Mesoscale Discussion 1696

Issued

Sep 6, 2021, 7:34 AM EDT (11:34 UTC)

Expired

Sep 6, 2021, 10:00 AM EDT

In force

2 hr

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch unlikely

Chance of a watch

20%

Counties Essex County, NY, Franklin County, NY, Hamilton County, NY, Herkimer County, NY, Jefferson County, NY, Lewis County, NY, Monroe County, NY, Oneida County, NY, Oswego County, NY, St. Lawrence County, NY, Wayne County, NY

The Ft Drum radar (KTYX), 32 km from the middle of the area, began a volume at 11:36 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.

640 
ACUS11 KWNS 061134
SWOMCD
SPC MCD 061134 
NYZ000-061400-

Mesoscale Discussion 1696
NWS Storm Prediction Center Norman OK
0634 AM CDT Mon Sep 06 2021

Areas affected...portions of western/northern NY -- near Lake
Ontario and eastward to the Adirondacks.

Concerning...Severe potential...Watch unlikely 

Valid 061134Z - 061400Z

Probability of Watch Issuance...20 percent

SUMMARY...Fast-moving thunderstorms may produce strong/locally
damaging wind, with a gust or two near severe/50-kt levels and
waterspouts possible, as they move along Lake Ontario.  Strong gusts
also may occur on adjoining shorelines and eastward over parts of
northern NY through at least 15Z.  The severe potential appears
isolated and marginal enough that a watch is not expected at this
time.

DISCUSSION...Satellite and radar imagery indicate an increasingly
organized band of thunderstorms over western/central Lake Ontario as
of 1130Z, moving eastward about 45 kt.  The convective band may
lengthen (especially northward) with time as well, into parts of
northern NY downshear from the lake.  

Cooling aloft -- superimposed on a relatively warm and moist
boundary layer located over Lake Ontario -- will support this
activity as it crosses the remainder of the lake during the next
couple hours.  Thereafter, pockets of early diurnal heating behind a
previous cloud/precip area may yield enough boundary-layer
destabilization to weaken MLCINH and enable surface-based buoyancy
eastward toward the Adirondacks, sustaining the convective/marginal
severe threat.  Modified forecast soundings suggest steepening
low/middle-level lapse rates over the lake, and surface dew points
in the mid 50s to near 60 F, foster MLCAPE in the 300-800 J/kg
range.  

Nearly unidirectional flow with height is evident from just above
the surface through the convective column, limiting bulk shear,
despite strong mid/upper flow.  Effective-shear magnitudes should
remain only in the 25-35-kt range over most of the area.  Still, the
fast-moving (40-45-kt) nature of the convection suggests enough
momentum transfer may occur to yield gusts approaching severe limits
and capable of minor damage with this activity.  The steep lapse
rates also may enable enough stretching of leading-edge
boundary-layer vorticity for waterspouts.

..Edwards.. 09/06/2021

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

ATTN...WFO...BTV...ALY...BGM...BUF...

LAT...LON   44977423 44547399 43997368 43337405 43177477 43117610
            43287823 43477813 43627799 43607685 44137645 44377585
            44467581 44757537 45007489 44977423

Mesoscale Discussions in New York, 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.