Special Weather Statement, NWS Flagstaff, AZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
1043 AM MST Wed Aug 18 2021

.SYNOPSIS...Scattered showers and thunderstorms will become
more widespread this afternoon and evening across northern
Arizona. Flash flooding will be possible in areas of heavy
rainfall. Drier conditions are expected Thursday through the
weekend. Cooler temperatures are also expected through the rest of
the week.

&&

.UPDATE...The latest high-res models prog thunderstorms developing
near the Prescott area this afternoon between the 2pm-6pm MST time
frame. Given the ample moisture in place, went ahead and expanded
the flash flood watch to include Yavapai County through this
evening.

Another active monsoon thunderstorm day is expected as plenty of
moisture, instability, and lift remains in place. However, storm
motions will be to the north-northeast and will be much faster
than yesterday given a strong low pressure system entering Idaho.
Better organized storms will be possible near the AZ/UT border
this afternoon closer to the strongest wind shear. Will continue
to monitor afternoon/evening trends.

&&

.PREV DISCUSSION /255 AM MST/...A few isolated showers have begun
to develop over the lower elevations south of the Mogollon Rim.
This activity is expected to continue to increase in coverage
through this morning. Heavy rainfall is expected to lead to a few
localized areas of flash flooding this morning over Gila County.
Showers and thunderstorms are expected to increase in coverage
this afternoon and into the evening, especially for areas along
and north of the Mogollon Rim. With increased moisture in place
once again and many areas saturated from heavy rainfall
yesterday, an enhanced threat of flash flooding remains over
portions of central and northwester Arizona. The Flash Flood
Watch has been extended as a result to include areas along the
Mogollon Rim northwestward into the Coconino and Kaibab Plateau
where HREF guidance continues to indicate the greatest potential
for heavy rainfall. While flash flooding will be the primary
threat this afternoon, a few strong to severe storms are also
possible with the potential to produce large hail and damaging
winds.

Longwave trough continues to move into the Intermountain West
today, with the center of the trough passing over Utah during the
day Thursday. Breezy and cooler conditions are expected as a
result today and again on Thursday. As the trough passes to the
north, the monsoonal moisture in place gets swept away with dryer
conditions expected in its wake Thursday and into the weekend.
Shower and thunderstorm chances do remain over mainly in the high
terrain of far northern Arizona near the Utah border Thursday and
Friday.

Dry conditions remain over much of the areas through the weekend.
Though temperatures begin to warm slightly each day as heights
rise from a ridge gradually building in from the east. Monsoonal
moisture does begin to creep back into Arizona, especially over
the eastern portions of the state, towards the first half of next
week as the ridge builds. However, confidence in any widespread
coverage of showers and thunderstorms is low at this point.

&&

.AVIATION...For the 18Z package...MVFR ceilings near KGCN-KFLG
should dissipate after 19Z. Showers and thunderstorms will become
widespread over northern Arizona this afternoon. Isolated IFR in
heavier storms with hail and gusty winds also possible. Outside of
storm activity, mainly VFR conditions and southwest winds around
10-15 kts with gusts around 25 kts. Aviation discussion not
updated for TAF amendments.

&&

.FIRE WEATHER...Scattered to numerous showers and thunderstorms
are expected again today. Large hail, localized flash flooding, and
very gusty outflow winds will be the main hazards. Winds will also
become breezy out of the southwest today with afternoon gusts around
30 mph. Much drier conditions are forecast Thursday with a continued
chance for storms along the far northern zones.

Friday through Sunday...Drier weather is expected through the
weekend, with below normal temperatures and breezy southwest winds.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...Flash Flood Watch through this evening FOR AZZ004>009-012-015-
016-018-037-038.

&&

PUBLIC...TM/Humphreys
AVIATION...TM
FIRE WEATHER...MCT

For Northern Arizona weather information visit
weather.gov/flagstaff

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
923 AM MST WED AUG 18 2021

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

0100 PM     FLASH FLOOD      DORTHA AVE.             35.22N 111.62W
08/17/2021                   COCONINO           AZ   COUNTY OFFICIAL

            WATER HAS OVERTOPPED THE BARRIERS AND
            OVERTOPPED THE ROADS WITH GREATER THAN 1.5
            FEET WATER DEPTH.

&&

TM

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
927 AM MST WED AUG 18 2021

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

0110 PM     FLASH FLOOD      CEDAR AVE. AND WEST ST. 35.22N 111.62W
08/17/2021                   COCONINO           AZ   COUNTY OFFICIAL

            SIGNIFICANT FLOODING NEAR SAFEWAY. CEDAR
            AVE. CLOSED BY THE CITY OF FLAGSTAFF.

&&

TM

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
1008 AM MST WED AUG 18 2021

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

0700 AM     FLASH FLOOD      1 NW LEES FERRY         36.87N 111.59W
08/18/2021                   COCONINO           AZ   MESONET

            USGS GAGE FOR THE PARIA RIVER AT LEES FERRY
            INDICATED A 4 FT. RISE BETWEEN 6AM-7AM.

&&

TM

Special Weather Statement
National Weather Service Flagstaff AZ
1037 AM MST Wed Aug 18 2021

AZZ008-015-016-037-038-181815-
Yavapai County Valleys and Basins-Western Mogollon Rim-Yavapai County
Mountains-Oak Creek and Sycamore Canyons-Eastern Mogollon Rim-
1037 AM MST Wed Aug 18 2021

...A strong thunderstorm will impact portions of I-17 south of Munds
Park through 1115 AM MST...

At 1035 AM MST, Doppler radar was tracking a strong thunderstorm near
Village At Oak Creek, or 7 miles southeast of Sedona, moving
northeast at 10 mph.

HAZARD...Winds in excess of 40 mph, half inch hail, and heavy
         rainfall.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

This storm will remain over mainly rural areas of Yavapai and
Coconino Counties.

This includes Interstate 17 between mile markers 304 and 321.

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.

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.

&&

LAT...LON 3472 11167 3476 11175 3483 11176 3497 11159
      3481 11145
TIME...MOT...LOC 1735Z 234DEG 8KT 3480 11168

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...40 MPH

EL

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