Severe Thunderstorm Warning 20, NWS Denver/Boulder, CO

941 
WWUS55 KBOU 040645
SVSBOU

Severe Weather Statement
National Weather Service Denver CO
1245 AM MDT Mon May 4 2020

COC121-040700-
/O.CON.KBOU.SV.W.0020.000000T0000Z-200504T0700Z/
Washington CO-
1245 AM MDT Mon May 4 2020

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 100 AM MDT
FOR NORTHEASTERN WASHINGTON COUNTY...

At 1245 AM MDT, a severe thunderstorm was located over Lone Star, or
16 miles north of Yuma, moving east at 35 mph.

HAZARD...60 mph wind gusts and half dollar size hail.

SOURCE...Radar indicated.

IMPACT...Expect damage to roofs, siding, and trees. Hail damage to 
         vehicles is expected.

Locations impacted include...
Lone Star.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 4035 10280 4017 10280 4017 10297 4044 10294
      4044 10278 4035 10278
TIME...MOT...LOC 0645Z 270DEG 32KT 4034 10283 

HAIL...1.25IN
WIND...60MPH
 
$$

RPK

647 
WWUS55 KBOU 040659
SVSBOU

Severe Weather Statement
National Weather Service Denver CO
1259 AM MDT Mon May 4 2020

COC121-040709-
/O.EXP.KBOU.SV.W.0020.000000T0000Z-200504T0700Z/
Washington CO-
1259 AM MDT Mon May 4 2020

...THE SEVERE THUNDERSTORM WARNING FOR NORTHEASTERN WASHINGTON COUNTY
WILL EXPIRE AT 100 AM MDT...
        
The storm which prompted the warning has moved out of the area.
Therefore, the warning will be allowed to expire.

LAT...LON 4035 10280 4017 10280 4017 10297 4044 10294
      4044 10278 4035 10278
TIME...MOT...LOC 0659Z 270DEG 32KT 4034 10266 

$$

RPK

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1204 AM MDT Mon May 4 2020

.UPDATE...
Issued at 1203 AM MDT Sun May 4 2020

As the upper trough over Idaho down into Utah gets closer,
continued lift ahead of it along with higher dewpoints moving
into the eastern Colorado plains, and slight upslope flow into
the foothills is increasing shower and storm coverage over the
forecast area. Have had several reports of the stronger storms
producing a lot of pea-sized hail, enough to clog some drains and
produce minor street flooding. With higher PWats, especially over
the northeastern corner of the state, these storms may end up
producing heavier rain for additional minor flooding issues.

Several outflows from convection have been mistakenly modeled as
the main cold front pushing into the state overnight. However the
main cold front is still up in Wyoming near Casper with the
highest pressure rises behind it. As a rule of thumb, it usually
takes about 6 hours to get down to Denver, although all this
convection may either delay or speed up that timing by an hour or
two.

UPDATE Issued at 736 PM MDT Sun May 3 2020

A corridor of 500-1000 J/kg CAPE from the far northeastern corner
back southwest toward the Palmer Divide is finally starting to be
able to be utilized evident on radar. Lift ahead of the upper
trough may be finally weakening the cap that has been shown on
ACARS soundings around 620mb. With the jet nearby and bulk shear
of 50-70 kts, will continue to see threats of large hail and
damaging winds tonight, and won't be able to rule out a tornado.
The biggest threat of severe strength storms will be mainly along
and east of a line from Sterling down to western Elbert County.
Main pressure rises still up in southwestern to northern Wyoming,
so a cold frontal timing of near midnight into the metro areas
still looks good. Will continue to see a chance of showers and
thunderstorms ahead of this front, as well as behind it into the
early morning hours with lift increasing ahead of the upper
trough.

&&

.SHORT TERM...(This evening through Monday)
Issued at 146 PM MDT Sun May 3 2020

Latest RAP/HRRR runs still want to initiate showers/thunderstorms
over the Cheyenne Ridge and Palmer Divide after 3 pm. A few storms
are developing along the northern border in closer to a broad 100+
kt jet stream that northern CA into eastern NE. Most of activity
through 8 pm this evening looks like it will be confined to these
areas. Temperatures have warmed up into the lower 70s, not enough
to break the cap and generate more storms. Sufficient CAPES
around to still produce an isolated severe thunderstorm with the
best chance along the northern border. Main concerns will be hail
to one inch and wind gusts to 60 mph. Outflow boundaries generated
by these storms may help get the storms going elsewhere. CAPES
over the northeast plains this afternoon, ranging from 500-1000
j/kg, highest over the northeast corner of the state. Models start
to enhance the thunderstorms over the northeast plains late this
evening and overnight. Better lift develops in the mid and upper
levels as an embedded short wave moved across northern. Good shear
profile as well, with the models showing stronger thunderstorms
developing mainly north and east of Denver from 9pm to 2am, with
some lingering activity continuing on the northern border through
6am Monday morning. Weak to moderate mid level QG ascent over the
forecast area this evening, weaker ascent after midnight, with
moderate subsidence spreading from northwest to southeast across
the forecast area on Monday. Late tonight into Monday morning, a
cold front will push north to south across the Denver area.
Coverage for showers and thunderstorms with be lower. Some low
level instability around on Monday, but overall the storms will be
weaker as well.

.LONG TERM...(Monday night through Sunday)
Issued at 146 PM MDT Sun May 3 2020

Flat upper level ridge will be over the western states with a
west- northwest flow aloft over Colorado. A cold front that pushes
through Colorado Monday should leave dry and stable conditions in
its wake. A few models show weak convection forming over the
higher terrain Monday evening and Tuesday afternoon. Will have low
PoPs for this. If anything forms it should be weak and short
lived. Temperatures on Tuesday will be near normal with highs in
the upper 60s to lower 70s.

The ridge over the western U.S. will slide east across the
Central Rockies Wednesday. This will bring warmer temperatures
with highs in the mid 70s across northeast Colorado. Surface high
pressure over the Northern and Central Plains will cause surface
winds to turn southeasterly Wednesday. This could transport enough
moisture for convection. With the ridge overhead, any convective
development will be battling warm air aloft and subsidence. Thus
will keep PoPs on the low side.

A ridge over the western U.S. will amplify into Canada Thursday.
This ridge will remain nearly stationary through Sunday. A long
wave trough will reside over the Great Lakes and eastern Canada
during this time frame. For Colorado, this will result in a
northwest flow aloft. Models show 2-3 short wave troughs embedded
in the northwest flow from Thursday to Sunday. Colorado will be on
the edge of the cooler air that each of these trough will bring.
Still a good amount of uncertainty on how far western each of
these troughs will dig. There should be a cold front sometime
Thursday, after this timing any front is difficult. Will have a
cooler day for Friday behind the front. For the weekend will keep
temperatures at or slightly below normal. This is not a good setup
for convection or precipitation. Can't rule out something late
next week due to the uncertainty, so will have low PoPs for this.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday evening)
Issued at 1203 AM MDT Mon May 4 2020

Expect scattered showers and thunderstorms over the terminals
through the nighttime hours. Some of the shorter term models are really
bringing in much lower ceilings into the area within the next few
hours, with ceilings as low as 1k-2k ft. Will monitor the ceilings
over the northeastern and northern plains over the next hour or
so. Ceilings around 050-060 kft are expected over the next hour or
so, with even lower ceilings to about 030 around 9z. With the main
cold front up near Casper, rule of thumb should have it around DEN
by 12z. The cold front may have winds of 15g25kts associated with
it, then the winds should trend down but stay northerly.
Northerly winds will persist through the day on Monday, with some
slight backing to the northwest during the afternoon.

&&

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

UPDATE...Kriederman
SHORT TERM...Cooper
LONG TERM...Meier
AVIATION...Kriederman

Hazardous Weather Outlook
National Weather Service Denver/Boulder CO
1032 AM MDT Sun May 3 2020

COZ030>051-041645-
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-
1032 AM MDT Sun May 3 2020

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

.DAY ONE...Today and Tonight

A few severe storms may develop this afternoon and evening over
the plains especially closer to the Wyoming, Nebraska border.
Further south over the plains activity may be more isolated. Hail
to one inch in diameter along with wind gusts to 60 mph will be
possible. Locally heavy rain will also be possible over the far
northeast plains tonight as thunderstorm activity becomes more
widespread.

Over the higher terrain look for scattered showers and
storms this afternoon with gusty winds to 50 mph and small hail.
Overnight there will be some accumulating snow above 10000 feet,
with amounts ranging from a trace to 3 inches.

.DAYS TWO THROUGH SEVEN...Monday through Saturday

Thunderstorms chances for the upcoming week will be very low. If
any storms from, they are expected to be weak.

.SPOTTER INFORMATION STATEMENT...

Spotter reports will be appreciated this afternoon and tonight.

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DENVER CO
915 PM MDT SUN MAY 3 2020

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

0830 PM     HAIL             6 SSW LONE STAR         40.27N 102.88W
05/03/2020  M1.00 INCH       WASHINGTON         CO   TRAINED SPOTTER

&&

Special Weather Statement
National Weather Service Denver CO
1019 PM MDT Sun May 3 2020

COZ043-040500-
Central and South Weld County CO-
1019 PM MDT Sun May 3 2020

...SIGNIFICANT WEATHER ADVISORY FOR WEST CENTRAL WELD COUNTY UNTIL
1100 PM MDT...

At 1019 PM MDT, Doppler radar was tracking a strong thunderstorm 4
miles northwest of Greeley, moving northeast at 25 mph.

Penny size hail will be possible with this storm.

Locations impacted include...
Greeley, Windsor, Evans, Eaton, Severance, Ault and Lucerne.

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 4058 10463 4052 10463 4052 10458 4046 10454
      4035 10480 4051 10494 4052 10494 4058 10482
TIME...MOT...LOC 0419Z 241DEG 21KT 4047 10481

RPK

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DENVER CO
1045 PM MDT SUN MAY 3 2020

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

1038 PM     HAIL             3 WSW PAWNEE PASS       40.61N 103.53W
05/03/2020  E1.00 INCH       LOGAN              CO   TRAINED SPOTTER

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DENVER CO
1047 PM MDT SUN MAY 3 2020

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

1038 PM     HAIL             3 WSW PAWNEE PASS       40.61N 103.53W
05/03/2020  E1.00 INCH       LOGAN              CO   TRAINED SPOTTER

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DENVER CO
1056 PM MDT SUN MAY 3 2020

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

0946 PM     HAIL             1 E CEDAR POINT         39.35N 103.80W
05/03/2020  M1.00 INCH       ELBERT             CO   TRAINED SPOTTER

1052 PM     HAIL             2 ESE LOGAN CORNERS     40.61N 103.32W
05/03/2020  M0.88 INCH       LOGAN              CO   TRAINED SPOTTER

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DENVER CO
1103 PM MDT SUN MAY 3 2020

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

1055 PM     HAIL             STERLING                40.63N 103.21W
05/03/2020  M1.75 INCH       LOGAN              CO   TRAINED SPOTTER

&&