Severe Thunderstorm Warning 151, NWS Flagstaff, AZ

555 
WWUS55 KFGZ 202216
SVSFGZ

Severe Weather Statement
National Weather Service Flagstaff AZ
316 PM MST MON AUG 20 2018

AZC025-202225-
/O.EXP.KFGZ.SV.W.0151.000000T0000Z-180820T2215Z/
Yavapai-
316 PM MST MON AUG 20 2018

...THE SEVERE THUNDERSTORM WARNING FOR YAVAPAI COUNTY HAS EXPIRED...
                
The storm which prompted the warning has weakened below severe
limits, and no longer pose an immediate threat to life or property.
Therefore the warning has been allowed to expire.  However gusty
winds and heavy rain are still possible with this thunderstorm.

LAT...LON 3453 11204 3460 11225 3489 11226 3478 11182
TIME...MOT...LOC 2215Z 201DEG 10KT 3472 11208 

$$

41

Area Forecast Discussion
National Weather Service Flagstaff AZ
1014 AM MST Mon Aug 20 2018

.SYNOPSIS...Expect limited storm activity today, with isolated
storms over Yavapai and Coconino counties. A significant moisture
increase will develop later tonight through Tuesday, with showers
and thundertorms becoming likely. This moisture will stay around
for the remainder of the week, with a good chance of afternoon
and evening showers and thunderstorms each day.

&&

.UPDATE...Little change to the forecast this morning. Monsoonal
moisture is pushing north with dew points already in the upper
50's south of the Mogollon Rim and in Yavapai County, and in the
low 50's in Coconino County. Strong southerly to southwesterly
flow will continue to to push moisture into Navajo and Apache
Counties this afternoon and evening leading to increased pops in
these areas. A concern to watch for is strong thunderstorms in
Yavapai County later this evening and over night caused by out
flow from earlier convective activity.

&&

.PREV DISCUSSION /420 AM MST/...Deeper moisture along and south of
the Mogollon Rim will be sufficient for isolated or scattered
storms today, possibly even pushing northward by afternoon, as
southwest flow increases.

The ridge position will be east of Arizona by tonight, with a weak
trough settling over the northern Great Basin. An upper level
disturbance moving north through the Gulf of California tonight
will bring a substantial moisture increase to the area on
Tuesday. Showers and thunderstorms will become widespread, all
the way northward to the Utah border.

A favorable flow pattern will remain in place all week. Expect an
active convective pattern, enhanced by the presence of shear.
There are some differences by the weekend and early next week,
with some models bringing in a trough and drying us out.
Confidence is low and will keep a standard monsoon forecast in
the seven day period for now.

&&

.AVIATION...For the 18Z package...Mainly VFR conditions over the
next 24 hours with localized gusty afternoon winds for KGCN and
KINW. After 19Z, be on the lookout for isolated afternoon and
evening thunderstorms, through 04Z, along a line southwest of KPGA-
KINW-KSOW. Anticipate areas of MVFR/IFR conditions and gusty/erratic
winds within the vicinity of thunderstorms. Aviation discussion not
updated for TAF amendments.

&&

.FIRE WEATHER...Today will see locally breezy south to southwest
winds with isolated showers and thunderstorms from the Kaibab
Plateau to the White Mountains southward. Moisture will continue to
push across Arizona tonight through Tuesday with an increasing
chance for showers and thunderstorms. Cooler on Tuesday by 5 to 10
degrees.

.Wednesday through Friday...Monsoon moisture will remain in place
across northern Arizona with a good chance of showers and
thunderstorms each day.

&&

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

&&

PUBLIC...DB/Peterson
AVIATION...NL
FIRE WEATHER...McCollum

For Northern Arizona weather information visit
weather.gov/flagstaff

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
901 AM MST MON AUG 20 2018

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

0222 PM     TORNADO          6 S COSNINO             35.11N 111.47W
08/18/2018                   COCONINO           AZ   TRAINED SPOTTER

            TIME LAPSE VIDEO SHOWS NARROW TORNADO AT
            APPROXIMATELY 30 DEGREE ANGLE TO THE GROUND
            PERSISTING FOR SEVERAL MINUTES.

&&

NWS FLAGSTAFF

Special Weather Statement
National Weather Service Flagstaff AZ
140 PM MST MON AUG 20 2018

AZZ008-015-037-038-202130-
Yavapai County Valleys and Basins-Western Mogollon Rim-Yavapai County
Mountains-Oak Creek and Sycamore Canyons-
140 PM MST MON AUG 20 2018

...SIGNIFICANT WEATHER ADVISORY FOR YAVAPAI AND COCONINO COUNTIES
UNTIL 230 PM MST...

At 139 PM MST, Doppler radar was tracking a cluster strong
thunderstorms along a line extending from 6 miles north of Clarkdale
to 9 miles northeast of Perkinsville. Movement was northeast at 15
mph.

Nickel size hail and wind gusts up to 50 mph will be possible with
these storms.

Locations impacted include...
Raymond Boy Scout Camp and White Horse Lake Campground.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

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

&&

LAT...LON 3489 11184 3531 11186 3503 11215 3473 11214
TIME...MOT...LOC 2039Z 226DEG 11KT 3485 11209 3501 11210

JDS