Mesoscale Discussion 249

Issued

Mar 21, 2016, 7:17 AM EDT (11:17 UTC)

Expired

Mar 21, 2016, 12:00 PM EDT

In force

5 hr

Issued by

the Storm Prediction Center

Counties Cumberland County, ME, Hancock County, ME, Knox County, ME, Lincoln County, ME, Sagadahoc County, ME, Waldo County, ME, Washington County, ME, York County, ME

The Portland,ME radar (KGYX), 109 km from the middle of the area, began a volume at 11:21 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.

600 
ACUS11 KWNS 211118
SWOMCD
SPC MCD 211117 COR
MEZ000-211600-

MESOSCALE DISCUSSION 0249
NWS STORM PREDICTION CENTER NORMAN OK
0617 AM CDT MON MAR 21 2016

AREAS AFFECTED...COASTAL AND INLAND PORTIONS OF SOUTHERN TO DOWNEAST
MAINE

CONCERNING...HEAVY SNOW 

VALID 211117Z - 211600Z

CORRECTED FOR TYPO IN FIRST SENTENCE OF THE DISCUSSION.

SUMMARY...MODERATE TO HEAVY SNOWFALL RATES /WITH GREATEST RATES
AROUND 1 INCH PER HOUR/ WITHIN ONE OR MORE BANDS WILL DEVELOP ACROSS
THE WESTERN PORTION OF THE DISCUSSION AREA THROUGH 12Z AND INTO
DOWNEAST MAINE BY 15Z.  ONCE SNOWFALL BEGINS...IT IS EXPECTED TO
PERSIST THROUGH THE MORNING AND SHOULD LINGER THE LONGEST INTO THE
EARLY AFTERNOON ACROSS PARTS OF DOWNEAST MAINE...WITH A CONTINUATION
OF MODERATE TO HEAVY SNOWFALL RATES.

DISCUSSION...TRENDS IN MOSAIC RADAR IMAGERY AND SURFACE OBSERVATIONS
SINCE 10Z INDICATED TWO BANDS OF MODERATE-HEAVY SNOWFALL RATES HAVE
TRANSITIONED INTO A SINGLE...PRIMARY BAND EXTENDING FROM CENTRAL MA
THROUGH SOUTHEAST NH TO SOUTHWEST AND SOUTH-CENTRAL MAINE.  SNOWFALL
RATES UP TO AROUND 1 INCH PER HOUR HAVE OCCURRED THUS FAR WITHIN THE
BANDS.  

THIS PRIMARY BAND IS LOCATED IN THE WEST/NORTHWEST PERIPHERY OF A
DEEPENING LOW PRESSURE AREA WHICH WAS TRACKING TO THE NORTHEAST FROM
EAST/SOUTHEAST OF 40N/70W EARLY THIS MORNING AND SHOULD REACH
WESTERN PART OF NOVA SCOTIA BY EARLY AFTERNOON.  THE DEEPENING
SURFACE LOW IS IN RESPONSE TO AN INCREASE IN UPWARD VERTICAL MOTION
AS 1/ A SHORTWAVE TROUGH TAKES ON MORE OF A NEGATIVE TILT TODAY
TRACKING THROUGH NEW ENGLAND AND 2/ THE DISCUSSION AREA BECOMES
JUXTAPOSED BENEATH COUPLED STRONG SWLY MID- TO UPPER-LEVEL JETS. 
GIVEN THE AFOREMENTIONED AND ALREADY FORMED BAND WITH ONGOING
MODERATE TO HEAVY SNOWFALL RATES...THE 06Z NAM APPEARS TO BE THE
BETTER MODEL WHICH SUGGESTED FAVORABLE MIDLEVEL /600-MB AND 700-MB/
FRONTOGENETICAL FORCING WILL PERSIST AND SPREAD ACROSS SOUTHERN AND
DOWNEAST MAINE THROUGH AT LEAST THIS MORNING.  THUS...ONE OR MORE
BANDS OF SNOW WILL BE LIKELY.  THIS INCREASING ASCENT WILL CONTINUE
TO OCCUR WITHIN THE DENDRITIC GROWTH ZONE SUPPORTIVE OF THE HEAVIER
SNOWFALL RATES.  AS THE SURFACE LOW MOVES CLOSER TO NOVA SCOTIA...
THE ORIENTATION OF THE BANDS BEING SW-NE IS EXPECTED TO SHIFT TO
SSW-NNE ACROSS THE DISCUSSION AREA...AS THIS REGION BECOMES
INFLUENCED MORE FROM THE NORTHWEST PERIPHERY OF THIS STORM SYSTEM.

..PETERS.. 03/21/2016

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

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

LAT...LON   43656991 43127073 43467094 43977038 44666943 45526798
            45676757 45126692 44786712 44276797 43866939 43656991

Mesoscale Discussions in Maine, 2016Every mesoscale discussion in 2016

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.