Areal Flood Advisory 162, NWS Tucson, AZ

Area Forecast Discussion
National Weather Service Tucson AZ
203 PM MST Fri Aug 13 2021

.SYNOPSIS...A disturbance moving in from the east today into the
weekend will increase convection for much of southeast Arizona.
Some storms will generate strong winds and very heavy rain which
will result in continued flooding concerns.

&&

.DISCUSSION...Current radar shows isolated thunderstorms along the
international border and the White Mountains. Through the
afternoon expect further development in these areas with coverage
expanding. There is ample moisture and instability for storms to
tap into along with a small upper level disturbance moving in from
New Mexico. Hi-res guidance shows the storms forming over the
Whites propagating southwestward late this afternoon into the
evening. These storms will likely make it into the Tucson metro by
this evening and possibly propagate into far western Pima County.
Colliding outflows from storms along the border will also lead to
further storm formation. The main threats will be heavy rainfall
and strong to severe wind gusts. The SPC has most of the CWA in a
marginal severe risk for wind. Storms will also be capable of
1"-2" per hour rainfall rates. The soil is already saturated from
previous rains so washes and rivers will be quick to start flowing.
Through tonight the HREF PMM QPF shows some of the sky islands
receiving up to 3 inches of rain. Flash and areal flooding will be
a threat today and tomorrow especially over area burn scars.
Tonight there could be a few lingering storms especially in
western Pima County.

The forecast Saturday is a little more uncertain than today and
will depend on how much nocturnal activity there is tonight. The
ingredients for storms with heavy rainfall will be there but the
atmosphere could be worked over leading to a later start. The
ECMWF EFI for QPF does show a chance for anomalously high
rainfall especially for eastern areas. A weak disturbance will
still be moving through which could lend some upper level support
Saturday as well. The main threat looks to be heavy rainfall with
severe winds taking a back seat, although winds in excess of 40
mph will still be possible. Areas that receive rainfall today
will be especially susceptible to flooding Saturday. Sunday
eastern areas begin to dry some with slightly reduced PWAT values,
but ample moisture will still be in place from Tucson westward.
Expect another round of scattered convection with heavy rainfall
being the primary threat.

Monday PWAT values will be back down to around normal for this
time of year, so expect more isolated to scattered showers and
thunderstorms. The steering flow will be out of the northwest
leading to the chance for a Rim shot. Little too early to tell how
far storms will propagate off the Rim. Tuesday and Wednesday look
to be low to mid grade monsoon days. Thereafter a trough moves
through to the north turning our flow southwesterly, which will
likely dry us out a little bit.

&&

.AVIATION...Valid through 15/00Z.
Isolated to scattered SHRA/TSRA this afternoon along the
international border and the White Mountains. Storms expand in
coverage by late afternoon into the evening covering most of
southeast Arizona. There is a chance some storms remain overnight
with another round of convection Saturday afternoon. Some of the
storms today could be severe with gusty winds and small hail.
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...Ample moisture this weekend along with periodic
mid level disturbances will result in scattered to numerous
showers and thunderstorms across southeastern Arizona. Storm
coverage then reduces starting Monday to isolated to scattered.
Given the higher levels of moisture and cloud coverage, temperatures
will be cooler this weekend into next. 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...
Flash Flood Watch through Sunday afternoon for AZZ501>515.

&&

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Special Weather Statement
National Weather Service Tucson AZ
704 PM MST Fri Aug 13 2021

AZZ507-508-513-140245-
Upper San Pedro River Valley including Sierra
Vista/Benson-Dragoon/Mule/Huachuca and Santa Rita Mountains including
Bisbee/Canelo Hills/Madera Canyon-Eastern Cochise County Below 5000
Feet including Douglas/Willcox-
704 PM MST Fri Aug 13 2021

...A strong thunderstorm will impact portions of southeastern Pima,
southwestern Cochise and northeastern Santa Cruz Counties through 745
PM MST...

At 704 PM MST, Doppler radar was tracking a strong thunderstorm near
Tombstone, or 17 miles southeast of Benson, moving south at 10 mph.

HAZARD...Wind gusts of 50 to 55 mph and half inch 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...
Sierra Vista, Whetstone, Huachuca City, St. David, Tombstone, Elgin,
Fort Huachuca, Fairbank and Charleston.

This includes the following highways...
 Route 80 between mile markers 303 and 332.
 Route 82 between mile markers 44 and 67.
 Route 90 between mile markers 302 and 315, and between mile markers
329 and 336.

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.

A Severe Thunderstorm Watch remains in effect until 300 AM MST for
southeastern Arizona.

&&

LAT...LON 3188 11021 3186 10982 3146 10982 3167 11057
TIME...MOT...LOC 0204Z 006DEG 11KT 3182 11006

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...55 MPH

JRM

Special Weather Statement
National Weather Service Tucson AZ
722 PM MST Fri Aug 13 2021

AZZ503-504-507-513-514-140300-
Santa Catalina and Rincon Mountains including Mount
Lemmon/Summerhaven-Upper San Pedro River Valley including Sierra
Vista/Benson-Dragoon/Mule/Huachuca and Santa Rita Mountains including
Bisbee/Canelo Hills/Madera Canyon-Upper Santa Cruz River and Altar
Valleys including Nogales-Tucson Metro Area including Tucson/Green
Valley/Marana/Vail-
722 PM MST Fri Aug 13 2021

...Strong thunderstorms will impact portions of east central Pima,
west central Cochise and northeastern Santa Cruz Counties through 800
PM MST...

At 722 PM MST, Doppler radar was tracking strong thunderstorms along
a line extending from 7 miles northeast of Elgin to 10 miles north of
Sonoita to near Vail. Movement was southwest at 25 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...
Vail, East Sahuarita, Patagonia, Sonoita, Elgin, Corona De Tucson and
Madera Canyon.

This includes the following highways...
 Interstate 10 between mile markers 280 and 290.
 Route 82 between mile markers 19 and 48.
 Route 83 between mile markers 17 and 58.
 Route 90 between mile markers 302 and 304.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

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

A Severe Thunderstorm Watch remains in effect until 300 AM MST for
southeastern Arizona.

&&

LAT...LON 3159 11093 3191 11094 3211 11057 3205 11054
      3182 11055 3179 11031 3148 11061
TIME...MOT...LOC 0222Z 050DEG 22KT 3172 11047 3182 11058 3206 11064

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

JRM

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE TUCSON AZ
947 PM MST FRI AUG 13 2021

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0528 PM     FLASH FLOOD      14 S SAFFORD            32.63N 109.69W
08/13/2021                   GRAHAM             AZ   DEPT OF HIGHWAYS

            US HIGHWAY 191 NEAR MILE POST 100 HAS
            FLOODED. REPORT FOUND ON AZ 511.

0223 PM     FLASH FLOOD      13 W BISBEE             31.38N 110.14W
08/13/2021                   COCHISE            AZ   DEPT OF HIGHWAYS

            FLOODING ON 92 EASTBOUND NEAR GUIDANCE WAY
            (MILE POST 339). CAUSED A VEHICLE ACCIDENT.

0714 PM     FLASH FLOOD      BENSON                  31.96N 110.31W
08/13/2021                   COCHISE            AZ   LAW ENFORCEMENT

            FLOODING ISSUES IN THE CITY OF BENSON FROM
            BENSON POLICE. THE BENSON COMMUNITY CENTER
            WAS IMPACTED AND LOCAL POLICE ARE
            REDIRECTING TRAFFIC AND CLOSING SECTIONS OF
            ROADS. A HOUSE WAS FLOODED OUT, DETAILS ON
            THE SPECIFICS ARE UNKNOWN.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE TUCSON AZ
1010 PM MST FRI AUG 13 2021

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0938 PM     FLASH FLOOD      4 NNW BISBEE            31.46N 109.95W
08/13/2021                   COCHISE            AZ   PUBLIC

            FLOODING ON ROADWAY ON SR-80 NORTHBOUND NEAR
            N OLD DIVIDE RD (339).

&&

JRM

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE TUCSON AZ
1011 PM MST FRI AUG 13 2021

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0942 PM     FLASH FLOOD      1 E SAINT DAVID         31.90N 110.21W
08/13/2021                   COCHISE            AZ   PUBLIC

            FLOODING ON ROADWAY ON SR-80 NORTHBOUND NEAR
            E BARLOW LN (301).

&&

JRM