- Intense storm monitoring until 9 pm Flood watch until 11 p.m. * 3:10 p.m. – Strong to severe storms are running in the northern suburbs of DC A series of thunderstorms swept south of Pennsylvania into northern Maryland, triggering a severe storm warning from northern Montgomery County north to the Mason Dixon Line. Includes Thurmont and Frederick. Thunderstorms – which extend from about Hagerstown to Westminster – can cause gusts of up to 60 mph in addition to torrential rain and lightning. This series of storms, booking south at 50 mph, could reach the western suburbs of Beltway and DC before 4 p.m. We will post our next update as they approach. 2:10 p.m. – Monitoring of intense storms until 9 p.m. As heavy storms have already broken out in the area, the National Meteorological Service issued a strong storm until 9 pm. Many storms will trigger torrential rains and dangerous thunderstorms, while some could cause catastrophic gusts of wind and hail. Heavy rains have been reported in the District of Columbia, Maryland, Pennsylvania, Virginia and West Virginia until 9 p.m. EDT pic.twitter.com/N7SIHDuZsp – NWS Severe Tstorm (@NWSSevereTstorm) June 22, 2022 The clock extends from central Virginia to central Pennsylvania, where thunderstorms develop and sweep south. It does not include counties along Chesapeake Bay where thunderstorms are expected to be somewhat less numerous and intense. Remember that a strong storm means that the conditions are favorable for strong storms, but it is not a guarantee. Stay informed about the weather. If a strong storm warning is issued for your location, it means that a strong storm is imminent and that you will need to seek shelter. The initial round of rain and storms that has already passed will open its place for another wave that will develop in southern Pennsylvania and will arrive late in the afternoon. It can be more intense. Original article from noon The pleasantly dry weather of the last few days is gone. a very warm, moist pattern takes its place. But cooler air lurks in our northeast and northwest. We are stuck in the transition zone where these opposing gas masses meet, a mature setting for intense storms. Thunderstorms are most likely between 3 and 11 p.m. about, and some can be severe – containing catastrophic winds and hail in addition to heavy rainfall and dangerous lightning. Some areas could be repeatedly hit by strong storms, increasing the risk of flooding. The National Weather Service has issued flood monitoring for much of the area, except southern Maryland and Chesapeake Bay counties, where rain and thunderstorms are likely to be less frequent. The #Flood Watch for possible flash floods this afternoon and evening has extended eastward on Corridor I-95. Heavy # rain from thunderstorms can lead to rapid rise of water in creeks, streams and areas with poor drainage. pic.twitter.com/MtfzQDadcQ – NWS Baltimore-Washington (@NWS_BaltWash) June 22, 2022 Heavy rainfall and the greatest threat of flooding are likely to be concentrated between interstate 95 and 81. Rainfall totals will be very variable throughout the area, depending on where the heaviest storm cells follow – something that cannot be predicted before they begin to form. Some areas could see less than a tenth of an inch, while some models show maximum sets of more than 5 inches, which is a heavy amount of rain. This amount of rain would require strong storms and repeated monitoring in the same area – a phenomenon known as training. The biggest threat of storm training lies west of Route 15, which runs from Frederick to Warrenton. The Meteorological Service has placed the western half of our area in a Level 2 of 4 danger zone for excessive rain. Our eastern regions are at level 1 risk. The threat of flooding may be somewhat mitigated by the fact that June has been dry so far – but if it drops 2 or more inches in a short time, it could quickly cause streams to overflow and flood poorly drained areas. “Excessive runoff can lead to flooding of rivers, creeks, streams and other low-lying, flood-prone locations,” the Meteorological Agency wrote. Remember to never try to cross a flooded road as the water level is difficult to judge. Turn around, do not drown. In addition to the threat of heavy rainfall, the Meteorological Service’s Storm Forecasting Center has put the area at a Level 2 of 5 risk for severe storms that could cause “catastrophic winds and isolated heavy hail”. A single tornado can also not be ruled out. The most likely time for strong thunderstorms would be late afternoon and early evening before the threat subsided into the dark. However, the risk of heavy rainfall could continue until 10 or 23:00 in parts of the area. An unusual pattern comes together for the next 12 to 18 hours. As shown in the surface forecast diagram (valid 8 pm) below, we have a cold front approaching from the west. Above the bay and corridor I-95, another sluggish frontier is approaching from the east: a strange direction, in fact, a process called retrograde. Along this limit, a weak low pressure area is expected to develop. Thus the area will be placed in a zone in which the liquid, unstable mass of air between the fronts is compressed from both directions. This is called air convergence and the result will be a large mass of air that is forced to rise. To the power is added the very high moisture content of the air. The Meteorological Balloon at Dulles has revealed that aggressive deep humidification is underway, to the point where the “precipitating water” (total equivalent depth of liquid water vapor) will be between 2 and 2.5 inches – a value that is quite too much for us . area in late June – close to record levels. These unusually high prices at 8 tonight can be seen from the red ribbon on the map below. So we have a very high moisture content, which is compressed upwards in the area between two fronts, in an atmosphere unstable enough to create storms. These factors will intensify late this afternoon and will likely persist until around midnight. The deep air flow up is also abnormal for this time of year, from the north – so stormy cells will grow in Pennsylvania and drift south into the Baltimore-Washington area. We believe that the retrograde front covered along I-95 will act as a conduit along which the storm cells will fire repeatedly and follow from north to south. It is difficult to say in advance the exact counties / locations affected, but this “training” effect could result in impressive rain sets for some, over 2 to 3 inches. One of the simulations of high-resolution radar coverage forecast models for tonight is shown below – you can choose the enhanced storm cell runway along and west of I-95. Another area of focused, heavy rain may be near or just west of runway I-81, where enhanced humidity from the mountains and the approaching cold front may release additional atmospheric moisture. Note, however, that the above radar simulation is only a rough guide to how storms can develop. the actual time and location of the storms could end up being quite different. Strong local storms can also create catastrophic gusts of wind, lightning, and possibly even a tornado. We do not expect severe weather coverage to be as widespread as the threat of flooding. But the shear of the wind (or the increase in wind speed and the change of direction with altitude) is sufficient, together with the local “rotation” created along the retrograde front, for the threat of an isolated tornado. Catastrophic linear winds are more likely, in the form of explosions, in which the heavy mass of descending water in the downstream hive carries the air down to the surface at high velocity.
