Looks sort of Hanna-like out there this morning. Heavy showers, then sunshine. But it's not Hanna Redux, just a new cold front crowding us from the north and west. The cold air is shoving up against very moist, warm air to the south and east. That makes the warm, wet air rise, cool and give up its moisture in the form of showers and (BOOM!) thunderstorms.

Here's the radar loop.

There is a Severe Thunderstorm Watch posted from Cecil and Harford to St. Mary's counties until 4 p.m. There is a LOT of water in these showers, so the NWS has also posted a Flash Flood Watch from noon until 8 p.,m. today for the western DC suburbs, the District and the Baltimore metro area.

The flooding is a risk because Hanna managed to fill up some streams that had been much lower a week ago, with more room to accommodate the runoff. Now a heavy storm could more easily put the creeks over their banks. Or so the reasoning goes. Here is the streamflow map. It does look a lot wetter than it did last week.

Forecasters out at Sterling say we can expect another quarter- to a half-inch of rain today and more tonight before the front finally passes by. That will usher in cooler weather. Tomorrow should be partly sunny, with highs only in the mid-70s. Tomorrow night will be a blanket night, with lows near 50 degrees.

The rest of the week should be very nice, with pleasant temperatures in the 70s to near 80 degrees, and partly to mostly sunny skies. There's a small chance for more showers on Friday.