Areal Flood Advisory 52, NWS Tucson, AZ

Area Forecast Discussion
National Weather Service Tucson AZ
253 PM MST Sun Jul 18 2021

.SYNOPSIS...Thunderstorms are expected through this evening, mainly
east and south of Tucson. Thereafter expect daily chances of showers
and thunderstorms through the work week. High temperatures will
remain below normal into the foreseeable future.

&&

.DISCUSSION...Convection east of Tucson developing a few hours
earlier than most CAM solutions suggested and speaks to the level of
instability we have. The storms are moving to the NW, however fairly
slowly and the few we have had have produce in excess of two inches
of rain in 1 to 1.5 hours. A few of them have shown a tendency to
redevelop in the same area as well.

The saturated soils were very evident after this morning which
resulted in flooding in Santa Cruz county with only one inch of rain.
We also had flow in the Pima, Finger Rock and Esperero canyons this
morning from 1/2 to 1 inches of rain, so we are definitely primed in
that respect.

For this afternoon and evening, all the CAM solutions show
significant storm development east and south of Tucson including
areas that have received recent heavy rains. Looking at the HREF,
it is indicating fairly high probabilities of local areas of greater
than an inch (in 3hr) this evening (5-8 pm) focused over eastern
Pima, Santa Cruz and Cochise county, peaking at 70% eastern Cochise.
There is even a 10% chance of greater than 3 inches in much of that
area. Then for the 03Z-06Z period (8-11pm) the focus shifts to
Cochise county with >50% of an inch and ~10% greater than 3 inches
and has an MCS look to it. Given that and the saturated conditions
we opted to issue a Flash Flood Watch through Midnight tonight east
and south of Tucson, including Mt Lemmon for the Bighorn fire scar.
Now we will have to see how this plays out, but the potential is
certainly there.

Monday through the work week the upper level high remains near or
north of the 4-corners area, a favorable location for activity with
deep easterly flow and plenty of moisture. Therefore there will be
daily rounds of convection through the week, primarily focused on the
afternoon and evening hours and varying from day to day. That said,
as we saw this morning convection will be possible at anytime day or
night depending on smaller forcing mechanisms. PWs remain as high as
they have been so showers and thunderstorms will continue to be
efficient rain producers and with the moist soil conditions, local
flooding will continue to be a concern.

Late in the week into the weekend there is some indication that
there could be a trough over the area which would serve as a focus
for convection if it becomes reality. Too soon to count on that but
either way, the wet and active monsoon season looks to continue
through next weekend.

&&

.AVIATION...Valid through 20/00Z.
SCT-BKN clouds at 8k-12k ft MSL with BKN layers above til 19/07Z the
clouds slowly diminishing. SCT-NMRS SHRA/TSRA developing and
persisting through the evening hours mainly east and south of Tucson
before diminishing late tonight. Wind gusts to 45 kts possible near
any TSRA along with MVFR conditions and mountain obscurations due to
heavy rain. Otherwise, SFC wind generally less than 12 kts. Aviation
discussion not updated for TAF amendments.

&&

.FIRE WEATHER...A wet monsoon pattern will continue through the
coming work week resulting in scattered showers and thunderstorms.
The convection will be primarily during the afternoon and evening
hours but will be possible at anytime of the day or night. Primary
concerns outside of the typical gusty winds is potential flooding due
to heavy rains. Afternoon temperatures will remain below normal
through the coming week with higher than average humidity levels
continuing.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch until midnight MST tonight for AZZ503-506>509-
511>514.

&&

Public...Cerniglia
Aviation...Cerniglia
Fire Weather....Cerniglia

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