Alert archive / Massachusetts / Mesoscale Discussions in 2021
Mesoscale Discussion 979
The Storm Prediction Center issued this mesoscale discussion at Jun 15, 2021, 2:38 PM EDT for 5 states. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Jun 15, 2021, 2:38 PM EDT (18:38 UTC)
- Expired
- Jun 15, 2021, 4:45 PM EDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 5%
All 27 counties
Bristol County, MA, Essex County, MA, Franklin County, MA, Hampden County, MA, Hampshire County, MA, Middlesex County, MA, Norfolk County, MA, Plymouth County, MA, Suffolk County, MA, Worcester County, MA, Franklin County, ME, Oxford County, ME, Belknap County, NH, Carroll County, NH, Cheshire County, NH, Coos County, NH, Grafton County, NH, Hillsborough County, NH, Merrimack County, NH, Rockingham County, NH, Strafford County, NH, Sullivan County, NH, Bristol County, RI, Kent County, RI, Newport County, RI, Providence County, RI, Essex County, VT
The radar
The Portland,ME radar (KGYX), 134 km from the middle of the area, began a volume at 18:41 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
Gray, ME (KGYX), launched 12:00Z, 6.6 hours before the alert went out and 134 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
- 659 m above ground
- 0-6 km bulk shear
- 50 kt
- 0-1 km storm-relative helicity
- 48 m²/s²
- 0-3 km storm-relative helicity
- 126 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
794
ACUS11 KWNS 151839
SWOMCD
SPC MCD 151838
MEZ000-MAZ000-NHZ000-RIZ000-VTZ000-CTZ000-152045-
Mesoscale Discussion 0979
NWS Storm Prediction Center Norman OK
0138 PM CDT Tue Jun 15 2021
Areas affected...Portions of New England
Concerning...Severe potential...Watch unlikely
Valid 151838Z - 152045Z
Probability of Watch Issuance...5 percent
SUMMARY...A few strong to locally severe storms are possible in
portions of southern/central New England. Damaging wind gusts will
be the primary threat with marginally severe hail more isolated. No
WW is expected this afternoon.
DISCUSSION...Visible satellite and NLDN lightning trends indicate
convection is deepening within the Connecticut River Valley. Surface
temperatures from western Maine into eastern Massachusetts have
risen into the mid 70s F with dewpoints holding in the upper 50s to
low 60s F. RAP-based objective mesoanalysis suggests 500-1000 J/kg
MLCAPE currently. Given RAP soundings are warmer at upper levels
than regional 12Z RAOBs and surface temperatures and dewpoints are
higher than forecast, it seems likely that MLCAPE will be skewed
toward the higher end of the objectively analyzed range and that
effective shear may be a touch higher given slightly deeper
convection. The greatest storm coverage will likely occur in New
Hampshire and western Maine where convergence is greatest within the
surface trough. Strong heating and 35-40 kts of mid-level flow
evident on the KBOX VWP will promote strong/damaging wind gusts. It
is cold enough aloft that marginally severe hail could occur with
any more organized/discrete storms.
Farther south towards the Boston Metro, convergence in the surface
trough is weaker and storm coverage is a bit more questionable. The
primary forcing for convection will likely be the Atlantic sea
breezes to the south and east. Shear is slightly greater in southern
New England. Isolated storms would be similarly capable of damaging
winds with marginally greater hail threat given the improved shear.
The marginal environment will not likely support more than isolated
severe coverage. No WW is expected.
..Wendt/Grams.. 06/15/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...GYX...BOX...BTV...OKX...ALY...
LAT...LON 43477257 44667197 45347101 45217030 43727070 42777083
41917070 41477132 41497192 41987266 42667267 43477257Nearby
Mesoscale Discussions in Massachusetts, 2021Mesoscale Discussions in New Hampshire, 2021Mesoscale Discussions in Rhode Island, 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.