Special Weather Statement, NWS Tucson, AZ

Area Forecast Discussion
National Weather Service Tucson AZ
933 AM MST Sat Aug 28 2021

.SYNOPSIS...
Scattered afternoon showers and storms are expected each afternoon
and evening this weekend. Early next week an increase in storm
activity is forecast as tropical moisture moves into the area and
lingers through mid to late in the week. Concerns for heavy
rainfall leading to flash flooding will also rise as a result.

&&

.DISCUSSION...The 12Z KTWC sounding came in with 1.3 inches
precipitable water and a little convective inhibition to fight
through late morning. Plenty of insolation should easily manage
storms near the mountains by early afternoon, with some support
for valley storms along outflows. Above average shear environment
for SE AZ could make a few of the storms interesting with
potentially more organized storm outflows and blowing dust
issues late afternoon into early evening. Current forecast handles
this pretty well, with best chances for Tucson metro between 3pm
and 6pm.

&&

.AVIATION...Valid through 29/12Z.
Isolated to scattered SHRA/TSRA develop this afternoon continuing
into the evening hours, with cloud bases down around 8k-12k ft MSL.
MVFR conditions and mountain-top obscurations near TSRA, along with
wind gusts up to 45 kts. Otherwise, SFC wind favoring an easterly
direction and generally less than 12 kts. Aviation discussion not
updated for TAF amendments.

&&

.FIRE WEATHER...Isolated to scattered showers and thunderstorms are
expected for much of the forecast area through the weekend. Moisture
increases further next week allowing for even better rain chances,
potentially becoming heavy at times. 20-foot winds will generally be
less than 15 mph when not influenced by thunderstorms gusts.

&&

.PREV DISCUSSION... /issued 234 AM MST Sat Aug 28 2021/
Through Monday, weak ridging will remain situated over the
southwest U.S. as weak troughs pass well to our north across the
PacNW and Great Basin. Temps won't be quite as hot as we have seen
the past few days but will still remain near to slightly above
normal. Isolated to scattered storms are expected each afternoon
with potential for some storms to linger into the late evening
hours each night. These days are expected to be fairly average in
terms of storm impacts with isolated strong to severe storms
carrying potential to produce damaging wind gusts and localized
flash flooding issues.

Monday will be the transition day as we move into a more active
period with moisture levels and storm chances beginning to rise.
The ridge will shift eastward Tuesday as a trough approaches the
West Coast which will shift our flow to a more southerly
direction. This will facilitate moisture associated with Hurricane
Nora to work northward into the area through mid to late next
week. This deep moisture along with remnants of Nora and an
approaching shortwave trough off the southern California coast
look to all work together to increase widespread storm chances
and elevate flash flood concerns by mid next week. Most active
days still look to be Tuesday into Wednesday for our area with
even some indication that Thursday could also be a very active
day. As the track of the remnants of Nora becomes more clear so
will the details on timing and location of highest flash flood
potential. In terms of strong winds associated with the Nora
remnants, we are not anticipating any winds high enough to cause
impacts outside of thunderstorm activity. Latest ensemble runs
still showing significant differences in handling this system
which would have large effects on local impacts. EPS remains the
wetter solution for southeast AZ in comparison with the GEFS,
keeping the moisture plume focused over Arizona. GEFS also shows
Nora weakening more quickly over Baja with the associated moisture
plume focused further west across southern CA and western AZ.
Later next week the deeper moisture looks to be pulled northward
into UT/CO by a northern stream trough allowing southern AZ to
transition back into a more normal monsoonal weather pattern. Stay
tuned for more details and keep the weather in mind when making
plans for next week.

&&

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

Guillet/Howlett/Meyer

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Special Weather Statement
National Weather Service Tucson AZ
234 PM MST Sat Aug 28 2021

AZZ503-513-282215-
Dragoon/Mule/Huachuca and Santa Rita Mountains including
Bisbee/Canelo Hills/Madera Canyon-Upper Santa Cruz River and Altar
Valleys including Nogales-
234 PM MST Sat Aug 28 2021

...A strong thunderstorm will impact portions of south central Santa
Cruz County through 315 PM MST...

At 233 PM MST, Doppler radar was tracking a strong thunderstorm near
Nogales International Airport, or 9 miles northeast of Nogales,
moving west at 10 mph.

HAZARD...Wind gusts up to 50 mph and half inch hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

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

This includes Route 82 between mile markers 3 and 20.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

This storm 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 3135 11091 3153 11095 3155 11073 3141 11070
TIME...MOT...LOC 2133Z 090DEG 10KT 3145 11081

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...50 MPH

Zell