Alert archive / North Carolina / Mesoscale Discussions in 2021
Mesoscale Discussion 15
The Storm Prediction Center issued this mesoscale discussion at Jan 7, 2021, 10:54 PM EST for 17 counties in North Carolina. It was in force for 3 hr.
The area
The outline as issued.
The facts
- Issued
- Jan 7, 2021, 10:54 PM EST (03:54 UTC)
- Expired
- Jan 8, 2021, 2:00 AM EST
- In force
- 3 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Heavy snow
Counties Alexander County, NC, Avery County, NC, Buncombe County, NC, Burke County, NC, Caldwell County, NC, Haywood County, NC, Henderson County, NC, Jackson County, NC, Madison County, NC, McDowell County, NC, Mitchell County, NC, Polk County, NC, Rutherford County, NC, Transylvania County, NC, Watauga County, NC, Wilkes County, NC, Yancey County, NC
The radar
The Greer radar (KGSP), 96 km from the middle of the area, began a volume at 03:55 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
Greensboro/Hi Pt, NC (KGSO), launched 00:00Z, 3.9 hours before the alert went out and 217 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.
- Mixed-layer CAPE
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 1252 m above ground
- 0-6 km bulk shear
- 35 kt
- 0-1 km storm-relative helicity
- 33 m²/s²
- 0-3 km storm-relative helicity
- 22 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
522
ACUS11 KWNS 080355
SWOMCD
SPC MCD 080354
NCZ000-TNZ000-080700-
Mesoscale Discussion 0015
NWS Storm Prediction Center Norman OK
0954 PM CST Thu Jan 07 2021
Areas affected...The Blue Ridge of western North Carolina and
adjacent portions of the southern Appalachians
Concerning...Heavy snow
Valid 080354Z - 080700Z
SUMMARY...Heavy snow is expected to develop along the North Carolina
Blue Ridge into Great Smoky Mountains, at rates up to 1-2 inches per
hour by 1-3 AM EST.
DISCUSSION...The exit region of an 80-90 kt, cyclonic 500 mb jet
streak is in the process of overspreading the southern Appalachians
vicinity, with associated forcing for ascent and cooling
contributing to steepening mid-level lapse rates. This includes the
eastern slopes of the North Carolina Blue Ridge into the Great Smoky
Mountains, where low-level warm advection to the east of an
approaching mid-level low will contribute to lift during the next
few hours.
Models suggest that orographic forcing will become maximized across
the higher terrain by 06-08Z, when strong upward vertical motion may
focus within the favorably cold mid-level temperatures conducive to
large dendritic ice crystal growth. Although lower levels near and
just above the surface may be initially relatively warm and dry,
quick saturation and cooling of this air mass is expected due to
evaporation and melting of heavy precipitation. Aided by
precipitable water increasing in excess of .5 inches, at least a
couple hour period of heavy snow rates on the order of 1-2 inches
per hour appears possible.
..Kerr.. 01/08/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...RNK...GSP...MRX...
LAT...LON 35778302 36098232 36408158 36108070 35628135 35258205
35148309 35548337 35778302Nearby
Mesoscale Discussions in North Carolina, 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.