Alert archive / Connecticut / Mesoscale Discussions in 2011

Mesoscale Discussion 8

January 7, 2011Berkshire County, Massachusetts; 4 counties in New York

The Storm Prediction Center issued this mesoscale discussion at Jan 7, 2011, 11:46 AM EST for Berkshire County, Massachusetts; 4 counties in New York. It was in force for 4 hr.

The area

The outline as issued.

The facts

Issued
Jan 7, 2011, 11:46 AM EST (16:46 UTC)
Expired
Jan 7, 2011, 3:45 PM EST
In force
4 hr
Issued by
the Storm Prediction Center

Counties Berkshire County, MA, Columbia County, NY, Dutchess County, NY, Nassau County, NY, Suffolk County, NY

The radar

The Brookhaven radar (KOKX), 75 km from the middle of the area, began a volume at 16:49 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

Brookhaven, NY (KOKX), launched 12:00Z, 4.8 hours before the alert went out and 75 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, Brookhaven, NY at 12:00Z on 2011-01-07Temperature 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, Brookhaven, NY at 12:00Z on 2011-01-07The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 126 square meters per square second.1939587897Sfc1 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
761 m above ground
0-6 km bulk shear
58 kt
0-1 km storm-relative helicity
126 m²/s²
0-3 km storm-relative helicity
128 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

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

469 
ACUS11 KWNS 071647
SWOMCD
SPC MCD 071646
RIZ000-CTZ000-NYZ000-MAZ000-072045-

MESOSCALE DISCUSSION 0008
NWS STORM PREDICTION CENTER NORMAN OK
1046 AM CST FRI JAN 07 2011

AREAS AFFECTED...PARTS OF THE LOWER HUDSON VALLEY / FAR SWRN MA / CT
/ LONG ISLAND

CONCERNING...HEAVY SNOW

VALID 071646Z - 072045Z

SWATH OF PRIMARILY MODERATE SNOWFALL RATES OVER NJ AND NYC METRO
LATE THIS MORNING IS EXPECTED TO CONSOLIDATE IN A
NARROW/INTENSIFYING BAND OF HEAVY SNOWFALL RATES EXCEEDING 1 INCH
PER HOUR AS IT DEVELOPS NEAR THE LOWER HUDSON VALLEY VICINITY AND
MOVES EWD ACROSS MOST OF CT BY EARLY EVENING.

RECENT SURFACE ANALYSIS PLACES A WELL-DEFINED TROUGH EXTENDING NW-SE
FROM THE MOHAWK VALLEY TO NRN NJ.  A COLD FRONT EXTENDS SWD FROM NJ
TO THE TIDEWATER VICINITY WHILE A RESIDUAL BAROCLINIC ZONE IS DRAPED
ACROSS NEW ENGLAND.  A LOW LEVEL THETA-E RIDGE EXTENDS NWWD FROM 150
MI S BID TO THE LOWER HUDSON VALLEY.  LONG LOOP OF WATER VAPOR
IMAGERY AT 1630Z SHOWS A PV ANOMALY BEGINNING TO EJECT NEWD FROM
NEAR THE MASON-DIXON LINE TOWARDS THE NYC METRO.  THIS IS EMBEDDED
WITHIN A STRONG CYCLONIC FLOW REGIME PROVIDED BY LEFT EXIT REGION OF
A 150 KT SPEED MAX OVER THE SRN APPALACHIANS/CAROLINAS.  AS THIS
OCCURS...LARGE SCALE ASCENT PROVIDED BY UPPER SYNOPTIC FORCING WILL
FAVORABLY JUXTAPOSE WITH THE PREVIOUSLY DESCRIBED LOW LEVEL THETA-E
PLUME--THEREBY ALLOWING A GREATER UPWARD VERTICAL MOTION RESPONSE.
ADDITIONAL LOW LEVEL FRONTOGENETIC FORCING SHOULD LEND SUPPORT IN
THE EVENTUAL NARROWING/INTENSIFICATION OF SHALLOW CONVECTION.

SUITE OF LATEST CONVECTIVE ALLOWING MODELS REINFORCES THE IDEA OF A
BAND OF SNOW DEVELOPING BY THE 18-20Z TIMEFRAME AND MOVING W TO E
ACROSS MUCH OF CT THROUGH 00Z.  THIS BAND WILL PROBABLY LEAD TO A
QUICK BURST OF HEAVY SNOWFALL RATES EXCEEDING 1 INCH/HR FOR A FEW
HOURS.  FARTHER S OVER LONG ISLAND...ALTHOUGH TEMPS HAVE WARMED INTO
THE MID-UPPER 30S IN PLACES...COLD PROFILE ALOFT WILL PROBABLY
SUPPORT PRIMARILY WET SNOW /PERHAPS BRIEF INTERMITTENT LIGHT
RAIN/...ESPECIALLY DURING THE HEAVIEST PRECIP RATES.

..SMITH.. 01/07/2011

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

ATTN...WFO...BOX...OKX...ALY...

LAT...LON   40607362 42187379 42457360 42477330 41917222 41197166
            40787262 40607362

Nearby

Mesoscale Discussions in Connecticut, 2011Mesoscale Discussions in New York, 2011Mesoscale Discussions in Massachusetts, 2011Every mesoscale discussion in 2011

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.