The weather we experience is mostly due to the position of the jet stream. It really doesn’t matter what time of year it is, if the jet stream is north, south, east or west of us we see different types of weather.

During a typical summer, especially in July and August the jet stream takes on a configuration which allows warm and humid air to ride north across the eastern half of the United States. This year, especially in August this didn’t happen and thus I and perhaps you, enjoyed a cooler and drier month.

This week the jet stream taken up a position that resembles early August, not early September. The map below shows the position of the jet as we head into Friday. That day is going to be a hot and humid day with highs in the upper 80s. The humidity is going to increase as well making it feel quite uncomfortable. The borders on the map aren’t the best, so I labeled Miami and Boston. The red line represents the mean flow at about 30,000 feet high in the atmosphere. This flow allows the heat and humidity over the southern part of the United States to flow northward.

jet stream09314

Temperatures this week are running about 5-9 degrees warmer than average. This will continue into Saturday. If you read the blog regularly you know I am not a fan of the word average as the weather here is rarely average. Look at any given month throughout the year and you will find very few days where the high and low are actually average. Unlike places like San Diego and Key West, our temperatures have huge potential ranges on any given day.
Sunshine is going to be abundant the next three days. I mentioned on Sunday that if you took this week for your summer vacation you certainly had some luck or amazing foresight to pick such a wonderful week of weather. Highs today through Friday will be in the lower to middle 80s, but on Friday some places over interior York and Cumberland Counties could reach 90F again.

It’s been rather uncomfortable for sleeping the past few nights, but the next couple of night will be much better for that and you should be able to keep the windows open and the air conditioning off. I’m thinking of leaving the air conditioning on today, but turning it off around 6PM when the temperatures will start to fall.

The weekend is going to be a 50/50 split between summer and early fall. Saturday, a cold front approaches the region and with it come more clouds, high humidity and somewhat warm temperatures. There is a high risk of showers and storms in the afternoon and evening. I will refine the timing of the wet weather later this week. As the front pushes eastward, the drier air will eventually win out. Sunday features partial sunshine a busy breeze and pleasant temperatures. Highs on that day will stay in the lower 70s, but some mountain areas will remain in the 60s. This more typical September weather will remain into next week.