As discussed in our latest article, strong pressure anomalies are underway in the stratospheric Polar Vortex. Disruptions around the Vortex established the first powerful Arctic Cold Outbreak in Canada and the United States.
This weekend, the Arctic cold pool will intensify over the northern U.S. and Canada, gradually spreading towards the deep South and East Coast before Halloween and into the early days of the final autumn month. Winter weather with snow is forecast to grip central North America into freezing cold in the coming days.
The Arctic cold pool gradually strengthened over Canada early this week and has now spread into the northern States. The northernmost states, Idaho, Montana, Wyoming, and western Dakotas, are already in deep freeze, as we see from the Thursday daytime high temperatures below.
Significantly warmer air mass remains over the rest of the Contiguous U.S., ahead of the Arctic front. The front is forecast to flip these temperatures much colder over the weekend and next week.
While those in Montana and Wyoming have heavy snow and freezing cold, millions across the rest of the U.S. are experiencing unseasonably warm days with daytime highs from the mid to upper-80s.
Here is a quick overview of the Arctic cold temperature blast across Canada and the United States over the weekend across Halloween and early November.
We can see the temperature anomaly will be quite extreme for this period, with significantly colder than normal days.
The official NOAA temperature forecast for the final days of October clearly indicates that the massive cold air anomaly will overspread the U.S. from the north.
Warmer than-normal temperatures will remain over the eastern United States but are forecasted to be flushed away as the Arctic cold wave progresses south and east early next week.
A DRAMATIC WEATHER PATTERN SHIFT OVER THE NORTH AMERICA
The general weather pattern over North America reveals a deep trough has established beneath the disrupted stratospheric Polar Vortex, gradually advancing south and east across Canada and the United States.
Over the weekend, the progress of the trough will sharpen the temperature and pressure gradient across the United States. A strong surface high-pressure system will establish under the cold across northern and northwestern CONUS, while lower pressure remains across the south and Southeast U.S.
This will help to transport the Arctic cold air mass towards the south and east over the weekend, sharpening the temperature contrast between the north and south.
The strong cold pool will first remain over the northern High Plains and Dakotas until Saturday when it spreads further south across the Great Plains towards Sunday.
The sharpest temperature gradient will be along the Arctic front. By the afternoon, the cold will reach the central Plains early Sunday and central Texas. Spread towards the Gulf Coast by Sunday evening.
Therefore, there will be a huge contrast in temperature between the northern states and the southeastern parts of the CONUS on Saturday and Sunday. While areas from Texas along the Gulf Coast to the East Coast will experience significantly warmer than normal weather, it will be much colder further north.
Peak daytime temperatures on Saturday will be in the mid to upper 80s across the South and Southeast U.S. but in the freezing mid-20s across Wyoming, Montana, and Dakotas.
This large and strong Arctic cold pool will advance south and east on Sunday and Monday. With dramatically lower temperature changes in a few hours as the Arctic front passes.
SIGNIFICANT SNOW AMOUNT COVERS NORTHERN U.S. AND SOUTHERN CANADA
Moderate snowfall that has already accumulated across the northern Rockies and Plains will remain on the ground as massive cold overspreads the region in the coming days. More heavy snow will follow across the Upper Midwest into Ontario, Canada, along the first frontal system on Friday.
Areas further south will see more snow on Saturday when the Arctic front triggers a new surface low across the central Rockies into the Midwest.
Heavy snowfall will be established across the central Rockies by Saturday morning, with southern Wyoming and northern Colorado under the heaviest snow. Accompanied by strong winds, blowing snow will create low visibility and travel disruptions.
This new snowstorm will move across the Midwest through Saturday night, dumping a few inches across Nebraska to Iowa, southern Minnesota to Wisconsin.
The most significant snow amounts are forecast across the central Rockies in Colorado due to strong northeasterly winds depositing heavy orography-driven snowfall into the mountains.
ARCTIC COLD OUTBREAK SPREADS TOWARDS EAST COAST AND DEEP SOUTH
Now, looking at the temperature forecast for early next week and the final days of October, the large pool of Arctic cold air mass will engulf much of Canada and the United States. This occurs as the lower Polar Vortex core area parks over the northeastern United States and northern Canada.
On the west, a strong blocking High pattern establishes over Alaska, the Pacific Northwest, and western Canada, thus allowing the Arctic cold to spread on its eastern side. This will strengthen the core of the upper low, moving across the Upper Midwest and the Great Lakes for Halloween and November 1st.
As a result, this releases unseasonably cold air to spread far south into the U.S. Gulf Coast and further on the eastern parts, reaching the East Coast, Southeast U.S., and Mid-Atlantic on Halloween Day. We will look at this cold air outbreak on a surface level.
The cold air outbreak will cover much of the United States, including the far deep South, the Gulf Coast, and the East Coast.
The chart for Tuesday, Halloween Day, below indicates quite an extreme temperature anomaly will be present across the central CONUS.
Around 20-25 °F colder than normal across Montana, Dakotas, central Plains and south Texas. This cold will spread east on the next day, Nov 1st.
The image below shows the morning temperature forecast for next Tuesday. We can see temperatures well-below freezing across about two-thirds of the United States. Reaching single digits in Montana and North Dakota.
The boundary between freezing and warmer temperatures will extend from the Northeast U.S. across the lower Ohio Valley to the lower Mississippi Valley and West Texas. North of this line, temperatures will be well below freezing. Low 40s across much of central Texas and lower Mississippi.
These cold temperatures are forecast to gradually vanish into late next week as a strong high-pressure system establishes over the CONUS and Canada, allowing temperatures to warm up again through early November.