Special Weather Statement, NWS Denver/Boulder, CO

Area Forecast Discussion
National Weather Service Denver/Boulder CO
328 PM MDT Sun Jul 2 2017

.SHORT TERM...(This evening through Monday)
Issued at 328 PM MDT Sun Jul 2 2017

Isolated thunderstorms are moving out of the mountains and across
northeast Colorado this afternoon with microburst activity.

A strong upper ridge will remain in place over the southwestern
U.S. through Monday, keeping warm temperatures in place across the
desert southwest and Colorado. Flow aloft over Colorado will be
light west-northwesterly with enough mid-level moisture present to
allow afternoon thunderstorms to develop again. It should be a
scenario quite similar to the present afternoon, with the showers
initially developing over the mountains and then moving onto the
plains. Gusty winds and light rainfall will be the main products
of the showers. High temperatures across the plains should again
reach the lower to mid 90s, as this typical summer weather pattern
prevails.

.LONG TERM...(Monday night through Sunday)
Issued at 328 PM MDT Sun Jul 2 2017

Models all show the upper ridge center moving into the CWA from
the west and southwest Monday night through mid week. By 12Z
Thursday morning, the upper ridge center is over western and
northwestern Colorado. Weak north and northwesterly flow aloft is
progged. There is benign synoptic scale energy. Normal diurnal
wind patterns seem to dominate through Wednesday night. There is
some moisture around Monday night and again late day Tuesday.
Wednesday dries out somewhat. Precipitable water values range
from 0.50 west to 1.00 inch far east Monday night through Tuesday
night. Wednesday and Wednesday night dry out a tad. Boundary layer
dew points are mostly in the 40s F over the plains with some
lower 50s F near the eastern border Monday night and Tuesday. They
are a bit higher Tuesday night. By mid Wednesday morning through
Wednesday night, they dry out into the mid 30s to mid 40s There
is limited CAPE progged Monday evening. There is more substantial
CAPE over the eastern plains and high country late day Tuesday.
There is less for late day Wednesday, with the highest number over
the mountains. It is pretty warm aloft, lapse rate fields show
caps in place, especially over the plains. Will keep pops pretty
low, mostly 10-30% Monday evening, late day Tuesday and late day
Wednesday in the mountains only. For temperatures, Tuesday's highs
are 0.5-2.0 C warm than Monday's. Wednesday's highs are up
another 0.5-1.5 C from Tuesday's. For the later days, Thursday
through Sunday, models keep the upper ridge centered over Utah
into western Colorado all four days. There is some moisture
around, mainly for alpine precipitation. Temperatures stay a bit
above seasonal normals all four days.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 328 PM MDT Sun Jul 2 2017

Isolated high-based thunderstorms with microburst activity will
move over the Denver area airports through about 6 PM. Gusts of 40
to 50 mph can be expected near showers. Ceilings and visibilities
should remain unaffected. Skies should clear out through the
evening with winds becoming southerly overnight. Isolated
thunderstorm activity with gusty winds but little rainfall can be
expected again Monday afternoon.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&

SHORT TERM...Dankers
LONG TERM...RJK
AVIATION...Dankers

Hazardous Weather Outlook
National Weather Service Denver/Boulder CO
1103 AM MDT Sun Jul 2 2017

COZ030>051-031715-
Jackson County Below 9000 Feet-
West Jackson and West Grand Counties Above 9000 Feet-
Grand and Summit Counties Below 9000 Feet-
South and East Jackson/Larimer/North and Northeast Grand/
Northwest Boulder Counties Above 9000 Feet-
South and Southeast Grand/West Central and Southwest Boulder/
Gilpin/Clear Creek/Summit/North and West Park Counties Above
9000 Feet-Larimer and Boulder Counties Between 6000 and 9000 Feet-
Jefferson and West Douglas Counties Above 6000 Feet/Gilpin/Clear
Creek/Northeast Park Counties Below 9000 Feet-
Central and Southeast Park County-
Larimer County Below 6000 Feet/Northwest Weld County-
Boulder And Jefferson Counties Below 6000 Feet/West Broomfield
County-
North Douglas County Below 6000 Feet/Denver/West Adams and
Arapahoe Counties/East Broomfield County-
Elbert/Central and East Douglas Counties Above 6000 Feet-
Northeast Weld County-Central and South Weld County-Morgan County-
Central and East Adams and Arapahoe Counties-
North and Northeast Elbert County Below 6000 Feet/North Lincoln
County-
Southeast Elbert County Below 6000 Feet/South Lincoln County-
Logan County-Washington County-Sedgwick County-Phillips County-
1103 AM MDT Sun Jul 2 2017

This hazardous weather outlook is for northeast and north central
Colorado.

.DAY ONE...This Afternoon and Tonight

Isolated showers and thunderstorms will develop over the
mountains and adjacent plains early this afternoon before
spreading east on the plains through the evening hours. Expect
gusty winds to 45 mph but only brief light rain over the mountains
and adjacent plains. More low level moisture will be available
further east with the potential for a few strong to severe storms
along and ahead of a dry line, generally east of a line from Limon
to Sterling. Damaging winds up to 60 mph and large hail are
possible with the stronger storms on the eastern plains.

An upper level disturbance over the Great Basin will bring the
moisture and better chance for storms this afternoon and evening.
Temperatures will continue to be warm with readings in the lower
90s on the plains.

.DAYS TWO THROUGH SEVEN...Monday through Saturday

Expect warmer than average temperatures through Friday, with
cooler temperatures through the weekend.

Isolated thunderstorms are expected over the mountains each day
through the week. There will be a slight chance of storms over
the plains Monday and Tuesday, dry Wednesday and Thursday, then
returning Friday and Saturday. The main impacts from the storms
will be gusty outflow winds and some hail possible.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed on the far eastern plains of
Colorado, mainly east of a line from Limon to Sterling after 2 pm.

Special Weather Statement
National Weather Service Denver CO
256 PM MDT SUN JUL 2 2017

COZ040-041-045-022115-
Elbert/Central and East Douglas Counties Above 6000 Feet CO-
Central and East Adams and Arapahoe Counties CO-
North Douglas County Below 6000 Feet/Denver/West Adams and Arapahoe
Counties/East Broomfield County CO-
256 PM MDT SUN JUL 2 2017

...SIGNIFICANT WEATHER ADVISORY FOR WESTERN ARAPAHOE...EASTERN DENVER
AND WESTERN ADAMS COUNTIES UNTIL 315 PM MDT...

At 252 PM MDT, Doppler radar was tracking a high based rain showers
producing strong microburst winds over western Arapahoe County. The
strongest wind gusts were detected by radar in the vicinity of
Watkins, or 19 miles east of Denver. These showers were moving
northeast at 30 mph.

Wind gusts of 50 to 55 mph will be possible with these high based
rain showers.

Locations impacted include...
Eastern Denver, Aurora, eastern Centennial, Greenwood Village, Denver
International Airport, Bennett, Watkins, Manila Village, D.I.A
Terminal and Concourses, Arapahoe Park, Strasburg and Buckley AFB.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Prepare for sudden gusty winds and considerable blowing dust. Secure
loose objects and move to a safe shelter inside a building or
vehicle. The blowing dust may also reduce visibilities to less than
a few hundred feet.

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 3986 10431 3970 10425 3957 10459 3957 10488
      3969 10492 4000 10451 4000 10449
TIME...MOT...LOC 2052Z 240DEG 49KT 3974 10459

BAKER

Special Weather Statement
National Weather Service Denver CO
319 PM MDT SUN JUL 2 2017

COZ040-043-045-022200-
Central and South Weld County CO-
Central and East Adams and Arapahoe Counties CO-
North Douglas County Below 6000 Feet/Denver/West Adams and Arapahoe
Counties/East Broomfield County CO-
319 PM MDT SUN JUL 2 2017

...SIGNIFICANT WEATHER ADVISORY FOR SOUTH CENTRAL WELD...NORTHWESTERN
ARAPAHOE...EASTERN DENVER AND WESTERN ADAMS COUNTIES UNTIL 400 PM
MDT...

At 315 PM MDT, Doppler radar was tracking a couple of high based
rain showers over western Adams County producing strong and very
gusty microburst winds. The shower producing the strongest winds was
4 miles west of Denver International Airport, or 13 miles northeast
of Denver. These showers were moving northeast at 25 mph.

Wind gusts of 45 to 55 mph will be possible with these showers.

Locations impacted include...
Eastern Denver, Aurora, northeastern Thornton, northeastern
Centennial, Commerce City, Brighton, Denver International Airport,
Lochbuie, Hudson, Bennett, Keenesburg, Manila Village, Arapahoe Park,
Strasburg, Buckley AFB, Watkins, Prospect Valley, D.I.A Terminal and
Concourses and Barr Lake.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Prepare for sudden strong gusty winds. Secure loose objects and move
to a safe shelter inside a building or vehicle.

Blowing dust may also reduce visibilities to less than a few hundred
feet.

&&

LAT...LON 4018 10441 3965 10426 3964 10449 3966 10450
      3965 10452 3964 10451 3962 10486 3997 10492
TIME...MOT...LOC 2115Z 246DEG 22KT 3986 10478

BAKER

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DENVER CO
344 PM MDT SUN JUL 02 2017

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

0331 PM     DOWNBURST        BRIGHTON                39.99N 104.79W
07/02/2017                   ADAMS              CO   TRAINED SPOTTER

            DRY MICROBURST WINDS ESTIMATED AT 60 MPH TO 70 MPH BROKE
            BRANCHES AND KNOCKED DOWN TREES IN A RESIDENTIAL AREA OF
            BRIGHTON.

&&

KF

Special Weather Statement
National Weather Service Denver CO
348 PM MDT SUN JUL 2 2017

COZ040-045-022230-
Central and East Adams and Arapahoe Counties CO-
North Douglas County Below 6000 Feet/Denver/West Adams and Arapahoe
Counties/East Broomfield County CO-
348 PM MDT SUN JUL 2 2017

...SIGNIFICANT WEATHER ADVISORY FOR NORTHEASTERN DENVER AND CENTRAL
ADAMS COUNTIES UNTIL 430 PM MDT...

At 342 PM MDT, Doppler radar was tracking a couple of high based
rain showers over northeast Denver and western Adams Counties. The
shower producing the strongest winds was over Denver International
Airport, or 18 miles northeast of downtown Denver, moving east at 25
mph. The second shower was near Watkins, or 6 miles southeast of
Denver International Airport.

Wind gusts of 45 to 55 mph will be possible with these showers.

Locations impacted include...Northeastern Aurora, Denver
International Airport, Bennett, D.I.A Terminal and Concourses,
Watkins and Manila Village.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Prepare for sudden gusty winds. Secure loose objects and move to a
safe shelter inside a building or vehicle. The strong winds may
produce considerable blowing dust which could reduce visibilities to
a few hundred feet.

&&

LAT...LON 3977 10417 3975 10460 3980 10472 3994 10476
      4000 10456 4000 10433
TIME...MOT...LOC 2142Z 260DEG 22KT 3986 10465

BAKER