Special Weather Statement, NWS Denver/Boulder, CO

Area Forecast Discussion
National Weather Service Denver/Boulder CO
238 PM MDT Sat Jul 3 2021

.SHORT TERM...(This evening through Sunday)
Issued at 219 PM MDT Sat Jul 3 2021

The upper level ridge can be seen on water vapor over the southwest
region with a dry conveyor belt along the northerly periphery across
Colorado. precipitable water values continue to be elevated with
values from 0.80 to over an inch across the plains. Storms motions
have improved since yesterday but continue to be lower with less
than 10kts through 600 mb. Further east model soundings continue to
show elevated PW values above an inch with hires ML CAPE nearing
1500 j/kg east of a Limon to Sterling line. Deep layer shear values
are on the lower side around 24 knots, however moderate to heavy
rain with golfball size hail will continue to be the main impacts
after 5 pm. Storms coverage is expected to improve after 8 pm this
evening.

For this evening, storms will clear leaving party cloudy
conditions and mild overnight temperatures.

On Sunday, the upper ridge will continue to build in with PW values
remaining high. Similar convective picture with less coverage given
any discernible source of aggressive lifting mechanism. Storms will
once again form over the higher terrain and progress ESE with
slightly faster flow aloft. Model soundings show CAPE values just
under 1000 j/kg with weak deep layer shear values but good lapse
rates. This will aid with convection and bring moderate to heavy
rain but could keep storms just below severe during the late
afternoon hours.

.LONG TERM...(Sunday night through Saturday)
Issued at 219 PM MDT Sat Jul 3 2021

For the 4th of July fireworks evening, high pressure ridge will
have built back eastward towards the four corners and western
Colorado with some amplification northward. This will likely keep
the majority of the storms over the mountains, Palmer Divide and
adjacent plains and then more isolated or no activity over the far
plains. By late evening and towards dusk, appears much of the
activity will have already cleared the area except for
southern/eastern portions of the county warning area and
especially Elbert and Lincoln counties. So probably not much of a
lightning fire works show for Northern Colorado. Should be good
viewing for man made fireworks displays across much of the area.

For Monday, moisture levels on the increase again with precipitable
water values increasing again to over an inch from the Front
Range foothills and eastward over the plains. Dewpoints will be
hold in the 50s for much of the day. This will result in an
increase in the flash flood threat, especially over the burn
scars. The high pressure ridge does retrograde a bit on Monday as
a weak trof rotates around the high pressure ridge for Monday
afternoon/evening. This wave will help enhance storm chances
through the day.

Slightly more subsident airmass moves in behind the trof for
Tuesday. There is still ample moisture around on Tuesday but
airmass looks to have stabilized some, so overall thunderstorm
chances may end up being at least lower on the plains, but
highest chances remaining over the mountains and higher terrain.

In the Wednesday through Thursday time frame, the high pressure
ridge aloft will be centered across the Great Basin region with a
resultant light to moderate northwest flow pattern across Colorado.
Temperatures through this period will be warmer and at or lightly
above seasonal normals for this time of year. Moisture appears to
be on the limited side through this period with only slight
chances of late day showers and thunderstorms. The GFS does
showing the next wave rotation around the big high for late
Thursday time frame which may increase thunderstorm chance
slightly.

For Friday and into next weekend, the high pressure ridge
retrogrades further west into California. This may open the door
for some weak waves in the northwest flow and for slightly cooler
temperatures and a slightly better chance for storms.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 219 PM MDT Sat Jul 3 2021

Light winds will prevail through the TAF period. Storms will
increase after 21z with gates being impacted from 21z to 01z.
There are increasing chances of storms at DEN after 22z with
coverage being limited. Wind directions could become erratic with
outflow boundaries from storms in the vicinity. Conditions will
improve after 01z with drainage expected after 05z.

&&

.HYDROLOGY...
Issued at 219 PM MDT Sat Jul 3 2021

For the burn scars, with storm motions slightly quicker there is
less of a concern for stationary convection. However, instability
has aided in creating scattered coverage with elevated moisture
levels that could bring a moderate to strong cell over the burn scar
areas dropping a quarter to half an inch in less than an hour.

Expect an increasing threat for flash flooding, especially over
the burn scars for Monday afternoon and evening as moisture levels
increase and some enhancement from an upper level disturbance.
Tuesday there will still be ample moisture but marginal instability
may limit storm strength. Beyond Tuesday, a slow warming and
drying trend through the end of the week with reduced chances for
flash flooding.

&&

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

SHORT TERM...Bowen
LONG TERM...Entrekin
AVIATION...Bowen
HYDROLOGY...Bowen

Hazardous Weather Outlook
National Weather Service Denver/Boulder CO
954 AM MDT Sat Jul 3 2021

COZ030>051-041600-
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-
954 AM MDT Sat Jul 3 2021

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

.DAY ONE...Today and Tonight

Scattered thunderstorms with heavy rainfall are expected this
afternoon and evening. Storms will initially form over the higher
terrain with a limited threat of flooding over the burn scars this
afternoon. Lightning will also accompany the storms which people
recreating outdoors should consider. Storms will progress off the
higher terrain and onto the plains after 2 pm bringing moderate to
heavy rain, lightning and small hail. Large hail will be possible
east of a Limon to Sterling line after 5 pm as storms progress and
become stronger into the evening hours. Storm coverage will
decrease during the early evening over the higher terrain and by 8
to 9 pm over the plains.

.DAYS TWO THROUGH SEVEN...Sunday through Friday

Scattered afternoon thunderstorms with heavy rain will be possible
Sunday. The thunderstorms will be moving at a decent speed, so the
flash flood threat for the burn areas will be limited. Else where,
very low to no threat of flash flooding is expected. Showers and
thunderstorms with heavy rainfall will be more numerous Monday.
This will increase the flash flood threat, especially over the
burn areas.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed today or tonight, but
reports of heavy rain, flooding and hail will be appreciated.

Special Weather Statement
National Weather Service Denver CO
445 PM MDT Sat Jul 3 2021

COZ044-045-032315-
Morgan County CO-Central and East Adams and Arapahoe Counties CO-
445 PM MDT Sat Jul 3 2021

...Brief Landspout Tornado Sighted...

At 444 PM MDT, trained weather spotters reported a landspout tornado
over southeast Morgan county. Conditions continue to favor the
potential for landspouts as storms develop; however at this time it
is unknown which if any storm would produce a landspout. Any
landspouts which develop are expected to pose a limited threat.

Locations impacted include...
Gary, Twelve-Mile Corner, Adena School and Adena.

Landspout tornadoes can form with a developing thunderstorm before
rain, hail, and even thunder is observed. Landspout tornadoes are not
usually associated with a wall cloud and are often difficult to
detect with weather radar.

&&

LAT...LON 4015 10357 4000 10356 4000 10370 3992 10371
      3992 10391 4014 10393

RPK

Special Weather Statement
National Weather Service Denver CO
514 PM MDT Sat Jul 3 2021

COZ041-046-032345-
Elbert/Central and East Douglas Counties Above 6000 Feet CO-
North and Northeast Elbert County Below 6000 Feet/North Lincoln
County CO-
514 PM MDT Sat Jul 3 2021

...Brief Landspout Tornadoes Possible...

At 513 PM MDT, conditions are becoming favorable for the development
of landspout tornadoes over south central Elbert county.  However,
at this time it is unknown which if any storm would produce a
landspout. Any landspouts which develop are expected to pose a
limited threat.

Locations impacted include...
Elbert.

Landspout tornadoes can form with a developing thunderstorm before
rain, hail, and even thunder is observed. Landspout tornadoes are not
usually associated with a wall cloud and are often difficult to
detect with weather radar.

&&

LAT...LON 3925 10476 3942 10407 3916 10404 3913 10423
      3913 10466

RPK

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DENVER CO
533 PM MDT SAT JUL 3 2021

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

0506 PM     HAIL             2 WSW TWIN BUTTES       40.89N 102.81W
07/03/2021  M1.25 INCH       LOGAN              CO   TRAINED SPOTTER

            L500.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DENVER CO
555 PM MDT SAT JUL 3 2021

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

0539 PM     TSTM WND GST     10 E ELBA               39.95N 103.03W
07/03/2021  M60 MPH          WASHINGTON         CO   TRAINED SPOTTER

            WA153.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DENVER CO
601 PM MDT SAT JUL 3 2021

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

0601 PM     TSTM WND GST     9 E ELBA                39.95N 103.06W
07/03/2021  M60 MPH          WASHINGTON         CO   TRAINED SPOTTER

            WA159, BRANCHES BREAKING.

&&

Special Weather Statement
National Weather Service Denver CO
614 PM MDT Sat Jul 3 2021

COZ050-051-040045-
Phillips County CO-Sedgwick County CO-
614 PM MDT Sat Jul 3 2021

...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN PHILLIPS AND
SEDGWICK COUNTIES UNTIL 645 PM MDT...

At 614 PM MDT, Doppler radar was tracking a strong thunderstorm near
Sedgwick, or 14 miles south of Chappell, moving east at 15 mph.

Nickel size hail and wind gusts up to 50 mph will be possible with
this storm.

Locations impacted include...
Julesburg, Ovid, Sedgwick and Marks Butte.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

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

&&

A Severe Thunderstorm Watch remains in effect until 1000 PM MDT for
northeastern Colorado.

LAT...LON 4071 10225 4072 10265 4100 10265 4100 10227
TIME...MOT...LOC 0014Z 287DEG 13KT 4089 10253

RPK