NowMuggy. A tornado watch is in effect to the northeast of the immediate DC area until 8pm. Nearby areas affected in Maryland include Baltimore City/County as well as Anne Arundel and Howard Counties.
Temperatures in the low to mid 90s and dewpoints as high as the mid 70s have pushed some heat index readings over 100 in the Washington metro area this afternoon. After holding at 91° with a southerly river breeze, the National Airport temperature popped up to 94° at 4pm with a more westerly wind direction.
Despite the juicy conditions and a weak low pressure area to the north, regional radar is not very impressive so far. A few very isolated showers had popped up by mid afternoon, mainly to the north and east of the Beltway. The heavier activity was just east of the Blue Ridge and south of I-66 in Virginia. This area has now moved eastward to I-95 south of the Beltway. Technically, the area's 2-week-plus rainless streak was broken by the 0.01" which fell around 6am this morning, but there are probably very few lawns which would be convinced of that.
Tonight and TomorrowChance of thunderstorms, then cooler and less humid. There is a 40% chance of showers and thunderstorms through this evening. Lows will be in the lower 70s in the city, near 70° in the cooler 'burbs, with gradually decreasing humidity. Tomorrow will be cooler and less humid with highs in the low 80s.
The outlook for the rest of the week and weekend is strongly dependent on the interaction of a northward-moving Ernesto with a high pressure area building to the north. Dan will update the outlook in his post tomorrow.
Tropical TopicsErnesto has maintained relatively minimal tropical storm strength (45 mph at 5pm) today moving northwestward across the Florida Straits, although it has been looking more respectable on radar and satellite imagery. At mid afternoon, radar showed outer rainbands from the storm reaching across the Florida Keys northward as far as Naples and Fort Lauderdale. There is a slight chance of strengthening before landfall in south Florida, but the storm has a better chance of getting back to hurricane strength after re-emerging over the Atlantic before making the next landfall in the Carolinas.
The storm's possible effects on the DC region have varied in the last 24 hours between missing most of the rain because the storm moves offshore from the Outer Banks to missing most of the rain because the remnants move west of the mountains. The latest track has now veered somewhat to the east again, closer to the local area. Stay tuned as the situation continues to develop.