There are two ways to get these data:

1) Go to the downloads webpage to select by date (HERE);

2) Copy a list of the URLs (HERE) from which to download many files using a programming language like Matlab

The returned files will be a 60-day forecast from 00Z of the date entered, using CFSv2. These should be updated daily around 8am Eastern Time. Again, please note that these are still experimental, so please use at your own risk!

The files are CSV formatted (about 1.7 MB each), with days as rows and grid-point locations as columns. The top two rows are the latitudes and longitudes (0-360); the first four columns of each file are date information (unique date, year, month, day).

All other data in each file are the forecasted GWTC types for the location and day. Please use the table at the bottom of the page to decode the weather types in the files. ALSO NOTE: each day's forecast for day-60 will be inaccurate because the dataset truncates prior to all 3-hourly forecast data being available.


59-Day Forecast Loop (updated daily around 12Z-13Z):


Today's GWTC Forecast (updated daily around 12Z-13Z):


Tomorrow's GWTC Forecast (updated daily around 12Z-13Z):


Day 3 GWTC Forecast (updated daily around 12Z-13Z):


The GWTC forecasts were derived using the same methodology as the original GWTC (described in Lee, 2014), except with pre-processing interpolation steps to align the CFSv2 dataset with the NARR dataset (used for the orignal GWTC) in space and time. Maps above have been modified to enhance spatial homogeneity, while data sets do not have this feature added (but can upon request).


11 Humid Cool HC
12 Humid H
13 Humid Warm HW
21 Cool C
22 Seasonal S
23 Warm W
31 Dry Cool DC
32 Dry D
33 Dry Warm DW
72 Cold Front Passage CFP
73 Warm Front Passage WFP


GWTC forecasts were originally developed in 2018 as part of a project funded by NASA grant number NNX16AH12G, "The Development of a Water Clarity Index for the Great Lakes as a Climate Indicator," (PI: Scott Sheridan, Kent State University, Department of Geography).