Alert archive / Colorado / Winter Weather Advisories in 2021

Winter Weather Advisory 10, NWS Denver/Boulder, CO

February 11, 20214 counties in Colorado

NWS Denver/Boulder, CO issued this winter weather advisory at Feb 11, 2021, 4:10 AM MST for 4 counties in Colorado. It took effect at Feb 11, 2021, 5:00 PM MST. It was in force for 36 hr.

The area

The counties it named.

The facts

Issued
Feb 11, 2021, 4:10 AM MST (11:10 UTC)
In effect from
Feb 11, 2021, 5:00 PM MST
Expired
Feb 13, 2021, 5:00 AM MST
In force
36 hr
Issued by
NWS Denver/Boulder, CO

Counties Boulder County, CO, Grand County, CO, Jackson County, CO, Larimer County, CO

The radar

The Cheyenne radar (KCYS), 121 km from the middle of the area, began a volume at 11:10 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

Riverton, WY (KRIW), launched 00:00Z, 11.2 hours before the alert went out and 368 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, Riverton, WY at 00:00Z on 2021-02-11Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 km2 km3 km6 km9 km12 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Riverton, WY at 00:00Z on 2021-02-11The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 333 square meters per square second.1939587897Sfc1 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
0 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
2300 m above ground
0-6 km bulk shear
71 kt
0-1 km storm-relative helicity
333 m²/s²
0-3 km storm-relative helicity
431 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 Feb 10, 9:09 PM MST, 7 hours 1 minute earlier.

Area forecast discussion, Feb 10, 9:09 PM MST, 7 hours 1 minute before
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Hazardous weather outlook, Feb 10, 10:39 AM MST, 17 hours 31 minutes before
Hazardous Weather Outlook
National Weather Service Denver/Boulder CO
1039 AM MST Wed Feb 10 2021

COZ030>051-111745-
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-
1039 AM MST Wed Feb 10 2021

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

.DAY ONE...Today and Tonight

Light snow showers and patchy fog will persist into the early
afternoon across the urban corridor and plains. Temperatures will
be cold today with highs in the low teens across much of the
eastern plains. Light snow will continue across the mountains with
an additional inch or two expected to accumulate throughout the
day. More fog is possible late tonight over the eastern plains.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday

Cold air will remain over the plains Thursday with even colder air
moving in Friday and this weekend. By the weekend temperatures
will be approaching records, with lows below zero and highs in
the single digits above zero expected across most of the plains.
Periods of light snow are likely, but little travel impact is
expected. The most likely time for accumulating snow looks like
Friday night and again Sunday.

For the mountains, light snow is likely over the ridges through
this weekend. There will be some increase in the snowfall late
Friday into early Saturday along with a bit more wind. The valleys
and foothills will have periods of light snow with a cooling
trend through the weekend.

Model forecasts are uncertain for the beginning of next week.
There will likely be some moderation in temperatures, but there
is also a chance of snow and windy conditions, especially in the
mountains.

.SPOTTER INFORMATION STATEMENT...

Spotter reports will not be needed today or tonight.

The office that day

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

IssuedProductOfficeCountiesLasted
Feb 11, 1:17 PM MSTWind Chill AdvisoryBOUElbert, Lincoln, Logan, Morgan, Phillips, Sedgwick and 2 more28 min
Feb 11, 1:45 PM MSTWind Chill AdvisoryBOUAdams, Arapahoe, Boulder, Broomfield, Denver, Douglas and 10 more4 days

Nearby

Winter Weather Advisories in Colorado, 2021Every 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.