Mesoscale Discussion 1161

Issued

Jul 6, 2021, 12:33 PM EDT (16:33 UTC)

Expired

Jul 6, 2021, 3:00 PM EDT

In force

2 hr

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch likely

Chance of a watch

80%

The Philadelphia radar (KDIX), 136 km from the middle of the area, began a volume at 16:32 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.

• Severe Thunderstorm Watch 335Jul 6, 1:15 PM EDT
• Severe Thunderstorm Watch 336Jul 6, 1:30 PM EDT

563 
ACUS11 KWNS 061633
SWOMCD
SPC MCD 061633 
MAZ000-RIZ000-CTZ000-NYZ000-NHZ000-VTZ000-NJZ000-PAZ000-DEZ000-MDZ000-061900-

Mesoscale Discussion 1161
NWS Storm Prediction Center Norman OK
1133 AM CDT Tue Jul 06 2021

Areas affected...MA...CT...RI...NJ...portions of southern NY and
eastern PA

Concerning...Severe potential...Watch likely 

Valid 061633Z - 061900Z

Probability of Watch Issuance...80 percent

SUMMARY...Thunderstorms are expected to increase in coverage and
move east-southeast across the area this afternoon.  Damaging winds
will be the primary threat, with hail also possible with the
strongest storms.  One or more Severe Thunderstorm Watches will
likely be required to address the developing risk.

DISCUSSION...Isolated to widely scattered strong/severe storms have
developed over western NY as of 16z within an air mass characterized
by moderate MLCAPE and generally weak (at or below 25 kts) effective
shear values. Despite the lack of large-scale forcing, additional
thunderstorm development is anticipated over central portions of NY
and in the vicinity of a surface trough from the Delaware Valley
into southern New England as remaining weak MLCIN is removed through
daytime heating, with multiple multicell clusters moving generally
east/southeast this afternoon.  A belt of enhanced westerly flow
averaging 35-40 kts will result in a risk for damaging downburst
winds with the stronger storms and clusters.  Generally weak
deep-layer shear and poor mid-level lapse rates will temper the hail
risk, however a few stronger updrafts may be capable of marginally
severe hail.

Given the expected development, one or more Severe Thunderstorm
Watches is expected by early afternoon.

..Bunting/Guyer.. 07/06/2021

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

ATTN...WFO...GYX...BOX...OKX...ALY...PHI...BGM...BUF...CTP...
LWX...

LAT...LON   41687786 42607741 43047427 42637193 42187107 41527111
            40957203 40427336 40127375 39457420 39487512 39747601
            40827728 41687786

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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.