Severe Thunderstorm Warning 4, NWS Flagstaff, AZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
829 AM MST Fri May 19 2023

.SYNOPSIS...Thunderstorm chances continue each afternoon and
evening through the weekend across northern Arizona, especially
over higher terrain. The main concerns include hail, gusty winds,
and brief downpours that may lead to localized flooding.
Thunderstorm chances decrease by early next week with a return to
dry, warmer and breezy conditions by midweek.

&&

.UPDATE...Remember Thursday? Look for the same thing today.
Afternoon and evening showers and thunderstorm are forecast with
the main focus from the Mogollon Rim and White Mountains
southward. Storms today will contain the usual cloud-to-ground
lightning, dime sized hail and wind gusts to 40 mph.

&&

.PREV DISCUSSION /241 AM MST/...The unusually active thunderstorm
pattern continues over northern Arizona today, with a particularly
active day in store along and south of the Mogollon Rim. The low
pressure circulation sitting over the Gulf of California has begun
to initiate a moisture surge, evidenced by the Yuma radar showing
a stout southerly flow (25-30+ kts) in the lowest 5,000 ft of the
atmosphere this morning. This moisture is expected to surge north
across the southern deserts and into Yavapai and Gila counties by
late this afternoon and evening. Precipitable water values here
are forecast to increase to near and slightly above 1.00".
Meanwhile, large scale high pressure building over the Great Basin
will keep a north/northeast steering flow over AZ. This pattern
should yield convective initiation first over the Mogollon
Rim/Coconino Plateau with activity moving south of the Rim later
in the day. The pooled moisture south of the rim and a slightly
better shear profile (about 20 kts) should promote better storm
organization with some multi-cell clusters capable of producing
heavy rainfall. This is consistent with the WPC excessive rainfall
outlook highlighting a marginal risk across this area. Isolated
strong to severe cells producing hail and damaging wind are also
possible given forecast instability (CAPE) values in the 500-1000
J/kg range. Convection will continue into the evening hours but
will wane by about midnight. Friday and Saturday...Scattered to
numerous thunderstorms (40 to 80 percent chance) today,
especially along and south of the Mogollon Rim and White
Mountains. Thunderstorms are expected again on Saturday with the
greatest chances (40 to 80 percent) along and north of the
Mogollon Rim.

Saturday will see a shift of the richest moisture to northern
portions of our forecast area. The best thunderstorm chances
(50-70%) will shift to areas along and north of a Prescott to Four
Corners line. Temperatures are forecast to trend about 5 degrees
cooler on Saturday as well. Shower and storm chances begin a
downward trend on Sunday, but still remain in the 30-60% range.
The decreasing trend will continue each day through early next
week as moisture profiles thin out. We expect to return to a
mostly dry and breezy pattern from Tuesday onward as we begin to
feel the influence of a trough deepening over the western states.
This trough will scour out the moisture and bring an end to this
thunderstorm pattern. In addition, we expect to see daytime
temperatures warm to a few degrees above normal by midweek.
Sunday through Tuesday...Thunderstorm chances generally decrease
Sunday into early next week. Storms that do form may create
frequent lightning, gusty erratic outflow winds, and heavy
downpours.

&&

.AVIATION...For the 18Z TAF Package...Expect another round of
scattered showers and thunderstorms, mainly between 19Z and 02Z.
Outflow winds to 25-35 knots and MVFR conditions are the main
hazards. Showers and storms diminishing and becoming isolated
overnight. Aviation discussion not updated for TAF amendments.

&&

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...NONE.

&&

PUBLIC...McCollum/MCT
AVIATION...McCollum/MAS
FIRE WEATHER...McCollum/MAS

For Northern Arizona weather information visit
weather.gov/flagstaff

Special Weather Statement
National Weather Service Flagstaff AZ
1228 PM MST Fri May 19 2023

AZZ015-016-038-192000-
Western Mogollon Rim-Oak Creek and Sycamore Canyons-Eastern Mogollon
Rim-
1228 PM MST Fri May 19 2023

...A strong thunderstorm cluster will impact areas from Munds Park
to near Mormon Lake through 100 PM MST...

At 1226 PM MST, Doppler radar was tracking a strong thunderstorm
cluster from Munds Park to near Mormon Lake. These storms were
nearly stationary.

HAZARD...Winds up to 40 mph, heavy rainfall and penny size 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...
Mormon Lake, Munds Park, Dairy Springs Campground, Double Springs
Campground, Pinegrove Campground and Ashurst Lake Campgrounds.

This includes the following highways...
 Interstate 17 between mile markers 312 and 326.

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.

If on or near Mormon Lake, get out of the water and move indoors or
inside a vehicle. Remember, lightning can strike out to 10 miles
from the parent thunderstorm. If you can hear thunder, you are close
enough to be struck by lightning. Move to safe shelter now! Do not
be caught on the water in a thunderstorm.

Persons in campgrounds should consider seeking sturdy shelter until
this storm passes.

&&

LAT...LON 3497 11173 3505 11140 3489 11126 3480 11151
      3482 11175
TIME...MOT...LOC 1926Z 342DEG 2KT 3494 11152

MAX HAIL SIZE...0.75 IN
MAX WIND GUST...40 MPH

Bain

Special Weather Statement
National Weather Service Flagstaff AZ
1235 PM MST Fri May 19 2023

AZZ015-038-192000-
Western Mogollon Rim-Oak Creek and Sycamore Canyons-
1235 PM MST Fri May 19 2023

...A strong thunderstorm will impact areas just west of Rogers Lake
through 100 PM MST...

At 1233 PM MST, Doppler radar was tracking a strong thunderstorm
just west of Rogers Lake, moving southwest at 5 mph.

HAZARD...Winds of up to 40 mph and penny size 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...
Rogers Lake, Raymond Boy Scout Camp and White Horse Lake Campground.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

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

&&

LAT...LON 3521 11203 3519 11186 3499 11185 3499 11216
TIME...MOT...LOC 1933Z 027DEG 5KT 3510 11199

MAX HAIL SIZE...0.75 IN
MAX WIND GUST...40 MPH

Bain

Special Weather Statement
National Weather Service Flagstaff AZ
1258 PM MST Fri May 19 2023

AZZ007-008-037-192030-
Yavapai County Valleys and Basins-Coconino Plateau-Yavapai County
Mountains-
1258 PM MST Fri May 19 2023

...A strong thunderstorm will impact portions of Coconino and Yavapai
Counties, near Seligman, through 130 PM MST...

At 1258 PM MST, Doppler radar was tracking a strong thunderstorm near
Seligman, or 44 miles northwest of Chino Valley, moving south at 25
mph.

HAZARD...Winds in excess of 30 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...
Seligman.

This includes the following highways...
 Business Interstate 40 near mile marker 141.
 Interstate 40 between mile markers 122 and 135.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

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 3543 11286 3543 11272 3522 11266 3521 11291
TIME...MOT...LOC 1958Z 359DEG 22KT 3536 11278

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...30 MPH

RKR

Special Weather Statement
National Weather Service Flagstaff AZ
103 PM MST Fri May 19 2023

AZZ015-037-038-192030-
Yavapai County Valleys and Basins-Western Mogollon Rim-Oak Creek and
Sycamore Canyons-
103 PM MST Fri May 19 2023

...A strong thunderstorm will impact portions of Coconino and Yavapai
Counties, south of Williams, through 130 PM MST...

At 102 PM MST, Doppler radar was tracking a strong thunderstorm 10
miles southeast of Williams, or 24 miles northwest of Sedona, moving
southwest at 10 mph.

HAZARD...Winds in excess of 30 mph and pea size 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...
Raymond Boy Scout Camp and White Horse Lake Campground.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

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 3523 11206 3512 11193 3497 11211 3510 11227
TIME...MOT...LOC 2002Z 043DEG 8KT 3512 11209

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...30 MPH

RKR

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