Observed temperatures at 1:00pm 9/16/11

Autumn like air has made itself right at home in the area today. Temperatures last night dove into the lower 40's throughout much of the interior, and dropped to near 50 in the metro area. Northwest winds and low dew points have the air feeling crisp and cool, even this morning and afternoon. The morning observations had the warmest stations around 52 degrees. Some warming has occurred since then, and at the top of the afternoon temperatures throughout most of the area were in the upper 50's to low 60's. Skies, which were perfectly clear, are beginning to show signs of some airmass change with high clouds moving in. They are moving our way in advance of a mid level disturbance, currently located over the Ohio Valley and Lower Great Lakes. This system is poised to move in our direction tonight into Saturday, and the high clouds could become more widespread. This has implications for tonight's forecast.

Why, you ask? The answer lies in the term "radiating". When the skies are clear under a cool airmass (or any airmass, really), the atmosphere can "radiate" overnight. Essentially, in the most simplistic of terms, the heat from the day at the surface (radiation) can escape into the atmosphere under clear skies and light winds. The calm winds are important, too, as they prevent the atmosphere from mixing..but we'll save the mixing of temperatures conversation for another day. Clouds, however, make the story more complicated. The clouds can hold the radiation near the surface, keeping the temperature warmer. This is way in some cases, on overcast nights, the temperature only drops a few degrees with the loss of the sunlight. On clear nights, it can drop several degrees. Forecast models have high and mid level clouds in the area tonight into Sunday, making for a complicated forecast. It appears that the clouds will be thicker over Central New Jersey and to the south--resulting in a gradient of low temperatures from south to north. Areas north of the city (Northern NJ, Southeast NY, CT) could fall into the low to mid 40's once again, while the city and points south stay in the low to mid 50's overnight.



Through Tonight: Sunny this afternoon, some high clouds moving in as the evening approaches. Temperatures in the mid 60's, northwest winds a bit gusty at first..but becoming less noticeable by evening. After sunset, clouds may increase across southern zones. Temperatures could drop into the low to mid 40's over most areas north of the city, should be in the low 50's in and around the city, and mid 50's south of the city through the overnight.

Saturday: Mid and high clouds will be an issue. We could see the sun shine through them, but we think partly to mostly cloudy is the best sky forecast. High temperatures again top out in the mid 60's. Winds will be light, and we aren't expecting much other than a widely isolated shower.

Article written by John Homenuk, September 16th, 2011 at 1:12pm. Looking for a forecast? See New York Metro Weather's Long Range Forecast for the upcoming weekend, or view our Technical Forecast Discussion for the more serious weather enthusiasts. Also, check out our new Forecast Overview tab. For up to the minute details on forecasts, watches, warnings, and alerts, follow us on Twitter and Facebook.