Alert archive / Colorado / Mesoscale Discussions in 2021

Mesoscale Discussion 390

April 15, 20214 counties in Colorado

The Storm Prediction Center issued this mesoscale discussion at Apr 15, 2021, 2:51 PM MDT for 4 counties in Colorado. It was in force for 4 hr.

The area

The outline as issued.

The facts

Issued
Apr 15, 2021, 2:51 PM MDT (20:51 UTC)
Expired
Apr 15, 2021, 6:45 PM MDT
In force
4 hr
Issued by
the Storm Prediction Center
Concerning
Heavy snow

Counties Adams County, CO, Logan County, CO, Morgan County, CO, Weld County, CO

The radar

The Denver radar (KFTG), 94 km from the middle of the area, began a volume at 20:55 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, 8.9 hours before the alert went out and 85 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 12:00Z on 2021-04-15Temperature 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, Denver, CO at 12:00Z on 2021-04-15The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 220 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
897 m above ground
0-6 km bulk shear
60 kt
0-1 km storm-relative helicity
220 m²/s²
0-3 km storm-relative helicity
296 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

911 
ACUS11 KWNS 152051
SWOMCD
SPC MCD 152051 
COZ000-NEZ000-160045-

Mesoscale Discussion 0390
NWS Storm Prediction Center Norman OK
0351 PM CDT Thu Apr 15 2021

Areas affected...Northeast Colorado

Concerning...Heavy snow 

Valid 152051Z - 160045Z

SUMMARY...Moderate to heavy snow, including rates up to 2 inches per
hour, may develop near the I-76 corridor of northeast Colorado
through 5-8 PM MDT.

DISCUSSION...A broad mid-level low is in the process of gradually
shifting east of the Great Basin into the Wyoming/Colorado Rockies. 
As this continues through late afternoon and early evening,
large-scale ascent is forecast to develop and intensify across the
Platte Basin/Interstate 76 vicinity.  Forcing for ascent will be
supported by strengthening lower/mid tropospheric warm advection,
beneath increasingly difluent upper flow.  Latest model forecast
soundings suggest lift will become maximized within and and above
favorably cold mid-levels supportive of large dendritic ice crystal
growth.  At the same time, near surface winds are forecast to
gradually back to a northeasterly component, contributing to weak
low-level cold advection.

As this occurs, moderate to heavy snow in excess of 1 inch per hour
appears likely to develop.  Recent runs of the Rapid Refresh have
indicated the development of rates approaching 2 inches per hour are
possible across an area focused around Fort Morgan, Sterling and
Akron as early as 23-00Z.

..Kerr.. 04/15/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...GLD...BOU...CYS...

LAT...LON   40420473 40980367 41120284 40550243 39830373 39880499
            40420473

Nearby

Mesoscale Discussions in Colorado, 2021Every mesoscale discussion 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.