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ECLIPSE FORECASTS
from the University of Illinois
Department of Atmospheric Sciences
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NASA live eclipse tv!

Update - 12:35 pm CDT Monday

Eclipse moving into Plains! Cheyenne peak eclipse at 12:47 central time (CDT).
Much is occurring as was forecast. TN and most of KY are looking good. Shown below/left is the IL forecast from the National Weather Service in Lincoln (gray=cloudy). On the right is a very recent cloud forecast valid 1 pm CDT from NOAA/ESRL (regions shown white are clear). Click on image for full-sized view.

Webcams along the eclipse path Click for full-sized view

Cheyenne, WY (peak 1247 CDT)

Exeter NE, near Grand Island (1:02 pm CDT)

St. Louis (peak 1:18 CDT)

Bowling Green, KY (peak 1:28 CDT)

Carthage, TN (peak 1:30 CDT)

Eclipse path - click image for full size  •  Follow this link for eclipse city & eclipse time details

PDFs available for downloading:   NASA eclipse poster  •  (UK) HM Nautical Almanic Office  •  U.S. Naval Observatory
Current visible satellite imagery

Central Plains - click for full size

NOAA/AWC   - Midwest

U.W. SSEC

Background

The University of Illinois Department of Atmospheric Sciences has partnered with the Department of Astronomy to offer daily cloud cover forecasts for the total solar eclipse on Monday, August 21, 2017. We hope to update our forecasts every afternoon until the day of the eclipse. The Astronomy Department will be holding an outreach event in Goreville, Illinois (see map above), while the Atmospheric Sciences Department will travel to wherever promises the best viewing within a reasonable drive of Champaign-Urbana along the path of totality - roughly from as far west as central Nebraska to as far east as Tennessee.

Eclipse Forecast - August 20, 2017

The forecast from yesterday is largely unchanged, so I will keep it in place below. The only substantial change is to increase the chances for clear patches across parts of northern Missouri, but committing to here still remains a risky proposition. Again, I cannot stress how important it may be tomorrow to be flexible and get an early start given the uncertainty that remains in the forecast. Travel safely everyone and tomorrow, I will see you on the dark side of the moon.

There is just one day to go, and a clearer picture of the weather pattern and resultant cloud cover is beginning to emerge for the eclipse across the Midwest and Mid South. I'm still seeing more clouds than clear skies across Nebraska and Missouri; southern Illinois is mixed, and the best viewing conditions still look to be across Kentucky and Tennessee, which is also where I see the greatest forecast uncertainty.

Likely best viewing location: Kentucky, Tennessee, possibly southern Illinois.

Goreville, IL, forecast for Monday: Increasing clouds in the afternoon. Warm and humid with highs near 90.

Technical Discussion

The overall weather pattern for Monday will be characterized by an area of low pressure and attendant cold front across the Central Plains, which will likely trigger thunderstorms Sunday night and into Monday. These storms and associated clouds will move eastward overnight Sunday and into Monday morning. It now appears likely that fairly widespread cloud cover will exist during eclipse time across much of eastern Nebraska, Iowa, and northern Missouri. As the storms dissipate, the expansive cloud shield generated by them will continue to move eastward, likely reaching the Mississippi River along the path of totality, and possibly moving into portions of southern Illinois, by early Monday afternoon. Farther east, across Kentucky and Tennessee, the cloud cover looks more spotty, although diurnal cumulus clouds should become more common with southeastward extent. Now, let's break down the regions from west to east in more detail.

Nebraska/Northeastern Kansas: If you have your heart set on living the good life in the Home of Arbor Day (that's Nebraska) for the eclipse, my best advice is to allow enough flexibility in your travel plans to be able to get as far west as possible. The models continue to suggest that there will be more clouds than clear skies across most of the central and eastern portions of the state; although a few localized breaks could form by noon, the small-scale nature of these features means that predictability is low at this time.

Missouri: Much of northern Missouri also looks to remain mostly cloudy for much of the day on Monday. Probably the best bet in the Show-Me State is to head to the St. Louis area, where clouds may be thinner or nonexistent. As in Nebraska, there could also be smaller regions of clearing embedded within the more expansive overcast, but no one can pin down the exact locations of these features until a couple of hours before eclipse time.

Southern Illinois: Current model guidance is mixed on the eastward extent of the cloud cover spilling eastward from Missouri, with some models keeping most of southern Illinois mostly clear, while others roll the clouds across most of the state by early afternoon. If you're planning on heading to southern Illinois, my advice is to leave enough flexibility in your travel plans to bail southeastward into Kentucky or Tennessee if conditions warrant.

Kentucky and Tennessee: These states look to be far enough east to be spared most of the cloud debris spilling eastward from the Plains, but guidance is still somewhat mixed on the degree of cloud cover even here. There could be a few patches of middle and upper-level clouds, and, given the warm and humid air mass that will be in place, I expect diurnal fair-weather cumulus clouds to form across parts of this region, particularly with greater southeastward extent. While I would word an official forecast here as "Partly cloudy," this allows for up to 30% cloud cover. You'll want to again try to be as flexible as you can and hope not to get unlucky with an ill-timed cumulus cloud.

The bottom line is this: Be as flexible as you can in your travel plans. For some folks (including me) this means leaving Sunday and trying to leave as many options open for Monday as possible. Get on the road early Monday; don't sleep in, even if you have a coveted overnight location along the path of totality. Look at the weather early and often Sunday evening and Monday morning. Traffic will likely be an issue in many locations, and it may take twice the suggested drive times or longer to get from Point A to Point B near the path of totality.

I am leaving Champaign-Urbana for points south Sunday morning. I will try to post an update from the road Sunday afternoon and/or Monday morning. For other updates, you can also follow my Twitter account, @VORTEXJeff

Jeff Frame
Clinical Assistant Professor
Dept. of Atmospheric Sciences