Alert archive / Colorado / Mesoscale Discussions in 2021

Mesoscale Discussion 164

March 13, 202118 counties in Colorado

The Storm Prediction Center issued this mesoscale discussion at Mar 13, 2021, 12:22 PM MST for 18 counties in Colorado. It was in force for 4 hr.

The area

The outline as issued.

The facts

Issued: Mar 13, 2021, 12:22 PM MST (19:22 UTC)
Expired: Mar 13, 2021, 4:15 PM MST
In force: 4 hr
Issued by: the Storm Prediction Center
Concerning: Heavy snow

Counties Adams County, CO, Arapahoe County, CO, Boulder County, CO, Broomfield County, CO, Clear Creek County, CO, Denver County, CO, Douglas County, CO, El Paso County, CO, Fremont County, CO, Gilpin County, CO, Grand County, CO, Jefferson County, CO, Lake County, CO, Larimer County, CO, Park County, CO, Summit County, CO, Teller County, CO, Weld County, CO

The nearest sounding before it

Denver, CO (KDNR), launched 12:00Z, 7.4 hours before the alert went out and 177 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: 664 m above ground
0-6 km bulk shear: 86 kt
0-1 km storm-relative helicity: 6 m²/s²
0-3 km storm-relative helicity: 238 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

244 
ACUS11 KWNS 131923
SWOMCD
SPC MCD 131922 
COZ000-WYZ000-132315-

Mesoscale Discussion 0164
NWS Storm Prediction Center Norman OK
0122 PM CST Sat Mar 13 2021

Areas affected...the Front Range of the Colorado Rockies

Concerning...Heavy snow 

Valid 131922Z - 132315Z

SUMMARY...Heavy snow is beginning along the Colorado Front Range.

DISCUSSION...Lee cyclogenesis is underway with a ~1006 mb surface
low analyzed in eastern New Mexico as of 18Z. Strengthening
low-level flow in response to this strengthening cyclone has
increased low-level moist upslope flow across eastern Colorado. In
addition, strong upper-level diffluence across this region is
providing substantial lift. Most of the lower elevations have
observed rain for much of the morning, but continued strong
lift/upslope flow, combined with cooling temperatures aloft will
cool the column and allow rain to change to snow for most locations
above 5kft. Many sites have already started to change to snow and
reports of rain changing to snow have started to arrive in the
Denver metro area in the last hour. 

Very heavy snowfall rates around 2 inches per hour are expected.
Some higher rates of 3+ inches per hour may be possible in the
foothills and Front Range where upslope flow will be maximized. The
heavier snowfall rates are expected to overspread southeast Wyoming
by 22-23Z and remain across northern Colorado and southern Wyoming
through much of the overnight period.

..Bentley.. 03/13/2021

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

ATTN...WFO...PUB...BOU...CYS...GJT...

LAT...LON   39030642 39460640 40130638 40720616 41130560 41230474
            41080412 40560412 39580407 39090420 38950429 38580454
            38370501 38430566 38590621 39030642

Nearby

Mesoscale Discussions in Colorado, 2021 Every 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.