Severe Thunderstorm Warning 53, NWS Phoenix, AZ

Area Forecast Discussion
National Weather Service Phoenix AZ
327 PM MST Mon Aug 8 2022

.SYNOPSIS...
The main storm chances for today will begin in the eastern
Arizona high terrain and parts of the western deserts this
afternoon before possibly spreading into the lower deserts and
Phoenix this evening and tonight. Storm chances will increase
noticeably tomorrow and then remain elevated through next weekend
and into early next week due to abundant moisture and an active
Monsoon pattern in place. Occasionally heavy rainfall, localized
flash flooding, gusty winds and localized blowing dust remain
likely through early next week. High temperatures will also remain
slightly below to near normal through early next week.

&&

.DISCUSSION...
The H5 Monsoon ridge is ideally positioned near the 4-Corners with
moist E flow through the mid-upper levels aloft. GOES WV imagery
indicated a very moist airmass across the region with inverted
disturbances pushing W into SE CA where GOES imagery and radar
also indicated an area of scattered showers and storms/MCS where
localized flash flooding is happening this afternoon including
near I-10 and JTNP. Early afternoon radar also showed widely
isolated to scattered distant thunderstorms across the high
terrain of N, E and S AZ. The E AZ storms were associated with
additional E wave vort clusters advancing from NM. The latest
ACARS soundings shows an increasingly moist airmass with PW
having climbed to 1.7->1.9" while mesoscale analysis indicated PW
>2" across SW AZ and into SE CA. MU and SB CAPE had also increased
to >2-3K j/kg.

Some HREF members still favor pronounced convection with locally
heavy rainfall developing this afternoon across the across S Gila
Cty and near Globe and burn scar areas before descending into the
lower deserts and parts of the Phoenix Metro around 04Z. The HRRR
however is an outlier and has recently backed off on that notion
by both delaying and weakening the convection coming off of the
high terrain this evening. However all members continue to favor a
gusty E outflow this evening pushing into the Phoenix metro and N
Pinal. The potential for patchy blowing dust moving west remains
possible, although most likely for N Pinal Cty and the SE-E Phx
Metro Valley

For tomorrow the HREF and ensembles are in agreement on an uptick in
storm chances and coverage from E to W across the region with POPs
increasing to near 50% for Phoenix and the lower deserts, to 60-70%
for the E AZ high country, and 20-30% for SW AZ and SE CA. WPC Day
2 ERO also features a "slight risk" over much of the region for
tomorrow. Some HREF members start with some shower activity W of
Phoenix in the Tue morning hours moving in from in S-SE AZ.
However the main convection will likely start in E-SE AZ
associated with the next E wave(S) and will push into the Phoenix
Metro and the lower deserts Tue evening. Good (>50% for >35 mph
gusts) chances of strong gusty winds, from both the S-SW and E and
locally dense blowing dust will likely be followed by locally
heavy rainfall and localized flash flooding in the high country
and the lower deserts.

Going through the rest of the week and possibly beyond, ensembles
continue to be in very good agreement that the subtropical high
pressure will remain situated northeast of the four corners
region. This overall positioning of the high will be favorable for
continuous moisture advection into the desert southwest with PWAT
values across the lower elevations ranging between 1.7 and 2.0
inches. In addition to the continuous moisture advection, there
will be periodic easterly waves that will migrate into the region,
which will aid in increasing the storm coverage. However,
determining the timing of each individual wave as it approaches
the region is difficult this far in advance. NBM PoPs through the
period range between 25-50% in the lower elevations and between
40-70% across the higher terrain. With the increased moisture and
potential cloud cover from convective debris, high temperatures
during the next several days will remain near to slightly below
normal.

&&

.AVIATION...Updated 1920Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Light winds, less than 10 kts, generally favoring a southerly
component will continue to veer toward the west through the
afternoon. Heading into the afternoon and evening hours,
convection over the high terrain east and southeast of Phoenix are
expected to generate an outflow that will progress toward the
Valley. The exact magnitude of outflow winds is uncertain, but the
latest HREF continues to indicate around a 30-40% chance of winds
exceeding 30 kts. Timing for this outflow looks to be around 03Z-06Z.
With the possibility of strong outflow winds, blowing dust will
be a concern particularly for KIWA. There is around a 30% chance
for isolated showers and thunderstorms to also develop as the gust
front moves through. Thereafter, winds will likely become
somewhat more variable before a light easterly flow redevelops
after midnight. Expect SCT-BKN mid and high clouds mostly aoa 10
kft to continue through the period.

Southeast California/Southwest Arizona including KIPL and KBLH:
Winds will generally retain a southerly component at both KIPL and
KBLH today and tonight, aside from erratic winds from any
showers/thunderstorms. Showers and thunderstorms continue to push
westward into SE CA and is impacting KBLH. Reduced visibilities at
KBLH due to heavy rain are expected to improve going forward as
activity continues to advance west. Additional shower/thunderstorm
activity will be possible this afternoon, which could once again
approach KBLH. Otherwise, expect SCT-BKN mid and high clouds to
mostly remain aoa 10 kft through the period.

&&

.FIRE WEATHER...
Active monsoon storm conditions are expected during the next
several days as moisture levels remain elevated across the area.
With the elevated moisture levels in place, MinRHs will range
between 25-40% with excellent overnight recoveries. Therefore, the
fire danger threat is expected to remain low for the foreseeable
future. Winds for the most part will remain light, with the
exception of thunderstorm outflows generating stronger gusts.

&&

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

DISCUSSION...Sawtelle/Lojero
AVIATION...Smith/Hirsch
FIRE WEATHER...Lojero

Special Weather Statement
National Weather Service Phoenix AZ
147 PM PDT Mon Aug 8 2022

CAZ560-564-568-570-082130-
Chuckwalla Mountains CA-Chuckwalla Valley CA-Chiriaco Summit CA-
Joshua Tree NP West CA-
147 PM PDT Mon Aug 8 2022

...A strong thunderstorm will impact portions of north central
Imperial and Riverside Counties through 230 PM PDT...

At 147 PM PDT, Doppler radar was tracking a strong thunderstorm 12
miles south of Desert Center, moving northwest at 10 mph.

HAZARD...Wind gusts up to 50 mph.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects.

Locations impacted include...
Desert Center and Chiriaco Summit.

This includes the following highways...
CA Interstate 10 between mile markers 85 and 112.
CA Route 177 between mile markers 1 and 4.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.

&&

LAT...LON 3376 11532 3358 11519 3340 11526 3349 11571
      3365 11575 3379 11572
TIME...MOT...LOC 2047Z 118DEG 9KT 3353 11536

MAX HAIL SIZE...0.00 IN
MAX WIND GUST...50 MPH

INS

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Special Weather Statement
National Weather Service Phoenix AZ
206 PM PDT Mon Aug 8 2022

CAZ560-568-082130-
Chiriaco Summit CA-Joshua Tree NP West CA-
206 PM PDT Mon Aug 8 2022

...A strong thunderstorm will impact portions of Riverside County
through 230 PM PDT...

At 206 PM PDT, Doppler radar was tracking a strong thunderstorm over
Cottonwood Visitor Center, or 7 miles northwest of Chiriaco Summit,
moving northwest at 5 mph.

HAZARD...Wind gusts up to 50 mph.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects.

Locations impacted include...
Cottonwood Visitor Center.

This includes CA Interstate 10 between mile markers 74 and 84.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.

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 3381 11593 3374 11571 3362 11577 3366 11595
      3373 11594 3375 11599
TIME...MOT...LOC 2106Z 144DEG 5KT 3372 11582

MAX HAIL SIZE...0.00 IN
MAX WIND GUST...50 MPH

INS

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PHOENIX AZ
323 PM MST MON AUG 8 2022

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0308 PM     FLASH FLOOD      8 N COTTONWOOD VISITOR  33.87N 115.80W
08/08/2022                   RIVERSIDE          CA   PARK/FOREST SRVC

            PINTO BASIN RD CLOSED DUE TO WASHES RUNNING
            OVER ROAD, 1 FT IN DEPTH.

&&

JM

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