Will it be cloudy during the solar eclipse?

There may be no sky forecast more consequential for Americans this spring than the one for April 8, when a solar eclipse sweeps across the Lower 48 states.

Predictions are especially meaningful for those in the path of totality — the roughly 115-mile-wide swath from Texas to Maine where the moon will completely block the sun, revealing the solar corona, the outermost part of its atmosphere. Millions of people are traveling into this path, but a cloudy forecast could spoil what many say is an incomparable experience. The United States won’t have another total solar eclipse until 2044.

Cloud forecasts may not be reliable until a few days before the eclipse, but computer simulations are beginning to show weather patterns that give a forecasters a general idea as to where either clear skies or clouds are most probable.

Note that historically, Texas has the best chance of being cloud-free, while the zone from Ohio to Maine has the highest odds of thick cloud cover.

The current pattern simulated by computer models appears more favorable than usual for sunshine along at least the middle and northern parts of the path of totality. The southern areas — which usually have higher chances for sunshine — are a bigger question mark.

The predicted pattern shows high pressure in the eastern United States, which promotes sunshine. Low pressure, which tends to produce more cloud cover, is shown in the West.

Although high pressure promotes sunshine, the clockwise flow around it tends to favor winds from the south on its western side which can draw moisture from the Gulf of Mexico and generate clouds and moisture. So areas in the south-central United States, including Texas, would have an increased chance of cloud cover if this pattern holds.

It’s also possible that this pattern results in a storm system forming just east of the Rockies that could spread cloud cover and showers and storms into the southern Plains and Lower Mississippi Valley. But it’s much too soon to be able to nail down the location and timing of clouds and precipitation. This far into the future, models could be a day or two fast or slow on how fast such a system develops and moves.

The high pressure zone currently predicted by models over the Northeast would tend to favor better-than-average chances for at least partial sunshine from the Ohio Valley through New England. But keep in mind that springtime weather is particularly fickle in this region and that this outlook could change.

We want to stress that cloud predictions will invariably change and may not become reliable until around April 5 or 6; even then, cloud cover often depends on processes happening at very small scales in the atmosphere — small enough that models don’t have enough detailed data to accurately simulate them. This initial outlook is only intended to offer a very general guide, and we would not advise changing plans based on it.

Here are preliminary forecasts for several large cities in the path of totality:

Dallas (62% cloud cover): Models lean toward cloudier conditions, but the weather pattern could favor a setup with sunshine during the first half of the day with clouds building during the afternoon and a chance of storms. Usually, thunderstorm days aren’t fully cloudy and feature partial sunshine in the afternoon. Warm and humid conditions seem a good bet.

Little Rock (62% cloud cover): Little Rock may also find itself near the battle zone between high pressure to the east and low pressure to the west. It’s essentially a coin flip whether it ends up cloudy. Should clouds develop, they may form later in the day.

Indianapolis (36% cloud cover): Closer to cloud-quashing high pressure, Indianapolis appears to have better odds of sunnier conditions. It may not be far from potential clouds or raindrops to the west, though. Temperatures should be warm.

Cleveland (31% cloud cover): With the city forecast to be under the influence of high pressure, odds of clouds are lower than normal in Cleveland. Proximity to the Great Lakes and their abundant clouds make this a very uncertain call. Temperatures may be warmer than normal.

Buffalo (35% cloud cover): Similar to Cleveland, Buffalo has higher-than-typical chances of sunshine. But since the city sits near the Great Lakes cloud machine, uncertainty here is likewise high. Mild to warm temperatures are favored.

Burlington, Vt. (51% cloud cover): It is a cloudy time of year in Burlington, but high pressure parked nearby boosts the chance of sunshine. Mild to warm temperatures are expected.

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Forecast data is from the Weather Service’s National Blend of Models. Type of eclipse data is from the U.S. Navy.

Emily Eng, Tim Meko, Szu Yu Chen, Emily Sabens and Dan Stillman contributed to this report.

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