AccuWeather.com reports changes in the position of the jet stream between Iceland and northern Europe will only be subtle over the next few days, but will still cause variations in where the ash plume from a volcano erupting in Iceland will spread over Europe.
Millions of airline passengers will continue facing flight delays and cancellations as a result.
Forecast Path of Ash Plume through Tuesday
It's the jet stream, which is an area of relatively strong winds concentrated within a narrow stream in the atmosphere extending from 10,000 to 40,000 feet above the ground that is controlling where the ash is spreading.
"It's like a spray can of ash coming from Iceland," AccuWeather.com Senior Meteorologist Margusity said. "The ash comes out of the volcano nozzle and spreads out into the atmosphere just like a spray can works."
As with a spray can, the plume of ash is not uniform. It becomes deformed and spreads out in different directions the farther away from the source it gets.
While no current satellite imagery was available Saturday morning, imagery from Friday showed the main plume of ash still spanning from Iceland over the northern portion of the U.K. and into southern Scandinavia.
As the plume started getting deformed, an ash cloud has also spread and formed over the northern Europe mainland, as seen on satellite imagery from Friday.
The jet stream is expected to maintain a general position that spans from Iceland over Scotland and southern Scandinavia through Sunday and shift only slightly northward Monday. The main, concentrated ash plume is expected to maintain a similar position.
Meanwhile, the ash cloud that has spread and formed over the northern mainland of Europe is located south of the jet stream in an area of weak wind flow. Therefore, this cloud is expected to move little through Monday.
Thousands of flights have been cancelled on a daily basis across Europe since Thursday. According to BBC News, nearly all of Europe's major airports remained closed Saturday.
The U.K.'s Civil Aviation Authority has extended its restriction of most non-emergency flights in U.K.-controlled airspace until at least 1 a.m. local time on Sunday.
Officials in Poland are worried that air travel will remain suspended for Sunday's state funeral of President Lech Kaczynski and his wife Maria. Leaders from around the world are expecting to fly into the southern city of Krakow for the ceremony.
Aviation authorities in Scandinavia and most of northern Europe have also restricted air travel.
The grounding of flights in reaction to this threat is creating nightmares for airline passengers across Europe and around the world.
Rather than impairing visibility, the real threat with this volcano is ash possibly affecting airplane engines and control systems. Volcanic ash is abrasive, and can scratch windshields and accumulate in engines, which could degrade performance perhaps to the point of failure.
Tuesday into Wednesday, the jet stream is expected to shift farther south, becoming oriented from Iceland into the northern U.K. and northern Germany. Correspondingly, the main ash plume is expected to follow this trajectory and have the greatest impact on air travel in these areas.
The plume is expected to become more concentrated Tuesday and Wednesday, posing a greater threat to air travel. However, it is also expected to become narrower, impacting a smaller area.
The shift of the jet stream farther south Tuesday into Wednesday could be good news for the rest of the northern mainland of Europe. The southward shift is expected to increase winds over the region, perhaps helping to stir up and clean out the ash cloud currently in place.
Potentially Beneficial Changes Forecast for Thursday
According to AccuWeather.com Meteorologist Rob Miller, a big change in the jet stream pattern will occur Thursday as a storm develops in the central Atlantic Ocean.
As this storm develops, the jet stream is expected to shift south of Iceland and become oriented out of the west-southwest rather than the northwest.
A southwest jet stream should help clean any remaining ash plume out of most of Europe and bring some relief for the aviation crisis, according to AccuWeather.com meteorologists.
Ash Plume's Impacts on Travel
The Eyjafjallajokull Volcano erupted Tuesday evening (EDT) under a glacier in southern Iceland. Fears of flooding from the melting glacier immediately prompted the evacuation of up to 800 people.
By AccuWeather.com's Gina Cherundolo, Kristina Pydynowski and Heather Buchman
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