Alert archive / Maine / Mesoscale Discussions in 2011

Mesoscale Discussion 41

January 21, 20119 counties in Maine; 4 counties in Massachusetts; Rockingham County, Strafford County, New Hampshire

The Storm Prediction Center issued this mesoscale discussion at Jan 21, 2011, 7:32 AM EST for 9 counties in Maine; 4 counties in Massachusetts; Rockingham County, Strafford County, New Hampshire. It was in force for 5 hr.

The area

The outline as issued.

The facts

Issued: Jan 21, 2011, 7:32 AM EST (12:32 UTC)
Expired: Jan 21, 2011, 1:00 PM EST
In force: 5 hr
Issued by: the Storm Prediction Center

Counties Essex County, MA, Norfolk County, MA, Plymouth County, MA, Suffolk County, MA, Androscoggin County, ME, Cumberland County, ME, Hancock County, ME, Kennebec County, ME, Lincoln County, ME, Sagadahoc County, ME, Waldo County, ME, Washington County, ME, York County, ME, Rockingham County, NH, Strafford County, NH

The radar

The Portland,ME radar (KGYX), 78 km from the middle of the area, began a volume at 12:32 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

Gray, ME (KGYX), launched 12:00Z, 0.5 hours before the alert went out and 78 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: 558 m above ground
0-6 km bulk shear: 93 kt
0-1 km storm-relative helicity: 360 m²/s²
0-3 km storm-relative helicity: 420 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.

231 
ACUS11 KWNS 211233
SWOMCD
SPC MCD 211232
MEZ000-MAZ000-NHZ000-211800-

MESOSCALE DISCUSSION 0041
NWS STORM PREDICTION CENTER NORMAN OK
0632 AM CST FRI JAN 21 2011

AREAS AFFECTED...PORTIONS NERN MA...SERN NH...SRN MAINE.

CONCERNING...HEAVY SNOW

VALID 211232Z - 211800Z

ALTHOUGH HEAVIEST PRECIP SHOULD SHIFT FROM SERN MA ACROSS GULF OF
MAINE THROUGH AT LEAST 16Z...NWRN PORTION OF PRECIP PLUME MAY
PRODUCE 1-2 INCH/HOUR SNOW RATES AS IT SHIFTS NEWD OVER DISCUSSION
AREA...MAINLY NEAR AND SE OF I-95.  ZONE OF HEAVIEST PRECIP THEN MAY
MAKE LANDFALL ACROSS DOWN-EAST MAINE AFTER ABOUT 17Z...BRINGING
POTENTIAL FOR CONVECTIVE SNOW BURSTS WITH LOCALLY HIGHER RATES.
BRIEF SNOW-RAIN TRANSITION MAY OCCUR ALONG IMMEDIATE DOWN-EAST COAST
IN 18-19Z TIME FRAME AS WAA FORCES NEAR-SFC TEMPS ABOVE FREEZING
TEMPORARILY...PRIOR TO CAA AND REDUCTION IN PRECIP THAT SHOULD
FOLLOW CYCLONE PASSAGE.  SNOW SHOULD REMAIN PREDOMINANT PRECIP MODE
ANY APPRECIABLE DISTANCE INLAND.

12Z SFC ANALYSIS SHOWS ELONGATED SFC LOW OVER CENTRAL/SWRN LONG
ISLAND.  CYCLONE IS FCST TO STRENGTHEN AND CONSOLIDATE AS IT CROSSES
CAPE COD DURING 14-15Z TIME RANGE.  LOW THEN SHOULD DEEPEN FURTHER
OVER WATERS OFFSHORE MAINE WITH APCH OF STG MID-UPPER SHORTWAVE
TROUGH NOW EVIDENT IN MOISTURE CHANNEL IMAGERY OVER WRN PORTIONS
NY/PA.  AS THIS OCCURS...ELEVATED LOW-LEVEL WAA CONVEYOR SHOULD
BECOME MORE INTENSE AROUND ITS NRN SEMICIRCLE.  RELATED LLJ --
POTENTIALLY REACHING 850-MB SPEEDS OF 60-70 KT OFFSHORE -- WILL
TRANSPORT INCREASING MOISTURE INTO LOWER PORTIONS OF STG 750-850 MB
LAYER FRONTOGENETIC FORCING REGIME THAT IS FCST TO SHIFT NEWD OVER
COASTAL MAINE.  ERN PORTION OF FRONTOGENESIS MAX WILL BE JUXTAPOSED
WITH NOSE OF STRONGEST LLJ SEGMENT...AND AS SUCH...MOST INTENSE ZONE
OF 285-291 K ISENTROPIC ASCENT...BASED ON RUC PROGS THAT VERIFY WELL
WITH RESPECT TO CURRENT POSITION OF STRONGEST PRECIP AND LOW-LEVEL
LIFT.  UPPER PORTION OF ZONE OF STRONGEST UVV ALSO SHOULD REACH INTO
IDEAL DENDRITIC GROWTH LAYER...BASED ON FCST SOUNDINGS THAT RESEMBLE
12Z CHH RAOB BUT WITH SUBFREEZING BOUNDARY LAYER AND SOMEWHAT COOLER
MID-UPPER TEMPS.

..EDWARDS.. 01/21/2011

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

ATTN...WFO...CAR...GYX...BOX...

LAT...LON   41917053 42177139 42837133 43417101 44237031 44866940
            45196848 45296742 45156737 45196718 44976704 44806694
            44606730 44616747 44446754 44546766 44336807 44456835
            44236826 44086836 44206862 44016859 43996866 44036885
            44116892 44186896 44026906 43926925 43856950 43716980
            43746997 43587018 43407039 43287056 43167057 43097061
            42887083 42637075 42707060 42567059 42347100 42247075
            41987068 41917053

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jan 21, 12:36 PM EST	Mesoscale Discussion	SPC	Penobscot, Piscataquis	3 hr
Jan 21, 12:30 AM EST	Mesoscale Discussion	SPC	Berkshire, Bristol, Essex, Franklin, Hampden, Hampshire and 5 more	5 hr

Nearby

Mesoscale Discussions in Maine, 2011 Mesoscale Discussions in Massachusetts, 2011 Mesoscale Discussions in New Hampshire, 2011 Every 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.