Alert archive / Colorado / Mesoscale Discussions in 2018

Mesoscale Discussion 1010

July 4, 201815 counties in Colorado; 13 counties in Nebraska; Albany County, Goshen County, Laramie County, Wyoming

The Storm Prediction Center issued this mesoscale discussion at Jul 4, 2018, 1:51 PM MDT for 15 counties in Colorado; 13 counties in Nebraska; Albany County, Goshen County, Laramie County, Wyoming. It was in force for 54 min.

The area

The outline as issued.

The facts

Issued: Jul 4, 2018, 1:51 PM MDT (19:51 UTC)
Expired: Jul 4, 2018, 2:45 PM MDT
In force: 54 min
Issued by: the Storm Prediction Center
Chance of a watch: 40%

All 31 counties

Adams County, CO, Arapahoe County, CO, Broomfield County, CO, Denver County, CO, Douglas County, CO, El Paso County, CO, Elbert County, CO, Jefferson County, CO, Larimer County, CO, Logan County, CO, Morgan County, CO, Phillips County, CO, Sedgwick County, CO, Washington County, CO, Weld County, CO, Arthur County, NE, Banner County, NE, Box Butte County, NE, Cheyenne County, NE, Deuel County, NE, Garden County, NE, Grant County, NE, Hooker County, NE, Keith County, NE, Kimball County, NE, McPherson County, NE, Morrill County, NE, Scotts Bluff County, NE, Albany County, WY, Goshen County, WY, Laramie County, WY

The radar

The Cheyenne radar (KCYS), 107 km from the middle of the area, began a volume at 19:54 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 (KDEN), launched 12:00Z, 7.9 hours before the alert went out and 99 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: 36 J/kg
Mixed-layer CIN: -425 J/kg
Mixed-layer LCL: 2663 m above ground
0-6 km bulk shear: 13 kt
0-1 km storm-relative helicity: 10 m²/s²
0-3 km storm-relative helicity: -28 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

911 
ACUS11 KWNS 041952
SWOMCD
SPC MCD 041951 
NEZ000-COZ000-WYZ000-042045-

Mesoscale Discussion 1010
NWS Storm Prediction Center Norman OK
0251 PM CDT Wed Jul 04 2018

Areas affected...eastern Colorado...southeastern Wyoming...and
western Nebraska

Concerning...Severe potential...Watch possible 

Valid 041951Z - 042045Z

Probability of Watch Issuance...40 percent

SUMMARY...Convection across central Colorado and adjacent far
southeastern Wyoming should continue to expand into a few
thunderstorms across the discussion area through the afternoon.  A
WW issuance is possible, although convective trends will be
monitored.

DISCUSSION...Towering cumulus has been confined to 1) higher
elevations of central Colorado/southeastern Wyoming and 2) eastward
along a cold front near El Paso County, CO recently.  Warming
surface temperatures, steepening low and mid-level lapse rates, and
weak low-level upslope flow will continue to allow for storms to
develop through the afternoon - similar to what has been observed
just west of Cheyenne recently.  Models (particularly the HRRR) also
indicate potential for at least isolated thunderstorm development
across the discussion area (including portions of west-central
Nebraska) through the afternoon hours - although convective coverage
remains a concern as much of the area of cumulus resides upstream of
a mid-level shortwave now over northeastern Colorado.  Weak
low-level wind fields/shear will promote loosely-organized clusters
of outflow-dominant storms, with potential for hail/damaging wind
gusts and upscale growth into linear segments should storms
materialize as expected.  Convective trends may necessitate a Severe
Thunderstorm Watch issuance - especially in eastern portions of the
discussion area where stronger buoyancy (amidst low-70s F dewpoints)
resides.

..Cook/Hart.. 07/04/2018

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

ATTN...WFO...LBF...GLD...PUB...BOU...CYS...

LAT...LON   41810612 41960587 42130484 42350294 42280086 41670055
            41370115 40430208 39740278 38990352 38470376 38320432
            38690505 40240541 41810612

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 3, 6:36 PM MDT	Mesoscale Discussion	SPC	Logan, Morgan, Phillips, Sedgwick	54 min
Jul 4, 9:27 AM MDT	Mesoscale Discussion	SPC	Burt, Cuming, Dodge, Thurston, Washington	2 hr
Jul 4, 1:01 PM MDT	Mesoscale Discussion	SPC	Antelope, Blaine, Boyd, Brown, Burt, Cedar and 16 more	119 min
Jul 4, 4:35 PM MDT	Mesoscale Discussion	SPC	Antelope, Blaine, Boyd, Brown, Cedar, Custer and 15 more	115 min
Jul 3, 8:38 PM MDT	Mesoscale Discussion	SPC	Crook, Niobrara, Weston	2 hr

Nearby

Mesoscale Discussions in Colorado, 2018 Mesoscale Discussions in Nebraska, 2018 Mesoscale Discussions in Wyoming, 2018 Every mesoscale discussion 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.