Two factors affecting our weather now and next week
Today’s (Thursday’s) clouds can be attributed to two separate weather features, the first of which is shown in this graphic:This is a forecast map of the 500 mb (~18,000 feet up) level of the atmosphere over the U.S. and the feature I’ve circled in red is a classic shortwave trough over the Carolinas. It is just far enough south that the associated precipitation will stay south of the Virginia / North Carolina line today, but it is streaming high level clouds overhead of the Fredericksburg area today. This shortwave trough will move off the coast later today and not affect us tomorrow (Friday).
The next feature that is creating low cloudiness overhead now is a surface high pressure system located over the northeastern U.S. that is “wedging” colder air southward along the Piedmont areas east of the mountains. This feature will keep the low clouds around most of today and will help suppress the high temperature under the 50 degree (F) mark. This will move out and sunshine and warmer temperatures – in the mid-50′s – will return Friday through Sunday, but then another high pressure will reestablish itself over the Northeast Sunday night with a vengeance as shown here:
This next high pressure system will affect our weather in two ways next week. First, as indicated by the white arrow I’ve overlain on the above graphic, cold air damming will return early next week as the clockwise flow around the high pressure ushers in northeasterly surface winds that will force low level moisture off the Atlantic westward over the Virginia Piedmont. This looks like it will sock us in with low clouds and light rain (or drizzle) from Monday through Wednesday of next week.
The second way this feature will affect us next week is that this strong high pressure system looks like it will cause a new storm – forecast to form off Cape Hatteras – to stay further off the East Coast than originally thought. That will keep the ‘Burg dry for Thanksgiving and, more importantly, prevent this new nor’easter from inflicting more misery on our neighbors to the north that are still reeling from the effects of Hurricane Sandy.
‘Nuff meteorology lessons. Have a good Thursday!