Severe Thunderstorm Warning 8, NWS Flagstaff, AZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
937 AM MST Sat Aug 1 2020

.SYNOPSIS...Hot temperatures and dry conditions can be expected
across much of northern Arizona through the weekend. Shower and
thunderstorm chances will mainly be limited to the White Mountains
with only isolated storms possible elsewhere through Tuesday. More
widespread showers and thunderstorms are possible by Thursday.

&&

.DISCUSSION...Heat continues to be the main story this weekend,
with strong high pressure dominating the weather over northern
Arizona. Excessive Heat Warnings remain in place for our lower
elevations through Sunday evening. The Grand Canyon looks to see
continued dangerous heat conditions through Tuesday.

Enough moisture is in place today for isolated thunderstorm
development, mainly along the higher terrain. Latest hi-res
guidance indicates the best chances and strongest storms will be
across the eastern Mogollon Rim into the White Mountains.
Mesoanalysis verifies this as a likely scenario with 0-6 km shear
values of 25-35 kts over this area. More isolated convective
development is possible as far west as the Grand Canyon and
Prescott, but storms will be short-lived and weaker for the most
part. The primary hazards with the stronger storms will be gusty
winds. The boundary layer remains fairly dry so measurable rain
will be tough to come by for many locations.

The forecast has been updated to account for the latest trends in
the hi-res guidance.

&&

.PREV DISCUSSION /425 AM MST/...Hot and dry conditions will
continue as a large high pressure system continues to remain
centered over Arizona. Some moisture in the flow will allow for
isolated storm development, with the best chances over the White
Mountains. Some chances for storm development will occur over the
higher terrain of Western Arizona too, but storm development will
be limited. Any precipitation from these storms will be light if
measurable, outside of the strongest storms. Drier air returns to
region on Sunday and lasts through Tuesday decreasing storm
chances.

With dry conditions continuing, afternoon temperatures will climb
to dangerously high levels. Therefore, the excessive heat warning
has been extended for all locations below 5000 feet through 8 pm
Sunday, and within the lowest 5000 feet of the Grand Canyon
through 8pm Tuesday.

By the middle of the week the ridge does move eastward allowing
for moisture laden southerly flow to once again bring increasing
precipitable water back over Arizona from the Gulf of California.
Current model solutions only point to a slight uptick in
potential monsoonal storm activity, but at this point these meager
increases in chances will be the best chances for precipitation
in the forecast period. Confidence remains low in the specifics of
this timing and location for the pattern shift and any subsequent
storm development late in the forecast period.

&&

.AVIATION...For the 18Z package...Expect mainly VFR conditions for
the 24 hour TAF forecast period. ISOLD-SCT SHRA/TSRA developing into
this afternoon near sites KFLG/KPRC, but mainly east of KFLG and
along the Mogollon Rim and White Mtns. Any stronger cells could
produce MVFR conditions and wind gusts from 35-45kts. Sfc winds
outside of storms SW-W5-15G20KT during the afternoon hours. Storms
dissipating after 02Z Sunday. Aviation discussion not updated for
amendments.

&&

.FIRE WEATHER...Hot weather will continue this weekend as high
pressure remains over Arizona. A slight increase in moisture will
bring isolated showers and thunderstorms mainly to the higher
terrain both afternoons. Winds will generally be light.

Monday through Wednesday...Temperatures will drop back to near
normal through this period. Moisture will mainly be confined to the
White Mountains before expanding westward on Wednesday.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...Excessive Heat Warning until 8
PM MST Sunday FOR AZZ005-018-037- 038.

Excessive Heat Warning until 8 PM MST Tuesday FOR AZZ006.

&&

PUBLIC...TPS/Suk
AVIATION...KD
FIRE WEATHER...MAS

For Northern Arizona weather information visit
weather.gov/flagstaff

Special Weather Statement
National Weather Service Flagstaff AZ
111 PM MST Sat Aug 1 2020

AZZ016-018-012100-
Northern Gila County-Eastern Mogollon Rim-
111 PM MST Sat Aug 1 2020

...SIGNIFICANT WEATHER ADVISORY FOR GILA AND NAVAJO COUNTIES UNTIL
200 PM MST...

At 109 PM MST, Doppler radar was tracking a strong thunderstorm 15
miles south of Aripine, or 20 miles southeast of Forest Lakes, moving
south at 15 mph.

Pea size hail and winds in excess of 40 mph will be possible with
this storm.

Locations impacted include...
Cibecue.

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 3428 11057 3424 11036 3391 11040 3398 11072
TIME...MOT...LOC 2009Z 014DEG 12KT 3419 11049

DB

Special Weather Statement
National Weather Service Flagstaff AZ
207 PM MST Sat Aug 1 2020

AZZ007-015-012130-
Western Mogollon Rim-Coconino Plateau-
207 PM MST Sat Aug 1 2020

...SIGNIFICANT WEATHER ADVISORY FOR COCONINO COUNTY UNTIL 230 PM
MST...

At 206 PM MST, Doppler radar was tracking a strong thunderstorm 12
miles southwest of Williams, or 26 miles northeast of Chino Valley,
moving east at 15 mph.

Half inch hail and wind gusts up to 50 mph will be possible with this
storm.

This storm will remain over mainly rural areas of Coconino County.

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 3517 11231 3520 11208 3499 11214 3502 11233
      3516 11233
TIME...MOT...LOC 2106Z 280DEG 13KT 3511 11228

DB