Much rain possible

It hasn’t been an especially wet week thus far for much of the northern Cumberland Plateau, as unpredictable convective precipitation has focused mainly on areas to our south. But that should change as we get into the end of the week, as a more organized system interacts with the very moist air mass that remains in place across the entire region.

For now, the GFS forecast model indicates about 2.5 inches of rain for the northern plateau through Sunday. But because most of the precipitation will be convective in nature, that’s only a rough baseline number. Rainfall could be much heavier where the stronger storms set up, especially if training occurs — meaning that multiple storms impact the same area.

In its forecast discussion this afternoon, the National Weather Service’s Morristown office pointed out that training could occur Thursday night into Friday, as a cold front moves through the region, because upper level flow will be almost parallel to the frontal boundary.

Rain chances decrease early in the day on Saturday, but then increase again later on Saturday, as the lower level jet increases. Strong thunderstorms are possible Friday and Saturday afternoons, particularly Saturday, and rain chances continue into Sunday as a short wave system rotates around the base of the trough that is going to develop over the region this weekend.

In a hazardous weather outlook posted this afternoon, NWS-Morristown says some storms “could be strong to possibly severe from the mid-afternoon to early evening” on Friday, with the main concerns being quarter-sized hail, damaging downburst winds up to 60 mph, heavy rainfall and lightning. The frontal boundary on Saturday will again produce a chance for strong to severe storms late Saturday afternoon and evening, the NWS said in the outlook, “producing large hail, strong damaging winds, heavy rainfall and frequent lightning.”

The NWS pointed out in the hazardous weather outlook that localized flash flooding is possible late Saturday and Saturday night.

There have been some indications of a cool-down late in the month, but the latest runs of the GFS aren’t depicting this. According to the forecast model, most of next week will be dry before the next system arrives as we get into the following weekend, April 29-30.

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