12:30 PM | ***Major rain event likely on Thursday/Thursday night in the Mid-Atlantic region***
Paul Dorian
Tropical moisture will feed into this system on Thursday with an influx from the Gulf of Mexico and southwestern Atlantic Ocean. This influx of moisture will combine with vigorous energy aloft and a very slowly-moving frontal system to increase the chances for a significant rain event in the Mid-Atlantic region. Map courtesy NOAA, tropicaltidbits.com
Overview
The active weather pattern that we have been experiencing in the Mid-Atlantic region and Northeast US over the past few weeks will continue well into May aided in part by a continuation of cold air outbreaks from Canada into the central and eastern US. The upper-level jet stream across the country as we close out the month of April is very active and has featured numerous strong waves of energy in recent days and another one is on the way. This next powerful wave of energy aloft will dive southeast from southwestern Canada into the Upper Midwest by tomorrow afternoon and then slide into the Mid-Atlantic region by late Thursday. The combination of this wave of energy in the upper atmosphere, a painfully slow-moving surface frontal system, and a strong flow of very humid air up along the east coast will likely result in a major rain event for the Mid-Atlantic region on Thursday and Thursday night. Given the well saturated grounds from recent rainfall, this type of potential significant rain event could very well lead to localized flash flooding conditions and will have to be closely monitored.
The 12Z GFS indicates the potential for significant rainfall on Thursday near and along the eastern seaboard. Map courtesy NOAA, tropicaltidbits.com
Details
As upper-level energy slides into the Upper Midwest later tomorrow Wednesday, low pressure will intensify over the Great Lakes region and will tend to stall out in that area for awhile. A trailing frontal system will grind its way towards the eastern seaboard on Thursday in a west-to-east fashion as it becomes aligned with the flow of air in the upper part of the atmosphere. This will become a very important development in this unfolding weather pattern as it will allow the atmosphere to become very moist along the east coast with a tropical inflow of moisture from south-to-north and it will allow the rainfall to last for an extended period of time. In fact, given the very slow movement of the frontal system and the high precipitable water amounts expected on Thursday, rainfall amounts could end up between 2 and 4 inches inches in the eastern states from the Carolinas to New York. Localized flash flooding may very well become a real concern during this major rain event due to the combination of 1) the expected heavy rainfall, 2) the already well-saturated grounds from recent storms, and 3) the fact that we have had a chilly April in the eastern US which has inhibited evaporation in the top soil layer.
Vigorous energy in the upper part of the atmosphere will contribute to a soaking rain event on Thursday in the Mid-Atlantic region. The trough axis will become somewhat “negatively-tilted” (i.e., oriented from northwest-to-southeast) on Thursday which will enhance upward motion in the Mid-Atlantic. Map courtesy NOAA, tropicaltidbits.com
Looking ahead, the overall active weather pattern is likely to continue in the month of May as cold air outbreaks into the central and eastern US look like they’ll continue right into at least the middle of the month.
Cold air outbreaks are likely to continue across the central and eastern US right into at least the middle of May. Maps courtesy NOAA, tropicaltidbits.com
These cold air outbreaks are combining with increasingly warm and humid air masses across the southern US to not only raise the chances for storms and rainfall in the Mid-Atlantic region, but also are raising the odds for severe weather across the southern US (today in south-central US, tomorrow across the Southeast US).
Meteorologist Paul Dorian
Perspecta, Inc.
perspectaweather.com
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