Areal Flood Advisory 151, NWS Tucson, AZ

Area Forecast Discussion
National Weather Service Tucson AZ
300 AM MST Wed Aug 11 2021

.SYNOPSIS...Increased shower and thunderstorm activity will bring
temperatures a few degrees below average into the weekend. Some
storms will generate strong winds and heavy rain which will result
in continued flooding concerns and localized storm damage.

&&

.DISCUSSION...The weak low near west central Arizona was joined by
another mid level impulse rotating up from the south late last
night. Combine that with a synoptic scale upper level diffluent
pattern, elongated shear axis, continued moisture amounts well
above average, and well organized deep convective outflows and you
get the past 8 hours of widespread heavy rain and nearly
continuous lightning. Rainfall amounts between 2 and 4 inches over
a broad area from northeast Tucson to the foothills continues to
cause flash flooding issues as that water pushes downstream into
areas that saw between 1 and 2 inches for most of the rest of the
city. Watching the impressive outflow from the earlier convective
complex in Yuma County, and you get the feeling we have more to
watch for this morning as storms redevelop through the Tohono
O'Odham Nation.

All that can be said at this point is that we probably will be too
worked over to get something organized across our current active areas
by the time this afternoon rolls around, but high PoP / low QPF
isn't out of the question.

We should be able to recover to average thunderstorm chances
Thursday afternoon/evening before we see another major feature
enter our weather picture.

Remember 3 weeks ago when the high was well north of us and we
were wide open to the strong inverted trough that pushed straight
in from the east? It's starting to look that way again for this
weekend. Current ensembles show another direct hit for southeast
Arizona Saturday. With deep moisture in place, we'll likely be
seeing another couple of days with excessive rainfall chances this
weekend. Watch for enhanced severe thunderstorm chances ahead of
this system for Thursday and/or Friday.

&&

.AVIATION...Valid through 12/12Z.
Mostly SCT-BKN clouds 10-14k ft MSL. Isolated to scattered
SHRA/TSRA through the forecast period. Local MVFR conditions and
gusty winds with SHRA/TSRA. Outside of SHRA/TSRA, SFC winds will
be less than 10 kts following a normal diurnal flow of sly/sely
during the night/early morning and mainly wly/nwly late morning
through afternoon. Aviation discussion not updated for TAF
amendments.

&&

.FIRE WEATHER...Ample moisture this week along with periodic
mid level disturbances will result in at least a mid grade monsoon
pattern. Given the higher levels of moisture and cloud coverage,
temperatures will be cooler this week. Strong, erratic winds and
locally heavy rainfall will be possible with any stronger storms
that develop. 20-foot winds will generally be less than 15 mph when
not influenced by thunderstorms.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
None.
&&

Meyer

Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson