1:30 PM | *Strong thunderstorm and heavy rain threat tonight…refreshing air mass for the weekend (and possibly another one for next weekend)…potential tropical activity next week to ten days*
Paul Dorian
12Z NAM (3-km version) forecast map at 10PM tonight with a band of showers and thunderstorms closing in on the I-95 corridor; courtesy NOAA, tropicaltidbits.com
Overview
There is a refreshing air mass headed our way for this weekend and there are signs that there could be a repeat performance for next (Labor Day) weekend as well with both air masses backed up by strong high pressure to the north and west. The transition from today’s warmth and high humidity to below-normal temperatures will likely come with one more round of heavy rainfall and strong thunderstorms as the cold from arrives late this evening. The threat for showers and thunderstorms will continue into Friday as the front grinds its way through the region, but late tomorrow and much of the weekend will feature drier weather and comfortable temperatures and humidity levels.
On the tropical scene, low pressure will meander off the eastern seaboard over the next several days and given the warm waters in that part of the western Atlantic, tropical storm formation is not out of the question. Later next week or during the Labor Day weekend, there are signs for some potential activity over the Gulf of Mexico where sea surface temperatures are quite warm as well.
12Z GFS forecast map at 2PM Saturday, August 24th with strong high pressure to our north and west anchoring a refreshing air mass for this time of year. Low pressure off the east coast will have to be monitored this weekend and next week for potential development into a tropical storm. Courtesy NOAA, tropicaltidbits.com
Strong thunderstorm/heavy rain threat tonight
There is a chance for some strong thunderstorm activity tonight as a strong cold front arrives and the potential exists for heavy rainfall. The most likely timetable for this activity is between 7 and 11 PM and the band of showers and thunderstorms will drop south and east into the I-95 corridor from the western part of the Mid-Atlantic.
Much cooler air will arrive in the I-95 corridor on Friday and high temperatures could actually be confined to the 70’s in most places from DC-to-Philly-to-NYC. Morning and mid-day clouds and lingering showers will be likely, but many areas should enjoy some sunshine during the late afternoon hours as the drier air mass envelops the region. Refreshing cool conditions are likely tomorrow night with low temperatures early Saturday in the 50’s across much of the Mid-Atlantic region. It’ll stay comfortable through the weekend thanks to strong high pressure to our north with pleasant temperatures and humidity levels along with some sunshine on each day.
2Z GFS forecast map at 8AM Sunday, September 1st with strong high pressure again situated to our north and west anchoring a second refreshing air mass for this time of year. Low pressure is predicted to be over the western Gulf of Mexico where sea surface temperatures are running at above-normal levels. Courtesy NOAA, tropicaltidbits.com
Tropical Update
The quiet stretch of weather in the Atlantic Basin that extended from mid-July to earlier this week was the first such quiet stretch this time of year with no named storms since 1982. This quiet stretch ended a few days ago when a weak tropical system reached tropical storm status and was named “Chantal”. This system has since been demoted to tropical depression status out over the open waters of the North Atlantic and is no threat to the US.
Warmer-than-normal sea surface temperatures this time of year are generally favorable for tropical storm formation or intensification. Two such areas currently exist in the western Gulf of Mexico and the western Atlantic. Courtesy NOAA, tropicaltidbits.com
Two areas to watch for potential tropical activity over the next week to ten days include just off the US east coast in the near term where low pressure will meander and then the Gulf of Mexico in the longer term. There is an increasingly better organized disturbance now near the Bahamas and a slow trek over warm waters of the western Atlantic over the next few days could result in intensification. In addition to the warmer-than-normal water in the western Atlantic, another favorable factor this time of year for tropical storm development or intensification is the formation of strong high pressure over southeastern Canada. This type of pattern often results in a tropical system “cutting underneath” and heading towards the southeast US coastline or the Gulf of Mexico. Not only will there be strong high pressure up across southeastern Canada this weekend and into the early part of next week, but signs point to a repeat performance in the atmosphere during Labor Day weekend. One final note, the next tropical storm to be named will be called “Dorian”.
Stay tuned.
Meteorologist Paul Dorian
Perspecta, Inc.
perspectaweather.com