time_requested = datenum('2018-07-24 00:00');

load('swrad_nam12km_2018072400_2018080600_01h.mat');
ttol = 1/48; % day
tind = find(abs(time - time_requested) < ttol);
if isempty(tind)
  disp('Requested time not found in file. Please choose another time.');
end
figure;
pcolor(LON,LAT,squeeze(SOLRAD(tind,:,:)));
shading interp;
colorbar;
colormap(jet);
clim([0 600]);
title(['NAM 12km Solar Radiation (W/m^2): ' ...
  datestr(time(tind),'yyyy-mm-dd HH:MMZ')]);

