Strong upper-level energy currently pushing across the central U.S. will reach the East Coast later Tuesday and initiate the rapid development of a coastal storm.
This coastal storm will "bomb-out" meaning extreme, rapid intensification with strong winds and heavy precipitation quickly taking hold later Tuesday night into Wednesday from extreme eastern New England then up into Atlantic Canada.
This could be the most intense storm of the season for the Maritimes, as the central pressure of the storm could bottom out as low as 956 mb (28.23 inches) on Wednesday.
The map below shows expected snow in inches. ( dark blue 12-18 inches=30-45 cm, light blue 6-12 inches=15-30 cm, white 3-6 inches=8-15 cm and grey 1-3 inches =2-8 cm)
In addition to the snow, winds will likely gust to hurricane force Wed/Wed evening over parts of Nova Scotia, PEI, southeastern New Brunswick and southwestern Newfoundland resulting in power outages and downed trees/branches.
Below is the ECMWF model forecast for highest wind gusts in knots at 10 meters above the surface valid Wednesday evening.
The center of the storm will track very close to Sydney, Nova Scotia late Wednesday night then slowly weaken as it tracks up through western Newfoundland early Thursday.
The expected track will likely lead to a change to sleet or rain over eastern Nova Scotia Wednesday evening and southern Newfoundland later Wednesday night, but not before many hours of heavy, windswept snow. This same region that mixes or changes over will also likely get dry slotted (precipitation ends or becomes light/intermittent) Wednesday evening.
The Halifax area of Nova Scotia will be all snow, but some mid-level drier air may wrap in from the south later in the day Wednesday and cause the snow to diminish for a time, thus I believe the heaviest accumulations will be north and west of Halifax.
It appears that the worst of the blizzard will impact extreme southeastern New Brunswick, including Moncton, northern and western half of Nova Scotia and all of PEI, including Charlottetown.
In the St. John's, NL area there will be about 3-8 cm of snow Wednesday evening before a quick change to a wind-driven rain.
Some forecast model clues through the end of August and an update on global sea surface temperatures.
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Latest weekly clues to the long range forecast through mid-August.
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Severe thunderstorm threat later Thursday and a general look at the upcoming weather pattern.
Latest long-range update and a look at global ocean temperatures.