Special Weather Statement, NWS Tucson, AZ

Area Forecast Discussion
National Weather Service Tucson AZ
245 PM MST Thu Jul 22 2021

.SYNOPSIS...An approaching weather system from the east will bring
widespread showers and thunderstorms to the area tonight through
Saturday night. Locally heavy rainfall combined with a saturated
ground from recent rains may result in flash flooding and flooding
during this period. Improving weather can be anticipated late
Sunday, although elevated flows in area washes and streams will
still be possible. Thereafter, a decrease in daily shower and
thunderstorm activity can be expected early next week. High
temperatures will be below normal for the next week with well
below normal highs Friday through Sunday.

&&

.DISCUSSION...Convection going on as expected this afternoon S/SW
of Tucson and NE of Tucson up to the White mountains. Storms will
be moving to the W/SW with portions of the area under marginal
risk for severe thunderstorms. Blowing dust will be issue into the
evening hours.

CAMs still indicating that a rim shot later this evening moving
SW into the lower deserts. This will be the beginning of a multi-
day heavy rain/flash flooding/flood event for the area with the
soils already saturated. A flash flood watch for the entire area
goes into effect at 6 pm this evening and runs through at least
Saturday night. This may end up being extended by future shifts.

The culprit for this heavy rain/flash flooding/flooding event is
an anomalous upper level low, currently near the Texas Big Bend
this afternoon, which will be retrograding west across Arizona
over the next 72 hours. Thus the forecast area will see periods of
moderate to heavy rain over the next three days as the dynamics
from this upper low rotate across the area. Latest 72 hr rainfall
totals for the area from WPC, except for wrn Pima County, has
1"-3" in the valleys and 3"-8" in the mountains. What is
interesting about this event is that once the upper low is west of
Tucson, likely Saturday evening, there will be a period of 10-20
kt upslope flow into the south facing portions of the Catalina
mountains and the Bighorn burn scar, which may enhance rainfall
rates in that time period.

Next week: We're back into a normal monsoon pattern with a chance
of afternoon and evening showers and thunderstorms. High
temperatures will be heating back up but remaining below normal.

&&

.AVIATION...Valid through 24/00Z.
SCT-BKN clouds at 8k-12k ft MSL much of the period. Scattered to
numerous SHRA/TSRA developing this afternoon and remain into the
nighttime period. Precipitation is expected to continue to develop
tomorrow as an active period of weather persists. Expect brief
MVFR CIGS/VSBYS and mountain obscurations around TSRA along with
gusty outflow winds, potentially in excess of 45 kts with the
strongest storms. Otherwise, SFC wind generally less than 12 kts
following diurnal trends. Aviation discussion not updated for TAF
amendments.

&&

.FIRE WEATHER...Periods of heavy rainfall are expected today into
the weekend, with scattered to numerous showers and thunderstorms.
Flooding issues are anticipated due to soils already being fairly
saturated from an active start to the monsoon. While in this
pattern, showers and storms will be possible at all hours of the day
and overnight. Gusty winds in excess of 40 mph and numerous
lightning strikes may accompany stronger storms. Daytime
temperatures will remain below normal. 20-foot winds will generally
be less than 15 mph when not influenced by thunderstorms.

&&

.HYDROLOGY...Given the chance for heavy rainfall and already
saturated soils the potential for flows in rivers and washes is
high. The latest river forecasts from the Colorado Basin River
Forecast Center show Sabino Creek, Pantano Wash near Vail, and
Santa Cruz River at Trico Road rising near or to flood stage on
Saturday. However, most river forecasts across southeast Arizona
show elevated stream flow over the weekend. With high enough
rainfall amounts other locations could reach flood stage and
possibly out of bank flow. Stream flow may also take longer to
recede if basin receives multiple days of rainfall. Potentially
leading to elevated stream flow into early next week.

River observations and forecasts can be found at the following
sites:
https://water.weather.gov/ahps2/index.php?wfo=twc
http://www.cbrfc.noaa.gov

&&

.CLIMATE...Daily rainfall records are likely to be broken across
southeast Arizona through Saturday. Interesting high temperature
note. There is a 13% chance that the high temperature in Tucson
on Saturday may may not get out of the 70s. Since 1895, there
have only been 10 days in July in which the high temperature was
in the 70s with the last occurrence being July 22, 1998 when the
high was 76. Interesting.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
 Flash Flood Watch from 6 PM MST this evening through Saturday
  evening for AZZ501>515.

&&

Public and Climate...74
Aviation and Fire Weather...Howlett
Hydrology...Boyle

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

Special Weather Statement
National Weather Service Tucson AZ
637 PM MST Thu Jul 22 2021

AZZ501-502-230215-
Western Pima County Including Ajo/Organ Pipe Cactus National
Monument-Tohono O'odham Nation including Sells-
637 PM MST Thu Jul 22 2021

...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN PIMA COUNTY UNTIL
715 PM MST...

At 636 PM MST, Doppler radar was tracking a strong thunderstorm 7
miles south of Hickiwan, or 25 miles east of Ajo. This storm was
nearly stationary.

Winds in excess of 40 mph and pea sized hail will be possible with
this storm.

Locations impacted include...
Hickiwan, Organ Pipe Cactus National Monument, San Simon, Why, Charco
27, Ventana, Gunsight, Vaya Chin and San Simon West.

LAT...LON 3250 11223 3214 11229 3216 11277 3250 11274
TIME...MOT...LOC 0136Z 103DEG 4KT 3226 11247

AH

Special Weather Statement
National Weather Service Tucson AZ
647 PM MST Thu Jul 22 2021

AZZ502-230230-
Tohono O'odham Nation including Sells-
647 PM MST Thu Jul 22 2021

...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN PIMA AND
SOUTHWESTERN PINAL COUNTIES UNTIL 730 PM MST...

At 646 PM MST, Doppler radar was tracking a strong thunderstorm 11
miles east of Kaka, or 32 miles southwest of Casa Grande. This storm
was nearly stationary.

Wind gusts up to 50 mph will be possible with this storm.

Locations impacted include...
Kohatk.

LAT...LON 3251 11221 3255 11220 3268 11220 3268 11216
      3271 11215 3269 11197 3251 11198 3250 11229
TIME...MOT...LOC 0146Z 103DEG 4KT 3257 11213

AH

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE TUCSON AZ
648 PM MST THU JUL 22 2021

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

0530 PM     TSTM WND DMG     3 SSW CHUICHU           32.70N 111.82W
07/22/2021                   PINAL              AZ   UTILITY COMPANY

            POWER OUTAGE AFFECTING CHUI CHU AND WHITE
            HORSE PASS. REPORTS OF A POWER POLE DOWN ON
            THE HIGHWAY ON RT 15 NEAR WHITE HORSE PASS
            TURN OFF. SOURCED FROM POWER UTILITY COMPANY
            TWEETER POST.

&&

KJS

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE TUCSON AZ
701 PM MST THU JUL 22 2021

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

0651 PM     TSTM WND GST     4 ENE SAFFORD           32.85N 109.63W
07/22/2021  M55 MPH          GRAHAM             AZ   ASOS

            ASOS STATION KSAD SAFFORD REGIONAL AIRPORT.

&&

KJS

Special Weather Statement
National Weather Service Tucson AZ
702 PM MST Thu Jul 22 2021

AZZ509-511-230230-
Upper Gila River and Aravaipa Valleys including
Clifton/Safford-Galiuro and Pinaleno Mountains including Mount
Graham-
702 PM MST Thu Jul 22 2021

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN GRAHAM AND SOUTH
CENTRAL GREENLEE COUNTIES UNTIL 730 PM MST...

At 701 PM MST, Doppler radar was tracking strong thunderstorms in
the area around Safford, moving south-southwest at 25 mph.

Wind gusts up to 50 mph will be possible with this storm.

Locations impacted include...
Safford, Thatcher, Solomon, Roper Lake State Park, Safford Regional
Airport, Pima, Central, Swift Trail Junction and Frye Mesa Dam.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

LAT...LON 3298 10981 3274 10921 3246 10940 3259 10972
      3284 11000
TIME...MOT...LOC 0201Z 062DEG 22KT 3278 10972

Cerniglia

Special Weather Statement
National Weather Service Tucson AZ
746 PM MST Thu Jul 22 2021

AZZ509>511-230345-
Upper Gila River and Aravaipa Valleys including Clifton/Safford-White
Mountains of Graham and Greenlee Counties including Hannagan
Meadow-Galiuro and Pinaleno Mountains including Mount Graham-
746 PM MST Thu Jul 22 2021

...SIGNIFICANT WEATHER ADVISORY FOR SOUTH CENTRAL GRAHAM COUNTY UNTIL
845 PM MST...

At 745 PM MST, Doppler radar was tracking a group of strong
thunderstorms near Pima and Fort Grant, moving southwest at 25 mph.

Wind gusts up to 50 mph will be possible with this storm.

Locations impacted include...
Safford, Thatcher, Roper Lake State Park, Pima, Central, Fort Thomas,
Swift Trail Junction, Fort Grant, Mount Graham, Bonita and Frye Mesa
Dam.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Frequent lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

LAT...LON 3308 10993 3298 10966 3244 10967 3248 11001
      3282 11014
TIME...MOT...LOC 0245Z 030DEG 22KT 3291 10984

Cerniglia