By Brandon Buckingham, AccuWeather Meteorologist
Snow covers cars in Paradise, Newfoundland, Canada, Jan. 18, 2020, in this image obtained from social media. (Kim Porter/via REUTERS)
A storm system that is expected to barely brush the
East Coast of the United States late in the week will end up bringing the brunt of the impactful weather to Atlantic Canada over the weekend.
The upcoming system is set to track over the same region that experienced record-breaking snowfall and storm-force wind gusts less than two weeks ago.
The atmospheric disturbance that will eventually bring unsettled weather to Atlantic Canada is currently taking shape over the northern Gulf of Mexico.
AccuWeather meteorologists will continue to monitor the storm as it first takes aim across the Southeast on Friday. With a lack of an atmospheric blocking pattern, the storm system is expected to maintain a quick pace as it is forecast to brush by the East Coast Friday night into Saturday.
As warm Atlantic air clashes with a cooler continental air mass in place over the Northeast, rapid strengthening is expected to take place over the ocean through the day on Saturday. As a result, increasingly gusty winds are expected to develop across much of Nova Scotia by Saturday evening.
Depending on the magnitude of strengthening, it is possible that bombogenesis may take place this weekend, which would make it the second
bomb cyclone to strike part of the region in a space of two weeks. Bombogenesis is generally defined as when the central pressure of a storm system drops at a rate of at least 0.71 of an inch of mercury in 24 hours.
As the storm system tracks closer to Atlantic Canada during the day Saturday, the location of the center of the storm system will play a major role in determining the expected impacts across the region. A shift of only 50 miles (80 kilometers) in the expected track can essentially make or break a forecast in a storm situation like this.
Current forecasts bring the center of the storm system very close to the coast of Nova Scotia. Moderate to heavy snow is likely to develop Saturday night into Sunday morning across much of the province, as well as Prince Edward Island. However, a change to rain will take place in the southeast part of Nova Scotia and then in southeastern Newfoundland.
Depending on the magnitude of the wind, blizzard conditions may be possible for a time where rain does not mix in over the northwestern parts of Nova Scotia and Newfoundland.
The transition between rain and snow will likely hang very close to the coast as the storm tracks northeastward this weekend. For places like Halifax, this will make all the difference in the forecast.
If the center of circulation can remain far enough offshore, that will result in the warmer air staying out to sea, yielding nearly all snow across the province. This scenario would bring heavy snow to the Halifax area with limited or no changeover to rain during the storm. In this scenario, snowfall totals of 20-30 centimeters (8-12 inches), with locally higher amounts could be realized.
A track closer to the coast will yield more mixed precipitation and much lower snowfall totals for coastal Nova Scotia. If the storm system trends toward this solution, much of coastal Nova Scotia could expect 10 centimeters (4 inches) or less.
Currently, a changeover to an icy mix or plain rain is in the forecast for the Halifax area sometime late Saturday night into Sunday morning before switching back to snow briefly on the back end of the storm. Again, the duration of this changeover will make major differences in the total snowfall accumulation.
Part of northern Nova Scotia and western Newfoundland are forecast to receive 30-45 centimeters of snow with an AccuWeather Local StormMax™ of 50 centimeters.
Newfoundland will experience the brunt of the storm on Sunday. Recall that less than two weeks ago, a storm system caused the city of St. John's to undergo a state of emergency for days following the storm as over 60 centimeters (2 feet) of snow fell, creating snowdrifts over 5 meters (16 feet) in spots.
A resident makes their way through the snow in St. John's, Newfoundland on Saturday, Jan. 18, 2020. The state of emergency ordered by the city of St. John's is still in place, leaving businesses closed and vehicles off the roads in the aftermath of the major winter storm that hit the Newfoundland and Labrador capital. (Andrew Vaughan/The Canadian Press via AP)
If the storm system continues along its expected track, a changeover to rain would likely occur around St. John's sometime on Sunday as warm air surges northward into Newfoundland.
Regardless of precipitation type, additional unsettled weather will not fare well for the recovery efforts across Newfoundland this weekend. If rain comes down for a time, it will act to compact the snowdrifts in place, but it will also raise the risk for flooding across the region. Where most of the precipitation falls as snow, new snowdrifts will just pile up on the existing snowpack in place, hindering cleanup efforts.
Currently, a "mainly snow" scenario looks unlikely across southeastern Newfoundland.
"While not enough rain is likely to fall to wash away all the snow and lead to disastrous flooding, street flooding can occur where massive piles of snow are blocking storm drains," according to AccuWeather Senior Meteorologist Alex Sosnowski.
"The deep snowpack is likely to absorb much of the rain, but that added water content in the snow may have to be dealt with as potential major flooding later in the season during a rapid thaw and/or rainstorm," Sosnowski said.
One bit of good news is that this storm system will likely move in and out of the region rather quickly, limiting the potential for major snowfall accumulations. In general, most locales will receive around 12-18 hours of wintry weather before the storm moves out.
"Although the storm this weekend is likely to be significant, it's not the same caliber of storm that hit on Jan. 19," Sosnowski said.
The storm is expected to lift off into the north
Atlantic during the day Monday, bringing an end to the winter weather and gusty winds. Aside from a few hit-or-miss snow showers early week, generally quiet conditions are expected into midweek in the wake of the storm.
