By The Washington Post
There may be no sky forecast more consequential for Americans this spring than the one for April 8, when a solar eclipse will sweep across the country. Central Indiana is expected to be one of the prime sites to view the event.
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 the sun’s 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 forecasters a general idea as to where either clear skies or clouds are most probable.
Based on past years’ weather in areas that will be in the path of totality—where 100% of the sun will be obscured—Texas has been most likely to be cloud-free on April 8, while the zone from Ohio to Maine has more often had thick cloud cover.
Key points
Confidence in sunny skies is highest in northern New England because of high pressure; however, a weak front in the area could produce patchy areas of clouds, especially just south of the front.
Weather models suggest a front may be sweeping through the central states into the Ohio and Tennessee valleys; this could increase clouds from the Great Lakes to the Gulf Coast. However, the presence of this front doesn’t mean overcast skies everywhere near it, and its location around the time of the eclipse could shift.
The clockwise flow around high pressure in the eastern United States will result in winds from the southeast along the Gulf Coast and into eastern parts of Texas that may increase cloud cover.
We want to stress that cloud predictions are uncertain and may not become more 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 outlook is intended to offer only a general guide, and we would not yet advise changing plans based on it.
How the forecast has changed over the last day
The main challenge remains predicting the location of a front and associated clouds that could affect areas along the southern two-thirds of the path of totality in the United States. The location has been shifting around, and the latest shifts in computer model simulations introduce a bit more cloud cover in Dallas and Little Rock. “The cloud forecast continues to be challenging as the consensus of model guidance has trended back slightly more pessimistic,” the National Weather Service office in Fort Worth wrote Wednesday morning.
Although predicted cloud percentages ticked up slightly in New England, confidence is still highest for considerable sunshine in this region.
Preliminary forecasts for several large cities in the path of totality
– Indianapolis (20% cloud cover – 39 percentage point decrease from previous forecast): It’s possible Indianapolis ends up on the west side of the front where sinking air would promote sunshine, which is what some of the latest model simulations suggest. However, if the front ends up slowing down, it could still end up cloudy. Odds of rain are low, and temperatures should be mild.
– Dallas (66% cloud cover – 26 percentage point increase from previous forecast made Tuesday): Cloud cover forecasts continue to make big day-to-day swings. The weather pattern could favor a setup featuring sunshine during the first half of the day, with clouds building during the afternoon and a chance of storms late. The chance of clouds increases south and east of Dallas while decreasing to the west, so small shifts in upcoming forecasts could be consequential. Warm and somewhat humid conditions seem a good bet.
– Little Rock (51% cloud cover – 12 percentage point increase from previous forecast): Little Rock also finds itself near a front and the battle zone between high pressure to the east and low pressure. As is the case for Dallas, considerably sunnier conditions are forecast just to its west, with thicker clouds south and east. The Weather Service in Little Rock wrote that “the slightest of changes” to the forecast could have “massive repercussions.” Scattered storms are possible late-day or into the night. Warm with modest humidity.
– Cleveland (46% cloud cover – 12 percentage point decrease from previous forecast): Some clouds could stream into the area ahead of the front approaching the region, but it’s a coin toss as to whether skies end up more cloudy or sunny. Temperatures may be warmer than normal, especially away from the lakeshore.
– Buffalo (52% cloud cover – six percentage point decrease from previous forecast): Similar to Cleveland, some clouds could enter the area ahead of the front pushing eastward, and it’s uncertain whether sun or clouds win in the end. Mild temperatures are favored.
– Burlington, Vermont (23% cloud cover – seven percentage point increase from previous forecast): It is a cloudy time of year in Burlington, and snow is expected in the coming days but—by Monday—high pressure parked nearby boosts the chance of sunshine. This has been the most stable forecast since late last week, and the city is likely to see a fair amount of sun but should keep an eye on some clouds to the west. Mild temperatures are expected.
Note that the cloud cover percentage forecasts provided by models do tend to err on the pessimistic side and don’t distinguish between high, thin clouds—through which the eclipse could be seen—and low, thick clouds that would obstruct it.
