Forecast of the Day • A National Weather Forecasting Contest

The high temperature could approach 60 F on Thursday in Great Falls, Montana according to the GFS MOS, but the NAM MOS keeps it in the 40's. If the GFS forecast is correct, it would be the warmest temperature of the spring so far, and could contribute to a problem with snowmelt flooding: "Flood advisories continue across much of north central Montana due to persistent lowland snowmelt flooding and areas of water over roadways. However, we have received reports from Hill and Blaine Counties of a few roads being washed out and several inches of water on other roads (making them impassable). As a result, areal flood warnings have been issued for those counties. Gradually warming temperatures with plenty of strong spring sun this week will continue to melt the snow, likely continuing or possibly increasing flooding coverage for many areas well into next week." Let's forecast the Tmax for Great Falls and see how warm it gets.

Question: In the NWS discussion above, what do they mean by "strong spring sun"?