It might be hard to imagine on this clear day after all the rain that just moved out, but we could have a very similar pattern to start off the weekend. The next system is the leading edge of an upper level pattern change that will usher in the coolest air we’ve felt in months. The last time Baltimore’s BWI dropped into the 40s was May 24th, and we could see that again Monday.  But first, the rain and radar simulation below.

Screen Shot2015-09-11 08_16_54Weather patterns like to repeat. I often refer to atmospheric memory, while some call it persistence. What the GFS Model is showing here looks very similar to the Thursday event with Low Pressure forming overhead and slowly moving east. This location of the Low forming to the south and east of the central Chesapeake will enhance the moisture flow off of the bay and ocean. If you remember seeing some of the radar imagery I posted Thursday showing smaller circulations that moved over with downpours… That was part of the pattern, and one aspect that led to pockets of flooding where rainfall exceeded 2 or 3 inches in an hour or so. Not everyone had heavy rain, but I do believe the rain will be more widespread with the next event.



Saturday Plans:

Screen Shot2015-09-11 08_56_43Rain will begin to move in during the morning. Especially in the hills and mountains. But the afternoon will show increased coverage of heavy rain, downpours, some lightning, and some flooding.  The heaviest rain is forecast to be in the mountains, but I think there will be a second bullseye near the Bay or Delmarva. Here is an idea of how it will develop. If you have outdoor plans in the afternoon or evening I would have a plan B indoors. That is when the rain will become the heaviest.

The simulated radar below is just a gauge, not gospel. But it gives a good idea of the timing during the afternoon with the most likely opportunity to get a soaking.

Simulated Radar (slider 9 AM to 8 PM—>):

Note: When I shared this model outlook the day before our last rain event, the result of the heavy rain result shifted about a hundred miles north and was a few hours earlier than expected.  So this is a general idea and I would plan around the rain threat being on the high side at any time after-noon

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Cooler Air Follows

The upper air pattern will be cool and unsettled. While most of next week will be dry, Sunday will be the transition day. Depending on how slow or fast the Low moves, some energy may linger to allow clouds and a few showers to redevelop during the afternoon. Winds will be strong, gusting 30 mph or higher. Afternoon temperatures will be in the lower 70s near the Bay and could stay in the 60s inland.  Then low temps drop into the 40s Monday morning.

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