Alert archive / New York / Severe Thunderstorm Watches in 2021

Severe Thunderstorm Watch 396

July 27, 20216 states

The Storm Prediction Center issued this severe thunderstorm watch at Jul 27, 2021, 2:47 PM EDT for 6 states. It was in force for 6 hr.

The area

The outline as issued.

The facts

Issued
Jul 27, 2021, 2:47 PM EDT (18:47 UTC)
Expired
Jul 27, 2021, 8:27 PM EDT
In force
6 hr
Issued by
the Storm Prediction Center
Largest hail expected
1 in
Strongest gust expected
60 kt
All 38 counties

Capitol Planning Region, CT, Northeastern Connecticut Planning Region, CT, Northwest Hills Planning Region, CT, Berkshire County, MA, Bristol County, MA, Essex County, MA, Franklin County, MA, Hampden County, MA, Hampshire County, MA, Middlesex County, MA, Norfolk County, MA, Plymouth County, MA, Suffolk County, MA, Worcester County, MA, Cheshire County, NH, Hillsborough County, NH, Albany County, NY, Columbia County, NY, Dutchess County, NY, Fulton County, NY, Greene County, NY, Hamilton County, NY, Herkimer County, NY, Montgomery County, NY, Rensselaer County, NY, Saratoga County, NY, Schenectady County, NY, Schoharie County, NY, Sullivan County, NY, Ulster County, NY, Warren County, NY, Washington County, NY, Bristol County, RI, Kent County, RI, Newport County, RI, Providence County, RI, Bennington County, VT, Windham County, VT

The radar

The Albany radar (KENX), 54 km from the middle of the area, began a volume at 18:46 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.

What SPC expected

The probabilities SPC published with the watch, for the watch area over its life.

Two or more tornadoes
5%
One or more EF2 to EF5 tornadoes
2%
Ten or more severe wind reports
40%
One or more gusts of 65 knots or more
20%
Ten or more severe hail reports
10%
One or more hailstones of 2 inches or more
5%
Six or more combined severe hail and wind reports
60%

Warnings issued inside it

14 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

IssuedProductOfficeCountiesLasted
Jul 27, 2:51 PM EDTSevere Thunderstorm WarningALYFulton, Montgomery, Saratoga, Schenectady54 min
Jul 27, 3:20 PM EDTSevere Thunderstorm WarningALYHerkimer23 min
Jul 27, 3:59 PM EDTSevere Thunderstorm WarningALYAlbany, Rensselaer, Saratoga46 min
Jul 27, 4:22 PM EDTSevere Thunderstorm WarningBGMDelaware, Sullivan53 min
Jul 27, 4:30 PM EDTSevere Thunderstorm WarningALYBerkshire43 min
Jul 27, 4:30 PM EDTSevere Thunderstorm WarningGYXCheshire, Sullivan45 min
Jul 27, 4:34 PM EDTSevere Thunderstorm WarningALYAlbany, Greene, Schoharie21 min
Jul 27, 5:04 PM EDTSevere Thunderstorm WarningBOXFranklin, Hampden, Hampshire56 min
Jul 27, 5:09 PM EDTSevere Thunderstorm WarningBGMSullivan18 min
Jul 27, 5:19 PM EDTSevere Thunderstorm WarningALYBerkshire41 min
Jul 27, 5:34 PM EDTSevere Thunderstorm WarningBOXCapitol Planning Region56 min
Jul 27, 6:33 PM EDTSevere Thunderstorm WarningBOXEssex, Middlesex, Norfolk, Plymouth, Suffolk, Worcester57 min
Jul 27, 7:01 PM EDTSevere Thunderstorm WarningBOXNortheastern Connecticut Planning Region44 min
Jul 27, 7:26 PM EDTSevere Thunderstorm WarningBOXBristol, Essex, Middlesex, Norfolk, Plymouth, Suffolk and 1 more64 min

Discussions around it

SPC mesoscale discussions over the same counties from four hours before the watch to its end.

The nearest sounding before it

Albany, NY (KALY), launched 12:00Z, 6.8 hours before the alert went out and 43 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-pSkew-T log-p diagram, Albany, NY at 12:00Z on 2021-07-27Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Albany, NY at 12:00Z on 2021-07-27The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 35 square meters per square second.19395878Sfc1 km3 km6 km9 kmRMLM
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
1464 m above ground
0-6 km bulk shear
44 kt
0-1 km storm-relative helicity
35 m²/s²
0-3 km storm-relative helicity
46 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

109 
WWUS20 KWNS 271845
SEL6  
SPC WW 271845
CTZ000-MAZ000-NHZ000-NYZ000-PAZ000-RIZ000-VTZ000-CWZ000-280200-

URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 396
NWS Storm Prediction Center Norman OK
245 PM EDT Tue Jul 27 2021

The NWS Storm Prediction Center has issued a

* Severe Thunderstorm Watch for portions of 
  Northern Connecticut
  Massachusetts
  Southern New Hampshire
  Eastern New York
  Northeast Pennsylvania
  Northern Rhode Island
  Southern Vermont
  Coastal Waters

* Effective this Tuesday afternoon and evening from 245 PM until
  1000 PM EDT.

* Primary threats include...
  Scattered damaging wind gusts to 70 mph possible

SUMMARY...Fast-moving thunderstorms over central New York will track
eastward across the watch area this afternoon and evening.  Damaging
winds will be possible with the strongest storms.

The severe thunderstorm watch area is approximately along and 55
statute miles north and south of a line from 45 miles north
northwest of Monticello NY to 10 miles southeast of Boston MA. For a
complete depiction of the watch see the associated watch outline
update (WOUS64 KWNS WOU6).

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A Severe Thunderstorm Watch means conditions are
favorable for severe thunderstorms in and close to the watch area.
Persons in these areas should be on the lookout for threatening
weather conditions and listen for later statements and possible
warnings. Severe thunderstorms can and occasionally do produce
tornadoes.

&&

OTHER WATCH INFORMATION...CONTINUE...WW 395...

AVIATION...A few severe thunderstorms with hail surface and aloft to
1 inch. Extreme turbulence and surface wind gusts to 60 knots. A few
cumulonimbi with maximum tops to 500. Mean storm motion vector
29035.

...Hart

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Jul 27, 2:01 PM EDTMesoscale DiscussionSPC89 min
Jul 27, 4:36 PM EDTMesoscale DiscussionSPC84 min
Jul 27, 6:09 PM EDTMesoscale DiscussionSPC96 min
Jul 27, 10:33 AM EDTMesoscale DiscussionSPCAllegany, Cattaraugus, Cayuga, Erie, Genesee, Livingston and 9 more117 min
Jul 27, 11:12 AM EDTSevere Thunderstorm WatchSPCAllegany, Broome, Cattaraugus, Cayuga, Chautauqua, Chemung and 23 more7 hr

Nearby

Severe Thunderstorm Watches in New York, 2021Severe Thunderstorm Watches in Massachusetts, 2021Severe Thunderstorm Watches in Connecticut, 2021Every severe thunderstorm watch 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.