Severe Thunderstorm Warning 17, NWS Flagstaff, AZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
1024 AM MST Wed Jul 18 2018

.SYNOPSIS...Expect a good chance of afternoon and evening showers
and thunderstorms through at least Saturday. The greatest
coverage and highest potential for stronger storms will be over
Coconino and Yavapai counties where areas of heavy rain could lead
to flooding.

&&

.UPDATE...No major updates were made to the forecast this morning.
Debris clouds from overnight thunderstorm activity continue to
dissipate and move northwestward this morning which will allow for
plenty of afternoon heating and destabilization today. Scattered
to numerous slow moving storms this afternoon will produce areas
of heavy rain. The greatest threat for flash flooding continues to
be across Coconino and especially Yavapai Counties where the most
saturated soils are. A few stronger downdrafts are also possible
this afternoon, primarily across central and western Arizona.

&&

.DISCUSSION...
For Today - plenty of residual cloud cover will be
found across much of the area through late morning. Storms should
develop first across the White mountains ( as it's clear there
now), and then spread slowly to other high terrain sites through
the afternoon. Storm motion should be to the west at less than 10
mph. The GFS model upper level streamlines show a weak inverted
trough feature across northwest Coconino county this afternoon and
evening, not confident this feature will develop but its
something to watch for.

Thursday through Saturday...the main story is deep monsoon
moisture overhead with very slow steering flow. Steering flow
should remain easterly through Thursday and then turning more
southerly for Friday and Saturday. This should keep the deeper
moisture across the western and central portions of the state,
with storms motions from south to north. Little change in forecast
sounding convective parameters on Saturday vs today and storm
chances were raised for the high country.

Sunday through Tuesday...Progs are in fair agreement for this
period showing the mid level high pressure circulation
strengthening over New Mexico with drier air aloft over Arizona.
Made no changes to the extended, which has only a slight chance of
tstorms, and max temperatures 2 to 5 degrees above normal for the
dates.

&&

.AVIATION...For the 18Z package...Expect sct-nmrs shra/tsra and
isold +tsra from 18Z-19Z until 02Z-04Z, decreasing activity after
04Z. Storm activity favoring Yavapai and Coconino counties, with a
secondary maxima possible this evening over southern Navajo and
Apache counties. The strongest storms will produce localized
MVFR/IFR conditions. Aviation discussion not updated for TAF
amendments.

&&

.FIRE WEATHER...Expect scattered to numerous afternoon and evening
showers and thunderstorms today and Thursday. Storm motion will
generally be east to west, with portions of Coconino and Yavapai
counties likely seeing the most activity.

Friday through Sunday...Flow becomes more southerly during this
period, ensuring that deep moisture remains in at least the western
and central zones. Somewhat dryer conditions may begin to develop
Sunday as flow turns more westerly.

&&

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

&&

PUBLIC...MCT/DL
AVIATION...Peterson
FIRE WEATHER...DL

For Northern Arizona weather information visit
weather.gov/flagstaff

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
856 AM MST WED JUL 18 2018

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

0430 AM     FLASH FLOOD      LEES FERRY              36.87N 111.59W
07/18/2018                   COCONINO           AZ   OFFICIAL NWS OBS

            A STREAM GAUGE AT LEES FERRY, WHERE THE
            PARIA RIVER REACHES THE COLORADO RIVER,
            REACHED A PEAK STAGE OF 7.82 FEET WITH A
            PEAK FLOW OF 1,436 CFS. THIS WAS ABOUT A 3
            FOOT RISE OF WATER IN THIS LOCATION.

&&

MCT

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
914 AM MST WED JUL 18 2018

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

1101 PM     TSTM WND GST     4 S YARNELL             34.16N 112.74W
07/17/2018  E65 MPH          YAVAPAI            AZ   PARK/FOREST SRVC

            RAWS AUTOMATED STATION REPORTED PEAK WIND
            GUST.

&&

MCT

Special Weather Statement
National Weather Service Flagstaff AZ
1129 AM MST WED JUL 18 2018

AZZ015-181900-
Western Mogollon Rim-
1129 AM MST WED JUL 18 2018

...SIGNIFICANT WEATHER ADVISORY FOR COCONINO COUNTY UNTIL NOON MST...

At 1128 AM MST, National Weather Service Doppler radar was tracking
a strong thunderstorm over Fort Valley, or 7 miles northwest of
Flagstaff. This storm was nearly stationary.

Dime size hail and winds in excess of 30 mph will be possible with
this storm.

Locations impacted include...
Fort Valley.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3532 11173 3525 11165 3520 11170 3525 11182
TIME...MOT...LOC 1828Z 032DEG 3KT 3525 11172