Mesoscale Discussion 1947

Issued

Nov 13, 2021, 4:09 PM EST (21:09 UTC)

Expired

Nov 13, 2021, 6:15 PM EST

In force

2 hr

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch possible

Chance of a watch

40%

Counties Barnstable County, MA, Bristol County, MA, Dukes County, MA, Norfolk County, MA, Plymouth County, MA, Suffolk County, MA, Bristol County, RI

The Boston radar (KBOX), 15 km from the middle of the area, began a volume at 21:10 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.

824 
ACUS11 KWNS 132109
SWOMCD
SPC MCD 132109 
MAZ000-RIZ000-132315-

Mesoscale Discussion 1947
NWS Storm Prediction Center Norman OK
0309 PM CST Sat Nov 13 2021

Areas affected...Parts of eastern Massachusetts

Concerning...Severe potential...Watch possible 

Valid 132109Z - 132315Z

Probability of Watch Issuance...40 percent

SUMMARY...A line of thunderstorms may be maintained, and overspread
much of eastern Massachusetts during the 5-7 PM EST time frame. 
This may be accompanied by a risk for localized, potentially
damaging, wind gusts.  It is not yet clear that another severe
weather watch will be needed, but trends will continue to be
monitored, and it is possible that Severe Thunderstorm Watch 549
could be locally extended in area  across parts of this region

DISCUSSION...As the deepening surface low tracks across
southern/southeastern New England into early evening,
clockwise-curved low-level hodographs appear likely to continue to
enlarge within its warm sector.  However, latest Rapid Refresh
forecast soundings indicate that southeasterly near surface flow off
the Atlantic will maintain relatively low surface dew points in the
lower/mid 40s F across much of eastern Massachusetts.  They do
indicate that a weak to modest elevated moisture return may
contribute to sufficient CAPE to maintain the approaching line of
thunderstorms, which continues to be supported by strong mid-level
forcing for ascent.  But it is not clear that there will be more
than a risk for localized strong surface gusts, aided by areas of
enhanced downward momentum transport.

..Kerr/Hart.. 11/13/2021

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

ATTN...WFO...BOX...

LAT...LON   42137151 42477119 42197067 41946987 41167041 41627143
            41547124 42137151

Mesoscale Discussions in Massachusetts, 2021Mesoscale Discussions in Rhode Island, 2021Every mesoscale discussion in 2021

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.