Special Weather Statement, NWS Tucson, AZ

Area Forecast Discussion
National Weather Service Tucson AZ
247 PM MST Sat Aug 14 2021

.SYNOPSIS...
An active weather period continues into Sunday with
scattered showers and thunderstorms expected across the area. Heavy
rain and flash flooding remain the primary concern with storms. More
typical monsoon days are expected to begin Monday and continue
through mid week. Temperatures will remain below normal for the next
few days.

&&

.DISCUSSION...Today through Friday.

Today and tonight...Mid-level trough, currently circulating over the
south central Arizona, will continue to slowly transition
westward through tomorrow. This feature will be interacting with
a very moist environment (PWAT values 1.2-1.9 inches) to produce
widespread convection this afternoon. Overcast skies this morning
over a large portion of the area cleared out very quickly which
has allowed for rapid destabilization. The higher elevations have
triggered first this afternon and will continue to increase in
coverage through this afternoon. Storm motion remains quite slow
leading to a high flash flood threat where any storms develop.
This is especially true across southern Pima, Santa Cruz, and
Cochise counties where the low is expected to pass overhead this
afternoon. Late in the day into this evening, storms are expected
to develop over the Mogollon Rim and push west southwest affecting
northern Greenlee, Graham, and Pinal counties into tonight.
Outflow from this activity could make it to far western Pima
County tonight where lingering instability could trigger a few
storms late tonight. These should be moving a slightly higher
speed but could still produce some localized flooding issues.
Can't completely rule out overnight activity in other portions of
southeast Arizona as low continues to hover over the area but
generally lower coverage and intensity is expected with
convection.

Sunday...The Flash Flood Watch continues Saturday into Sunday. The
aforementioned low will slowly make an exit on Sunday across Baja
as the ridge shifts westward over northern NV and CA. A parade of
weak disturbances will continue to work around the ridge across
the area helping trigger activity as there will be little change
in available moisture. Even with the main forcing mechanism
exiting, we could still see some influence from this feature
through tomorrow. Sunday's activity is not expected to as
widespread as today but with antecedent conditions allowing for
more rapid flooding issues, the Flash Flood Watch will remain in
effect for Sunday. Best chances for Sunday look to be south and
east of Tucson.

Monday through Wednesday...Interesting pattern sets up early next
week as ridge weakens and reconsolidates in the eastern Pacific with
the entrance of a mid-level trough moving into the PacNW and across
the Great Basin through Wednesday. The coming days will become more
average monsoon days in terms of activity level with the focus on
Tuesday as a shortwave works southward across the Four Corners
region, enhancing storm activity over the local area. By
Wednesday, the trough will be working across the Great Basin and
looks to even pull up the remnants of our disturbance from this
weekend back up across the area as an open wave.

Thursday onward...Behind the exiting trough, weak ridging will
settle back in over the region along with some drier southwest flow
which will lead to at least a couple of relatively down days late
this week.

&&

.AVIATION...Valid through 16/00Z.
Scattered to numerous SHRA/TSRA will continue thru 17/04Z, then
becoming more isolated thru the overnight into Sunday morning.
SHRA/TSRA coverage will likely increase again Sunday afternoon.
Gusty winds up to 40 kts psbl with stronger afternoon and evening
thunderstorms, otherwise expect sfc winds 10 kts or less. Clouds
will be SCT-BKN 7k-10k ft MSL through the period with occasional
MVFR conditions in SHRA/TSRA. Aviation discussion not updated for
TAF amendments.

&&

.FIRE WEATHER...The active monsoon continues through mid-next
week as a series of weather disturbances transition across the
area and plenty of moisture remains in place. Flash flooding
remains the primary concern with storms that develop with a more
isolated threat for strong to severe winds and hail. A slight
decrease in the coverage of activity is expected as we go into
Monday with storms remaining more scattered each day. Below normal
temperatures are expected through mid-week before a gradual warm
up begins late in the week. Min RH values remain well above
critical levels. 20-foot winds will generally be less than 15 mph
when not influenced by thunderstorms.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through Sunday afternoon for AZZ501>515.

&&

Public/Fire Weather...Guillet
Aviation...Lader

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Special Weather Statement
National Weather Service Tucson AZ
356 PM MST Sat Aug 14 2021

AZZ507-508-512-513-142345-
Upper San Pedro River Valley including Sierra
Vista/Benson-Dragoon/Mule/Huachuca and Santa Rita Mountains including
Bisbee/Canelo Hills/Madera Canyon-Chiricahua Mountains including
Chiricahua National Monument-Eastern Cochise County Below 5000 Feet
including Douglas/Willcox-
356 PM MST Sat Aug 14 2021

...A strong thunderstorm will impact portions of southeastern Cochise
County through 445 PM MST...

At 355 PM MST, Doppler radar was tracking a strong thunderstorm 16
miles east of Tombstone, or 20 miles north of Bisbee, moving
northeast at 10 mph.

HAZARD...Winds in excess of 40 mph and pea size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
Pearce-Sunsites, Elfrida, Sunizona, McNeal and Rucker Canyon.

This includes the following highways...
 Route 181 between mile markers 39 and 47.
 Route 191 between mile markers 16 and 50.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.

&&

LAT...LON 3149 10945 3164 10991 3197 10985 3180 10930
TIME...MOT...LOC 2255Z 203DEG 9KT 3169 10979

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...40 MPH

JRM