Backward-moving storm fouling second straight Friday-Saturday in D.C.

WEATHER NEWS: Backward-moving storm fouling second straight Friday-Saturday in D.C.

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Storms are supposed to move in and move out. But the one spreading clouds and showers over the D.C. area this weekend isn’t playing by the rules.

This same storm system unleashed more than 2 inches of rain on the area last Friday and Saturday. Now it’s back for a second appearance. The consequence of this bizarre curtain call is yet another unsettled weekend this year, when the weather has been disproportionately cool and wet.

The storm’s return visit is kinder and gentler than its first pass, however. The deluge last Friday and Saturday sent several area waterways over their banks; the Potomac flooded for days. Temperatures were abnormally cold last Saturday and Sunday, hovering in the 50s when “normal” is in the 70s.

Water rages at Great Falls after the weekend deluge

As it meandered off the Mid-Atlantic coast, pounding shoreline beaches and dragging two North Carolina homes into the sea, the storm lost its cold air supply. So on this second visit, temperatures are some 20 degrees warmer and pretty close to normal.

The storm is also much less organized this time around, and weakening rather than strengthening. It’s only spraying intermittent showers instead of unloading a drenching rain.

Still, these showers are tough to predict and plan around. Since Thursday, the storm has pushed east- to westbound showers through the area while perched offshore. They’ve been hit or miss — barely dampening the pavement in some areas. Rainfall has generally been under 0.25 inches.

North Carolina beach homes collapse from lumbering coastal storm

As the storm moves inland over the southeast into Saturday, the showers will pivot and start coming in from the south. As on Thursday and Friday, there should still be plenty of dry time, but if you have outdoor plans, have a place to shelter — especially Saturday and Sunday afternoon and evening, when there could be some thunder and locally heavy downpours.

Forecast models generally only project about 0.25 to 0.5 inches of additional rain through Saturday night, although locally heavier amounts are possible, especially south of the District.

By Sunday, the storm system will have dissipated over the South, but leftover moisture may fuel some more scattered showers and thunderstorms, this time coming from the west thanks to a newly approaching disturbance.

Why did the same storm come back?

When the storm first lumbered through the area a week ago, it had become cut off from the jet stream, the high-altitude steering current for storms. That’s why it took so long to clear last weekend.

The storm has remained divorced from the jet stream all week while a large area of high pressure over the central Atlantic has acted as a block, locking the storm’s position near the Mid-Atlantic shores.

That block remains in place, but — as it joins forces with another high pressure zone moving over the Northeast — the resulting circulation is nudging the storm system westward into the Southeast.

It required a rare set of atmospheric circumstances for this system to hit the area twice.

Storm contributes to underwhelming spring

The double-whammy storm is part of a less-than-perfect spring so far and, as some have mentioned, it seems the worst of the weather has been focused on the weekends.

Sunday has been the most consistently chilly day, with half of Sundays coming in at 6 degrees or more cooler than normal.

By other metrics, it’s been even less friendly. A little less than 40 percent of days have featured partly sunny or better skies since April 1. Only four of those days have come on Saturday or Sunday. Five of six Saturdays in the stretch featured rain, as did four of six Sundays.

The wind has also been howling, as it tends to at this time of year, with only 33 percent of days having peak gusts of less than 25 mph. The calmest day of the week has been Monday for the past few weeks.

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