Special Weather Statement, NWS Pueblo, CO

Area Forecast Discussion
National Weather Service Pueblo CO
1241 PM MDT Mon May 17 2021

.UPDATE...
Issued at 1240 PM MDT Mon May 17 2021

No real big change with the forecast for today, with strong to
severe storms possible across the plains, and with an increased
risk of flash flooding continuing across the burn scars.

Latest radar imagery depicting development occurring over most of
the higher terrain, with a few stronger storms already occurring.
Despite some cloud cover in place this morning, conditions have
become rather unstable, with high moisture content air advecting
ahead of an approaching upper level system. As this system
continues to approach today, will see lee troughing occur across
far southern CO with low/mid level easterly flow increasing. This
moist advection and now moist upslope flow along with building
instability into this afternoon, will assist with expansion of
already occurring thunderstorms. Additionally, think
intensification of these storms will be quick, with all of this
occurring through early to mid afternoon. Strong to severe storms
will be possible through this time frame, with the strongest
storms initially developing within surface trough and
moisture/instability axis located along the southern I-25
corridor. Further expansion will occur later this afternoon into
the evening, as these storms push east through the plains. While
strong to severe storms will be possible anywhere across the
plains, think the highest threat will be along and south of the
HWY 50 corridor. In this location, surface trough and boundary
will be where the highest instability and moisture will reside.
Additionally, the highest shear will be located here as well,
possibly in the 30-35 kt range. Similar thoughts with the expected
hazards remain, with large hail and damaging winds the main
threats/hazards. Boundary in place could once again serve as an
area of enhanced low level helicity, and think there is the
potential for a few weak tornadoes as well.

Concerns continue to grow for flash flooding across the burn
scars. With development already occurring around all of the burn
scars and development expected to continue into this afternoon,
have tried to continue to message the high potential for flash
flooding today. The Flash Flood Watch in place is still definitely
valid going into this afternoon and early evening. By mid to late
evening, the flash flood risk should lower significantly.

&&

.SHORT TERM...(Today and tonight)
Issued at 348 AM MDT Mon May 17 2021

Main Forecast Concerns/Challenges:

1) Flash Flood Watch in effect for the Sangre de Cristo Mountains
and the Wet Mountains for burn scar flash flooding. Main concern is
the Spring burn scar.

2) Severe storms are expected to develop this afternoon. Main
concerns are the southern I-25 corridor and the far eastern plains.
Main risks are 1-2" hail, 60-70 mph winds, and isolated landspout
tornados.

Meteorological Discussion:

Another round of severe weather is expected and there is a higher
risk of flash flooding over burn scars, in particular, the Spring
burn scar. Synoptically, the upper level low is expected to
propagate to the east-southeast, ending up just south of the four
corners area by this afternoon. Moist recycled air is being and will
continue to be advected from the east-northeast. While looking at
satellite imagery, one can infer that the Gulf of Mexico origins of
where the true moisture tap is. The mid to upper level flow over the
mountains is expected to be from the south-southeast during the
early parts of the day, which is expected to keep the thunderstorms
over the mountains through the early parts of the afternoon. Cumulus
will start to begin to develop over the eastern mountains at around
12pm today, but the strongest storms aren't expected to develop
until the 700hPa winds increase and shift to the east as the upper
low moves east. By around 2-4pm stronger convection is expected over
the mountains. Drier air aloft and moist air at the surface will put
the mountain top CAPE values are expected to range from 1000-1600
J/kg. With all of this information, we've decided to issue a Flash
Flood Watch over the Sangre de Cristo and Wet Mountains for burn
scar flash flooding, with an emphasis on the Spring burn scar. The
one major concern is hail contamination with thunderstorms. Since
CAPE values are expected to be so high over the mountains, hail is
expected to form, which would cut down of rainfall rates below the
thunderstorms, but the base reflectivity returns will be high. In
fact, this did happen yesterday, according to local EMs that cover
the Spring burn scar. We have high confidence that thunderstorms
will initiate near burn scars, but there is uncertainty of the exact
location and the precipitant within the storms.

Now onto the severe risk for Monday afternoon... There is a Marginal
and Slight risk of severe weather over the plains this afternoon
according the Storm Prediction Center. Moist air from the east is
expected to be advected towards the mountains which will initiate
thunderstorms (see above), eventually, the 500hPa flow shifts from
the south the the southeast and vorticity maxima reach further east,
which will allow thunderstorms anchored over the mountains to
propagate east and for storms to develop over the eastern plains
where a favorable environment for severe storms is expected to be
located. My current thoughts are that the cells will start entering
that environment over the I-25 corridor from 3pm-5pm. The best
environment over the I-25 corridor is expected to be from Pueblo
County and south to the New Mexico border. The pre-initiation
environment near Trinidad and Walsenburg show +1500 J/kg of CAPE, a
curved hodograph from the surface to 3km (Sfc-3km SRH ~180 m2/s2),
LCLs around 1km, and near dry-adiabatic lapse rates. Moving further
north, CAPE values decrease with a more moisture being analyzed in
the mid-levels. There is a surface boundary being resolved over the
eastern plains, extending towards the Trinidad area, so low level
vorticity values are expected to be enhanced over the surface
boundary which increases the landspout tornado risk. So overall, the
main concern for the southern I-25 corridor from 3PM-8PM will be 1
to 2 inch hail, wind gusts ranging from 60-70 mph, and an isolated
weak tornado possible. During this time, weaker thunderstorms are
possible over El Paso County, but there are concerns that weak
heating will create a cap that cannot be overcome, similar to what
happened the last two days.

Storms that develop over the southern I-25 corridor will begin to
advance to the northeast and a cluster of storms that is expected to
develop over northern New Mexico will also advance to the northeast
clipping the far southeastern plains as they head to Kansas. Storms
will develop east of the I-25 corridor from 5pm through around
midnight. The environment over Springfield when the storm reach
there will be favorable for rotating updrafts. Ample amounts of
shear is expected and for that shear to create curved hodograph with
a little below 2000 J/kg of CAPE. That type of environment is fairly
uniform to the north-northeast where the storms will be advancing.
As previously mentioned, there is a surface boundary being resolved
south of the Highway 50 corridor which may enhance low level
vorticity - increasing the landspout tornado risk. Main risks that
are expected from 6pm-Midnight will 1 to 2 inch hail, 60 to 70 mph
wind gusts, and an isolated weak landspout tornado. Once again, a
major concern is that lingering cloud cover will inhibit maximum
daytime heating, therefore creating a capped environment and lower
values of CAPE. At this point in time, it seems that we will heat up
enough, if that doesn't happen, there is the possibility that storms
will struggle to form.

.LONG TERM...(Tuesday through Sunday)
Issued at 348 AM MDT Mon May 17 2021

There are two potential concerns during this period.  The first will
occur Tuesday as the very moist upper low moves over the forecast
area. This system will have the potential to produce heavy rain over
the region Tuesday along with the potential of some stronger storms.

The second concern will be later this week into the weekend. Models
are showing a deep trough developing over the western US. This
system is then forecast to move rather slowly to the east. The
longitudinal extent of this system is quite extensive, and will
allow for a direct tap of moisture from the Gulf of Mexico. It
appears at this time an extended period of strong, deep south-
southwesterly flow will be over the forecast area. Although
directional shear is limited, strong speed shear will be in place,
and this shear combined with the potential of plenty of lower level
moisture may set the stage for an extended period of strong storms
and heavy rains for parts of the region. Although it still too early
to know the extent of how this system will impact us, this large
scale pattern is remnant of the 1997 and 1965 weather patterns that
brought high impact events to the forecast area.

Tuesday...

Upper low will be moving over the region. Guidance indicates 500 to
1000 J/Kg of CAPE will likely be over the region during the
afternoon, and this instability combined with deep southeasterly
flow over southeast Colorado may allow for thunderstorms capable of
producing heavy rain to occur over the east facing slopes of the
mountains. Flash flooding will be possible along the mtns/plains
interface, with the Spring Burn scar most susceptible to flooding.
Deep shear will be minimal, but the combination of abundant low
level moisture and cold air aloft will have the potential to allow
for rapid upward vertical motions within the updrafts, and any
boundaries that are in place will be susceptible to landspouts.

Wednesday and Thursday...

For Wed, area will be on the backside of the low. Sufficient llvl
moisture will be in place and scattered showers and thunderstorms
will be possible during the afternoon. On Thursday, deep
southwesterly flow will develop in advance of the deepening trough
out west. We may see an active dryline set up along the CO/KS
border.

Late week into the Weekend...

Deep longitudinal trough is forecast to develop over the west and is
forecast to bring strong southerly flow over the forecast area
during this period. Deterministic guidance products show a clear tap
of moisture advecting in from the Gulf of mexico Friday into the
weekend. NAEFS percentile tables showing unseasonably strong V
components to the wind fields along with very moist PWATS and
moisture transports in the western US. Although details still need
to be refined, this pattern will have the potential to bring an
active weather pattern to the region from late in the week into the
weekend. Overall, how much active weather we see with this event
will be dependent on how deep the trough develops and how slow it
moves. A deeper, slow moving event will have a higher potential to
effect the region versus a more progressive and less amplified
trough. \/Hodanish

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1214 PM MDT Mon May 17 2021

Another period of active weather across all the sites, as showers
and storms and low ceilings are once again possible. An upper
level system will approach today, with showers and storms
developing out ahead of it. This development is already occurring
across the mountains, and expect it to spread across the adjacent
lower levels by early to mid afternoon. Showers with a few
thunderstorms are expected at ALS this afternoon, with similar
trends expected at COS. However, COS may observe some stronger
thunderstorms later this afternoon into the evening. The highest
confidence for more prevailing and longer in duration thunder is
at PUB, where stronger storms are expected to occur this afternoon
into early evening. The strongest storms, possibly severe, are
once again expected at PUB. Thunderstorm activity should diminish
later this evening, though the upper level system will move
overhead through the remainder of the period and likely provide a
longer duration of light rain. In this rain, think MVFR ceilings
are possible, especially across COS. Some possibility for IFR
ceilings, but confidence is low at this time.

&&

.PUB WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch until midnight MDT tonight for COZ072>075-079-
080.

&&

UPDATE...RODRIGUEZ
SHORT TERM...SKELLY
LONG TERM...HODANISH
AVIATION...RODRIGUEZ

Hazardous Weather Outlook
National Weather Service Pueblo CO
1158 AM MDT Mon May 17 2021

COZ058>089-093>099-181800-
Western Mosquito Range/East Lake County Above 11000 Feet-
Leadville Vicinity/Lake County Below 11000 Feet-
Eastern Sawatch Mountains Above 11000 Feet-
Western Chaffee County Between 9000 and 11000 Feet-
Central Chaffee County Below 9000 Feet-
Western Mosquito Range/East Chaffee County Above 9000 Feet-
Saguache County West of Continental Divide Below 10000 Feet-
Saguache County East of Continental Divide Below 10000 Feet-
La Garita Mountains Above 10000 Feet-
Upper Rio Grande Valley/Eastern San Juan Mountains Below
10000 Feet-Eastern San Juan Mountains Above 10000 Feet-
Del Norte Vicinity/Northern San Luis Valley Below 8500 Feet-
Alamosa  Vicinity/Central San Luis Valley Below 8500 Feet-
Southern San Luis Valley-
Northern Sangre de Cristo Mountains Between 8500 And 11000 Feet-
Northern Sangre de Cristo Mountains Above 11000 Feet-
Southern Sangre de Cristo Mountains Between 7500 and 11000 Feet-
Southern Sangre de Cristo Mountains Above 11000 Feet-
Northwestern Fremont County Above 8500 Feet-
Western/Central Fremont County Below 8500 Feet-
Wet Mountain Valley Below 8500 Feet-
Wet Mountains between 6300 and 10000 Feet-
Wet Mountains Above 10000 Feet-
Teller County/Rampart Range Above 7500 Feet/Pikes Peak Between
7500 And 11000 Feet-Pikes Peak Above 11000 Feet-
Canon City Vicinity/Eastern Fremont County-
Northern El Paso County/Monument Ridge/Rampart Range Below
7500 Feet-
Colorado Springs Vicinity/Southern El Paso County/Rampart Range
Below 7400 Feet-Pueblo Vicinity/Pueblo County Below 6300 Feet-
Walsenburg Vicinity/Upper Huerfano River Basin Below 7500 Feet-
Trinidad Vicinity/Western Las Animas County Below 7500 Feet-
Crowley County-La Junta Vicinity/Otero County-
Eastern Las Animas County-Western Kiowa County-
Eastern Kiowa County-Las Animas Vicinity/Bent County-
Lamar Vicinity/Prowers County-Springfield Vicinity/Baca County-
1158 AM MDT Mon May 17 2021

This hazardous weather outlook is for portions of central...east
central...south central and southeast Colorado.

.DAY ONE...This Afternoon and Tonight

Strong to severe thunderstorms are expected over the southern
I-25 corridor and the far eastern plains this afternoon into the
evening. Main risks will be 1 to 2 inch hail, 60 to 70 mph winds,
and isolated weak tornados under the strongest storms. Strong,
possibly severe, storms could occur over the mountain valleys and
the northern I-25 corridor.

Flash flooding is possible over the Spring, Junkins, Decker, and
Hayden Pass burn scars, with an emphasis for the Spring burn scar,
as strong thunderstorms develop over the mountains.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday

Strong to severe thunderstorms will be possible Tuesday across
the plains and the eastern mountains. Hail the size of quarters
and wind gusts to 60 mph will be possible. An isolated tornado
cannot be ruled out.

Heavy rain is likely to occur across the plains and east slopes
of the mountains Tuesday. Burn scar flooding will be possible. In
addition, flash flooding may also occur in urban areas.

On Wednesday, scattered afternoon and evening thunderstorms are
expected. Small hail and gusty winds will be possible.

On Thursday, the dryline is expected to become active. There will be
a chance of severe thunderstorms along the Colorado and Kansas state
line during the afternoon and evening. Large hail, damaging winds
and isolated tornadoes will be possible.

From Friday into the weekend, the potential will exist for an active
weather pattern to occur as a deep trough of low pressure develops
over the Western United States. This trough will have the potential
to bring abundant low level moisture onto the plains. In the
meantime, this trough will bring strong winds throughout the
atmosphere. The combination of the strong winds and abundant low
level moisture will allow for the potential for strong to severe
storm with heavy rain to occur.

.SPOTTER INFORMATION STATEMENT...

Weather conditions that meet reporting criteria for spotters will be
possible this afternoon and evening across eastern mountains and
the eastern plains.

RODRIGUEZ

Special Weather Statement
National Weather Service Pueblo CO
115 PM MDT Mon May 17 2021

COZ077>080-083-086-087-172000-
Pueblo Vicinity/Pueblo County Below 6300 Feet CO-
Wet Mountains between 6300 and 10000Ft CO-
Western/Central Fremont County Below 8500 Ft CO-
Walsenburg Vicinity/Upper Huerfano River Basin Below 7500 Ft CO-
Wet Mountain Valley Below 8500 Ft CO-
Canon City Vicinity/Eastern Fremont County CO-
Wet Mountains above 10000 Ft CO-
115 PM MDT Mon May 17 2021

...SIGNIFICANT WEATHER ADVISORY FOR NORTH CENTRAL HUERFANO...
SOUTHEASTERN FREMONT...NORTHEASTERN CUSTER AND SOUTHWESTERN PUEBLO
COUNTIES UNTIL 200 PM MDT...

At 115 PM MDT, Doppler radar was tracking scattered strong
thunderstorms developing along a line extending from near Florence
to 8 miles northeast of Greenhorn Mountain. Movement was north at 5
mph.

Half inch hail and winds in excess of 40 mph will be possible with
these storms.

Locations impacted include...
Junkins Burn Scar, Florence, Greenhorn Mountain, Canon City, Rye,
Beulah, Wetmore, San Isabel and Colorado City.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3843 10537 3849 10513 3786 10474 3774 10477
      3775 10491 3830 10535
TIME...MOT...LOC 1915Z 199DEG 6KT 3832 10517 3794 10488

Cohen

Special Weather Statement
National Weather Service Pueblo CO
117 PM MDT Mon May 17 2021

COZ074-075-171945-
Southern Sangre De Cristo Mountains Between 7500 and 11000 Ft CO-
Southern Sangre De Cristo Mountains Above 11000 Ft CO-
117 PM MDT Mon May 17 2021

...SIGNIFICANT WEATHER ADVISORY FOR SOUTH CENTRAL HUERFANO...
NORTHEASTERN COSTILLA AND WESTERN LAS ANIMAS COUNTIES UNTIL 145 PM
MDT...

At 117 PM MDT, Doppler radar was tracking a strong thunderstorm over
Cuchara, or 7 miles south of Indian Creek on the southeastern Spring
Burn Scar, moving north at 5 mph.

Half inch hail and winds in excess of 40 mph will be possible with
this storm.

Locations impacted include...
Indian Creek on the southeastern Spring Burn Scar, southeastern
Spring Burn Scar south of Highway 160 in Huerfano county, Cuchara and
Cuchara Pass.

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 3729 10504 3729 10514 3744 10519 3746 10499
TIME...MOT...LOC 1917Z 186DEG 5KT 3735 10510

Cohen

Special Weather Statement
National Weather Service Pueblo CO
126 PM MDT Mon May 17 2021

COZ060-065-069-172000-
Saguache County East of Continental Divide below 10000 Ft CO-
Del Norte Vicinity/Northern San Luis Valley Below 8500 Ft CO-
Eastern Sawatch Mountains above 11000 Ft CO-
126 PM MDT Mon May 17 2021

...SIGNIFICANT WEATHER ADVISORY FOR NORTHERN ALAMOSA AND SOUTH
CENTRAL SAGUACHE COUNTIES UNTIL 200 PM MDT...

At 126 PM MDT, Doppler radar was tracking strong thunderstorms along
a line extending from 10 miles southwest of Bonanza to near Hooper.
Movement was northwest at 5 mph.

Half inch hail and wind gusts up to 50 mph will be possible with
these storms.

Locations impacted include...
Saguache.

LAT...LON 3819 10638 3829 10616 3775 10581 3775 10603
TIME...MOT...LOC 1926Z 128DEG 5KT 3821 10628 3779 10594

Cohen

Special Weather Statement
National Weather Service Pueblo CO
128 PM MDT Mon May 17 2021

COZ074-075-087-172000-
Southern Sangre De Cristo Mountains Between 7500 and 11000 Ft CO-
Walsenburg Vicinity/Upper Huerfano River Basin Below 7500 Ft CO-
Southern Sangre De Cristo Mountains Above 11000 Ft CO-
128 PM MDT Mon May 17 2021

...SIGNIFICANT WEATHER ADVISORY FOR SOUTH CENTRAL HUERFANO AND EAST
CENTRAL COSTILLA COUNTIES UNTIL 200 PM MDT...

At 128 PM MDT, Doppler radar was tracking a strong thunderstorm over
Cuchara, or near Indian Creek on the southeastern Spring Burn Scar,
moving north at 5 mph.

Penny size hail and winds in excess of 40 mph will be possible with
this storm.

Locations impacted include...
Indian Creek on the southeastern Spring Burn Scar, southern Spring
Burn Scar south of Highway 160 in Huerfano county, southeastern
Spring Burn Scar south of Highway 160 in Costilla county and Cuchara.

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 3733 10506 3731 10517 3745 10521 3748 10502
TIME...MOT...LOC 1928Z 165DEG 6KT 3737 10511

Cohen

Special Weather Statement
National Weather Service Pueblo CO
130 PM MDT Mon May 17 2021

COZ077-079-172000-
Wet Mountains between 6300 and 10000Ft CO-
Western/Central Fremont County Below 8500 Ft CO-
130 PM MDT Mon May 17 2021

...SIGNIFICANT WEATHER ADVISORY FOR SOUTH CENTRAL FREMONT COUNTY
UNTIL 200 PM MDT...

At 130 PM MDT, Doppler radar was tracking a strong thunderstorm 10
miles southwest of Royal Gorge, or 20 miles east of Hayden Pass Burn
Scar. This storm was nearly stationary.

Penny size hail and winds in excess of 40 mph will be possible with
this storm.

This storm will remain over mainly rural areas of south central
Fremont County.

LAT...LON 3847 10536 3826 10529 3826 10543 3844 10552
TIME...MOT...LOC 1930Z 131DEG 4KT 3833 10540

Cohen

Special Weather Statement
National Weather Service Pueblo CO
139 PM MDT Mon May 17 2021

COZ070-071-172030-
Southern San Luis Valley CO-
Alamosa  Vicinity/Central San Luis Valley Below 8500 Ft CO-
139 PM MDT Mon May 17 2021

...SIGNIFICANT WEATHER ADVISORY FOR WESTERN ALAMOSA...SOUTHEASTERN
RIO GRANDE...SOUTHEASTERN SAGUACHE AND EASTERN CONEJOS COUNTIES UNTIL
230 PM MDT...

At 138 PM MDT, Doppler radar was tracking scattered strong
thunderstorms developing along a line extending from near Hooper to
near Manassa. These storms were nearly stationary.

Pea size hail and wind gusts up to 50 mph will be possible with these
storms.

Locations impacted include...
Alamosa, Manassa, Sanford, La Jara, Romeo, Hooper, Alamosa East,
Mosca and Bountiful.

LAT...LON 3772 10608 3775 10604 3775 10581 3712 10576
      3708 10604
TIME...MOT...LOC 1938Z 079DEG 3KT 3774 10596 3719 10589

Cohen