Special Weather Statement, NWS Tucson, AZ

Area Forecast Discussion
National Weather Service Tucson AZ
157 PM MST Mon Jul 29 2019

.SYNOPSIS...An active period of shower and thunderstorm
thunderstorm activity will continue through Wednesday,
later today and continue through Wednesday, with a bit less
thunderstorm coverage to end the week. High temperatures will
moderate to near normal levels Tuesday, then below normal Wednesday
before warming again later in the week and the weekend.

&&

.DISCUSSION...The active period that we've been discussing over the
past few days is just starting to get underway this afternoon. GPS
PWAT values currently average about 1.25" to 1.50" across the
forecast area. The mid/upper level high is now located near the Four
Corners which has turned our mid level steering flow into a more
favorable easterly direction. Latest visible satellite imagery shows
skies have adequately cleared across most of southeast Arizona with
good solar insolation. Shower and thunderstorm development has been
a bit slow to get started but we are seeing a few storms now
developing over the higher terrain of Cochise County and the Gila
region of New Mexico that is pushing westward. Latest CAMs are in
good agreement on depicting scattered showers and thunderstorms
primarily across Graham, Greenlee, Santa Cruz and Cochise County
through much of the afternoon. The mid level steering flow of around
15 kts will push these storms west into eastern Pinal, eastern
Pima and Santa Cruz counties by late this afternoon and early this
evening. Still some uncertainty on just how strong these storms will
be as they push into the lower elevations but with MLCAPE values of
around 1000 J/kg and DCAPE of 1000 J/kg, a few of the storms
will be strong perhaps severe with gusty outflow winds later this
afternoon. Will maintain the mention of blowing dust to the north
and west of Tucson this evening but confidence is still low on this
scenario. Meanwhile, with the aforementioned mid level steering flow
of around 15 kts, some of these storms will be heavy rainers but
given the motion, rain amounts of greater than 1 inch per hour and
thus the flash flood threat would be localized in nature. Residual
shower activity with a few embedded thunderstorms are expected to
continue well into the evening and overnight hours aided by the
anomalously deep moisture and an inverted trough.

For Tuesday, deep moisture will be entrenched across southeast
Arizona with PWAT values ranging from about 1.25 inches
along the New Mexico border to around 2 inches in the
Western Deserts. PWAT levels from Tucson westward will be
1 to 2 sigma above the mean for this time of year. The biggest
uncertainty will be just how much clearing from any overnight
convection occurs helping to result in greater instability and
renewed convective development. We do think that the 15-20 kts
mid level steering flow should be enough to result in some areas of
clearing but confidence is still below average. Given the
aforementioned mid level flow, the quicker movement of these storms
should preclude widespread flash flooding issues but a few storms
may result in areas of localized flash flooding. Areas of blowing
dust will also be possible Tuesday afternoon to the north and west
of Tucson.

The flow becomes more southerly on Wednesday as the larger scale
feature/inverted trough shifts to the north into northern Arizona.
As deep moisture remains, it will once again be a favorable setup
for showers and thunderstorms but there is no evident larger scale
forcing which could result in lesser coverage overall. With that
said, storm motions are expected to slow down slightly on Wednesday
which could enhance the heavy rain risk with the storms that do
develop.

Thereafter, the mid/upper level high is progged to remain over New
Mexico or near the New Mexico/Arizona border with general
southeasterly flow as PWAT values lower to near normal values for
early August. While the period from Thursday into the weekend is
overall shaping to be less active than the period through Wednesday,
it will be close to climatological normals for this time of year
with isolated to scattered showers and thunderstorms with the best
coverage to the south and east of Tucson.

Temperatures are expected to cool to seasonal normal Tuesday.
Wednesday is shaping up to be the coolest day with highs about 5
degrees below normal before warming up starting Thursday with highs
a few degrees above normal for the weekend.

&&

.AVIATION...Valid through 31/00Z.
SHRA/TSRA continue to develop this afternoon becoming scattered to
numerous during the evening. Models indicate that activity will be
slow to dissipate overnight, with widespread SHRA/TSRA blossoming
again tomorrow afternoon. Wind gusts of over 40 kts possible along
with brief MVFR cigs/vsbys with any afternoon/evening storms.
Outside of TSRA winds, expect generally WLY-NWLY winds 10-15 kts
during the afternoon then becoming light and variable again
overnight. Aviation discussion not updated for TAF amendments.

&&

.FIRE WEATHER...With high pressure now in a more favorable
position, widespread thunderstorms will continue to develop each day
through Wednesday. This added moisture brings high temperatures
below normal Tuesday through Thursday, with minimum RHs that hover
in the 30s across the lower deserts. Later in the week, southeast
Arizona transitions into a slightly drier pattern that will still
feature the daily cycle of thunderstorms. 20-ft winds generally
follow diurnal trends at less than 15 mph except near thunderstorms
where gusty and erratic winds above 40 mph will be possible.

&&

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

&&

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Special Weather Statement
National Weather Service Tucson AZ
406 PM MST Mon Jul 29 2019

AZZ504-507-514-292345-
Santa Catalina and Rincon Mountains including Mount
Lemmon/Summerhaven-Upper San Pedro River Valley including Sierra
Vista/Benson-Tucson Metro Area including Tucson/Green
Valley/Marana/Vail-
406 PM MST Mon Jul 29 2019

...SIGNIFICANT WEATHER ADVISORY FOR EAST CENTRAL PIMA AND
NORTHWESTERN COCHISE COUNTIES UNTIL 445 PM MST...

At 404 PM MST, Doppler radar was tracking strong thunderstorms 10 to
15 miles east of Saguaro National Park East, or 20 miles west and
northwest of Benson, moving west at 10 mph.

Winds in excess of 45 mph and small hail will be possible with these
storms.

Locations impacted include...
Tanque Verde, Saguaro National Park East, Mescal and Cascabel.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

These storms 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 3242 11037 3201 11027 3192 11057 3240 11077
TIME...MOT...LOC 2304Z 081DEG 10KT 3222 11051

Meyer

Special Weather Statement
National Weather Service Tucson AZ
415 PM MST Mon Jul 29 2019

AZZ506-509>511-292345-
Upper Gila River and Aravaipa Valleys including
Clifton/Safford-Southeast Pinal County including
Kearny/Mammoth/Oracle-White Mountains of Graham and Greenlee Counties
including Hannagan Meadow-Galiuro and Pinaleno Mountains including
Mount Graham-
415 PM MST Mon Jul 29 2019

...SIGNIFICANT WEATHER ADVISORY FOR GRAHAM...EAST CENTRAL PINAL AND
WEST CENTRAL GREENLEE COUNTIES UNTIL 445 PM MST...

At 412 PM MST, Doppler radar was tracking a cluster of strong
thunderstorms approaching the towns of Safford , Fort Thomas and
Bylas from the northwest. These storms were moving southwest at 15
mph.

Winds in excess of 40 mph will be possible with these storms.

Locations impacted include...
Safford, Thatcher, Solomon, Roper Lake State Park, Safford Regional
Airport, Pima, Bylas, Central, Fort Thomas, Point-Of-Pines, Calva,
Klondyke, Swift Trail Junction, Fort Grant, Mount Graham, Bonita and
Frye Mesa Dam.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

The storms 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 3359 10956 3245 10936 3244 11006 3301 11055
TIME...MOT...LOC 2312Z 046DEG 14KT 3303 10961

Special Weather Statement
National Weather Service Tucson AZ
501 PM MST Mon Jul 29 2019

AZZ504-506-507-513-514-300045-
Santa Catalina and Rincon Mountains including Mount
Lemmon/Summerhaven-Southeast Pinal County including
Kearny/Mammoth/Oracle-Upper San Pedro River Valley including Sierra
Vista/Benson-Dragoon/Mule/Huachuca and Santa Rita Mountains including
Bisbee/Canelo Hills/Madera Canyon-Tucson Metro Area including
Tucson/Green Valley/Marana/Vail-
501 PM MST Mon Jul 29 2019

...SIGNIFICANT WEATHER ADVISORY FOR NORTHEASTERN PIMA AND
SOUTHEASTERN PINAL COUNTIES UNTIL 545 PM MST...

At 459 PM MST, Doppler radar was tracking strong thunderstorms along
a line extending from near Mount Lemmon/Summerhaven to 7 miles
southeast of Vail. Movement was west at 10 mph.

Winds in excess of 45 mph and small hail will be possible with these
storms, along with heavy rain.

Locations impacted include...
Tucson, Davis-Monthan Air Force Base, Tanque Verde, Vail,
Saddlebrooke, Mount Lemmon/Summerhaven, Sabino Canyon Recreation
Area, Catalina Foothills, Corona De Tucson, Saguaro National Park
East, Catalina State Park, Rita Ranch and Seven Falls.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3253 11093 3185 11082 3193 11051 3247 11062
TIME...MOT...LOC 2359Z 085DEG 9KT 3240 11068 3200 11060

Meyer

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