Areal Flood Advisory 21, NWS Tucson, AZ

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

.SYNOPSIS...An active period of shower and thunderstorm activity
will 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...Broad organized outflow in a deepening easterly
storm level flow is pushing showers and thunderstorms further west
this evening. A solid gulf surge continues into Western Pima and
Yuma counties with dewpoints up 5 to 10 degrees; into the 60s for
most of the area. Overall we'll see a slow decrease in convection
overnight with some showers embedded in decaying debris well into
the early morning. The upswing in activity will continue and
expand Tuesday into Wednesday with the current forecast trends
looking good. Deep moisture with wet microburst activity a
concern, and enough shear for some organization. Please see the
previous discussion below for additional details.

&&

.AVIATION...Valid through 31/06Z.
Scattered SHRA/TSRA into the early morning hours before
dissipating, with widespread SHRA/TSRA again tomorrow afternoon.
Wind gusts of over 40 kts possible along with brief MVFR
cigs/vsbys with 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.

&&

.PREV DISCUSSION... /issued 157 PM MST Mon Jul 29 2019/
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.

&&

.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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