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Tuesday 8:30 a.m.
Drier air advanced into the northeast quarter of the nation yesterday, but its tenure is temporary and will be quickly terminated. As a high pressure area moves off the East Coast and a low pressure area forms near the lower Great Lakes, more humid air will be drawn northward... and the chance of showers and thunderstorms will increase. This looks like the kind of setup that can unleash 1-2 inches of rain in some areas. However, until we see exactly where the storm forms and how the moisture becomes arranged around it, forecasting rainfall amounts for various places is risky. The video has more.
On this date in 1918, Philadelphia had a high temperature of 106, the highest official reading ever for that city. What did the weather map look like that day? NOAA maintains an archive of weather maps for each day back to 1871. You can view them here The map for Aug. 7, 1918 is below. The map time is 1 a.m., and you may be able to see the 80-degree isotherm for that hour.
In those days, weather records were kept at the Customs House in Center City, Philadelphia. In later years, the observation site was shifted to Philadelphia International Airport. Airport locations are typically somewhat cooler than the middle of our big cities.
During the late afternoon and early evening hours, the cold front of a knife will slice through the turkey and cause it to accumulate 1-2 inches on plates...
This satellite picture shows clouds over parts New York and Pennsylvania, as well as areas of low clouds, fog and snow cover from Michigan to Illinois. Most of the Northeast should have at least some sunshine through Thanksgiving Day.
As we go through the week, the flow aloft over the East will become southwesterly. This will promote a major warmup. This map shows the projected upper-air flow for Thanksgiving afternoon:
A major snowstorm will affect the area from Iowa to Michigan tonight and tomorrow. At first, snow can melt on streets, but as it continues and the temperature drops, the area impacted by slippery conditions will increase dramatically. This map shows expected accumulations:
This map shows two cold fronts in the northeast quarter of the nation; 9 a.m. ET temperature are plotted. The isobars are closest together over the central and western Great Lakes, and this is where the strongest winds were occurring.
This map shows how large an area is directly affected by precipitation on Tuesday morning. The low pressure center was in Kansas early today but will move all the way to Hudson Bay by Thursday while sending a cold front eastward on its south side.