Alert archive / Massachusetts / Mesoscale Discussions in 2021
Mesoscale Discussion 1501
The Storm Prediction Center issued this mesoscale discussion at Aug 12, 2021, 3:50 PM EDT for 8 counties in Massachusetts; 5 counties in New Hampshire. It was in force for 55 min.
The area
The outline as issued.
The facts
- Issued
- Aug 12, 2021, 3:50 PM EDT (19:50 UTC)
- Expired
- Aug 12, 2021, 4:45 PM EDT
- In force
- 55 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 60%
Counties Essex County, MA, Franklin County, MA, Hampden County, MA, Hampshire County, MA, Middlesex County, MA, Norfolk County, MA, Suffolk County, MA, Worcester County, MA, Cheshire County, NH, Hillsborough County, NH, Merrimack County, NH, Rockingham County, NH, Strafford County, NH
The radar
The Boston radar (KBOX), 114 km from the middle of the area, began a volume at 19:53 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
Albany, NY (KALY), launched 12:00Z, 7.8 hours before the alert went out and 141 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
- 58 J/kg
- Mixed-layer CIN
- -212 J/kg
- Mixed-layer LCL
- 1178 m above ground
- 0-6 km bulk shear
- 22 kt
- 0-1 km storm-relative helicity
- 62 m²/s²
- 0-3 km storm-relative helicity
- 56 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
300
ACUS11 KWNS 121951
SWOMCD
SPC MCD 121950
MEZ000-MAZ000-NHZ000-RIZ000-CTZ000-VTZ000-122045-
Mesoscale Discussion 1501
NWS Storm Prediction Center Norman OK
0250 PM CDT Thu Aug 12 2021
Areas affected...southern NH...much of MA
Concerning...Severe potential...Watch possible
Valid 121950Z - 122045Z
Probability of Watch Issuance...60 percent
SUMMARY...A small severe thunderstorm watch is being considered for
the areas east of an ongoing cluster near the VT/MA/NY border. This
activity is expected to move to the I-95 corridor. Isolated strong
to severe gusts are possible.
DISCUSSION...Radar mosaic shows a cluster of storms near the
VT/MA/NY border as of 345pm. This activity is located to the east
of an eastward-moving MCV currently located over central NY. The
Albany, NY ASOS recently observed a gust of 39 kt. The airmass over
southern New England has warmed into the lower 90s with dewpoints
generally in the lower 70s. It appears at least an isolated risk
for strong to locally severe gusts will materialize east of severe
thunderstorm watch 432. The overall coverage of damaging gusts is
still in question but some risk appears to be increasing through the
early evening.
..Smith/Thompson.. 08/12/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...GYX...BOX...ALY...
LAT...LON 42987274 43327232 43337051 42087059 41907283 42247301
42987274SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 12, 1:42 PM EDT | Severe Thunderstorm Watch | SPC | Berkshire | 6 hr |
| Aug 12, 6:44 PM EDT | Mesoscale Discussion | SPC | Bristol, Essex, Franklin, Hampden, Hampshire, Middlesex and 4 more | 61 min |
Nearby
Mesoscale Discussions in Massachusetts, 2021Mesoscale Discussions in New Hampshire, 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.