Mesoscale Discussion 932

Issued

May 31, 2017, 7:34 PM EDT (23:34 UTC)

Expired

May 31, 2017, 9:00 PM EDT

In force

86 min

Issued by

the Storm Prediction Center

The Albany radar (KENX), 105 km from the middle of the area, began a volume at 23:37 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.

277 
ACUS11 KWNS 312335
SWOMCD
SPC MCD 312334 
MEZ000-MAZ000-NHZ000-CTZ000-VTZ000-NYZ000-PAZ000-010100-

Mesoscale Discussion 0932
NWS Storm Prediction Center Norman OK
0634 PM CDT Wed May 31 2017

Areas affected...Northeast PA...Southeast
NY...CT...MA...NH...Western ME

Concerning...Severe Thunderstorm Watch 300...

Valid 312334Z - 010100Z

The severe weather threat for Severe Thunderstorm Watch 300
continues.

SUMMARY...The damaging wind and isolated large hail threat continues
in and near WW 300. Some severe threat may extend downstream of the
watch, but should diminish with eastward extent.

DISCUSSION...At 2330Z, a loosely organized QLCS is ongoing from
southeast NY northeastward into western ME. In addition, a discrete
supercell is ongoing just ahead of the line near Poughkeepsie, NY.
The strongest instability is located across southeast NY into
western CT/MA, with recent mesoanalyses indicating SBCAPE of
500-1250 J/kg. Effective shear of 35-45 kts will continue to support
some organized structures in the short term. The primary threat is
expected to be damaging wind given the primary linear mode, but the
supercell across southeast NY will pose some tornado threat as long
as it remains discrete, with locally backed southeasterly flow
supporting a modest amount of low-level shear/helicity. 

As the QLCS advances eastward, it will eventually encounter a cooler
and more stable airmass. This will occur first across portions of
southern ME, where a marginal damaging wind risk may exist
downstream of WW 300, but should diminish with eastward extent.
Further south, there is some potential for a severe threat to extend
east of the watch and local extensions may eventually be needed. 

Back to the southwest across northeast PA, a separate line segment
has recently intensified. This will pose some damaging wind risk as
it advances eastward into the southwest portion of WW 300, though it
will encounter an increasingly worked-over environment from earlier
convection. 

Finally, some severe threat may extend a small distance south of WW
300 across southeast NY/southwest CT, but the spatiotemporal extent
of this threat appears too limited for new watch issuance.

..Dean.. 05/31/2017

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

ATTN...WFO...CAR...GYX...BOX...OKX...ALY...BGM...

LAT...LON   41987641 42217471 42657250 43597210 44827073 45387039
            45326968 44486995 43187076 42287139 42067183 41517239
            41427313 41347384 41457524 41737636 41987641

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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.