The week ahead: Rain early, slightly cooler temperatures later next week

We’ve gone almost a full week without rain, but that streak is going to come to an end by Monday. Rain and even cooler temperatures in store for the week ahead.

September 14, 2012; 3:23 PM • by Weather Dan

September, fundamentally, is a month of change. The average high and low on September 1 are 86 and 65. By September 30, they are 76 and 54. March and November are the only other months with as great a temperature swing. September also marks the peak of the Atlantic hurricane season, the beginning of meteorological autumn, and is (along with July and August) one of the three wettest months on average, thanks to many of those tropical systems. It doesn’t have the status that March does regarding its weather potency (think about March’s lamb and lion), but it can be just as unsettled.

The Week Ahead

After a very humid, unstable first week of the month, and an incredibly tranquil second week, the pendulum swings back toward the unsettled end of the spectrum again. The forecast this time around is on the challenging side, due to questions about the timing of some features expected to develop beginning early next week.

A weak cold front approaches Virginia beginning today, forcing the ridge of high pressure that’s been around this week off the coast. Temperatures won’t change much – highs Saturday and Sunday are only going to run a couple degrees cooler than they have the last couple days. The noticeable change, at least for the weekend, will come in the form of some humidity relief. Dewpoints that were in the 50s earlier this week have bubbled back up into the 60s over the last 24 hours, making Friday feel a little more tropical that it might otherwise. More dry air will infiltrate behind the front, and we’ll get some relief just in time to spend a beautiful weekend outdoors. Temperatures will peak in the upper 70s over both Saturday and Sunday and stay warm overnight, with lows above 60.

High pressure will return behind the front, but again be quickly forced off the coast for the start of the work week. Easterly winds will begin to funnel moisture off the Atlantic, setting up a traditional “wedge” pattern (where cooler, moist Atlantic air is trapped from moving any further west by the Appalachians. By later on Monday and especially into Tuesday, rain returns to the picture.

This is the forecast precipitation accumulation from 8am Monday through 8am Wednesday. While the Appalachians are currently forecast to collect the bulk of the rain, central Virginia isn’t excluded by any means. Showers are most likely from Monday night through the day Tuesday, but may run into Wednesday, especially if the system is slow to arrive next week.

High pressure will return as the cold front slides out to sea by midweek, giving us another blast of cooler temperatures. The 8-14 day temperature outlook from the NOAA Climate Prediction Center shows a nearly 50% chance of temperatures below the statistical average for the period.

By next weekend, we may only be seeing highs near 70 and lows in the 50s. In case there was any doubt remaining, summer is definitely over.

September 14, 2012 3:23 PM 0