Winter Storm Warning 2, NWS Tucson, AZ

200 
WWUS45 KTWC 202210
WSWTWC

URGENT - WINTER WEATHER MESSAGE
National Weather Service Tucson AZ
310 PM MST Wed Feb 20 2019

...MAJOR WINTER STORM TO BRING SIGNIFICANT SNOWFALL TO THE
MOUNTAINS OF SOUTHEAST ARIZONA THURSDAY AND FRIDAY...

AZZ509-211300-
/O.EXA.KTWC.WS.W.0002.190222T0600Z-190223T0000Z/
Upper Gila River Valley-
Including the city of Clifton
310 PM MST Wed Feb 20 2019

...WINTER STORM WARNING IN EFFECT FROM 11 PM THURSDAY TO 5 PM MST
FRIDAY ABOVE 3500 FEET ...

* WHAT...Heavy snow expected. Plan on difficult travel conditions.
  Total snow accumulations of 3 to 8 inches.

* WHERE...Upper Gila River Valley.

* WHEN...11 PM Thursday to 5 PM Friday.

* ADDITIONAL DETAILS...Look for significant reductions in 
  visibility at times.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Winter Storm Warning means heavy snow accumulations are
expected. Gusty winds and blowing snow are also possible. This
will make travel very difficult or impossible...especially in the
mountains. 

Stay tuned to NOAA Weather Radio...commercial television or radio
stations...or your cable television service provider for updates
on this Winter Storm.

&&

$$

AZZ510-511-513>515-211300-
/O.CON.KTWC.WS.W.0002.190221T1200Z-190223T0000Z/
White Mountains of Graham and Greenlee Counties-
Galiuro and Pinaleno Mountains-
Dragoon and Mule and Huachuca and Santa Rita Mountains-
Catalina and Rincon Mountains-Baboquivari Mountains-
Including the cities of Hannagan Meadow, Mount Graham, Bisbee, 
Canelo Hills, Mount Lemmon, and Summerhaven
310 PM MST Wed Feb 20 2019

...WINTER STORM WARNING REMAINS IN EFFECT FROM 5 AM THURSDAY TO
5 PM MST FRIDAY ABOVE 5000 FEET...

* WHAT...Heavy snow and blowing snow expected. Travel will be very
  difficult to impossible. Tree branches could fall as well. Total
  snow accumulations of 12 to 24 inches between 5000 feet and 7000
  feet and 20 to 40 inches with localized higher amounts above 
  7000 feet.

* WHERE...White Mountains of Graham and Greenlee Counties, 
  Galiuro and Pinaleno Mountains, Dragoon and Mule and Huachuca 
  and Santa Rita Mountains, Catalina and Rincon Mountains and 
  Baboquivari Mountains.

* WHEN...5 AM Thursday to 5 PM Friday.

* ADDITIONAL DETAILS...Winds gusting as high as 50 mph will 
  cause widespread blowing and drifting snow.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Winter Storm Warning means heavy snow accumulations are
expected. Gusty winds and blowing snow are also possible. This
will make travel very difficult or impossible...especially in the
mountains. 

Stay tuned to NOAA Weather Radio...commercial television or radio
stations...or your cable television service provider for updates
on this Winter Storm.

&&

$$

AZZ512-211300-
/O.CON.KTWC.WS.W.0002.190222T0600Z-190223T0000Z/
Chiricahua Mountains-
Including the city of Chiricahua NM
310 PM MST Wed Feb 20 2019

...WINTER STORM WARNING REMAINS IN EFFECT FROM 11 PM THURSDAY TO
5 PM MST FRIDAY...

* WHAT...Heavy snow and blowing snow expected. Plan on difficult
  travel conditions. Damage to trees and power lines is possible.
  Total snow accumulations of 10 to 16 inches, with localized
  amounts up to 20 inches, are expected.

* WHERE...Chiricahua Mountains.

* WHEN...11 PM Thursday to 5 PM Friday.

* ADDITIONAL DETAILS...Winds gusting as high as 55 mph will 
  cause widespread blowing and drifting snow.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Winter Storm Warning means heavy snow accumulations are
expected. Gusty winds and blowing snow are also possible. This
will make travel very difficult or impossible...especially in the
mountains. 

Stay tuned to NOAA Weather Radio...commercial television or radio
stations...or your cable television service provider for updates
on this Winter Storm.

&&

$$

AZZ506-211300-
/O.CON.KTWC.WS.W.0002.190222T0600Z-190223T0000Z/
Southeast Pinal County-
Including the city of Oracle
310 PM MST Wed Feb 20 2019

...WINTER STORM WARNING REMAINS IN EFFECT FROM 11 PM THURSDAY TO
5 PM MST FRIDAY ABOVE 3500 FEET...

* WHAT...Heavy snow expected. Plan on difficult travel conditions,
  including during the morning commute on Friday. Total snow
  accumulations ranging from 3 to 8 inches between 3500 and 4000
  feet and up to 8 to 16 inches in the Oracle area.

* WHERE...Southeast Pinal County.

* WHEN...11 PM Thursday to 5 PM Friday.

* ADDITIONAL DETAILS...Look for significant reductions in 
  visibility at times.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Winter Storm Warning means heavy snow accumulations are
expected. Gusty winds and blowing snow are also possible. This
will make travel very difficult or impossible...especially in the
mountains. 

Stay tuned to NOAA Weather Radio...commercial television or radio
stations...or your cable television service provider for updates
on this Winter Storm.

&&

$$

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

778 
WWUS45 KTWC 211003
WSWTWC

URGENT - WINTER WEATHER MESSAGE
National Weather Service Tucson AZ
303 AM MST Thu Feb 21 2019

...MAJOR WINTER STORM TO BRING SIGNIFICANT SNOWFALL TO THE
MOUNTAINS OF SOUTHEAST ARIZONA THURSDAY AND FRIDAY...

AZZ507-508-220000-
/O.EXA.KTWC.WS.W.0002.190222T0600Z-190223T0000Z/
Upper San Pedro River Valley-
Eastern Cochise County below 5000 feet-
Including the cities of Sierra Vista and Willcox
303 AM MST Thu Feb 21 2019

...WINTER STORM WARNING IN EFFECT FROM 11 PM THIS EVENING TO 5 PM
MST FRIDAY...

* WHAT...Heavy snow expected. Plan on difficult travel conditions.
  Total snow accumulations of 2 to 6 inches.

* WHERE...Upper San Pedro River Valley and Eastern Cochise 
  County below 5000 feet.

* WHEN...11 PM today to 5 PM Friday.

* ADDITIONAL DETAILS...Look for significant reductions in 
  visibility at times.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Winter Storm Warning means heavy snow accumulations are expected.
Gusty winds and blowing snow are also possible. This will make 
travel very difficult or impossible...especially in the mountains.

Stay tuned to NOAA Weather Radio...commercial television or radio
stations...or your cable television service provider for updates
on this Winter Storm.

&&

$$

AZZ510-511-513>515-220000-
/O.CON.KTWC.WS.W.0002.190221T1200Z-190223T0000Z/
White Mountains of Graham and Greenlee Counties-
Galiuro and Pinaleno Mountains-
Dragoon and Mule and Huachuca and Santa Rita Mountains-
Catalina and Rincon Mountains-Baboquivari Mountains-
Including the cities of Hannagan Meadow, Mount Graham, Bisbee, 
Canelo Hills, Mount Lemmon, and Summerhaven
303 AM MST Thu Feb 21 2019

...WINTER STORM WARNING REMAINS IN EFFECT UNTIL 5 PM MST FRIDAY...

* WHAT...Snow developing this morning, then becoming heavy at
  times this afternoon into Friday. Travel will be very difficult
  to impossible. Tree branches could fall as well. Total snow
  accumulations of 12 to 24 inches between 5000 feet and 7000 feet
  and 20 to 40 inches with localized higher amounts above 7000
  feet.

* WHERE...White Mountains of Graham and Greenlee Counties, 
  Galiuro and Pinaleno Mountains, Dragoon and Mule and Huachuca 
  and Santa Rita Mountains, Catalina and Rincon Mountains and 
  Baboquivari Mountains.

* WHEN...5 AM today to 5 PM Friday.

* ADDITIONAL DETAILS...Winds gusting as high as 50 mph will cause
  widespread blowing and drifting snow.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Winter Storm Warning means heavy snow accumulations are expected.
Gusty winds and blowing snow are also possible. This will make 
travel very difficult or impossible...especially in the mountains.

Stay tuned to NOAA Weather Radio...commercial television or radio
stations...or your cable television service provider for updates
on this Winter Storm.

&&

$$

AZZ506-509-512-220000-
/O.CON.KTWC.WS.W.0002.190222T0600Z-190223T0000Z/
Southeast Pinal County-Upper Gila River Valley-
Chiricahua Mountains-
Including the cities of Oracle, Clifton, and Chiricahua NM
303 AM MST Thu Feb 21 2019

...WINTER STORM WARNING REMAINS IN EFFECT FROM 11 PM THIS EVENING
TO 5 PM MST FRIDAY...

* WHAT...Heavy snow expected tonight into Friday. Plan on  
  difficult travel conditions. Total snow accumulations of 4 to 12
  inches between 3500 feet and 5000 feet and 12 to 18 inches 
  above 5000 feet are expected.

* WHERE...Southeast Pinal County, Upper Gila River Valley and 
  Chiricahua Mountains.

* WHEN...11 PM today to 5 PM Friday.

* ADDITIONAL DETAILS...Look for significant reductions in 
  visibility at times.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Winter Storm Warning means heavy snow accumulations are expected.
Gusty winds and blowing snow are also possible. This will make 
travel very difficult or impossible...especially in the mountains.

Stay tuned to NOAA Weather Radio...commercial television or radio
stations...or your cable television service provider for updates
on this Winter Storm.

&&

$$

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

150 
WWUS45 KTWC 212059
WSWTWC

URGENT - WINTER WEATHER MESSAGE
National Weather Service Tucson AZ
159 PM MST Thu Feb 21 2019

...MAJOR WINTER STORM TO BRING SIGNIFICANT SNOWFALL TO PORTIONS 
OF SOUTHEAST ARIZONA THROUGH FRIDAY...

AZZ510-511-513>515-221200-
/O.EXT.KTWC.WS.W.0002.000000T0000Z-190223T0300Z/
White Mountains of Graham and Greenlee Counties-
Galiuro and Pinaleno Mountains-
Dragoon and Mule and Huachuca and Santa Rita Mountains-
Catalina and Rincon Mountains-Baboquivari Mountains-
Including the cities of Hannagan Meadow, Mount Graham, Bisbee, 
Canelo Hills, Mount Lemmon, and Summerhaven
159 PM MST Thu Feb 21 2019

...WINTER STORM WARNING NOW IN EFFECT UNTIL 8 PM MST FRIDAY...

* WHAT...Heavy snow occurring. Travel will be very difficult to
  impossible, including during the morning commute on Friday. Tree
  branches could fall as well. Total snow accumulations of 10 to
  20 inches between 5000 feet and 7000 feet and 20 to 40 inches 
  with localized higher amounts above 7000 feet. 

* WHERE...White Mountains of Graham and Greenlee Counties, 
  Galiuro and Pinaleno Mountains, Dragoon and Mule and Huachuca 
  and Santa Rita Mountains, Catalina and Rincon Mountains and 
  Baboquivari Mountains.

* WHEN...Until 8 PM Friday. The Bisbee area isn't expected to see
  Winter Storm conditions start until Friday morning. 

* ADDITIONAL DETAILS...Look for significant reductions in 
  visibility at times.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Winter Storm Warning means heavy snow accumulations are
expected. Gusty winds and blowing snow are also possible. This
will make travel very difficult or impossible...especially in the
mountains. 

Stay tuned to NOAA Weather Radio...commercial television or radio
stations...or your cable television service provider for updates
on this Winter Storm.

&&

$$

AZZ506>509-512-221200-
/O.EXT.KTWC.WS.W.0002.190222T0600Z-190223T0300Z/
Southeast Pinal County-Upper San Pedro River Valley-
Eastern Cochise County below 5000 feet-Upper Gila River Valley-
Chiricahua Mountains-
Including the cities of Oracle, Sierra Vista, Willcox, Clifton, 
and Chiricahua NM
159 PM MST Thu Feb 21 2019

...WINTER STORM WARNING NOW IN EFFECT FROM 11 PM THIS EVENING TO
8 PM MST FRIDAY...

* WHAT...Heavy snow expected. Plan on difficult travel conditions,
  including during the evening commute on Friday. Total snow
  accumulations of 1 to 4 inches between 3500 and 4500 feet, 2 to
  12 inches between 4500 and 5000 feet with the lower amounts in
  Cochise County and the highest amounts near Oracle. 8 to 16
  inches above 5000 feet is expected with locally higher amounts
  in the Chiricahuas.

* WHERE...Southeast Pinal County, Upper San Pedro River Valley, 
  Eastern Cochise County below 5000 feet, Upper Gila River 
  Valley and Chiricahua Mountains.

* WHEN...11 PM today to 8 PM Friday. Winter Storm conditions will
  not greatly impact the valley floors of Cochise County until
  late Friday morning. 

* ADDITIONAL DETAILS...Look for significant reductions in 
  visibility at times.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Winter Storm Warning means heavy snow accumulations are
expected. Gusty winds and blowing snow are also possible. This
will make travel very difficult or impossible...especially in the
mountains. 

Stay tuned to NOAA Weather Radio...commercial television or radio
stations...or your cable television service provider for updates
on this Winter Storm.

&&

$$

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

239 
WWUS45 KTWC 221054
WSWTWC

URGENT - WINTER WEATHER MESSAGE
National Weather Service Tucson AZ
354 AM MST Fri Feb 22 2019


AZZ506>515-222100-
/O.CON.KTWC.WS.W.0002.000000T0000Z-190223T0300Z/
Southeast Pinal County-Upper San Pedro River Valley-
Eastern Cochise County below 5000 feet-Upper Gila River Valley-
White Mountains of Graham and Greenlee Counties-
Galiuro and Pinaleno Mountains-Chiricahua Mountains-
Dragoon and Mule and Huachuca and Santa Rita Mountains-
Catalina and Rincon Mountains-Baboquivari Mountains-
Including the cities of Oracle, Sierra Vista, Willcox, Clifton, 
Hannagan Meadow, Mount Graham, Chiricahua NM, Bisbee, 
Canelo Hills, Mount Lemmon, and Summerhaven
354 AM MST Fri Feb 22 2019

...WINTER STORM WARNING REMAINS IN EFFECT UNTIL 8 PM MST THIS
EVENING...

* WHAT...Heavy snow in the mountains. Expect total snow
  accumulations in the mountains of 10 to 20 inches between 5000
  feet and 7000 feet and 20 to 40 inches with localized higher
  amounts above 7000 feet. The snow level will lower throughout 
  the day with snow developing as low as 3500 feet. Total snow 
  accumulations of 1 to 4 inches between 3500 and 4500 feet with 
  higher amounts above 5000 feet can be anticipated. 

* WHERE...Portions of Southeast Arizona.

* WHEN...Snow was already occuring in the mountains early this
  morning. The snow level will lower throughout the day bringing
  snow to higher valley locations like Oracle, Sierra Vista and
  Willcox by this evening. Snow flurries have already been
  reported by the public in Oracle and south of Vail on State
  Route 83 early this morning.
  

* ADDITIONAL DETAILS...Look for significant reductions in 
  visibility at times, especially in the mountains.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Winter Storm Warning means heavy snow accumulations are
expected. Gusty winds and blowing snow are also possible. This
will make travel very difficult or impossible...especially in the
mountains. 

Stay tuned to NOAA Weather Radio...commercial television or radio
stations...or your cable television service provider for updates
on this Winter Storm.

&&

$$

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

866 
WWUS45 KTWC 222000
WSWTWC

URGENT - WINTER WEATHER MESSAGE
National Weather Service Tucson AZ
100 PM MST Fri Feb 22 2019


AZZ506>515-230300-
/O.CON.KTWC.WS.W.0002.000000T0000Z-190223T0300Z/
Southeast Pinal County-Upper San Pedro River Valley-
Eastern Cochise County below 5000 feet-Upper Gila River Valley-
White Mountains of Graham and Greenlee Counties-
Galiuro and Pinaleno Mountains-Chiricahua Mountains-
Dragoon and Mule and Huachuca and Santa Rita Mountains-
Catalina and Rincon Mountains-Baboquivari Mountains-
Including the cities of Oracle, Sierra Vista, Willcox, Clifton, 
Hannagan Meadow, Mount Graham, Chiricahua NM, Bisbee, 
Canelo Hills, Mount Lemmon, and Summerhaven
100 PM MST Fri Feb 22 2019

...WINTER STORM WARNING REMAINS IN EFFECT UNTIL 8 PM MST THIS
EVENING...

* WHAT...Heavy snow in the mountains. Expect total snow
  accumulations in the mountains of 10 to 20 inches between 4500 
  feet and 7000 feet and 20 to 40 inches with localized higher 
  amounts above 7000 feet. Total snow accumulations of 1 to 4 
  inches between 2000 and 3500 feet with higher amounts above 3500
  feet can be anticipated.

* WHERE...Portions of Southeast Arizona, mainly east of Tucson.

* WHEN...Until 8 PM today. The changeover to snow has occurred
  across the lower elevations Cochise and Graham Counties and
  continues in the mountains. 

* ADDITIONAL DETAILS...Look for significant reductions in
  visibility at times, especially in the mountains. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Winter Storm Warning means heavy snow accumulations are
expected. Gusty winds and blowing snow are also possible. This
will make travel very difficult or impossible...especially in the
mountains. 

Stay tuned to NOAA Weather Radio...commercial television or radio
stations...or your cable television service provider for updates
on this Winter Storm.

&&

$$

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

017 
WWUS45 KTWC 230303
WSWTWC

URGENT - WINTER WEATHER MESSAGE
National Weather Service Tucson AZ
803 PM MST Fri Feb 22 2019

AZZ506>515-230415-
/O.EXP.KTWC.WS.W.0002.000000T0000Z-190223T0300Z/
Southeast Pinal County-Upper San Pedro River Valley-
Eastern Cochise County below 5000 feet-Upper Gila River Valley-
White Mountains of Graham and Greenlee Counties-
Galiuro and Pinaleno Mountains-Chiricahua Mountains-
Dragoon and Mule and Huachuca and Santa Rita Mountains-
Catalina and Rincon Mountains-Baboquivari Mountains-
803 PM MST Fri Feb 22 2019

...WINTER STORM WARNING HAS EXPIRED...

The Winter Storm Warning has been allowed to expire. Any remaining
snow showers the rest of tonight will be light with little if any
additional snow accumulation expected.

$$

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

Area Forecast Discussion
National Weather Service Tucson AZ
912 PM MST Tue Feb 19 2019

.SYNOPSIS...Cold conditions are on tap for tonight into Wednesday
morning, with a brief spell of dry weather. Then, a strong winter
storm produces valley rain and substantial mountain snow Thursday
and Friday. Dry conditions return by the weekend, with daytime
temperatures that gradually warm closer to normal next week.

&&

.DISCUSSION...Drier conditions have settled in across southeast
Arizona this evening as the upper trough axis progresses through the
eastern Rockies. Satellite imagery shows generally clear skies save
for some lingering cloudiness over the White Mountains. The theme
for tonight and Wednesday morning shifts toward a widespread hard
freeze. Strong cold advection on northwesterly flow combined with
sufficient radiative cooling will help produce temperatures well
below average for this time of year.

A significant winter storm still looks on track for Thursday into
Friday as a deep upper low dives down the Great Basin and briefly
stalls nearby to our west. For more details on how this system
impacts our area, please see the previous discussion below.

&&

.AVIATION...Valid through 22/06Z.
Predominantly clear skies except for some lingering cumulus
northeast of KSAD across the higher terrain. Surface winds generally
remain less than 12 kts, with occasional gusts of 15-20 kts
Wednesday afternoon. Aviation discussion not updated for TAF
amendments.

&&

.FIRE WEATHER...After a short dry spell through Wednesday, a
significant winter storm arrives Thursday into Saturday morning with
valley rain and heavy mountain snowfall. 20-ft winds become breezy
at times, especially Thursday afternoon as southwesterly winds reach
15-25 mph. After Saturday expect dry conditions into the beginning
of next week.

&&

.PREV DISCUSSION...The upper trough axis has shifted east into
western New Mexico, however, cold air aloft has resulted in isolated
instability showers across eastern portions of the forecast area, in
Cochise, Graham and Greenlee counties. These showers are expected to
come to an end early this evening shortly after sunset. Otherwise,
daytime highs (so far) have only warmed into the lower 40s to lower
50s across southeast Arizona this afternoon, or 15-20 degrees below
normal.

Expect rapidly clearing skies this evening, with much colder
temperatures tonight. Most (if not all) of southeast Arizona will
experience below freezing temperatures. The coldest valleys east and
south of Tucson will bottom out in the teens Wednesday morning, with
areas from Tucson westward in the mid 20's to around 30 degrees. A
Hard Freeze/Freeze warning remains in effect from Tucson west from
11 pm MST tonight through 8 am MST Wednesday morning.

Wednesday's high temperatures will warm 2-4 degrees (versus today),
but still remain around 15 degrees below normal. Overnight lows
Wednesday night/Thursday morning will be up 5-10 degrees as cloud
cover from the next system to impact the region begins to overspread
the area.

Attention then turns a large upper low and major winter storm that
will impact the region Thursday into early Saturday. A slight chance
of precipitation starts early Thursday morning. Increasing valley
rain/mountain snow chances then overspread the area from northwest
to southeast during the day Thursday and continue areawide Thursday
night and Friday. Have upped POPS/QPF and Snowfall amounts with this
system Thursday through Friday. This system will result in
widespread lower elevation rainfall, with QPF totals ranging from
0.75" to 1.50". Impressive snowfall totals are expected in the
mountains with this system, with one to three feet of snowfall
accumulation expected. Overall, looking at 12-18 inches in the
Baboquivari, Mule, Huachuca and Chiricahua mountains, with 24-36
inches in the Rincon, Catalina, Santa Rita, Mount Graham and White
Mountains. Snow levels start around 5000 feet on Thursday, lowering
to near 4500 feet by Friday morning, ending near 3800 feet late
Friday. These snow levels mean that locations such as Oracle and
Bisbee could end up with 6-12 inches of snowfall. A Winter Storm
Watch remains in effect for the mountains of southeast Arizona from
late morning Thursday through Friday afternoon. Have lowered the
Watch down to the 5000 foot level and also included Oracle in Zone
506. Expect gusty winds with this system and that may lead to
localized blizzard conditions in the mountains along with blowing
and drifting snow. The lower elevations, mainly east and south of
Tucson, will also see some accumulating snow Friday night into
Saturday morning as snow levels continue to lower on the back side
of the system.

Well below normal high temperatures continue Thursday into Saturday.
The lower deserts from Tucson west could see another Hard Freeze
Saturday morning. Dry conditions and warmer temperatures are
expected Sunday and Monday, although temperatures will remain below
normal. Near normal temperatures make an appearance by the middle of
next week as ridge builds across the southwestern United States.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...

 Hard Freeze Warning from 11 PM this evening to 8 AM MST
  Wednesday for AZZ502-504>506.

 Freeze Warning from 11 PM this evening to 8 AM MST Wednesday for
  AZZ501.

 Winter Storm Watch from Thursday morning through Friday
  afternoon for AZZ506-510-511-513>515.

 Winter Storm Watch from Thursday evening through Friday
  afternoon for AZZ512.

&&

Discussion...Howlett
Prev Disc...Zell

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