Projecting imagesc function onto a map plot

Hello. I'm working with plotting over a map projection with the built in mapping tools. Using contourm, I'm able to plot my geolocated data on a contour map (contourm(lat,lon,Z)). However, it takes a looonnnnnggg time to run. A function like imagesc would probably be faster.

What would be the best way to use imagesc with geolocated lat/long points?

Really, all I need is something that takes in coordinates X and Y and puts a color based on Z at that point.

ax = usamap(latlim,longlim);
states = shaperead('usastatehi','UseGeoCoords', true, 'BoundingBox', [longlim', latlim']);
geoshow(ax, states, 'FaceColor', [1 1 1])

contourm(lat,long,DBZ(:,:,1),10,'Fill', 'on') %want imagesc here

[Kyle Chudler]

I found the function pcolor. However, it turns out much coarser than contourm...and too washed out with interpolated shading....