Thursday 9 a.m. EDT
Showers and thunderstorms are moving eastward from the Great Lakes/Ohio Valley region today and will become more frequent in the I95 corridor tomorrow and tomorrow night. In the meantime, the thunderstorm activity will become stronger and more plentiful as we go through the afternoon today. The National Weather Service Storm Prediction Center has issued this risk map for today:
In today's video, we step through the next few days and look at early next week as well.
Fog can cause a variety of problems, so it is important to know where it is, how dense it is, where it will become foggy and when it will evaporate. Because of the challenges involved with fog, research has been done on how to detect it remotely and depict it usefully on maps. The National Environmental Satellite, Data and Information Service (NESDIS) has been at the forefront of this effort. Here is their description of fog products they develop and issue:
"Image data from two GOES or NOAA AVHRR InfraRed (IR) channels are combined to create a product for the detection of fog and low stratus clouds at night. The "Fog Image" is obtained by a subtraction of the shortwave IR window channel (3.9 micron wavelength) temperatures from the longwave IR window channel (10.7 micron) temperatures. An example of this bi-spectral technique shows fog and stratus forming and spreading into the valleys of Central and Southern California. An experimental Low Cloud Base (LCB) product helps to identify ceilings <1000 ft for aviation users with help from surface temperatures. The "Fog Depth" image is a special enhancement that estimates the thickness of a low cloud layer, based on the temperature difference between the two IR channels."
Here is one of their pictures from early this morning:
The fog is contained within the gray areas.
Snowfall amounts yesterday were low from Philadelphia to New York City. Accumulations increased toward the north and northeast.
This map shows the NAM's projection for this Friday night. The isobaric pattern suggests there is a southwesterly flow of mild air from the Gulf states to the Middle Atlantic region. Farther north, we see evidence of the frontal boundary that separates the mild air from chillier air.
A new area of snow now over southern Minnesota should expand southeastward to reach Chicago this afternoon, streak to Pittsburgh this evening, then reach the Philadelphia/New York City area late tonight or early tomorrow morning. This map shows a low pressure area over Missouri.
This map shows expected accumulations.
Check AccuWeather.com's latest info as the forecast ideas mature. This is a draft of the Thursday morning snow accumulation idea.
Here is one snapshot from this morning's NAM run, depicting the precipitation it predicts for Saturday between 1 and 7 p.m. ET. The rain/snow line should be close to the Pennsylvania-Maryland border.