Weather! Some first signs of winter pattern in place

This past weekend’s setup is one that’s reminiscent of what we’ll continue to see for the next few months. Thankfully there’s a little thermodynamic relief in sight in the meantime.

September 19, 2011; 2:04 PM • by Weather Dan

That’s right, I said winter. I’ve jumped straight from fall into winter.

The setup in place right now, called a “wedge,” or more scientifically, “cold air damming,” is one we often see in the cooler months in Virginia.

While high pressure over southeastern Canada is funneling cold air into the Atlantic seaboard states, low pressure situated in the western Atlantic is sending warmer, moist air our way as well. As these two airmasses mix and flow west, they encounter the Appalachians, where the air is forced vertically and cools even more, where the moisture contained within it condenses and becomes a thick cloud layer. You can still see evidence of the wedge in place over Virginia today from the visible satellite imagery, which shows a thick layer of clouds across most of Virginia, especially closer to the Blue Ridge mountains.

Unfortunately, despite the cooler temperatures and additional rain over the last few days, the Lateral West fire in the Great Dismal Swamp is still burning. The fire is now almost entirely a smoldering peat fire, which means most of the burning is happening in the peat matter at or just below the ground. This not only creates ash pits that firefighters can fall in, but also can weaken or destroy the root systems of trees that otherwise appear to be alive, making falling trees a serious hazard to anyone on the ground. The fire is still considered to be 90% contained, with 6,377 acres burned to date.

It’s pretty gloomy in Blacksburg today, but Richmond seems to be getting a bit more sun today. Temperatures are already in the low 70s, compared to a balmy 60 here. Plan on temperatures to continue to climb into the mid 70s this afternoon, before cooling back down into the low 60s tonight.

A weak frontal boundary will cross the Appalachians tomorrow, and with any luck, will help clear out the wedge setup a bit. The passing front will also destabilize the atmosphere some, bringing with it both the chance for some showers starting late tonight and into Tuesday morning, and then a chance of thunderstorms in the afternoon. Plan on high temperatures in the upper 70s to near 80 under mostly cloudy skies, and temperatures overnight back into the low 60s.

Another stronger frontal system is slowly making its way east, and will be here later this week. In the meantime, the next several days will be consistent: warm, cloudy, with chances of showers/storms for the next few days.

September 19, 2011 2:04 PM 0