Alert archive / New York / Mesoscale Discussions in 2021

Mesoscale Discussion 1413

August 1, 202120 counties in New York; 16 counties in Pennsylvania

The Storm Prediction Center issued this mesoscale discussion at Aug 1, 2021, 12:27 PM EDT for 20 counties in New York; 16 counties in Pennsylvania. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Aug 1, 2021, 12:27 PM EDT (16:27 UTC)
Expired: Aug 1, 2021, 2:30 PM EDT
In force: 2 hr
Issued by: the Storm Prediction Center
Concerning: Severe potential...watch possible
Chance of a watch: 40%

All 36 counties

Albany County, NY, Broome County, NY, Chemung County, NY, Chenango County, NY, Cortland County, NY, Delaware County, NY, Fulton County, NY, Greene County, NY, Madison County, NY, Montgomery County, NY, Onondaga County, NY, Otsego County, NY, Schenectady County, NY, Schoharie County, NY, Schuyler County, NY, Steuben County, NY, Sullivan County, NY, Tioga County, NY, Tompkins County, NY, Ulster County, NY, Bradford County, PA, Cameron County, PA, Clinton County, PA, Elk County, PA, Forest County, PA, Lackawanna County, PA, Luzerne County, PA, Lycoming County, PA, McKean County, PA, Potter County, PA, Sullivan County, PA, Susquehanna County, PA, Tioga County, PA, Venango County, PA, Wayne County, PA, Wyoming County, PA

The radar

The Binghamton radar (KBGM), 36 km from the middle of the area, began a volume at 16:30 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 12:00Z, 4.5 hours before the alert went out and 214 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 1357 m above ground
0-6 km bulk shear: 37 kt
0-1 km storm-relative helicity: 138 m²/s²
0-3 km storm-relative helicity: 179 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

682 
ACUS11 KWNS 011627
SWOMCD
SPC MCD 011627 
NYZ000-PAZ000-011830-

Mesoscale Discussion 1413
NWS Storm Prediction Center Norman OK
1127 AM CDT Sun Aug 01 2021

Areas affected...portions of northern Pennsylvania into central and
eastern New York

Concerning...Severe potential...Watch possible 

Valid 011627Z - 011830Z

Probability of Watch Issuance...40 percent

SUMMARY...Damaging gusts may accompany the stronger storms/linear
segments. A brief instance or two of large hail also cannot be ruled
out. Conditions are being monitored for the need of a WW issuance.

DISCUSSION...MRMS mosaic radar data depicts predominantly linear
convection becoming gradually more widespread immediately ahead of a
cold front approaching the Hudson Valley. Current visible satellite
shows clearing ahead of the ongoing storms, with some CU development
underway, indicative of a destabilizing boundary layer. Cool
temperatures aloft are promoting modest (i.e. 6-6.5 C/km) mid-level
lapse rates atop a warming boundary layer (where up to 7 C/km
low-level lapse rates are developing per 16Z mesoanalysis).
Thunderstorms that can intensify amid these lapse rates may produce
damaging gusts and small hail (with one or two larger hailstones
possible).

However, temperatures/dewpoints well below 80F/60F should result in
relatively short and skinny CAPE profiles this afternoon despite the
aforementioned lapse rates, with MLCAPE likely remaining below 500
J/kg. A near-unidirectional vertical wind profile will also promote
weak to modest deep-layer shear. As such, severe wind/hail may be on
the more isolated/brief side. Nonetheless, conditions will continue
to be monitored for the need of a WW issuance should a more
widespread severe threat become apparent.

..Squitieri/Grams.. 08/01/2021

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

ATTN...WFO...ALY...BGM...BUF...CTP...PBZ...CLE...

LAT...LON   41568036 42167790 43097608 43267485 43147391 42627362
            42147375 41827423 41627462 41397515 41187586 41057649
            41017705 41167888 41568036

Nearby

Mesoscale Discussions in New York, 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.