It appears to be ... raining ... in Silver Spring. Not very much, but I hear the distinctive sound of repeated bits of water falling from the sky on to the leaves.

Visual confirmation of incoming rain. Time to break out the Icelandic chocolate.

Happy Fourth every one!

Jason, realizing both Saturday and Sunday will feature rain/t-storms, which of the two days appears less stormy?

Thanks!

Post #2:

Dear Mother Nature:

So I wake up this morning to see that you released your bladder right over Leesburg just in time to make mud of Ida Lee Park for the 4th of July Festivities. I also hear the doom and gloom reports coming from the weather casters that you are going to take another pee on us between 4-10pm to put us on edge all afternoon and evening.

Maybe I should not blame you mom nature --- I will just blame President Bush since he has nothing to lose ---let's just lower his approval ratings to 4% for the 4th.

Why can't our summertime climate be more like Southern California, where you know every day is going to be hot and sunny with low humidity (except near the beach) and every night will be pleasantly cool?

Why don't you move to California so you can have your hot and sunny weather with low humidity and your cool nights?

David-- Both weekend days have about the same rain/storm potential

With that wetting overnight, I bet we're going to get some crazy action this afternoon especially if the sun peeks out for an hour or two to stoke things up.

Hopefully the DC Split kicks in when we need it.

Annandale. Morning cloud cover is gone. Sunny blues skies on the menu for lunch.

I hear people talk about the DC Split a lot, but can anyone explain why it happens? You'd think it's the mountains, but it often seems to me that it occurs after a storm has already passed them. Maybe it has something to do with the micro-climate around a big city tending to be warmer or something?

Forgive me if this has been covered previously, but a brief search turned up nothing.

Fenriss--it may just be that "splits" happen everywhere, but here in DC we feel like it happens more often than normal. Maybe the heat island creates an updraft inside the beltway? Who knows...personally I doubt we'll see it today.

I thought tomorrow (60%) was supposed to be more stormy than Sunday (40%).

The "kicker" in this forecast seems to relate to when the front will dissipate (assuming it does, as predicted). Most forecasters, including NWS, think this will happen very late Sunday or early Monday.

Any thunderstorms which form over the weekend will influence the future weather by way of their outflow boundaries. More often than not, a heavy or intense thunderstorm tends to stabilize the air in its wake. The exceptions involve entrained ("training") systems and tropical events. Usually "training" occurs underneath an upper air jetstreak or jet stream. We could have a "training" setup if there's a jet right above the stalled front, assuming the front stalls right over us. It's possible that a few Midwestern MCS's could "train" over us, one after the other. However, they have to pass over the West Virginia Appalachians first. Generally the mountains tend to DECREASE the intensity of Ohio Valley systems moving in fom the Midwest.

Fenriss, here's my theory on the "D.C. Split".

I think it's the mountains, not the heat island. Generally heat islands tend to intensify, rather than dampen convection. This would mean more rather than fewer thunderstorms in the urban heat island (explaining in part why we seem to be seeing more thunderstorm days in recent years).

By contrast, the mountains tend to break up rather than intensify mesoscale formations. This is why so many storms coming in from the Midwest tend to fizzle out in West Virginia.

In addition the Blue Ridge may be deflecting the path of those mesoscale systems that make it "over the top", so to speak. Often they are being deflected to the north or the south of D.C. It seems to happen very often in winter with snow coming in from the west. A lot of the winter snow fields accompanying "clipper" storms seem to be mesoscale in size.

Happy 4th of July everyone! There are nice sunny skies here in Lake Ridge.

Regarding the DC Split...you know darn well that only happens when we want a snowstorm or a good thunderstorm ;). Now that we DON'T want it, we'll take the full brunt of this sluggish "cold" front and get the 2+ inches of rain that map that Jason linked to shows us possibly getting.

Hope everyone stays safe out there today...and don't blow yourself up with fireworks! Seriously, I've been there when fireworks have malfunctioned and put people in danger...it's NOT fun. Leave it to the professionals!

Jason, thanks for the reply!