Earth is entering a stream of solar wind flowing from a sprawling hole in the sun’s atmosphere. First contact with the gaseous material on Nov. 20th produced an outburst of auroras over Scandinavia. Markus Varik sends this picture from Tromsø, Norway:
US: Heavy rain will continue to pose a threat for flash flooding from portions of southern California to Arizona into Thursday. Some of the flooding could be locally significant
Stormy weather could disrupt parts of the central U.S. during busy Thanksgiving travel period
An active jet stream pattern favors stormy weather around the Thanksgiving holiday but details are still coming into focus.
A sprawling storm system may take shape over the nation’s midsection toward the early half of next week, blasting east and potentially disrupting pre-Thanksgiving travel in parts of the Central U.S.
Pockets of heavy rain, snow, and strong winds may in the offing for some as the potential storm system develops beginning Tuesday and sweeps up through the Plains and Great Lakes into Wednesday. However, forecast models show substantial differences in the timing of this storm, how strong it will be and where it will track. It’s possible it will be delayed until later in the week and not particularly potent.
A second storm is also possible to close out the Thanksgiving holiday weekend, though uncertainty in the specifics abounds.
The possible pre-Thanksgiving storm
The main system to watch is predicted to begin as a high-altitude disturbance dives out of Colorado late Monday, passing through Oklahoma and Kansas early Tuesday. It will help spawn a zone of low pressure, growing it into a storm system that could eventually race northeast through the Upper Midwest and Great Lakes late Tuesday into early Wednesday.
It is worth noting that this system is favored primarily on the American (GFS) model, while the European model leans toward the development of a much weaker system later in the week toward Black Friday.
The GFS model’s depiction of the storm as it develops over the Plains before moving northeastward toward the Great Lakes and New England. (WeatherBell.com)
It’s important to remember that this system — whose upper-level instigator hasn’t even moved ashore over the West Coast — is five days away at the least. An enormous amount can change, so confidence is very low in the details, and it’s uncertain if this storm, as modeled, will even develop. However, an active pattern favors at least one storm to dominate headlines next week.
“The jet stream pattern across North America will become quite active next week,” wrote the National Weather Service in Chicago, “so ingredients could come together to support a stronger storm system at some point.”
The potential system, hinted at especially by the American model, will get going over Oklahoma during the day on Tuesday, tracking up the Interstate 44 corridor. It then could move up the Mississippi River Valley, aiming toward Chicago and the Great Lakes before straddling the U.S./Canada border into northern New England on Wednesday.
The German model also forecasts a strong storm system to develop over the Plains and Heartland. The Canadian and European models, meanwhile, also depict a storm, but tamer and delayed toward Thanksgiving Day or Black Friday.
If the storm materializes as predicted by the American model, snow is possible in the northwest quadrant of the system, where moisture wrapping in from the south will meet cold air surging in behind the storm. From Denver through Kansas and eventually up into parts of Missouri or Iowa, some snow is possible. As the storm matures, a healthier dose of winter looks to be in the cards in parts of the Corn Belt, potentially up into Wisconsin or Minnesota as well.
Of course, it’s way too early to predict specific impact areas or amounts. In the meantime, it’s important to keep checking back for updates.
The system will also drag a sharp cold front through parts of the Deep South and Mississippi Valley. Places like Little Rock, Shreveport, Memphis, and Birmingham may all see a sharp drop in temperatures Wednesday.
It’s looking like severe weather will not be a widespread concern with this system, thanks to a lack of instability in the “warm sector” ahead of the front across the South.
The system could also bring strong winds, especially in parts of the Ohio Valley, eastern Great Lakes, and Northeast. This could hamper air travel across some of the busiest airports in the nation leading up to the Thanksgiving holiday if the American model forecast plays out.
It’s likely that the strongest winds will occur after the system has departed. That’s because Arctic high pressure may build in quickly, the intense high tightening the pressure gradient adjacent to the low and thus intensifying strong winds. Clear-air winds of 40 mph may occur over a large portion of the Ohio Valley and Northeast Wednesday evening and into early Thursday.
More storms thereafter?
In the storm’s wake, a briefly cooler air mass will overspread the Appalachians eastward. Models are hinting that a second storm system could develop in the eastern half of the nation on the Saturday after Thanksgiving but details are still murky.
A look at the longer-term pattern favors repeated storminess for the eastern half the U.S., with each successive storm dragging brief cold shots down from the north – but temperatures averaging somewhat above average on balance.
Wet and windy Sunday evening into Monday as the UK finds itself on the east side of the jet, Low pressure sweeps up the side of the country.
Netflix day? pic.twitter.com/8iPANugzxF
— DavidIBirch – UK- (@dbirch214) November 21, 2019
This Evening and Tonight:
Some clear spells in the northwest, along with patchy frost. Many other areas will be cloudy, with showery rain in places, heavy in parts of the south and southwest.
Many areas staying mostly cloudy, with showery rain, this turning heavy and persistent in parts of southwest Britain. Northwestern areas likely to be brightest again. Slightly less cold generally.
Outlook for Saturday to Monday:
Continuing unsettled with showers or longer spells of rain for many places. Milder than of late, especially overnight. Windy at times, especially in the east.
Make sure you get your orders in time!
NH Snow cover extent to wk44, highest since 1999
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