Mesoscale Discussion 1046

Issued

Jun 21, 2021, 12:31 PM EDT (16:31 UTC)

Expired

Jun 21, 2021, 2:00 PM EDT

In force

89 min

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch likely

Chance of a watch

80%

The Ft Drum radar (KTYX), 107 km from the middle of the area, began a volume at 16:33 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 300Jun 21, 1:10 PM EDT
• Severe Thunderstorm Watch 303Jun 21, 3:45 PM EDT

867 
ACUS11 KWNS 211632
SWOMCD
SPC MCD 211631 
NHZ000-VTZ000-NYZ000-211800-

Mesoscale Discussion 1046
NWS Storm Prediction Center Norman OK
1131 AM CDT Mon Jun 21 2021

Areas affected...Vermont and northern New York

Concerning...Severe potential...Watch likely 

Valid 211631Z - 211800Z

Probability of Watch Issuance...80 percent

SUMMARY...Storms are expected to develop in the next one to two
hours. A watch is likely.

DISCUSSION...A very moist airmass is in place across the Northeast
with widespread dewpoints in the upper 60s to near 70. In addition,
mostly sunny skies have allowed temperatures to quickly warm into
the low to mid 80s. Despite this heating, dewpoints have not fallen
appreciably as the moist airmass is quite deep across this region.
This has already allowed for an erosion of MLCIN and MLCAPE around
1500 J/kg per SPC mesoanalysis. Additional warming and some cooling
temperatures aloft should lead to additional destabilization with
MLCAPE likely 2000 to 2500 J/kg.

A cumulus field has already expanded across eastern New York and
thunderstorms are expected to emerge from this cumulus field in the
next 1 to 2 hours given the CINH is already limited and the boundary
layer continues to warm. 

The KCYX WSR-88D VWP already shows 60 knots of flow around 2km with
40 knots at 1km. Additionally, the KBUF WSR-88D is sensing a 50 knot
low-level jet at 1km. This matches 12Z guidance well which also show
this low-level jet overspreading much of Vermont and northern New
York this afternoon. This strong low-level wind profile will support
a damaging wind threat from any storms, and especially where any
bowing segments develop. In addition, the shear profile will support
some supercells which will be capable of large hail, damaging winds
and perhaps a tornado or two. Low-level flow will be mostly
unidirectional, but low-level speed shear will be strong, and more
backed surface flow is forecast in far northern New York and
northern Vermont which could support a locally higher tornado
threat, especially given the expectation for at least a few
supercells. However, the greater tornado threat will likely remain
north of the border in southern Quebec near the warm front.

..Bentley/Hart.. 06/21/2021

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

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

LAT...LON   43417609 43777614 44387599 44847542 45127459 45167173
            45077147 43807216 42887261 42547439 42827573 43417609

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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.