Saturday, August 19, 2017

Solar Eclipse Weather Forecast: Will Clouds Block Your View?

Linda Lam
Published: August 19,2017

We are just a couple of days away from the first total solar eclipse in the Lower 48 states in over 38 years, and details of the weather pattern are beginning to come into place, which could determine whether you'll get a clear view of this historic event.
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A swath from Oregon to South Carolina will see the moon completely mask the sun Aug. 21. Nearly all other parts of North America – as well as parts of South America, Africa and Europe – will see at least a partial eclipse.
(MORE: See the Eclipse on Our Interactive Map)
Eclipse coverage percentage is shown.
The eclipse will start mid-morning in the Pacific Northwest, around midday in the nation's heartland and early afternoon in the Southeast, ending in the Lower 48 states after 4 p.m. EDT.
(MORE: 10 Best States to See the Total Solar Eclipse)
Overall, the biggest trouble spot for viewing the eclipse may be in parts of the Midwest and northern/central Plains as showers and thunderstorms rumble through parts of those regions. Portions of the Southeast may also have to contend with scattered patches of clouds.
Meanwhile, much of the Northwest should be free of cloud cover.

Cloud Cover Forecast 2 P.M. Monday
Here's a closer look at the regional details.

East Outlook

Without suppressing high pressure overhead, scattered thunderstorms are possible from the northern Gulf Coast to the coastal Carolinas, including the Florida Peninsula, as is typical on a summer afternoon.
The eclipse will take place in the early to mid-afternoon hours along the East Coast, typically the time during which thunderstorms will flare up.
So, you may have to cross your fingers poorly-timed thunderstorms don't block your view.
Patches of cloud cover may affect other parts of the Southeast, as well.
Selected Cities In Path of Totality: Nashville, Tennessee | Columbia, South Carolina | Charleston, South Carolina

Monday's Outlook
High pressure currently looks to be in place over the Northeast on Monday. This may bring clearer and sunnier conditions to much of the region, especially New England and New York.
However, areas toward the mid-Atlantic have the highest odds of having their view obscured by a few clouds or even a shower or thunderstorm.

Monday's Outlook

Central Outlook

A low-pressure system is expected to be pushing through the northern Plains into the Midwest, and this means parts of the region will have to deal with thunderstorm clusters. The good news is that this system does not appear to be particularly strong at this time.
Those clusters of storms could rumble through parts of the path of totality in Nebraska, northeast Kansas and Missouri.
However, the timing of the eclipse in the nation's heartland, roughly midday into early afternoon, may allow any morning thunderstorm cluster(s) to die off by the time the eclipse happens.
The remnant thunderstorm clusters and/or the cloud cover associated with them may obscure the view in some areas, but details as to exactly where remain uncertain.
Selected Cities In Path of Totality: North Platte, Nebraska | Grand Island, Nebraska | Kansas City, Missouri | St. Louis, Missouri | Carbondale, Illinois | Paducah, Kentucky

Monday's Outlook
Southern Plains/Lower Mississippi Valley
Farther south in the central states, the thunderstorm chances are typically less in late summer, and that may hold true on Aug. 21.
High pressure aloft is forecast to be in place across the south-central states, which may suppress cloud cover and thunderstorm chances in much of Oklahoma and Texas.
The chance for showers and storms increases farther east into the lower Mississippi Valley.

Monday's Outlook

West Outlook

The timing of the eclipse works to the West's advantage.
There will be some afternoon thunderstorms from the Rockies to the Desert Southwest, as is par for the course in August.
However, a late-morning/midday eclipse should avoid most of those pop-up thundershowers.
One hiccup may be some areas of low clouds near the immediate West Coast in areas where winds blow onshore. If they remain stubborn enough to linger into the late-morning hours, this could impact the view of the eclipse.
Another consideration that may impact conditions in a few locations is smoke from wildfires in the Northwest.
Selected Cities In Path of Totality: Corvallis, Oregon | Idaho Falls, Idaho | Casper, Wyoming

Monday's Outlook

Thunderstorms and the Eclipse

In summer, we don't typically have large-scale storm systems that can sock in dozens of states with clouds and precipitation as we do in colder months.
That leaves us with, for the most part, thunderstorms.
A single thunderstorm won't last long enough to affect the entire two- to three-hour viewing period of the eclipse in any given area.
However, one of these stray thunderstorms could be so poorly timed it occurs over part of the area seeing an eclipse for the roughly two- to three-minute period of totality.
(MORE: NASA's Eclipse Timing Maps)
Posing more of a threat to block out the eclipse, clusters of thunderstorms known as mesoscale convective systems – MCS, for short – are common in the summer. Their rain or cloud shield can linger over a given location for more than an hour.
However, these clusters are typically more active during the nighttime and early-morning hours – not necessarily during the early-afternoon hours, when the August eclipse will occur in the central and eastern U.S.

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.

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