* Flash Flood Watch 2 pm today until 2 am on Friday *
7:00 pm – Storms come out in the east, light to moderate showers persist
Tonight's storms, which crossed fairly quickly to avoid major floods despite heavy showers, spread to the east and southeast of the metropolitan area. A persistent band of light to moderate showers will continue in the western region in the east during the next two hours before the onset of drying out.
This is our last update scheduled for this post. Keep reading for Ian Livingston's predictions until tomorrow …
Through this evening: Once the showers and storms are over, the sky is partly cloudy with temperatures ranging from the mid-60s to a low of 70. The winds turn to come from northwest to dawn. Since the winds are light, it will not be possible to exclude part of the fog late at night.
Tomorrow (Friday): The sky is usually sunny and the air dries a little over time as the breeze from the west and northwest continues. Moisture is down, at a moderately high level, while peaks reach 80 to 90%.
6:15 pm – Torrential rains but widespread floods did not materialize. End of the storm in sight.
Rain showers and storms across the area since this afternoon have been fast enough to prevent flash floods in most of the area. In addition, this second wave of storms crossing, at least north of the city center, is not as intense as expected, as the energy it could draw was used at times from the first wave.
That said, we are seeing heavy rains and frequent lightning south of downtown Washington via Fredericksburg, and these heavy thunderstorms will sweep south Maryland over the next hour or so.
To the north and west of the ring road, we see only light to moderate rains expected to cross the area in the next two hours. By 20 or 21 hours, many of us should take a break in the rain.
17.45 – Second wave of storms with very heavy rain and gusty winds, especially in the south
The leading edge of the second wave of storms moves into the immediate area and is about to move into the Beltway. He is currently expanding from Frederick to Dale City, then winds up to southwest in central Virginia. The heaviest activity is along the southern half of this storm zone, just north of Manassas, south and southwest. It is pushing eastward at about 25 mph and will move to the interior of the district around 6 pm. and reach the east side of the ring at around 18:15.
Expect abundant rains as well as strong gusts of wind (up to 40 to 50 mph) generally along Interstate 66 and Route 50 and south of it. when it goes to the east.
"The heavy local rainfall can cause a build-up of water on the roads and cause the release of small streams," warns the Meteorological Service. "Be alert to the potential of stagnant water and hydroplaning."
17:00. – First wave of storms but second largest wave coming from west and southwest
The first series of storms quickly swept the immediate area and already reached Anne Arundel County after leaving the Beltway. Its rapid advance speed (25 mph) prevented widespread flooding, although we have seen some isolated reports of high water. We also saw some cases of tree felling caused by the strong winds of the intense storm that went through Takoma Park, Silver Spring and College Park.
The next wave is now heading from the west and southwest and extends from south central Loudoun to Fauquier County. This activity is moving eastward to 20 mph and is expected to affect all of our areas located just west of the ring road, including Leesburg, Poolesville, Manassas, Centerville, Reston and possibly Fairfax of & # 39; 39, here 30 to 45 minutes. It should reach the ring road between 17:30 and 17:45.
This area of rain and storms coming in, which is larger than the first, has a higher flood potential. So plan extra time if you plan on going in the next two hours and do not forget to turn around and find a different route if you encounter high levels of water.
In addition to very heavy rains, some gusts of wind ranging from 40 to 50 mph are possible with these incoming storms.
16:00. – The storms of Silver Spring at Mt. Vernon, passing through District; violent storm warning from College Park in Odenton until 4:45 pm.
Storms extend from Silver Spring to the district through the district. Vernon. They are particularly heavy between downtown Washington and Silver Spring, but they move fast enough (east to 25 mph) so that floods have not been reported yet. All this line of storms will leave the east side of the Beltway in the next 30 minutes. He should hit Bowie, Clinton and Waldorf between 16:15 and 16:30.
The weather service issued a violent thunderstorm warning until 4:45 pm. for the area from Silver Spring to Odenton, including Landover and Bowie, where gusts of wind could reach 60 mph. The radar shows very strong winds between Silver Spring and the Greenbelt, all around College Park and pointed towards the Greenbelt.
3:35 pm – First wave of storms in the Beltway with heavy rain and lightning
A series of storms extends from Woodbridge to Annandale, McLean, Bethesda and up to Olney with heavy rains and lightning. Until now, no flash flood warning has been issued, but it is expected that visibility will decrease as storms dissipate and the water s accumulates on the roads, especially in poor drainage areas. Some locally strong winds are also possible, with gusts above 30 mph.
The storms are moving east-northeast at about 15-15 km / h and are expected to cross Interstate 95 and pass through the district in the next hour or so.
This is only the first wave of storms and a second round is expected from the west from 17h.
3:00 p.m.. – Weather Service warns of the risk of "major" floods during the first wave of storms in the region
A storm zone has developed between Manassas and Gaithersburg, with pockets of very heavy rain and frequent lightning. The most intense activity is the southwest of Centerville, moving northeast towards Fairfax County Center. We will have to watch this storm for the flash flood potential.
This area of storms is ahead of the main line of storms in eastern West Virginia that is expected to cross the region tonight.
Meanwhile, the national meteorological service has published special discussion for our region with the title "likely flash flood" and that storms "will likely produce precipitation rates of 2" / hr or more in an unusually wet environment. "The discussion indicates that the models simulate" pockets of 4 "rainfall, if not locally higher" and that "flash floods could be important" if storms were crossing the same areas repeatedly.
Summer has returned to a thick humidity, and a northward-going low-pressure system, accompanied by associated weather features, will likely help ignite a series of violent to violent thunderstorms this afternoon until evening. .
The most likely time for thunderstorms is around 15 hours. in our western regions around 19 or 20 hours well south and east. In the immediate vicinity, near the ring road, the most likely window is between 16 and 18 hours, with a focus around 17 hours. – coinciding with the journey.
Given the rain that has fallen recently, flood areas are worrisome.
"Torrential rainfall can lead to totals greater than two inches over a short period of time. Isolated places can receive three or four inches, "warns the National Meteorological Service.
However, we do not expect an event as intense and widespread as the major event of Monday's flash flood. That said, it would be wise to consider delaying your ride when it is raining heavily and remember never to attempt driving on flooded roads. Turn around, do not drown.
In addition to the risks associated with heavy rain and lightning, these storms can produce pockets of devastating winds.
Approximate time of arrival of the storm:
- 14h to 16h in the western areas.
- 4 pm to 6 pm in the immediate vicinity, including Capital Beltway.
- 5:00 pm to 7:00 pm in areas east of Interstate 95 and up to 20 hours. or so in the south of the Md.
Isolated thunderstorms are possible earlier, in the early afternoon in the entire region.
Everything is clear: from 20h to 22h from west to east, possible showers after.
Duration of the storm: 30 to 60 minutes, although the rain may last longer.
Chance of measurable rainfall regardless of location: 75 percent.
Storm movement: from west to east.
Probable storm effects: heavy rain, lightning, isolated flash floods, gusty winds.
Possible storm effects: scattered flash floods, damaging wind gusts, hail.
Precipitation potential: considerable variability; average can be as low as 0.5 inches, but some areas could see one to three inches and others very little.
Today, the probability of widespread showers and thunderstorms is high, given the approach of a front and generalized disturbance of the level of the upper currents. In addition, the air mass is quite humid. With the recent extreme rains in the Pacific region, the flood threshold is low. The most likely period for these storms is about 15 hours. west at 20h south or east.
A continuous convection line has formed west of the Appalachian spine and is gradually moving east-southeast. This is our main goal. Models such as high resolution HRRR and NAM maintain the line together while regenerating it to the east of the mountains. It then crosses the continental region during the afternoon and evening.
So what can we expect when this line of storms arrives?
Despite cloud cover in some parts of the region (starting in the morning), the atmosphere should be sufficiently unstable to withstand strong to perhaps severe storms. A warning comes from the launch of the early morning balloon at Dulles, which showed a fairly stable (or hot) temperature layer at mid-level of the atmosphere. If this prevails in the afternoons, this could mitigate the intensity of the storms.
It is likely that the biggest risk this afternoon is the prospect of more torrential rain.
The entire Washington area is under flood monitoring, and the Weather Prediction Center (WPC) has placed in a moderate risk zone for excessive precipitation. This is due to a combination of factors, including the arrival of organized storms, near-maximum atmospheric moisture, and other processes that will encourage abundant airflow.
This line of storms should pass faster than what was seen during Monday's flood; we do not expect pockets of rain from four to six inches. However, a mere inch or two inches is all that may be needed to cause flood problems again. These amounts are certainly possible and we can not exclude fully isolated amounts over three inches.
The Storm Prediction Center also exposed our area to a slight risk of severe thunderstorms, level 2 out of 5 on the probability scale. The combination of an unstable atmosphere and modest wind shear (increasing winds with altitude) is conducive to multicellular storms, which tend to be more intense and durable than ordinary pop-up cells. .
A combination of instability, heavy rainfall and shear can produce some moist microburst with isolated wind damage.
We will update the evolution of the situation.