Severe Thunderstorm Warning 9, NWS Denver/Boulder, CO

828 
WWUS55 KBOU 100328
SVSBOU

Severe Weather Statement
National Weather Service Denver CO
928 PM MDT Tue May 9 2023

COC087-123-100400-
/O.CON.KBOU.SV.W.0009.000000T0000Z-230510T0400Z/
Weld CO-Morgan CO-
928 PM MDT Tue May 9 2023

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 1000 PM MDT
FOR SOUTH CENTRAL WELD AND SOUTHWESTERN MORGAN COUNTIES...

At 924 PM MDT, a severe thunderstorm was located 8 miles southwest of
Wiggins, or 22 miles west of Fort Morgan, moving northeast at 15 mph.

HAZARD...Quarter size hail and 40 mph wind gusts.

SOURCE...Radar indicated.

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

Locations impacted include...
Wiggins.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Remain alert for a possible tornado! Tornadoes can develop quickly
from severe thunderstorms. If you spot a tornado go at once into the
basement or small central room in a sturdy structure.

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

Prepare immediately for large hail and deadly cloud to ground
lightning. Seek shelter inside a well-built structure. Stay away from
windows.

&&

LAT...LON 4035 10417 4009 10389 4001 10413 4009 10424
      4018 10430
TIME...MOT...LOC 0324Z 236DEG 13KT 4014 10419 

TORNADO...POSSIBLE
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...1.00 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH

$$

DIRENZO

294 
WWUS55 KBOU 100345
SVSBOU

Severe Weather Statement
National Weather Service Denver CO
945 PM MDT Tue May 9 2023

COC123-100354-
/O.CAN.KBOU.SV.W.0009.000000T0000Z-230510T0400Z/
Weld CO-
945 PM MDT Tue May 9 2023

...THE SEVERE THUNDERSTORM WARNING FOR SOUTH CENTRAL WELD COUNTY IS
CANCELLED...
    
The severe thunderstorm which prompted the warning has moved out of 
the warned area. Therefore, the warning has been cancelled.

LAT...LON 4009 10389 4003 10414 4023 10415 4026 10407
TIME...MOT...LOC 0344Z 236DEG 13KT 4018 10411 

$$

COC087-100400-
/O.CON.KBOU.SV.W.0009.000000T0000Z-230510T0400Z/
Morgan CO-
945 PM MDT Tue May 9 2023

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 1000 PM MDT
FOR SOUTHWESTERN MORGAN COUNTY...

At 944 PM MDT, a severe thunderstorm was located near Wiggins, or 17
miles west of Fort Morgan, moving northeast at 15 mph.

HAZARD...Ping pong ball size hail and 60 mph wind gusts.

SOURCE...Radar indicated.

IMPACT...Expect damage to roofs, siding, and trees. People and 
         animals outdoors will be injured. Expect hail damage to 
         roofs, siding, windows, and vehicles.

Locations impacted include...
Wiggins.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Remain alert for a possible tornado! Tornadoes can develop quickly
from severe thunderstorms. If you spot a tornado go at once into the
basement or small central room in a sturdy structure.

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

Prepare immediately for large hail and deadly cloud to ground
lightning. Seek shelter inside a well-built structure. Stay away from
windows.

&&

LAT...LON 4009 10389 4003 10414 4023 10415 4026 10407
TIME...MOT...LOC 0344Z 236DEG 13KT 4018 10411 

TORNADO...POSSIBLE
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...1.50 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH

$$

HEAVENER

Area Forecast Discussion
National Weather Service Denver/Boulder CO
611 PM MDT Tue May 9 2023

.SHORT TERM...(This evening through Wednesday)
Issued at 313 PM MDT Tue May 9 2023

...SEVERE THUNDERSTORM POTENTIAL INCREASING WEDNESDAY...

Key Messages...
1. A conditional threat of severe weather still
exists this evening through most of the overnight hours across the
I-25 corridor and eastern plains

2. A more organized round of severe storms appears likely
Wednesday afternoon into Wednesday evening... with all severe
hazards possible...

An approaching trough axis will bring a variety of weather
hazards to Colorado over the next few days... with severe weather,
heavy rain, and mountain snow possible through the end of the
week. RAP Mesoanalysis and water vapor satellite show the center
of this upper trough just off central California coast this
afternoon. Broad southwesterly flow aloft is present ahead of this
trough axis, and the flow should strengthen and slowly back to
the south-southwest through tomorrow afternoon. This trough should
continue to progress eastward, eventually transitioning to a more
negatively tilted trough axis by Wednesday evening.

Before getting into Wednesday's details... we can't forget about
tonight's more conditional severe threat. ML/MUCAPE is expected to
increase this evening and into the early overnight hours as
better low-level moisture streams back into the region, with an
EML/steep lapse rates aloft. Recent CAMs have gradually come on
board with isolated to scattered storms developing near the best
moisture convergence (I-25 corridor) this evening, shifting this
activity into the northeastern plains overnight. With MLCAPE
values increasing to 1000-1500 J/kg with deep layer shear near
40-50kt... large hail would certainly be a threat tonight, along
with a marginal severe wind threat. However, guidance has
struggled handling sfc moisture throughout the day, and has
largely been inconsistent with convective initiation/evolution
overnight. We may be stuck in "wait and see mode" for quite some
time, but the SPC's marginal risk appears well-justified.

Any elevated convection overnight tonight should be out of the
area by Wednesday morning. Moisture advection should still be
ongoing with at least some low stratus across the plains, with dew
points sitting near 50F... setting the stage for a potentially
widespread severe weather event across the Colorado plains. From a
ingredients-based perspective, this does check most (if not all)
of the boxes for Colorado severe weather: (1) A strong, negatively
tilted trough axis approaching from the southwest, (2) ample
boundary layer moisture, (3) synoptic scale ascent from upper
level height falls/PVA, (4) moderate instability and shear.
Largely straight line hodographs would support both hail and
damaging wind threats from both left/right split supercells, with
a tornado risk also accompanying the latter of these two splits.

However... there is still quite a bit of uncertainty, and several
things that could deviate from our current forecast. The ongoing
struggles with the handling of tonight's convection leaves a lot
of questions regarding the evolution of the low-level moisture
across the area overnight. There's also the possibility that low
cloud cover remains too thick Wednesday morning, leading to poor
surface heating (and thus, stronger capping/weaker instability) in
the afternoon. And, like in almost any severe weather event here,
there is still questions about the overall convective evolution
through the afternoon hours. Still, the general thought remains
unchanged from last night... with scattered supercells developing
near noon, with gradual upscale growth through the evening hours.
A lot can change in 12-24 hours... so users are encouraged to
check back for frequent updates.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 223 PM MDT Tue May 9 2023

An upper level storm system will move from nwrn New Mexico into sern
CO by Thu morning and then track slowly northeast into far ern
CO/wrn KS by Thu night.  Cross-sections show favorable QG ascent and
lapse rates will affect the area Wed night thru Thu night with
abundant moisture.

Showers and tstms will become numerous Wed night with some potential
for svr storms Wed evening across the plains.  On Thu, rain and
tstms will continue with areas of heavy rain possible thru Thu
night.

By Fri morning, the storm system will be located over far nern
CO/swrn NE.  Current data shows precip continuing on the back side
of the upper level low mainly along the I-25 Corridor into the
higher terrain.  There certainly is potential for heavy snow, in the
mtns above 10000 ft, Thu aftn thru Fri morning north of I-70.

Total rainfall amounts from both the ECMWF and GFS show 1 to 3
inches possible across portions of the plains, I-25 Corridor and
foothills thru Fri morning.

For Fri aftn thru Fri night the upper level low weaken and will move
away from the area.  As a result, precip chances should gradually
decrease by Fri aftn over the region.

On Sat, a secondary piece of energy will move into WY.  There are
significant differences on how this feature is handled this weekend.
The ECMWF moves it westward into Idaho by Sun while the GFS has it
moving into Utah.  Both models show lingering moisture affecting the
area as a surge of cooler air moves in behind a cold front.  Overall
it looks cool and somewhat unsettled with a chc of showers and a few
storms.  It appears most of this activity would occur over the
higher terrain.

By early next week, an upper level ridge will develop over the area.
This should lead to a drier pattern with temperatures near seasonal
levels.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 610 PM MDT Tue May 9 2023

A few storms are starting to pop in the vicinity of the terminals.
A few may be capable of gusty outflow winds. As higher moisture
moves in from the east tonight, there will be a threat for lower
clouds and perhaps another shot at convection late tonight. Timing
of the lower stratus remains uncertain and will depend on if
convection does develop in this late evening timeframe, but will
stick with 06-09z period for this to develop. Stratus continues
through the morning hours, eroding mid to late morning.

Main concern for Wednesday will be the thunderstorm potential in
the afternoon. Some uncertainty in the timing of first initiation
of storms. There should be storms initiating after 20z. There is a
threat for strong to sever storms as well which may entail gusty
winds and hail.

&&

.FIRE WEATHER...
Issued at 223 PM MDT Tue May 9 2023

Near critical to critical fire weather conditions have been
observed across the Red Flag Warning area. This will remain in
effect until 7PM when moisture begins to increase. Fire danger
will decrease Wednesday through the rest of next week.

&&

.HYDROLOGY...
Issued at 223 PM MDT Tue May 9 2023

Increasing coverage of showers and thunderstorms on Wednesday will
lead to at least a minor risk of flash flooding across the burn
areas Wednesday.

There will be some risk of flash flooding in the burn scars
Wednesday night into Thursday due to the potential for heavier
rainfall.  At this time it appears Cameron Peak would be the most
favored.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 7 PM MDT this evening for COZ214-216-241.

&&

SHORT TERM...Hiris
LONG TERM...RPK
AVIATION...Mensch
FIRE WEATHER...Hiris
HYDROLOGY...Hiris/RPK

Hazardous Weather Outlook
National Weather Service Denver/Boulder CO
1043 AM MDT Tue May 9 2023

COZ030>051-101645-
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-
1043 AM MDT Tue May 9 2023

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

.DAY ONE...Today and Tonight

Critical fire weather conditions are expected in parts of Park
county, the southern foothills, and the Palmer Divide where the
combination of wind gusts up to 25 mph and relative humidity near
15% could lead to fire spread. A Red Flag Warning is in effect
from 11 AM MDT to 7 PM MDT.

There is a marginal risk of severe storms across the urban
corridor and plains this evening through much of the overnight
hours. The primary threat would be large hail, with heavy rain and
gusty winds also possible.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

Severe thunderstorms containing damaging winds, large hail, and a
few tornadoes are possible Wednesday afternoon and evening from
the I-25 corridor and eastward.

Heavier rains are possible Thursday across portions of the
region, possibly impacting our area burn scars.

High elevation heavy snow is expected on Thursday.

.SPOTTER INFORMATION STATEMENT...

Spotter reports of hail, strong wind gusts and rainfall would be
appreciated.

Special Weather Statement
National Weather Service Denver CO
604 PM MDT Tue May 9 2023

COZ040-043-100045-
Central and South Weld County CO-
North Douglas County Below 6000 Feet/Denver/West Adams and Arapahoe
Counties/East Broomfield County CO-
604 PM MDT Tue May 9 2023

...A strong thunderstorm will impact portions of southwestern Weld,
eastern Broomfield and northwestern Adams Counties through 645 PM
MDT...

At 602 PM MDT, Doppler radar was tracking a strong thunderstorm over
northeastern Thornton, or 14 miles north of Denver, moving north at
15 mph.

HAZARD...Winds in excess of 40 mph and penny size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
Thornton, northeastern Westminster, northeastern Broomfield, northern
Commerce City, Northglenn, Brighton, Erie, Federal Heights,
Firestone, Frederick, Fort Lupton, Lochbuie, Dacono, Barr Lake and
Todd Creek.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

LAT...LON 3988 10484 3986 10503 4018 10501 4020 10454
TIME...MOT...LOC 0002Z 192DEG 14KT 3994 10492

MAX HAIL SIZE...0.75 IN
MAX WIND GUST...40 MPH

COOPER

Special Weather Statement
National Weather Service Denver CO
719 PM MDT Tue May 9 2023

COZ038-043-100200-
Central and South Weld County CO-
Larimer County Below 6000 Feet/Northwest Weld County CO-
719 PM MDT Tue May 9 2023

...A strong thunderstorm will impact portions of west central Weld
and southeastern Larimer Counties through 800 PM MDT...

At 719 PM MDT, Doppler radar was tracking a strong thunderstorm near
Windsor, or 7 miles northwest of Greeley, moving north at 20 mph.

HAZARD...Winds in excess of 40 mph and penny size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
Fort Collins, Greeley, Loveland, Windsor, Evans, Johnstown, Milliken,
Berthoud, Eaton, Mead, Severance, LaSalle, Ault, Gilcrest, Pierce,
Timnath, Purcell and Lucerne.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

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.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

LAT...LON 4067 10456 4060 10457 4058 10459 4058 10463
      4052 10463 4052 10458 4027 10461 4026 10512
      4065 10507
TIME...MOT...LOC 0119Z 193DEG 30KT 4047 10487

MAX HAIL SIZE...0.75 IN
MAX WIND GUST...40 MPH

COOPER

PRELIMINARY LOCAL STORM REPORT...SUMMARY
NATIONAL WEATHER SERVICE DENVER CO
749 PM MDT TUE MAY 9 2023

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

0623 PM     HAIL             3 WNW HENDERSON         39.93N 104.91W
05/09/2023  M0.75 INCH       ADAMS              CO   TRAINED SPOTTER

            AD1166.

0656 PM     HAIL             4 S COMMERCE CITY       39.76N 104.91W
05/09/2023  M0.88 INCH       DENVER             CO   TRAINED SPOTTER

            DE712.

0612 PM     HAIL             2 NE THORNTON           39.91N 104.92W
05/09/2023  M1.00 INCH       ADAMS              CO   PUBLIC

            FROM TWITTER, WITH PHOTO.

0710 PM     HAIL             1 NE BRIGHTON           39.99N 104.78W
05/09/2023  M1.00 INCH       ADAMS              CO   TRAINED SPOTTER

            VIA SPOTTERNETWORK.ORG, NOT THE LARGEST
            STONE.

0723 PM     HAIL             BRIGHTON                39.99N 104.80W
05/09/2023  M1.00 INCH       ADAMS              CO   TRAINED SPOTTER

            AD1150?.

0735 PM     HAIL             5 ESE LOCHBUIE          39.97N 104.64W
05/09/2023  M1.75 INCH       ADAMS              CO   TRAINED SPOTTER

            FROM TWITTER.

&&

Special Weather Statement
National Weather Service Denver CO
818 PM MDT Tue May 9 2023

COZ043-100245-
Central and South Weld County CO-
818 PM MDT Tue May 9 2023

...A strong thunderstorm will impact portions of southern Weld County
through 845 PM MDT...

At 818 PM MDT, Doppler radar was tracking a strong thunderstorm
capable of producing a landspout tornado 4 miles southwest of
Prospect Valley, or 31 miles southeast of Greeley, moving northeast
at 10 mph.

HAZARD...Landspouts possible, winds in excess of 40 mph, and penny
         size hail.

SOURCE...Radar indicated.

IMPACT...Landspout tornadoes can damage mobile homes, roofs,
         vehicles, and trees. Outdoor objects may be tossed about.
         Gusty winds could knock down tree limbs and blow around
         unsecured objects.

Locations impacted include...
Keenesburg and Prospect Valley.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

If a tornado is spotted seek shelter inside a sturdy building.

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.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

LAT...LON 4000 10430 4000 10451 4005 10456 4019 10444
TIME...MOT...LOC 0218Z 239DEG 10KT 4002 10447

LANDSPOUT...POSSIBLE
MAX HAIL SIZE...0.75 IN
MAX WIND GUST...40 MPH

DIRENZO

Special Weather Statement
National Weather Service Denver CO
844 PM MDT Tue May 9 2023

COZ043-044-100315-
Central and South Weld County CO-Morgan County CO-
844 PM MDT Tue May 9 2023

...A strong thunderstorm will impact portions of south central Weld
and southwestern Morgan Counties through 915 PM MDT...

At 844 PM MDT, Doppler radar was tracking a strong thunderstorm
capable of producing a landspout tornado 7 miles east of Prospect
Valley, or 29 miles southwest of Fort Morgan, moving northeast at 25
mph.

HAZARD...Landspouts possible, winds in excess of 30 mph, and half
         inch hail.

SOURCE...Radar indicated.

IMPACT...Landspout tornadoes can damage mobile homes, roofs,
         vehicles, and trees. Outdoor objects may be tossed about.
         Gusty winds could knock down tree limbs and blow around
         unsecured objects.

Locations impacted include...
Roggen.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If a tornado is spotted seek shelter inside a sturdy building.

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.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

LAT...LON 4001 10432 4005 10438 4015 10443 4031 10424
      4007 10404
TIME...MOT...LOC 0244Z 239DEG 20KT 4005 10428

LANDSPOUT...POSSIBLE
MAX HAIL SIZE...0.50 IN
MAX WIND GUST...30 MPH

DIRENZO