From the ABC 7 Weather team

Rain, Rain, Go Away: How Long This Grey Pattern Will Last

May 7, 2013 - 05:00 AM
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A wet weather pattern setting up for this week means you'll want the umbrella for the next several days. 



After an absolutely gorgeous first weekend of May, the start of the work week weather took a turn in the opposite direction.  Unfortunately, for those of you not a fan of the grey skies and showers, this weather pattern is here to stay... at least for a good chunk of the work week.  So why the unsettled weather?  Let's explore.

Check out yesterday's satellite image.  Notice the big "swirl" from space.


I went ahead and drew the features that are present from this system.  The 'L' represents the area of low pressure that is spinning, counterclockwise, over the southeast US.  The blue arrows indicate the onshore, or easterly, flow bringing in Atlantic moisture to the mid-Atlantic.  Air circulates around the low in this counterclockwise fashion.

The low will track northeast over the coming days, but will be slow to do so.  Take a look at the upper level low from about 18,000 ft (500mb).  This is a simulation of where the low will be later this afternoon. 


As the low tracks northeast, cloudy and damp weather will persist across the region.  It won't be a complete washout each day this week, but scattered showers will be possible through at least Thursday.  Check out the Weather Prediction Center's quantitative precipitation forecast through Thursday evening.  This forecast shows between 1 and 2 inches of rain over our region, with locally higher amounts over southwestern VA.



With moderate rain possible over an extended period of time, the National Weather Service has issued a flood watch for parts of the Shenandoah valley through late tonight.  Remember, if you encounter standing water, never drive through it. The latest Flood Watch was extended north into Clarke, Frederick (VA), Hampshire and Mineral Counties as well.

By late Thursday, the low weakens its grip and gets caught back in the overall pattern.  Compare the 500mb heights in this forecast (below) for Thursday night to the same map shown above.  Notice there is a slight dip in the wave pattern, but nothing cut-off (like in the similar image a few graphics up). 


For us, this means a less unsettled weather pattern.... sort of, for Friday at least. High temperatures will climb to near 80 degrees by the end of the week, which could initiate a few airmass thunderstorms to develop, but nothing widespread.  A cold front will then slide through this weekend bringing continued chances for showers but drier and slightly cooler air can be expected for early next week. 

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