Cold shot late next week?

Main focus at the moment is of course the imminent flood threat as well as potential impact from Tropical Storm Kyle. All details on this situation will be updated regularly in the Tropical Weather Outlook.

Strong mid to upper level low in the Carolinas will begin to turn northeast tomorrow. The associated warm front will lift north of the region by tomorrow morning around 9am. This will likely coincide with a line of heavy showers with embedded tropical downpours. Warm air advection will allow daytime highs to reach about 10 degrees above today. Dew points will shoot up into the 60's, staying close to the air temp throughout the day and into Sunday. A constant flow of tropical moisture will being rounds of heavy rain through the day and night Saturday. Depending on the exact track of Kyle, which continues to shift east, we could be done with rain by late Sunday morning, but some scattered showers are not out of the question through Sunday night. Total rainfall in Keene will be on the order of 3" to 4.5". This is generally below flood guidence as it is drawn out over 60 hours, but small streams will likely be significantly affected. Further east, rainfall totals of 4 to 8 inches are likely and flooding will be a greater threat.

Mid level low lifts north into Nova Scotia on Monday. The cold front crosses western New England early Monday morning around 3am, so drying will take place thereafter, however some cloudiness will remain in the area.

The pattern becomes very amplified by Monday Night, as a strong mid level low enters the eastern Pacific, forcing western US ridging and allows an intense polar vortex to drop south into the Great Lakes region Tuesday afternoon. A few rounds of showers will are possible Tuesday afternoon through Thursday night as a weaker leading shortwave develops and moves through. The exact evolution of the pattern is far from being nailed down, but the GFS has been adament (and the ECMWF is starting to tag along) in dropping the 850mb 0C isotherm into the mid Atlantic region by Friday 10/3 with 500mb heights under 540dm into New England. This is a recipe for a notable shot of cold air. At this point it looks like a couple of days with highs in the low 50's (about 12 below norm), and lows in the lower 30's (about 6 below norm). This pattern will likely lead to someone in the Great Lakes region getting their first flakes of the season. How far south and east that can extend is the question.

Temperatures should start to moderate by days 9 and 10.