Special Weather Statement, NWS Salt Lake City, UT

Area Forecast Discussion
National Weather Service Salt Lake City UT
959 PM MDT Sun Aug 4 2019

.SYNOPSIS...High pressure over the Four Corners will shift west
into Arizona later tonight, bringing a slight drying trend
through Tuesday morning. As the ridge returns east by Wednesday,
moisture will return for the latter half of the work week.

&&

.SHORT TERM (Tonight)...A shortwave lifting northeast across
northeast Nevada through west-central Utah has generated scattered
showers/thunderstorms this evening. A few strong storms have been
noted, with gusty winds appearing to be the main impact along
with the possibility of brief heavy rain/small hail. This activity
should weaken after midnight as the flow aloft turns more anti-
cyclonic and greatly weakens any dynamic forcing.

Across central and southern Utah convection from this afternoon
and early evening is weakening rapidly late this evening.
Persistent deep convection which generated very heavy precip
earlier this evening has settled into the Lake Powell area and
continues to generate some thunderstorm activity at this time.
This activity should exit the forecast area over the next hour or
two.

The flood surge that developed along the Escalante River drainage
late this afternoon has likely made it into the Glen Canyon Rec
Area. This flood surge should make it into Lake Powell around
midnight where it will finally dissipate. The current flash flood
warning is scheduled to expire at 1000 pm MDT. Will allow the
warning to expire with wording that elevated but decreasing flows
still exist late this evening.

.PREVIOUS SHORT TERM (Monday 12Z Through 00Z Thursday)...Center
of the ridge remains over the Four Corners this afternoon, keeping
a moist airmass over Utah and southwest Wyoming. Satellite
derived PWs are predominately in the 0.8 to 1.0 inch range, with
some higher values over eastern Utah. Earlier cloud cover has
diminished, allowing for showers and thunderstorms to develop in
this moist airmass, primarily over the higher terrain. Any storms
that develop have the potential to produce heavy rain that could
lead to flash flooding. Shortwave energy moving over northwest
Utah will allow for some additional storms over that area through
the early evening. Maxes are generally running near to just above
seasonal normals across the area.

The ridge will retreat west tonight into early tomorrow, with the
axis moving over Utah. As a result, the flow aloft will become
more westerly, allowing drier air to move into the forecast area.
PWs are anticipated to drop into the 0.6 to 0.8 inch range by
Tuesday morning. Though enough moisture will exist for some
afternoon/evening convection over the higher terrain, coverage
will be noticeably less than the past few days.

High pressure is then expect to move back east over the Four
Corners beginning late Tuesday, bringing monsoon moisture back
northward and allowing coverage of showers and thunderstorms to
ramp back up for Wednesday. Have increased POPs a bit for
Wednesday afternoon with increasing confidence. Increasing cloud
cover will also drop high temperatures slightly, with maxes
running near seasonal normals.

.PREVIOUS LONG TERM (After 00Z Thursday)...The southern Rockies
ridge will remain in place to start the long term forecast period.
On the western periphery of this ridge...a shortwave will
progress northeastward across eastern Nevada/western Utah
Wednesday into Thursday. Operational/ensemble model solutions vary
in positioning of this shortwave which will ultimately have a
large impact on convective coverage across Utah. For now trended
toward an ensemble approach...with higher pops than the
operational EC would warrant.

While  net drying is expected across the CWA in the wake of the
Thursday wave...expect higher terrain to continue to support
convection into at least Friday and potentially the weekend.
Coverage will gradually decrease as mid-level dry air advection
continues.

&&

.AVIATION...An area of thunderstorms will track east across
southern Salt Lake county between 04Z and 05Z. Not looking at a
direct impact from these storms, though outflow winds could pick
up out of the south then southeast through around 07Z.

Convection will end near the terminal after 07z. Prevailing
southeast winds and VFR conditions will through Monday afternoon.

&&

.PREVIOUS FIRE WEATHER...High pressure over the Four Corners will
retreat west beginning tonight, bringing a drying trend to the
area through Tuesday morning. The ridge will move back east over
the Four Corners starting Tuesday night, allowing moisture to
return. This will result in increasing coverage of showers and
thunderstorms for the middle to latter part of the work week.
Temperatures will be near to just above seasonal normals with
generally light and terrain driven winds.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...None.
WY...None.
&&

CONGER/KRUSE/TRAPHAGAN

For more information from NOAA's National Weather Service visit...
http://weather.gov/saltlakecity

For frequently asked questions about the Area Forecast Discussion
visit...
http://weather.gov/saltlakecity/general/afd_faqs.php

Hazardous Weather Outlook
National Weather Service Salt Lake City UT
549 AM MDT Sun Aug 4 2019

UTZ001>016-019>021-517-518-WYZ021-051300-
Cache Valley/Utah Portion-Northern Wasatch Front-
Salt Lake and Tooele Valleys-Southern Wasatch Front-
Great Salt Lake Desert and Mountains-Wasatch Mountain Valleys-
Wasatch Mountains I-80 North-Wasatch Mountains South of I-80-
Western Uinta Mountains-Wasatch Plateau/Book Cliffs-
Western Uinta Basin-Castle Country-San Rafael Swell-
Sanpete/Sevier Valleys-West Central Utah-Southwest Utah-
Utahs Dixie and Zion National Park-South Central Utah-
Glen Canyon Recreation Area/Lake Powell-Central Mountains-
Southern Mountains-Southwest Wyoming-
549 AM MDT Sun Aug 4 2019

This Hazardous Weather Outlook is for the western two thirds of
Utah and southwest Wyoming.

.DAY ONE...Today and Tonight

Moisture will remain in place across Utah today, and locally
heavy rainfall will be possible. There is a risk of flash
flooding, particularly near burn scars, slot canyons, normally dry
washes, and areas of poor drainage.

.DAYS TWO THROUGH SEVEN...Monday through Saturday

The airmass will trend a bit drier for the first half of the
week, but isolated to scattered showers and thunderstorms will
linger. Some of the stronger storms will be capable of producing
heavy rain.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

For more information from NOAA/s National Weather Service visit...
http://weather.gov/saltlakecity

For information on potential road travel impacts visit...
http://www.udottraffic.utah.gov/roadweatherforecast.aspx

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
433 PM MDT SUN AUG 4 2019

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

0412 PM     HEAVY RAIN       8 NNW ESCALANTE         37.87N 111.66W
08/04/2019  M1.57 INCH       GARFIELD           UT   MESONET

            RAINFALL TOTAL OVER A LESS THAN 2 HOUR PERIOD, WITH 1.34
            INCHES IN LESS THAN AN HOUR. MEASUREMENT FROM THE BUCK
            FLATS RAWS SITE BUKU1.

&&

MCONGER

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
717 PM MDT SUN AUG 4 2019

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

0430 PM     FLASH FLOOD      ESCALANTE               37.76N 111.60W
08/04/2019                   GARFIELD           UT   EMERGENCY MNGR

            NUMEROUS REPORTS OF FLASH FLOODING AROUND THE TOWN OF
            ESCALANTE ALONG THE ESCALANTE RIVER. BACKCOUNTRY TRAVEL
            NOT RECOMMENDED. THE ESCALANTE RIVER WENT FROM 1 TO 2273
            CFS WITH THE PEAK FLOOD WAVE. REPORTS ARE FROM THE
            ESCALANTE VISTORS CENTER AND THE GARFIELD COUNTY SD.

&&

MCONGER

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