Alert archive / Colorado / Severe Thunderstorm Warnings in 2021
Severe Thunderstorm Warning 105, NWS Denver/Boulder, CO
NWS Denver/Boulder, CO issued this severe thunderstorm warning at Jul 9, 2021, 4:44 PM MDT for Logan County, Colorado. It was in force for 36 min. 4 reports came from inside the area while it was in force.
The area
The outline as issued, with what was reported inside it.
The facts
- Issued
- Jul 9, 2021, 4:44 PM MDT (22:44 UTC)
- Expired
- Jul 9, 2021, 5:20 PM MDT
- In force
- 36 min
- Issued by
- NWS Denver/Boulder, CO
- Area
- Storm-based polygon
- Hail
- 1.0 in
- Wind
- 60.0 mph
County Logan County, CO
The radar
The Cheyenne radar (KCYS), 168 km from the middle of the area, began a volume at 22:47 UTC, the scan nearest the moment this went out.
Open the radar archive at this moment
The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.
What was reported inside it
| Time | Report | Where | Remark |
|---|---|---|---|
| Jul 9, 4:45 PM MDT | TSTM WND GST 70 | 5 Sw Iliff, CO | TRAINED SPOTTED ESTIMATED 70 MPH WIND GUST BETWEEN STERLING AND ILIFF. |
| Jul 9, 4:52 PM MDT | TSTM WND GST 66 | 2 Ese Sterling, CO | CORRECTS PREVIOUS NON-TSTM WND GST REPORT FROM 2 ESE STERLING. MESONET STATION CO035 076E125 STERLING. |
| Jul 9, 4:52 PM MDT | NON-TSTM WND GST 66 | 2 Ese Sterling, CO | MESONET STATION CO035 076E125 STERLING. |
| Jul 9, 5:00 PM MDT | TSTM WND DMG | 3 Sse Reiradon Hill, CO | POWER POLES KNOCKED DOWN. TIME ESTIMATED. |
Local storm reports filed while the alert was in force, from inside its polygon or its counties.
The watch it was issued in
The SPC watch in force over the same counties when this warning went out.
| Issued | Product | Office | Lasted |
|---|---|---|---|
| Jul 9, 2:16 PM MDT | Severe Thunderstorm Watch | SPC | 9 hr |
The nearest sounding before it
Denver, CO (KDNR), launched 12:00Z, 10.7 hours before the alert went out and 93 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.
- Mixed-layer CAPE
- 5 J/kg
- Mixed-layer CIN
- -346 J/kg
- Mixed-layer LCL
- 3383 m above ground
- 0-6 km bulk shear
- 29 kt
- 0-1 km storm-relative helicity
- 70 m²/s²
- 0-3 km storm-relative helicity
- 50 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
223
WUUS55 KBOU 092244
SVRBOU
COC075-092330-
/O.NEW.KBOU.SV.W.0105.210709T2244Z-210709T2330Z/
BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Denver CO
444 PM MDT Fri Jul 9 2021
The National Weather Service in Denver Colorado has issued a
* Severe Thunderstorm Warning for...
Southeastern Logan County in northeastern Colorado...
* Until 530 PM MDT.
* At 444 PM MDT, a severe thunderstorm was located 4 miles southwest
of Iliff, or 7 miles northeast of Sterling, moving southeast at 40
mph.
HAZARD...60 mph wind gusts and quarter size hail.
SOURCE...Radar indicated.
IMPACT...Expect damage to roofs, siding, and trees. Hail damage to
vehicles is expected.
* Locations impacted include...
Sterling, Fleming, Iliff, St Petersburg, Proctor and Padroni.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
For your protection move to an interior room on the lowest floor of a
building.
Heavy rainfall is occurring with this storm, and may lead to flash
flooding. Do not drive your vehicle through flooded roadways.
&&
LAT...LON 4079 10266 4044 10267 4044 10311 4071 10324
4083 10311
TIME...MOT...LOC 2244Z 309DEG 33KT 4072 10313
HAIL...1.00IN
WIND...60MPH
$$
RJK3 follow-up statements
038
WWUS55 KBOU 092259
SVSBOU
Severe Weather Statement
National Weather Service Denver CO
459 PM MDT Fri Jul 9 2021
COC075-092330-
/O.CON.KBOU.SV.W.0105.000000T0000Z-210709T2330Z/
Logan CO-
459 PM MDT Fri Jul 9 2021
...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 530 PM MDT
FOR SOUTHEASTERN LOGAN COUNTY...
At 457 PM MDT, a severe thunderstorm was located 6 miles southwest of
Fleming, or 13 miles east of Sterling, moving southeast at 40 mph.
HAZARD...70 mph wind gusts and quarter size hail. A 70 mph wind
gust was reported with this storm at 4:45 PM MDT between
Sterling and Iliff.
SOURCE...Radar indicated.
IMPACT...Expect considerable tree damage. Damage is likely to mobile
homes, roofs, and outbuildings. Hail damage to vehicles is
expected.
Locations impacted include...
Fleming and St Petersburg.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
For your protection move to an interior room on the lowest floor of a
building.
Heavy rainfall is occurring with this storm, and may lead to flash
flooding. Do not drive your vehicle through flooded roadways.
&&
LAT...LON 4079 10266 4044 10267 4044 10305 4065 10310
4080 10293
TIME...MOT...LOC 2257Z 307DEG 36KT 4063 10294
HAIL...1.00IN
WIND...70MPH
$$
RJK751
WWUS55 KBOU 092316
SVSBOU
Severe Weather Statement
National Weather Service Denver CO
516 PM MDT Fri Jul 9 2021
COC075-092330-
/O.CON.KBOU.SV.W.0105.000000T0000Z-210709T2330Z/
Logan CO-
516 PM MDT Fri Jul 9 2021
...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 530 PM MDT
FOR SOUTHEASTERN LOGAN COUNTY...
At 513 PM MDT, a severe thunderstorm was located 5 miles southwest of
Haxtun, or 21 miles west of Holyoke, moving southeast at 45 mph.
Spotters reported winds gusts in the 65 to 70 mph in and around
Sterling and iliff from 4:45 PM MDT to 4:52 PM MDT
HAZARD...70 mph wind gusts and quarter size hail.
SOURCE...Radar indicated.
IMPACT...Expect considerable tree damage. Damage is likely to mobile
homes, roofs, and outbuildings. Hail damage to vehicles is
expected.
Locations impacted include...
Fleming and St Petersburg.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
For your protection move to an interior room on the lowest floor of a
building.
Torrential rainfall is occurring with this storm, and may lead to
flash flooding. Do not drive your vehicle through flooded roadways.
&&
LAT...LON 4044 10267 4044 10287 4060 10292 4074 10289
4074 10266
TIME...MOT...LOC 2313Z 295DEG 38KT 4061 10272
HAIL...1.00IN
WIND...70MPH
$$
RJK747
WWUS55 KBOU 092320
SVSBOU
Severe Weather Statement
National Weather Service Denver CO
520 PM MDT Fri Jul 9 2021
COC075-092329-
/O.CAN.KBOU.SV.W.0105.000000T0000Z-210709T2330Z/
Logan CO-
520 PM MDT Fri Jul 9 2021
...THE SEVERE THUNDERSTORM WARNING FOR SOUTHEASTERN LOGAN COUNTY IS
CANCELLED...
The storm which prompted the warning has weakened below severe
limits, and has exited the warned area. Therefore, the warning has
been cancelled.
Spotters reported winds gusts in the 65 to 70 mph in and around
Sterling and iliff from 4:45 PM MDT to 4:52 PM MDT.
A Severe Thunderstorm Watch remains in effect until 900 PM MDT for
northeastern Colorado.
LAT...LON 4044 10267 4044 10287 4060 10292 4074 10289
4074 10266
TIME...MOT...LOC 2318Z 309DEG 33KT 4060 10271
$$
RJKThe office that day
Everything else NWS Denver/Boulder, CO issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 8, 6:02 PM MDT | Special Weather Statement | BOU | Phillips | 43 min |
| Jul 9, 2:34 PM MDT | Severe Thunderstorm Warning | BOU | Weld | 41 min |
| Jul 9, 3:00 PM MDT | Areal Flood Advisory | BOU | Grand | 2 hr |
| Jul 9, 3:25 PM MDT | Severe Thunderstorm Warning | BOU | Weld | 38 min |
| Jul 9, 3:58 PM MDT | Severe Thunderstorm Warning | BOU | Logan | 47 min |
| Jul 9, 5:22 PM MDT | Special Weather Statement | BOU | Phillips | 38 min |
| Jul 9, 5:40 PM MDT | Special Weather Statement | BOU | Morgan | 35 min |
Nearby
Severe Thunderstorm Warnings in Colorado, 2021Every severe thunderstorm warning in 2021
Sources
The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.