evening. Main threats will be heavy rain and gusty winds. Some
localized blowing dust cannot be ruled out for portions of Pima
and Pinal Counties if outflows are organized and strong.

Activity continues Monday and potentially into Tuesday with the
main focus for areas west of Tucson. We will have to wait and see
how Sunday works out. If we have a big day, this could be tempered
a bit.

Still expecting a downward trend in activity mid to late week as
high pressure strengthens in the region and meanders south. This
will provide a less than optimal pattern for storm activity. By
next weekend, there are hints another upswing in activity is
possible. Confidence is marginal at this time as the pattern
appears to be a little messy across the west.

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.AVIATION...Valid through 24/00Z. FEW-BKN clouds 7k-12k ft MSL
much of the period. ISOLD-SCT TSRA/SHRA this afternoon into this
evening. Some +TSRA will be possible with brief reductions in
CIGS/VIS and MTN obscurations. Expect another round of ISOLD-SCT
TSRA/SHRA Sunday afternoon into the evening, especially for KTUS
and KOLS. +TSRA with aviation impacts once again possible. Wind
gusts over 40 kts possible with any TS. SFC winds generally less
than 10 kts this evening and Sunday morning becoming NWLY 5-10 kts
with gusts to 20 kts. Aviation discussion not updated for TAF
amendments.

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.FIRE WEATHER...Moisture remains in place with isolated to
scattered afternoon and evening showers and thunderstorms into
Monday. Greatest coverage appears to be Sunday. Min RH 25-30
percent across the valleys and 30-45 percent in the mountains
through Sunday along with good/excellent overnight RH recoveries.
20-foot winds generally remain less than 15 mph outside of any
thunderstorm gusts which could reach 40+ mph. Drier conditions and
hotter temperatures next week slightly reduces shower/thunderstorm
coverage and daytime humidity values by 5 to 10 percent.

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.TWC WATCHES/WARNINGS/ADVISORIES...
Excessive Heat Watch from Monday morning through Tuesday evening
for AZZ501-502-504>506-509.

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