Alert archive / New York / Mesoscale Discussions in 2021

Mesoscale Discussion 1322

July 20, 20215 states

The Storm Prediction Center issued this mesoscale discussion at Jul 20, 2021, 10:01 PM EDT for 5 states. It was in force for 59 min.

The area

The outline as issued.

The facts

Issued: Jul 20, 2021, 10:01 PM EDT (02:01 UTC)
Expired: Jul 20, 2021, 11:00 PM EDT
In force: 59 min
Issued by: the Storm Prediction Center
Concerning: Severe thunderstorm watch 384

All 35 counties

Berkshire County, MA, Franklin County, MA, Hampden County, MA, Hampshire County, MA, Worcester County, MA, Belknap County, NH, Carroll County, NH, Cheshire County, NH, Hillsborough County, NH, Merrimack County, NH, Rockingham County, NH, Strafford County, NH, Sullivan County, NH, Albany County, NY, Broome County, NY, Chemung County, NY, Columbia County, NY, Delaware County, NY, Dutchess County, NY, Greene County, NY, Orange County, NY, Putnam County, NY, Rensselaer County, NY, Sullivan County, NY, Ulster County, NY, Bradford County, PA, Lackawanna County, PA, Potter County, PA, Sullivan County, PA, Susquehanna County, PA, Tioga County, PA, Wayne County, PA, Wyoming County, PA, Bennington County, VT, Windham County, VT

The radar

The Albany radar (KENX), 7 km from the middle of the area, began a volume at 02:00 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 00:00Z, 2.0 hours before the alert went out and 21 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.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 1226 J/kg
Mixed-layer CIN: -24 J/kg
Mixed-layer LCL: 1198 m above ground
0-6 km bulk shear: 37 kt
0-1 km storm-relative helicity: 89 m²/s²
0-3 km storm-relative helicity: 82 m²/s²
Significant tornado parameter: 0.4
Supercell composite: 4.6

Open this sounding in Storm Lab

The text

As transmitted.

296 
ACUS11 KWNS 210201
SWOMCD
SPC MCD 210201 
MEZ000-NHZ000-MAZ000-CTZ000-VTZ000-NYZ000-PAZ000-210300-

Mesoscale Discussion 1322
NWS Storm Prediction Center Norman OK
0901 PM CDT Tue Jul 20 2021

Areas affected...Northeast

Concerning...Severe Thunderstorm Watch 384...

Valid 210201Z - 210300Z

The severe weather threat for Severe Thunderstorm Watch 384
continues.

SUMMARY...A wind-damage threat will likely continue for another hour
or two across parts of northern Pennsylvania, southeast New York and
New England. The threat should become more isolated with time this
evening and new weather watch issuance will be unlikely.

DISCUSSION...The latest mosaic radar imagery shows a convective line
located from western Pennsylvania extending northeastward across
southeast New York into New England. The airmass ahead of the line
is moderately unstable with the RAP showing MLCAPE mostly in the
1000 to 1500 J/kg range. This combined with moderate deep-layer
shear and steep low-level lapse rates will support a wind-damage
threat early this evening with the stronger cells embedded in the
line. This threat is expected to be most prominent over the next
hour with some of the storms affecting areas just to the east of WW
384. However, the boundary layer will continue to cool this evening,
resulting in weakening instability. As a result, the severe threat
will become more isolated and marginal with time.

..Broyles/Edwards.. 07/21/2021

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

ATTN...WFO...GYX...BOX...BTV...OKX...ALY...BGM...BUF...CTP...

LAT...LON   41347384 41427671 41617790 41827814 42107803 42197721
            42157595 42887338 43867188 44537107 44487060 44127041
            43547058 42337158 41347384

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 21, 10:32 AM EDT	Mesoscale Discussion	SPC		58 min
Jul 21, 11:56 AM EDT	Severe Thunderstorm Watch	SPC	Greater Bridgeport Planning Region, Capitol Planning Region, Lower Connecticut River Valley Planning Region, Naugatuck Valley Planning Region, Southeastern Connecticut Planning Region, Northeastern Connecticut Planning Region	7 hr
Jul 21, 2:39 PM EDT	Mesoscale Discussion	SPC	Barnstable, Bristol, Dukes, Nantucket, Plymouth	2 hr

Nearby

Mesoscale Discussions in New York, 2021 Mesoscale Discussions in New Hampshire, 2021 Mesoscale Discussions in Pennsylvania, 2021 Every 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.