Mesoscale Discussion 18

Issued

Jan 4, 2017, 2:16 AM EST (07:16 UTC)

Expired

Jan 4, 2017, 8:15 AM EST

In force

6 hr

Issued by

the Storm Prediction Center

Counties Aroostook County, ME, Franklin County, ME, Kennebec County, ME, Oxford County, ME, Penobscot County, ME, Piscataquis County, ME, Somerset County, ME, Carroll County, NH, Coos County, NH

The Caribou radar (KCBW), 131 km from the middle of the area, began a volume at 07:18 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.

260 
ACUS11 KWNS 040717
SWOMCD
SPC MCD 040716 
MEZ000-NHZ000-041315-

Mesoscale Discussion 0018
NWS Storm Prediction Center Norman OK
0116 AM CST Wed Jan 04 2017

Areas affected...Northern New Hampshire and much of Maine

Concerning...Winter mixed precipitation 

Valid 040716Z - 041315Z

SUMMARY...A mix of wintry precipitation, including freezing rain,
sleet, and snow, will continue overnight across parts of Maine and
New Hampshire. Freezing rain rates could reach 0.05 inch/hour, and
the snowfall rates may locally exceed 1 inch/hour.

DISCUSSION...Observational data from area surface observations,
radar, satellite imagery, and local storm reports indicate a narrow
band of generally light freezing rain with some sleet is occurring
across parts of central and Down East Maine and northern NH as of
07Z, while moderate to locally heavy snow is present across northern
Maine. As a shortwave trough evident on water vapor satellite
imagery over northern New England continues moving northeastward
into Canada, ascent associated with this feature and low-level warm
air advection will contribute to continued maintenance of freezing
rain, sleet, and snow potential across parts of Maine through 13Z.

A surface low analyzed just off the coast of Cape Cod, MA will
develop northward to the Maine/New Brunswick border around 12Z, and
strong low-level warm air advection centered around 850 mb will
contribute to a warm nose aloft, while a cold near-surface layer
remains at or below freezing. Result will be potential for a narrow
band of freezing rain and perhaps some sleet across parts of Maine
through the early morning. This band will shift northward some over
the next few hours as the shortwave trough and surface low likewise
develop northward.

Latest short-term guidance is consistent in showing potential for
freezing rain rates around 0.05 inch/hour, and a recent local storm
report from Bangor, Maine recorded 0.15 inch of freezing rain
accumulation already. Across northern Maine, a band of precipitation
evident on the KCBW radar is a mix of sleet and moderate to heavy
snow per dual-pol CC data. The snow band will have the potential to
produce snowfall rates locally in excess of 1 inch/hour. The highest
freezing rain and snowfall rates should begin to diminish beyond
12-13Z as the strongest lift moves northward into Canada.

..Gleason.. 01/04/2017

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

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

LAT...LON   45276711 44766899 44067046 43787108 43807160 44347152
            45277120 45847050 46707011 47536922 47396811 47056767
            45756764 45606733 45276711

Mesoscale Discussions in Maine, 2017Mesoscale Discussions in New Hampshire, 2017Every mesoscale discussion in 2017

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.