   An active pattern continues for portions of the Mid-Atlantic Friday into Saturday. The pattern is similar to East Coast snow storms with a ridge in western and central portions of the United States, a ridge in eastern Canada, a trough in the eastern United States, as well as a ridge in Greenland. These factors point to a rare summer coastal storm developing late tomorrow into the day on Saturday.
This storm will track off the Delmarva Peninsula, and meander there for a while before weakening and moving out into the open waters. With PWAT values over 2 inches and dew-points temperatures in the lower to mid 70 degrees across portions of the region Friday night, as shown in the images above (credit: WeatherTap.com), there is plenty of moisture to work with which will lead to rounds of heavy showers and some embedded thunderstorms. National weather service offices have issued flash flood watches across portions of Pennsylvania, West Virginia, northern Virginia, Maryland, central and southern New Jersey, and Delaware, for flooding rains as shown in the image above. A general 2-4 inches will accumulate across the area with locally heavier amounts likely. Breezy winds on the coast will also be a threat as it intensifies and tightens up the pressure gradient along the coast. One thing is for certain, if this type of pattern, and much of this summer’s overall pattern were in place this past winter, the Northeast and Mid-Atlantic would have experienced a more active and colder winter. This also begs the question; will this pattern have any influence on this winter? To learn more about other high-impact weather events occurring across North America, be sure to click here! ©2017 Forecaster Joseph DeLizio
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Increasing Convective Threat in Mid-Atlantic (Credit: NWS Storm Prediction Center and WeatherTAP)7/22/2017   DISCUSSION: As the steaming hot weather trends continue to persist across much of the nation, this also favors the re-occurrence of classic Summer-time thunderstorm activity. Often times, during the hottest days of the Summer, there occasionally can still be instances in which weak areas of low-pressure propagate across large regions over the course of 1 to 3-day periods. Such thunderstorm events are very often observed and recognized as mesoscale convective systems (MCS). MCS's are large, intense thunderstorm clusters which often form during the late Spring to Summer-time period (i.e., anywhere from late May to mid-August). Most often, these types of thunderstorm events are observed in association with the coldest cloud top temperatures (on infrared satellite imagery) near or around the center of the upper-most parts of the thunderstorm complex.
For the particular situation which is developing today, there is a previously intense MCS trying to become re-invigorated by the diurnal mixing (i.e., the vertical mixing of temperature imbalances) being induced by the intense heat and humidity in place across the Northeastern and Mid-Atlantic states. Having said that, as shown in the upper-most image attached above (courtesy of the National Weather Service Storm Prediction Center), there is an increasing concern for strong to severe thunderstorm activity across portions of the Mid-Atlantic region of the United States over the course of the next few hours. Therefore, if you live in these areas, it is imperative to remain weather-ready and keep your eyes to the skies. To learn more about other high-impact weather events occurring across North America, be sure to click here! ©2017 Meteorologist Jordan Rabinowitz  DISCUSSION: As mid-summer approaches, the western United States experiences a monsoonal type pattern. Hot and dry weather typically dominates the early parts of the summer months, as seen this June with record breaking high temperatures across portions of the Desert Southwest. As mid and later July approaches, showers and thunderstorms break out day after day across the western United States. Most of the annual precipitation the Southwestern United States receives is from these showers and thunderstorms that feature frequent lightning, large hail, and heavy downpours.
These storms can be dangerous to the population in these areas. Flash flooding is frequent under heavy thunderstorms which can stagnate producing inches of rainfall within an hour or less. Just this past weekend, at least 9 people lost their lives in Arizona due to flash flooding. This is not the only danger from these thunderstorms, aside from the fact that lightning and large hail have their own destructive properties, dry microbursts are also a common occurrence in the western U.S. Temperatures commonly soar from the 90s to over 100 degrees Fahrenheit with dew points 40, to 50+ degrees less than the ambient temperature. Any little shower or thundershower that can survive in this sort of environment has a high probability of mixing winds from upper levels of the atmosphere to the surface that could gust 60 to 70 mph, or more. This poses danger not only to people and property, but transportation as trains could easily derail by the magnitude of these wind gusts. Shown above is an example of storm wind/hail reports from SPC for July 17th. One thing to keep in mind, the observations are sparse out in the western U.S. as opposed to abundant in more populated areas such as the Northeast U.S. Many of the storms could be producing high wind gusts but since there are no observations or reports from people, there is no way to know the exact magnitude or number of reports. In this respect, caution is needed with any storms that develop across this area for the potential of high wind gusts and hail. These types of storm reports will be a common occurrence throughout the rest of July, August, and into September. Out west these storms are beneficial, but as with all good things, too much is harmful. To learn more about other high-impact weather events affecting North America, be sure to click here! ⓒ 2017 Forecaster Joseph DeLizio  The Pacific Coastal Temperate Rainforest is located along the Pacific coastline of Alaska, south through Washington State into North America. This particular area is the largest coastal temperate rainforest in the world where annual rain is measured in feet! Annual precipitation can be measured from as little as 60 inches to as much as 200 inches. The fog contributes to the rainfall amounts by as much as 12 inches a year. At almost 100 miles wide and 2,500 miles down the coast, this temperate rainforest is filled with lush vegetation and a variety of wildlife.
The differences between a tropical and temperate are location, temperature, and rainfall totals. Tropical rainforests are located near the tropics where the temperatures remain very warm all year long, with rain exceeding as much as 400 inches per year. Even though temperate rainforests are located in the higher latitudes, temperatures can be mild. Temperatures decrease with height, however, resulting in the snow-capped mountains seen in the picture above. A combination of the Pacific Storms, mountain ranges and the relatively warmer Alaska current make this type of climate in the temperate rainforest possible. It is noted that the temperatures seldom fall below freezing despite being in the higher latitudes where the climate is normally colder. The image above was taken outside of Skagway, Alaska in the Tongass National Forest. For more information on the Pacific Coastal Temperate Rainforest, click here! For more interesting facts about North America, click here! Source: World Wildlife Fund ⓒ 2017 Meteorologist Brandie Cantrell |
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