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

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

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

0450 PM     FLASH FLOOD      4 E TUCSON              32.21N 110.83W
07/22/2021                   PIMA               AZ   FIRE DEPT/RESCUE

            CORRECTS PREVIOUS FLASH FLOOD REPORT FROM 4
            E TUCSON. SWIFT WATER RESCUE ON A CHILD IN
            THE AREA EAST OF KOLB RD AND 22ND STREET.

&&

KJS

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

AZZ502-505-230115-
Tohono O'odham Nation including Sells-South Central Pinal County
including Eloy/Picacho Peak State Park-
536 PM MST Thu Jul 22 2021

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHWESTERN PINAL COUNTY UNTIL
615 PM MST...

At 536 PM MST, Doppler radar was tracking a strong thunderstorm over
Chui-Chu, or 12 miles south of Casa Grande, moving west at 5 mph.

Winds in excess of 40 mph will be possible with this storm.

Locations impacted include...
Chui-Chu, Cockleburr, Jack Rabbit, Shopishk and East Chui-Chu.

LAT...LON 3276 11177 3276 11174 3273 11174 3273 11167
      3261 11166 3258 11208 3272 11210 3273 11205
      3277 11205 3277 11188 3279 11187 3279 11178
TIME...MOT...LOC 0036Z 103DEG 6KT 3273 11179

AH

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

AZZ501-502-230130-
Western Pima County Including Ajo/Organ Pipe Cactus National
Monument-Tohono O'odham Nation including Sells-
544 PM MST Thu Jul 22 2021

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

At 543 PM MST, Doppler radar was tracking a strong thunderstorm 7
miles north of Hickiwan, or 22 miles east of Ajo, moving west at 5
mph.

Half inch hail and winds in excess of 40 mph will be possible with
this storm.

Locations impacted include...
Hickiwan and Vaya Chin.

LAT...LON 3251 11228 3231 11233 3228 11276 3251 11276
TIME...MOT...LOC 0043Z 103DEG 5KT 3247 11250

AH

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

AZZ502-230145-
Tohono O'odham Nation including Sells-
619 PM MST Thu Jul 22 2021

...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN PIMA AND
SOUTHWESTERN PINAL COUNTIES UNTIL 645 PM MST...

At 619 PM MST, Doppler radar was tracking a strong thunderstorm 15
miles northeast of Kaka, or 27 miles southwest of Casa Grande, moving
west at 10 mph.

Winds in excess of 40 mph will be possible with this storm.

This storm will remain over mainly remote areas of northwestern Pima
and southwestern Pinal Counties.

LAT...LON 3251 11221 3268 11220 3268 11216 3272 11215
      3272 11205 3273 11205 3272 11201 3252 11201
      3247 11231 3251 11231
TIME...MOT...LOC 0119Z 106DEG 10KT 3264 11211

AH

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