Alert archive / Colorado / Winter Weather Advisories in 2021

Winter Weather Advisory 25, NWS Denver/Boulder, CO

April 18, 202122 counties in Colorado

NWS Denver/Boulder, CO issued this winter weather advisory at Apr 18, 2021, 1:56 PM MDT for 22 counties in Colorado. It took effect at Apr 19, 2021, 12:00 PM MDT. It was in force for 15 hr.

The area

The counties it named.

The facts

Issued: Apr 18, 2021, 1:56 PM MDT (19:56 UTC)
In effect from: Apr 19, 2021, 12:00 PM MDT
Expired: Apr 20, 2021, 3:00 AM MDT
In force: 15 hr
Issued by: NWS Denver/Boulder, CO

All 22 counties

Adams County, CO, Arapahoe County, CO, Boulder County, CO, Broomfield County, CO, Clear Creek County, CO, Denver County, CO, Douglas County, CO, Elbert County, CO, Gilpin County, CO, Grand County, CO, Jackson County, CO, Jefferson County, CO, Larimer County, CO, Lincoln County, CO, Logan County, CO, Morgan County, CO, Park County, CO, Phillips County, CO, Sedgwick County, CO, Summit County, CO, Washington County, CO, Weld County, CO

The radar

The Denver radar (KFTG), 21 km from the middle of the area, began a volume at 19:59 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 (KDNR), launched 12:00Z, 7.9 hours before the alert went out and 120 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-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 1962 m above ground
0-6 km bulk shear: 29 kt
0-1 km storm-relative helicity: 84 m²/s²
0-3 km storm-relative helicity: 111 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this winter weather advisory went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Denver/Boulder, CO wrote its last area forecast discussion before this winter weather advisory went out at Apr 18, 10:55 AM MDT, 3 hours 1 minute earlier.

Area forecast discussion, Apr 18, 10:55 AM MDT, 3 hours 1 minute before

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Hazardous weather outlook, Apr 18, 11:16 AM MDT, 2 hours 40 minutes before

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The office that day

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

Issued	Product	Office	Counties	Lasted
Apr 18, 4:35 AM MDT	Winter Storm Watch	BOU	Boulder, Grand, Jackson, Larimer	9 hr

Nearby

Winter Weather Advisories in Colorado, 2021 Every winter weather advisory 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; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.