Special Weather Statement, NWS Tucson, AZ

Area Forecast Discussion
National Weather Service Tucson AZ
225 PM MST Mon Aug 3 2020

.SYNOPSIS...High pressure over the region will continue to maintain
hotter than normal temperatures over the region. The high will weaken
slightly through mid-week allowing for slight cooling and a continued
chance of afternoon thunderstorms. As the weekend approaches, dry
southwest flow and then the high building again will result in less
thunderstorm activity and hotter temperatures Friday onward.

&&

.DISCUSSION...Well convection really fired up with a couple of
impressive storms already. Expect this to continue into the evening,
with outflow boundaries beginning to play a role at some point. Some
concern for portions of the Tohono O'odham Nation for later this
afternoon with the potential for a strong, dust kicking outflow
moving westward from the convection that is in the Arivaca/Green
Valley area. All this will all settle down by midnight with clearing
thereafter.

With the upper level ridge overhead, we were initially thinking that
Tuesday would be a down day, however that is in question at this
time. HRRR, the two UA WRF runs and the HREF all point to an active
day and given what we have seen thus far I'm good with leaning
heavier toward that direction. From the look of things with the
position of the upper level high, there is potential for the
development of a down I-10 haboob or west across the northern part of
the Tohono O'odham Nation during the afternoon. For the time being I
raised pops across this area and strengthened the mention of
thunderstorms. The night shift will need to evaluate the blowing dust
potential in the usual areas NW of Tucson.

On Wednesday the upper level high has shifted a bit further east
with SSW flow across the area and a favorable thermal profile for
convection. We will begin to see drier air begining to move into far
western part of Pima county. That afternoon and evening should have
thunderstorms developing from just west of the Tucson/Nogales area
east to New Mexico and this time they should move more to the N to
NE.

On Thursday the SW flow aloft strengthens with the drier air aloft
pushing further east limiting any convection to east of the Tuscon
area although what does form will be in a slightly better shear
environment.

Friday through the weekend looks like we will trend toward drier with
temperatures climbing once again, unfortunately validating the
Climate Prediction Center's hotter than normal August outlook. We
start out with a drying SW flow aloft then the upper ridge builds
toward the area again along the international border, a bad position
for moisture transport given the elongated NE/SW axis of the ridge.
So at this time I maintained the mostly dry forecast for the coming
weekend and tweaked temps up a degree or so, but even that is a
couple of degrees conservative with current thickness values.

&&

.AVIATION...Valid through 05/00Z.
Isolated to scattered TSRA/SHRA continuing into this evening with
the potential to affect KTUS, but especially terminals near the
Int'l border. Tstm gusts around 45 kts and MVFR conditions may occur
at times. Otherwise, SFC wind NWLY at 6-13 kts with gusts around 20
kts this afternoon and easing to variable less than 10 kts this
evening. Westerly wind increasing again Tuesday afternoon to 10-15
kts along with isolated to scattered TSRA/SHRA. Aviation discussion
not updated for TAF amendments.

&&

.FIRE WEATHER...Above normal temperatures into this weekend.
Isolated to scattered mainly afternoon and evening thunderstorms
favoring locations east to south of Tucson through Tuesday. The
coverage of thunderstorms extends further westward by midweek and
includes areas from Tucson eastward. By the weekend, thunderstorms
will once again be limited to areas east to south of Tucson. Except
for some slightly elevated 20-foot northwest winds in the upper Gila
River valley this afternoon, 20-foot winds will generally follow
typical diurnal patterns at less than 15 mph. However, thunderstorms
may produce wind gusts in excess of 40 mph.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
None.
&&

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Aviation...Carpenter
Fire Weather....Carpenter

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Special Weather Statement
National Weather Service Tucson AZ
143 PM MST Mon Aug 3 2020

AZZ502>504-513-032130-
Tohono O'odham Nation including Sells-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-
143 PM MST Mon Aug 3 2020

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN PIMA AND NORTH
CENTRAL SANTA CRUZ COUNTIES UNTIL 230 PM MST...

At 142 PM MST, Doppler radar was tracking a strong thunderstorm 7
miles southwest of Green Valley, moving south at 10 mph.

Half inch hail and wind gusts up to 50 mph will be possible with this
storm.

Locations impacted include...
Sahuarita, Green Valley, Three Points, Amado and Arivaca Junction.

LAT...LON 3203 11142 3201 11101 3168 11090 3161 11133
TIME...MOT...LOC 2042Z 342DEG 10KT 3179 11112

AH

Special Weather Statement
National Weather Service Tucson AZ
201 PM MST Mon Aug 3 2020

AZZ507-513-032130-
Upper San Pedro River Valley including Sierra
Vista/Benson-Dragoon/Mule/Huachuca and Santa Rita Mountains including
Bisbee/Canelo Hills/Madera Canyon-
201 PM MST Mon Aug 3 2020

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHWESTERN COCHISE COUNTY UNTIL
230 PM MST...

At 201 PM MST, Doppler radar was tracking a strong thunderstorm over
Huachuca City, moving south at 10 mph.

Nickel size hail and wind gusts up to 50 mph will be possible with
this storm.

Locations impacted include...
Sierra Vista, Hereford, Huachuca City, Fort Huachuca and Ramsey
Canyon Preserve.

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.

&&

LAT...LON 3165 11043 3166 11022 3143 11013 3141 11044
TIME...MOT...LOC 2101Z 354DEG 8KT 3160 11032

Carpenter

Special Weather Statement
National Weather Service Tucson AZ
206 PM MST Mon Aug 3 2020

AZZ508-509-511-032145-
Upper Gila River and Aravaipa Valleys including
Clifton/Safford-Eastern Cochise County Below 5000 Feet including
Douglas/Willcox-Galiuro and Pinaleno Mountains including Mount
Graham-
206 PM MST Mon Aug 3 2020

...SIGNIFICANT WEATHER ADVISORY FOR SOUTH CENTRAL GRAHAM AND NORTH
CENTRAL COCHISE COUNTIES UNTIL 245 PM MST...

At 206 PM MST, Doppler radar was tracking a strong thunderstorm 20
miles northwest of Willcox, moving east at 10 mph.

Pea sized hail and wind gusts up to 50 mph will be possible with
this storm.

This storm will remain over mainly remote areas of south central
Graham and north central Cochise Counties.

LAT...LON 3242 11016 3254 11013 3253 10986 3231 10995
TIME...MOT...LOC 2106Z 286DEG 7KT 3247 11008

AH

Special Weather Statement
National Weather Service Tucson AZ
316 PM MST Mon Aug 3 2020

AZZ503-513-032300-
Dragoon/Mule/Huachuca and Santa Rita Mountains including
Bisbee/Canelo Hills/Madera Canyon-Upper Santa Cruz River and Altar
Valleys including Nogales-
316 PM MST Mon Aug 3 2020

...SIGNIFICANT WEATHER ADVISORY FOR EASTERN SANTA CRUZ COUNTY UNTIL
400 PM MST...

At 316 PM MST, Doppler radar was tracking a strong thunderstorm near
Patagonia, moving southwest at 10 mph.

Nickel size hail and wind gusts up to 50 mph will be possible with
this storm.

Locations impacted include...
Patagonia, Sonoita, Nogales International Airport and Patagonia Lake
State Park.

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.

&&

LAT...LON 3169 11071 3157 11056 3134 11075 3152 11098
TIME...MOT...LOC 2216Z 043DEG 9KT 3158 11070

Carpenter