Alert archive / Connecticut / Mesoscale Discussions in 2021
Mesoscale Discussion 1138
The Storm Prediction Center issued this mesoscale discussion at Jun 30, 2021, 6:58 PM EDT for 7 states. It was in force for 92 min.
The area
The outline as issued.
The facts
- Issued
- Jun 30, 2021, 6:58 PM EDT (22:58 UTC)
- Expired
- Jun 30, 2021, 8:30 PM EDT
- In force
- 92 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 329...330
All 30 counties
Bristol County, MA, Norfolk County, MA, Plymouth County, MA, Carroll County, MD, Frederick County, MD, Montgomery County, MD, Bergen County, NJ, Essex County, NJ, Morris County, NJ, Passaic County, NJ, Sussex County, NJ, Warren County, NJ, Bronx County, NY, Orange County, NY, Putnam County, NY, Rockland County, NY, Westchester County, NY, Adams County, PA, Berks County, PA, Lancaster County, PA, Lebanon County, PA, Lehigh County, PA, Northampton County, PA, York County, PA, Bristol County, RI, Kent County, RI, Newport County, RI, Providence County, RI, Washington County, RI, Loudoun County, VA
The radar
The Philadelphia radar (KDIX), 83 km from the middle of the area, began a volume at 23:01 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
Brookhaven, NY (KOKX), launched 12:00Z, 11.0 hours before the alert went out and 131 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
- 658 J/kg
- Mixed-layer CIN
- -190 J/kg
- Mixed-layer LCL
- 1595 m above ground
- 0-6 km bulk shear
- 17 kt
- 0-1 km storm-relative helicity
- 48 m²/s²
- 0-3 km storm-relative helicity
- 67 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
848
ACUS11 KWNS 302259
SWOMCD
SPC MCD 302258
MAZ000-RIZ000-CTZ000-NYZ000-NJZ000-PAZ000-MDZ000-VAZ000-010030-
Mesoscale Discussion 1138
NWS Storm Prediction Center Norman OK
0558 PM CDT Wed Jun 30 2021
Areas affected...central Maryland and eastern Pennsylvania into
southern New England
Concerning...Severe Thunderstorm Watch 329...330...
Valid 302258Z - 010030Z
The severe weather threat for Severe Thunderstorm Watch 329, 330
continues.
SUMMARY...Locally severe gusts remain possible over the next couple
hours, but a weakening trend is expected especially after 00Z. As
such, additional watches appear unlikely.
DISCUSSION...Objective analysis shows a corridor of 2000 J/kg MUCAPE
remains ahead of a composite cold front/outflow boundary. This front
is oriented roughly parallel to the midlevel winds especially across
northeast PA into southern NY and CT, and this is allowing outflow
to undercut ongoing convection. A bit more cross-boundary flow
exists farther south into MD and northern VA, as well as over
eastern MA, and this may aid storm longevity in these areas.
As the boundary layer slowly cools, a weakening trend is
anticipated, and storms may weaken substantially between 00-01Z.
Until then, ample PWAT and a warm boundary layer may support locally
strong to severe gusts. Small hail may also occur over the next hour
or so with the stronger cells.
..Jewell.. 06/30/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...BOX...OKX...ALY...PHI...BGM...CTP...LWX...
LAT...LON 41187505 41587412 41937266 42377089 42077053 41737056
41477096 41307172 41197243 41227289 40987352 40817387
40677449 40717486 40327559 39767608 39337690 39017711
38957752 39057776 39467747 39967718 40437648 41187505SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jun 30, 2:16 PM EDT | Mesoscale Discussion | SPC | 119 min | |
| Jun 30, 3:21 PM EDT | Severe Thunderstorm Watch | SPC | Greater Bridgeport Planning Region, Capitol Planning Region, Northwest Hills Planning Region, Lower Connecticut River Valley Planning Region, Naugatuck Valley Planning Region, Southeastern Connecticut Planning Region and 1 more | 7 hr |
| Jun 30, 4:41 PM EDT | Mesoscale Discussion | SPC | Allegany, Baltimore, Carroll, Frederick, Garrett, Howard and 2 more | 2 hr |
| Jun 30, 4:51 PM EDT | Severe Thunderstorm Watch | SPC | Allegany, Carroll, Frederick, Washington | 3 hr |
| Jun 30, 4:48 PM EDT | Mesoscale Discussion | SPC | Berkshire, Franklin, Hampden, Hampshire, Middlesex, Norfolk and 2 more | 87 min |
| Jun 30, 11:04 AM EDT | Mesoscale Discussion | SPC | Albany, Allegany, Broome, Cayuga, Chemung, Chenango and 29 more | 116 min |
| Jun 30, 11:47 AM EDT | Severe Thunderstorm Watch | SPC | Albany, Allegany, Broome, Cattaraugus, Cayuga, Chautauqua and 27 more | 7 hr |
| Jun 30, 12:06 PM EDT | Severe Thunderstorm Watch | SPC | Essex | 7 hr |
| Jun 30, 1:52 PM EDT | Mesoscale Discussion | SPC | Fulton, Montgomery, Saratoga, Schenectady, Warren, Washington | 83 min |
| Jun 30, 11:30 AM EDT | Mesoscale Discussion | SPC | Allegheny, Armstrong, Beaver, Blair, Butler, Cambria and 23 more | 2 hr |
| Jun 30, 12:46 PM EDT | Severe Thunderstorm Watch | SPC | Bedford, Blair, Cambria, Cameron, Centre, Clearfield and 20 more | 7 hr |
| Jun 30, 3:29 PM EDT | Mesoscale Discussion | SPC | Allegheny, Armstrong, Bedford, Blair, Cambria, Centre and 16 more | 2 hr |
Nearby
Mesoscale Discussions in Connecticut, 2021Mesoscale Discussions in Pennsylvania, 2021Mesoscale Discussions in New Jersey, 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.