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Posted at 03:01 PM ET, 07/18/2012

More extreme heat milestones met as severe thunderstorms dot region

7:15 p.m. update: The area remains rain and storm free for now, and that should generally continue into the night. Additional showers or storms (probably not severe) are possible though (about a 40% chance), particularly late. Lows should settle into the low 70s in the cool spots to the mid-or-upper 70s in the warm. Heat relaxes a bit tomorrow, with highs ranging from near 90 to the mid-90s. More showers and storms are likely during the day, some of which could be strong or severe.

We’ll update again if necessary.

6:45 p.m. update: Radar is largely quiet at this point, with storms still ongoing southwest and northeast of the area. As such, the earlier flash flood warning for DC and surrounds has been canceled. The Severe T’storm watch has also been canceled except for Prince William, Stafford and Charles counties. At least 15,000 customers lost power during the height of the storm in D.C. and Maryland. Some flooding was reported in Bloomingdale, the site of similar issues last week. Isolated reports of trees down have also come in from places like Chevy Chase.

6:15 p.m. update: Storms around here are mainly pushing off to the east, though we’ll keep an eye on a few still off to the west as well as several smaller pop-ups in the area. It does appear that the severe threat is dwindling as we head into evening. So far, severe weather reports in the immediate area are comparatively few and far between. More widespread storminess impacted the I-95 corridor through New York City and Boston. One particularly striking image (shown below) was captured of New York City from a plane leaving La Guardia!


A rain shaft or downburst is seen over New York City earlier today. Photo by d0057 on Instagram.

Overview: Triple digit heat is once again baking the metro region and establishing new records (see below). Meanwhile, a cold front closing in on the area is triggering widespread severe storms to our north and northwest. A severe thunderstorm watch is in effect through 11 p.m. Storms are likely to contain heavy rain, dangerous lightning and the possibility of damaging winds to 70 mph.

A very large region of the Ohio Valley, mid-Atlantic and Northeast is covered by severe thunderstorm watches as incoming cooler air clashes with this excessive heat. Widespread airport groundstops are in effect due to the developing severe weather.

Storm Timing and Likelihood: Storms are most likely to reach the immediate D.C. metro region between 4 and 7 p.m. (from west to east - Loudoun county to near the Bay). The area inside the beltway is most likely to get storms between 5 and 6 p.m. or so. Note, however, storm chances decrease a bit south of the beltway (less than 40 percent chance), and increase dramatically north of the beltway (greater than 60 percent chance)

Heat records: Reagan National Airport has logged its 7th 100+ day of the year, tying 1988 for the second most record. The recordholder is 1930 which tallied 11 such days. The 6 100+ days this month ties July , 1930 for the most in a single month on record.

Earlier updates....

5:30 p.m. update: The worst of the weather has moved out of the District and storms, for the most part, have weakened. But downpours, lightning and patches of gusty winds continue in central and northern Prince George’s county. The heaviest activity is now affecting the area around Annapolis and extreme eastern Anne Arundel county.

There are more isolated storms to the west and northwest which could affect the area as the evening wears on.

One piece of good news? The heat advisory has been discontinued.

5:15 p.m. update: Strong to severe storms continue from the east side of Arlington through downtown D.C. and east to Bowie and Severna Park, along and just north of Rt. 50. This activity is moving east southeast towards Suitland and Upper Marlboro in Prince George’s county and Annapolis in Anne Arundel county. Severe thunderstorm warnings are in effect for these areas through 5:45 due to the potential for damaging winds, but the main hazards from these storms are lightning and flooding rain (see update below). Delay your commute or allow extra time if passing through these storms.

5:05 p.m. update: Flash flood warning for the District, southeast Montgomery and central Prince George’s county through 7 p.m. Slow moving, torrential storms have produced more than 1” of rain in some areas. Do not try to cross flooded roadways. Turn around, don’t drown.

4:50 p.m. update: Worst of storms stretch from just north of downtown (near Petworth) through Chillum in Prince George’s county. Small hail has been reported with these storms moving east, southeast towards southeast D.C. and central Prince George’s county in next half hour. Another area of strong to severe storms has developed over western Anne Arunel county east of Laurel to around Odenton. This activity is moving towards Severna Park in next 15 minutes.

4:30 p.m. update: Severe thunderstorm warning for the District, SE Montgomery, Arlington county, central Prince George’s county, western Anne Arunel and northeast Fairfax county through 5 p.m. As the outflow (cold air) from the main line of storms to our northwest clashed with our hot air, a large thunderstorm has blossomed in southeast Montgomery county and has grown southward into NW D.C. and even into Arlington. The storm is heading east, with the worst of it heading towards Beltsville, College Park, and Takoma Park and Laurel in the next half hour or so.

4:20 p.m. update:A little good news: the line of once severe storms (which produced damaging winds in western Frederick, Hardy and Shenandoah counties) in northern and western Maryland has shown signs of weakening a bit and is not making it a southward push closer to the immediate D.C. area. But...

A cluster of strong storms has develop over eastern Montgomery county with a history of producing some strong winds, small hail and quite a bit of lightning. This is heading towards southern Howard and northern Prince George’s county in the next 30-45 minutes.

3:50 p.m. update: The line of storms to our north and northwest remains very impressive, but it’s not making a lot of southward progress. The Md/Va. border between Frederick and Loudoun counties represents the southern edge. At this point, there’s a chance most of the severe storms from this line will occur in Frederick, Carroll, northern Howard and Baltimore counties and locations to the south may deal with more isolated, hit or miss, storms - at least for the next few hours. For example, a small cell has developed in southern Montgomery county and is moving east.

3:25 p.m. update: Severe thunderstorms are now into western Frederick county and probably about 15 minutes from NW Loudoun county. Frederick, Md is within minutes of receiving possible severe weather including wind gusts of 40-60 mph.

By the way, the heat index at Reagan National Airport at 3 p.m. was 109 (air temperature 101) - giving you an idea of the juice in the atmosphere.

3:10 p.m. update: The severe thunderstorms to our north and northwest mean business. The radar from east central Pennsylvania to the eastern panhandle of West Virginia is lit up like a Christmas tree and littered with severe thunderstorm warnings. That entire line may not reach far enough south to impact the entire D.C. metro region, but the northern suburbs stand a solid chance of dealing with severe weather from west to east between now (Frederick county) and 7 p.m. (Baltimore and Annapolis)

By and  |  03:01 PM ET, 07/18/2012

Categories:  Latest, Thunderstorms, Extreme Heat

 
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