Mesoscale Discussion 1715

Issued

Sep 8, 2021, 4:15 PM EDT (20:15 UTC)

Expired

Sep 8, 2021, 6:15 PM EDT

In force

2 hr

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch possible

Chance of a watch

40%

The Binghamton radar (KBGM), 154 km from the middle of the area, began a volume at 20:15 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 491Sep 8, 7:55 PM EDT

235 
ACUS11 KWNS 082016
SWOMCD
SPC MCD 082015 
NYZ000-NJZ000-PAZ000-MDZ000-082215-

Mesoscale Discussion 1715
NWS Storm Prediction Center Norman OK
0315 PM CDT Wed Sep 08 2021

Areas affected...Eastern Pennsylvania...northwest New
Jersey...southeastern New York

Concerning...Severe potential...Watch possible 

Valid 082015Z - 082215Z

Probability of Watch Issuance...40 percent

SUMMARY...The threat for severe weather will gradually increase into
early evening across parts of the Mid-Atlantic. Damaging wind gusts
and isolated large hail are the main concerns. A conditional tornado
threat exists in eastern Pennsylvania and southeastern New York.
Timing and coverage of severe storms is uncertain. Trends will be
monitored for a possible watch.

DISCUSSION...The 18Z observed Albany sounding showed relatively weak
capping, but signs of subsidence aloft. This general profile seems
to capture what is being observed on visible satellite across the
Mid-Atlantic. Areas of cumulus, particularly within eastern
Pennsylvania where temperatures are in the mid 80s F, have shown a
gradual increase in depth. The subsidence aloft is likely limiting
vertical development. With time, and additional mid-level cooling,
storms should be able to initiate in the warm sector. Farther west,
warm conveyor belt precipitation has generally been weak with only
small embedded convective elements. A gradual increase in convective
character may occur as this activity encounters more buoyant air.

The greatest severe potential likely exists with any warm sector
storms that can develop. Damaging winds, isolated large hail, and
perhaps a tornado could occur. Eastern Pennsylvania into
southeastern New York would be the favored zone for low-level
rotation given slightly backed surface winds. Storms within the warm
conveyor belt should exhibit a more linear storm mode and pose
primarily a damaging wind gust risk.

There is some uncertainty as to when storms will intensify this
afternoon. Much of the guidance suggest it may not be until around 
or after 8 PM EDT. With potentially unfavorable timing diurnally,
trends will have to continue to be monitored for a possible watch
later this afternoon.

..Wendt/Hart.. 09/08/2021

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

ATTN...WFO...OKX...ALY...PHI...BGM...CTP...LWX...

LAT...LON   39887582 39527639 39527675 39657708 39877720 40147709
            40387698 40697677 40887660 40987650 41707602 42567512
            42937433 42527370 41857365 40957458 39887582

Mesoscale Discussions in Pennsylvania, 2021Mesoscale Discussions in New York, 2021Mesoscale Discussions in New Jersey, 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.