Alert archive / Colorado / Flash Flood Warnings in 2018

Flash Flood Warning 13, NWS Denver/Boulder, CO

August 17, 2018Washington County, Colorado

NWS Denver/Boulder, CO issued this flash flood warning at Aug 17, 2018, 6:32 PM MDT for Washington County, Colorado. It was in force for 3 hr. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued
Aug 17, 2018, 6:32 PM MDT (00:32 UTC)
Expired
Aug 17, 2018, 9:30 PM MDT
In force
3 hr
Issued by
NWS Denver/Boulder, CO
Area
Storm-based polygon
Flood severity
None

County Washington County, CO

The radar

The Denver radar (KFTG), 85 km from the middle of the area, began a volume at 00:34 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.

The nearest sounding before it

Denver, CO (KDEN), launched 00:00Z, 0.5 hours before the alert went out and 29 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.

Skew-T log-pSkew-T log-p diagram, Denver, CO at 00:00Z on 2018-08-18Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 785 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Denver, CO at 00:00Z on 2018-08-18The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 128 square meters per square second.193958Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.
Mixed-layer CAPE
785 J/kg
Mixed-layer CIN
-50 J/kg
Mixed-layer LCL
1931 m above ground
0-6 km bulk shear
32 kt
0-1 km storm-relative helicity
128 m²/s²
0-3 km storm-relative helicity
145 m²/s²
Significant tornado parameter
0.0
Supercell composite
4.1

Open this sounding in Storm Lab

The text

As transmitted.

124 
WGUS55 KBOU 180032
FFWBOU
COC121-180330-
/O.NEW.KBOU.FF.W.0013.180818T0032Z-180818T0330Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Denver CO
632 PM MDT FRI AUG 17 2018

The National Weather Service in Denver Colorado has issued a

* Flash Flood Warning for...
  Southwestern Washington County in northeastern Colorado...

* Until 930 PM MDT.

* At 632 PM MDT, Doppler radar indicated thunderstorms producing
  heavy rain across the warned area. Up to three inches of rain have
  already fallen. Flash flooding is expected to begin shortly.

* Some locations that will experience flooding include...
  Woodlin School, Lindon, Last Chance and Woodrow. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Excessive runoff from heavy rainfall will cause flooding of small
creeks and streams, country roads, farmland, and other low lying
spots.

&&

LAT...LON 3963 10370 4000 10370 4000 10335 3963 10332

$$

RPK
1 follow-up statement
288 
WGUS75 KBOU 180329
FFSBOU

Flash Flood Statement
National Weather Service Denver CO
929 PM MDT FRI AUG 17 2018

COC121-180333-
/O.EXP.KBOU.FF.W.0013.000000T0000Z-180818T0330Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Washington CO-
929 PM MDT FRI AUG 17 2018

...THE FLASH FLOOD WARNING FOR SOUTHWESTERN WASHINGTON COUNTY WILL
EXPIRE AT 930 PM MDT...

The heavy rain has ended. Flooding is no longer expected to pose a 
threat. Please continue to heed any remaining road closures.

Rainfall amounts of 2 to 3 inches earlier this evening will cause 
drainages like Plum Bush Creek, Vega Creek and Sand Creek will 
continue to run at or above bankfull stages through the rest of 
tonight. 

Do not try to cross water-covered roads. It may be difficult to tell 
how deep the water is.  

LAT...LON 3963 10370 4000 10370 4000 10335 3963 10332

$$

DANKERS

The office that day

Everything else NWS Denver/Boulder, CO issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Aug 17, 7:08 PM MDTSpecial Weather StatementBOUElbert37 min
Aug 17, 7:25 PM MDTAreal Flood AdvisoryBOUElbert, Lincoln95 min
Aug 18, 11:33 AM MDTSpecial Weather StatementBOUDouglas, Jefferson42 min
Aug 18, 12:16 PM MDTSpecial Weather StatementBOUElbert44 min
Aug 18, 1:05 PM MDTSpecial Weather StatementBOUElbert40 min
Aug 18, 1:46 PM MDTSpecial Weather StatementBOUElbert44 min

Nearby

Flash Flood Warnings in Colorado, 2018Every flash flood warning in 2018

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.