Severe Thunderstorm Warning 53, NWS Phoenix, AZ

551 
WWUS55 KPSR 102053
SVSPSR

Severe Weather Statement
National Weather Service Phoenix AZ
153 PM MST THU AUG 10 2017

AZC012-102100-
/O.CON.KPSR.SV.W.0053.000000T0000Z-170810T2100Z/
La Paz AZ-
153 PM MST THU AUG 10 2017

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 200 PM MST
FOR CENTRAL LA PAZ COUNTY...

At 152 PM MST, a severe thunderstorm was located near Brenda, or 33 
miles southeast of Parker, moving north at 10 mph. The storm is 
still strong. Please seek shelter now!

HAZARD...60 mph wind gusts and nickel size hail. 

SOURCE...Radar indicated. 

IMPACT...Expect damage to roofs, siding, and trees. 

Locations impacted include...
Brenda.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 3354 11395 3359 11407 3382 11409 3372 11375
TIME...MOT...LOC 2052Z 190DEG 8KT 3372 11398 

HAIL...0.88IN
WIND...60MPH
 
$$

Hernandez

Area Forecast Discussion
National Weather Service Phoenix AZ
855 AM MST Thu Aug 10 2017

&&

.SYNOPSIS...
Expect humidity to increase in many areas today as Monsoon
moisture returns to the region. Accordingly, storm chances return
to the lower deserts of Arizona and expand into much of southeast
California by Saturday. With higher humidity and more cloudiness,
high temperatures will trend downward as well. A drying trend
begins from west to east on Monday.

&&

.DISCUSSION...

A turn towards a more active monsoon pattern can already be seen
across the region this morning. Outflow from the remains of a very
large MCV over northern Sonora, Mexico has pushed into SW AZ/SE CA
this morning, pushing the dewpoints across the Yuma area well up
into the 70s/very close to 80 degrees! Mid-level moisture/cloudiness
has also pushed into our cwa, with latest 88-D radar imagery showing
virga/light showers across eastern Pinal/southern Gila Counties at
this hour. The latest HRRR high-res model output is showing these
showers dissipating/clearing during the day today, with more
showers/TS developing late this afternoon/evening across southern AZ,
and outflows from these storms moving into south-central AZ during
the mid/late evening hours. As far as the very short-term is
concerned, other than some minor edits to the hourly temp/dewpoint
grids, inherited forecasts are holding up well.

&&

.PREVIOUS DISCUSSION...
Today and Tonight...
Very active convection over Sonora this past evening is now
weakening early this morning. With such widespread activity which
has spilled over to the Gulf of California, would anticipate an
outflow Gulf "surge" moving into our forecast area today. This
slab of maritime tropical air will get thinner the further away
from the Gulf it gets, but expect we will see it overspread most
of our forecast area by late this afternoon. That will mean a more
humid but less hot boundary layer. Both hi-res and larger scale
models depict this scenario to varying degrees. There are pros
and cons to that situation in terms of convective potential
depending upon how much boundary layer cooling there is which
means more CIN. The decaying MCS will likely send some debris
clouds over portions of southern Arizona and possibly some
isolated light showers. Just how much we see will depend a lot on
the strength and track of an MCV (from the Sonora convection). The
models have varying ideas on that. Meanwhile, there will be a
push of lower level easterly winds into southeast Arizona and
possibly into eastern portions of our forecast area. Some of the
hi-res models indicate sufficient convergence to get some isolated
storms to develop over portions of Pinal and Gila Counties. They
also depict redevelopment of storms today over much of Pima
County. Despite the outflows they depict, they are generally
reluctant to develop strong convection over our lower elevations.
However, that would still mean dust storm potential for south-
central AZ.

Friday through Sunday...
Steering flow will initially have a southerly component with the
subtropical high centered over Texas. That changes by Sunday as
troughing over the West Coast makes its presence felt leading to
southwesterly steering aloft. The upper troposphere turns
southwesterly sooner than that. There is good model agreement
that moisture adequate for storms will be in place through Sunday.
Of course that doesn't mean there won't be CIN to contend with
and thus PoPs are not overwhelmingly high. An X factor will be
an inverted trough (currently centered near southern Baja). Models
are slow to track it north of the border and weaken it in the
process. High temps return to normal during this period - possibly
dipping a little below normal over south-central AZ.

Monday through Wednesday...
A Pacific deepens over the West Coast and areas far inland early
next week leading to dry advection and another break in the
Monsoon. PoPs trend down Monday with only slight chances over the
higher terrain of south-central AZ on Tuesday and even more
retreat on Wednesday. Though we have a drying trend, lower heights
and thicknesses keep temps from rebounding much.

&&

.AVIATION...
South-Central Arizona including KPHX, KIWA, and KSDL:

Moisture return into southern Arizona will occur today leading to
scattered showers approaching but not affecting the Phoenix area
this morning. Thunderstorm development this afternoon should be
focused mainly to the south of the area, but outflow winds from
these storms are likely to move into the Phoenix area early this
evening. Blowing dust will be a possibility, but still too far out
to include in TAFs besides HZ mention for KIWA. Isolated
shower/thunderstorm activity is possible this evening as a result
of outflows over Phoenix, with mainly showers lingering into
early Friday morning. Wind directions will mostly follow diurnal
trends, but should be influenced this evening by storm outflows.

Southeast California/Southwest Arizona including KIPL and KBLH:

Little to no aviation impacts expected across southeast California
through Friday morning. Winds will favor a southerly direction
with gusty afternoon winds at KBLH. Should see some mid and high
clouds increasing this evening or tonight due to storm activity in
Arizona.

Aviation discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Saturday through Wednesday:
Thunderstorm chances will increase markedly heading into the
weekend with the best opportunities for wetting rains building
into the lower elevations Saturday and Sunday. Somewhat less
storm activity is likely by Tuesday. With moisture surging north,
minimum humidity levels will increase to a 20-40% range while
overnight recovery similarly improves towards a good to excellent
range. Temperatures will cool back to near normal over the weekend
with the increased humidity levels. Outside of thunderstorm
outflows, winds will remain on the light side.

&&

.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&

Visit us on Facebook, Twitter, and at weather.gov/phoenix

DISCUSSION...Percha/AJ
AVIATION...Kuhlman
FIRE WEATHER...MO

Special Weather Statement
National Weather Service Phoenix AZ
125 PM MST THU AUG 10 2017

AZZ533-102115-
Central La Paz AZ-
125 PM MST THU AUG 10 2017

...SIGNIFICANT WEATHER ADVISORY FOR CENTRAL LA PAZ COUNTY UNTIL 215
PM MST...

At 125 PM MST, Doppler radar was tracking a strong thunderstorm over
Brenda, or 36 miles southeast of Parker. This storm was nearly
stationary.

Winds in excess of 40 mph will be possible with this storm.

Locations impacted include...
Brenda.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 3357 11393 3362 11407 3378 11405 3369 11380
TIME...MOT...LOC 2025Z 205DEG 3KT 3367 11397

Hernandez