Alert archive / Colorado / Freeze Warnings in 2018

Freeze Warning 1, NWS Denver/Boulder, CO

October 8, 201816 counties in Colorado

NWS Denver/Boulder, CO issued this freeze warning at Oct 8, 2018, 3:01 PM MDT for 16 counties in Colorado. It took effect at Oct 9, 2018, 12:00 AM MDT. It was in force for 4 hr. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued
Oct 8, 2018, 3:01 PM MDT (21:01 UTC)
In effect from
Oct 9, 2018, 12:00 AM MDT
Expired
Oct 9, 2018, 4:25 AM MDT
In force
4 hr
Issued by
NWS Denver/Boulder, CO

Counties Adams County, CO, Arapahoe County, CO, Boulder County, CO, Broomfield County, CO, Denver County, CO, Douglas County, CO, Elbert County, CO, Jefferson County, CO, Larimer County, CO, Lincoln County, CO, Logan County, CO, Morgan County, CO, Phillips County, CO, Sedgwick County, CO, Washington County, CO, Weld County, CO

The radar

The Denver radar (KFTG), 42 km from the middle of the area, began a volume at 21:01 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

Grand Junction, CO (KGJT), launched 12:00Z, 9.0 hours before the alert went out and 385 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, Grand Junction, CO at 12:00Z on 2018-10-08Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 17 joules per kilogram.LCLLFCEL10008507005003002001001 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, Grand Junction, CO at 12:00Z on 2018-10-08The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -22 square meters per square second.19395878Sfc1 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
17 J/kg
Mixed-layer CIN
-9 J/kg
Mixed-layer LCL
841 m above ground
0-6 km bulk shear
64 kt
0-1 km storm-relative helicity
-22 m²/s²
0-3 km storm-relative helicity
24 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 freeze warning 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 freeze warning went out at Oct 8, 10:23 AM MDT, 4 hours 38 minutes earlier.

Area forecast discussion, Oct 8, 10:23 AM MDT, 4 hours 38 minutes before
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Hazardous weather outlook, Oct 8, 11:21 AM MDT, 3 hours 40 minutes before
Hazardous Weather Outlook
National Weather Service Denver/Boulder CO
1121 AM MDT Mon Oct 8 2018

COZ030>051-091730-
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-
1121 AM MDT Mon Oct 8 2018

...COLD NIGHTS AHEAD WITH FREEZING TEMPERATURES...

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

.DAY ONE...This Afternoon and Tonight

Periods of drizzle, rain, and snow will continue this afternoon
and gradually diminish during the evening. Cold air moving into
the area will allow a few snowflakes to mix in at times across the
plains, especially as we head into the late afternoon and evening
hours. A couple brief heavier showers may produce a light dusting
of snow on the grass and other elevated surfaces. Most of the
accumulating snow will be confined to the high country. Up to 3
inches can be expected on grassy and elevated surfaces in the
foothills, while in the mountains anywhere from a dusting to 4
inches of additional snow will be possible through this evening.
The mountain passes may see snow or slush accumulation on the
roadways under the heavier snow showers, as well as overnight as
temperatures drop.

Temperatures will drop to or just below freezing across the plains
tonight, so protective measures should be taken for outdoor plants
and above ground sprinkler systems. There is a chance of some
light freezing drizzle late tonight as well, but any icing would
be confined to elevated surfaces.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday

It will remain unseasonably cool and unsettled through Tuesday
night with periods of snow in the high country, and a chance of
rain and snow showers at lower elevations. High country areas
could see an additional 2 to 5 inches of snow by Wednesday
morning, with little to no snow accumulation on the plains.

If skies clear sufficiently Tuesday night, the plains could see a
hard freeze late Tuesday night and early Wednesday morning. It
would be prudent to protect tender plants and outdoor water
irrigation systems today and tomorrow, before the sub-freezing
temperatures arrive Tuesday night.

Later in the week, there will be a couple more chances of wintry
weather in the mountains, the first chance late on Wednesday and
the other Thursday night. The storm system moving in on Thursday
may produce several inches of snow in the mountains along with gusty
winds that could create hazardous winter driving conditions.
Lower elevations will see rain showers, though some areas could
see a mix of rain and snow during the overnight hours. Drier and
warmer conditions are expected to return to northern Colorado by
late Friday and Saturday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed today or tonight. However,
any reports of snow accumulation will be appreciated.

Nearby

Freeze Warnings in Colorado, 2018Every freeze 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.