Mesoscale Discussion 1735

Issued

Sep 12, 2021, 9:14 PM EDT (01:14 UTC)

Expired

Sep 12, 2021, 10:45 PM EDT

In force

91 min

Issued by

the Storm Prediction Center

Concerning

Severe thunderstorm watch 494

County Erie County, NY

The Buffalo radar (KBUF), 176 km from the middle of the area, began a volume at 01:12 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 495Sep 12, 10:25 PM EDT

232 
ACUS11 KWNS 130115
SWOMCD
SPC MCD 130114 
NYZ000-MIZ000-130245-

Mesoscale Discussion 1735
NWS Storm Prediction Center Norman OK
0814 PM CDT Sun Sep 12 2021

Areas affected...Parts of southeastern lower Michigan through parts
of northern Lake Erie and western New York State

Concerning...Severe Thunderstorm Watch 494...

Valid 130114Z - 130245Z

The severe weather threat for Severe Thunderstorm Watch 494
continues.

SUMMARY...An organized cluster of storms may continue to rapidly
move across southeastern Ontario, across parts of eastern Lake Erie
into the Buffalo vicinity by Midnight EDT.  It remains unclear
whether this will be accompanied by an appreciable risk for damaging
wind gusts,  but trends will continue to be monitored for the
possibility of an additional severe weather watch downstream of WW
494.

DISCUSSION...An organized cluster of storms is generally maintaining
considerable strength, east and southeast of a cyclonic mid-level
vorticity maxima.  Forward propagation has been rapid, in excess of
50 kt, aided by strong cloud-bearing layer mean flow.  However,
convection is generally rooted above moist low-levels with weak to
stable lapse rates and modest to weak ambient flow.  This has
inhibited, or at least considerably limited, strong surface gusts
from reaching the surface, and may continue to do so as the cluster
progresses across southeastern Ontario during the next couple of
hours.  Based on its current motion, along the northern periphery of
the plume of elevated mixed-layer air emanating from the Great
Plains (roughly coinciding with the 700 mb thermal gradient), it may
reach the Buffalo vicinity by 04Z.  It is possible that downward
transfer of somewhat stronger low-level wind fields across eastern
Lake Erie into western New York State could contribute to some
increase in surface gusts with the convection.  However, it appears
that storm inflow will gradually become more stable with eastward
progression, and convection may tend to weaken, reducing this risk.

..Kerr.. 09/13/2021

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

ATTN...WFO...BUF...DTX...

LAT...LON   43348161 43368051 43207894 42777856 42397988 42388216
            42638262 43258223 43348161

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.