Today was just about perfect headlined by a light-to-moderate breeze, low humidity, a few clouds and highs in the low-to-mid 80s. How quickly things will change. A strong, dynamic frontal system charges into the region Friday, triggering thunderstorms - which may be severe - especially into the evening hours.

Through Tonight: Partly cloudy and pleasant. Low temperatures range from 60-65 (suburbs-city). Towards morning a warm front will approach elevating humidity levels a bit.

Friday: The morning warm front could produce a shower or rumble of thunder (20-30 percent chance). Then we may have a number of hours of partly sunny skies, with increasing humidity and warm temperatures. Highs range from 80-85. Out towards the Shenandoah Valley and I-81 corridor, thunderstorms may develop in the mid-late afternoon hours, a few of which may be severe.

The way it looks right now, thunderstorms will affect the immediate metro region beginning around 5 p.m. and onward. There may be a couple waves of storms affecting the region through midnight or so with heavy rain, gusty winds and dangerous lightning. Some storms may contain damaging winds and large hail with the outside chance of isolated tornadoes. For a complete breakdown of the severe threat, see my earlier post. (Note I am now favoring a slightly later start to the storms, by 1-2 hours, compared to before.) The timing is still subject to change, so stay tuned for updates tomorrow.

See David Streit’s forecast through the weekend. And if you haven’t already, join us on Facebook and follow us on Twitter. For related traffic news, check out Dr. Gridlock.

Pollen: Trees are LOW-MODERATE, mold MODERATE, grasses MODERATE-HIGH

Carbon dioxide in Arctic hits record high: The carbon dioxide concentration in the Arctic reached 400 parts per million this spring, reports the Associated Press. Excerpt: “It’s an important threshold,” said Carnegie Institution ecologist Chris Field, a scientist who helps lead the Nobel Prize-winning Intergovernmental Panel on Climate Change. “It is an indication that we’re in a different world.”