Alert archive / Vermont / Mesoscale Discussions in 2012

Mesoscale Discussion 1391

July 4, 20124 states

The Storm Prediction Center issued this mesoscale discussion at Jul 4, 2012, 4:48 PM EDT for 4 states. It was in force for 57 min.

The area

The outline as issued.

The facts

Issued: Jul 4, 2012, 4:48 PM EDT (20:48 UTC)
Expired: Jul 4, 2012, 5:45 PM EDT
In force: 57 min
Issued by: the Storm Prediction Center
Chance of a watch: 40%

All 35 counties

Androscoggin County, ME, Cumberland County, ME, Franklin County, ME, Oxford County, ME, York County, ME, Belknap County, NH, Carroll County, NH, Coos County, NH, Grafton County, NH, Merrimack County, NH, Strafford County, NH, Sullivan County, NH, Clinton County, NY, Essex County, NY, Franklin County, NY, Hamilton County, NY, Herkimer County, NY, Saratoga County, NY, St. Lawrence County, NY, Warren County, NY, Washington County, NY, Addison County, VT, Bennington County, VT, Caledonia County, VT, Chittenden County, VT, Essex County, VT, Franklin County, VT, Grand Isle County, VT, Lamoille County, VT, Orange County, VT, Orleans County, VT, Rutland County, VT, Washington County, VT, Windham County, VT, Windsor County, VT

The radar

The Burlington radar (KCXX), 30 km from the middle of the area, began a volume at 20:48 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 watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

Severe Thunderstorm Watch 463Jul 4, 6:10 PM EDT

The nearest sounding before it

Albany, NY (KALY), launched 12:00Z, 8.8 hours before the alert went out and 187 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: 97 J/kg
Mixed-layer CIN: -69 J/kg
Mixed-layer LCL: 864 m above ground
0-6 km bulk shear: 31 kt
0-1 km storm-relative helicity: 175 m²/s²
0-3 km storm-relative helicity: 167 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.3

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

752 
ACUS11 KWNS 042048
SWOMCD
SPC MCD 042048 
MEZ000-NHZ000-VTZ000-NYZ000-042145-

MESOSCALE DISCUSSION 1391
NWS STORM PREDICTION CENTER NORMAN OK
0348 PM CDT WED JUL 04 2012

AREAS AFFECTED...NRN NY / VT / NH / SRN MAINE

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 042048Z - 042145Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...ISOLD-SCTD STORMS WILL CONTINUE TO MOVE SEWD FROM NEAR THE
CANADIAN BORDER INTO THE ADIRONDACKS AND PORTIONS OF NEW ENGLAND.  A
LARGE HAIL/DMGG WIND THREAT WILL ACCOMPANY THE STRONGER STORMS.

DISCUSSION...SATELLITE IMAGERY SHOWS A POTENT SHORTWAVE TROUGH
MOVING ACROSS SRN QUEBEC AND INTENSE STORMS ARISING OUT OF A CU
FIELD OVER THE REGION DURING THE PAST FEW HOURS.  AS THE VIGOROUS
MID LEVEL VORT MAX CONTINUES TO APPROACH NEW ENGLAND...SUPPORT FOR
STRONG-SEVERE STORM DEVELOPMENT WILL LIKELY CONTINUE THROUGH THE
LATE AFTERNOON AND INTO THE EARLY EVENING HOURS.  DESPITE MODEST
MID-LEVEL LAPSE RATES...STRONG HEATING HAS YIELDED TEMPS RISING INTO
THE 80S WITH DEWPOINTS IN THE LOWER-MID 60S AND A MODERATELY
UNSTABLE AIRMASS /1500-2000 J/KG MLCAPE PER RAP FORECAST SOUNDINGS/.
STRONG NWLY FLOW ALOFT ACCOMPANYING THE APPROACHING UPPER LEVEL
DISTURBANCE IS CONTRIBUTING TO AROUND 40 KTS 0-6 KM SHEAR AND
SUPPORTIVE OF ORGANIZED SEVERE STORMS...INCLUDING THE POTENTIAL FOR
A SUPERCELL OR TWO.  MARGINALLY SEVERE HAIL AND WIND DAMAGE WILL BE
THE THREATS WITH THE STRONGER STORMS.

..SMITH/THOMPSON.. 07/04/2012

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...GYX...BOX...BTV...ALY...BUF...

LAT...LON   44487577 44967483 45007185 45507065 44456976 43347051
            42857323 43327484 44487577

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 4, 6:10 PM EDT	Severe Thunderstorm Watch	SPC	Androscoggin, Cumberland, Oxford, York	4 hr
Jul 4, 8:38 AM EDT	Mesoscale Discussion	SPC	Chautauqua	2 hr
Jul 4, 6:46 PM EDT	Mesoscale Discussion	SPC	Bronx, Broome, Delaware, Kings, New York, Orange and 4 more	59 min

Nearby

Mesoscale Discussions in Vermont, 2012 Mesoscale Discussions in New York, 2012 Mesoscale Discussions in New Hampshire, 2012 Every mesoscale discussion in 2012

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.