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A low pressure system to our northwest may pull a warm front northward on the Fourth of July. This front may serve to trigger some showers and thunderstorms, and could act as a guide-wire of sorts for any thunderstorm clusters that form in the Ohio Valley. Something Fourth of July festivity planners will want to keep an eye on is whether any of this storminess will arrive in our region by Saturday night about fireworks time. It's a coin flip or lesser chance now ... just keep an eye on things, especially national and regional radar, Saturday.

Sunday looks to be a much better chance of showers and storms (slight risk of severe weather) as a cold front moves into the region and winds, at least temporarily, turn to the southeast to build moisture. But this front will have the net effect of reinforcing the recent mild, dry weather next week, and the familiar recent pattern of high pressure in the south-central U.S. and our region in a northwest flow looks to return.

Our local weather is pretty much in a repetitive pattern of inactivity ... nice for outside activities, by and large, with mostly dry days and highs no higher than the mid 80s for the foreseeable future, but not much new to really write about.

So let's take a look at some other topics, starting with efforts to classify a new type of cloud. Here are a couple of different links to that story, which was widely reported last month when I was occupied with some other things, both weather-related and not.

Associated Press report

National Geographic report

Any thoughts on these clouds? Have you ever seen any like this, or do you have any pics that could be these clouds locally?

ADDED 7/3 5:30 PM: Here is a link to a photo from Blacksburg in November 2006 of clouds that at least suggest the wavy appearance of the possible new cloud classification. These were sent by Taylor White, a recent Virginia Tech graduate who was aboard for Storm Chase 2008.

Looking at Wednesday's 8-to-14-day temperature forecast map from the Climate Prediction Center, it looks a lot like we've seen lately, with hot weather building in the south-central states and our region on the rim of that. Perhaps the heat dome is expanding a little our way by this period. Until then, looks like much of the same ... warm but not hot, mostly dry except for whatever passing disturbances and fronts can squeeze out of limited moisture. Wednesday showed that even with some favorable upper-level wind dynamics, decent instability and at least some lift, the downsloping winds and lack of moisture will be hard to overcome for widespread thunderstorm activity in our region, until we can get more of a southerly or southeasterly flow to bump up the moisture and add more upslope-terrain component to the mix.

Disturbances moving through the northwest-to-southeast upper air flow and a weak front moving in from the west may trigger a few storms this afternoon, and the Storm Prediction Center has placed much of our region in a slight risk of severe weather. These disturbances provide some colder air aloft and some increased wind flow that could allow some storms to organize, despite less than optimal moisture. Locations east of the Roanoke Valley in the Piedmont will have  the better chance of stronger storms, as westerly downslope flow may cut off some of the potential nearer the mountains. Still, something to keep an eye on this afternoon on what will otherwise yet another rather pleasant July day.

On the excitement scale, the weather this week rates very low. Maybe, just maybe, there will be a scattered shower or storm a day or two later this week, with Sunday showing the best chance right now. But on the enjoyment scale leading into the Fourth of July weekend, this week should rate very high for almost anyone. Days will see highs in the upper 70s to mid 80s, very slowly warming through the week, with relatively low humidity. Nights will be cool with lows in the mid 50s to low 60s most nights in most places. The days will be warm enough for kids to hit the swimming pool but not unberably hot for those doing outside work. Our air flow is generally from the northwest, which is the cool, dry direction, with little input of hotter, more moist air from the Gulf of Mexico or Atlantic.

Enjoy this now. Summer is young, so a run of humid, stormy weather or sizzling hot weather still has plently of time to develop.

The weather pattern has been pretty stagnant this week, with hot high pressure in the south-central U.S. deflecting any fronts and significant storm systems up and over it. Here in Southwest Virginia, we've been on the eastern edge of the high, so we've not really got into the really hot stuff but have been a little above normal with very little rain, the most occurring today with a few scattered thunderstorms aided by a passing weak front. There are signs of a pattern shift later this week, with the high pressure in the central U.S. shifting westward. This would allow its clockwise circulation to pull down some cooler air from Canada toward our region by mid to late next week. The 6-to-10-day temperature forecast map from the Climate Prediction Center reflects this expectation, with its blue colors over most of the nation east of the Mississippi River (except Florida and parts of nearby states). As for rain expectations around the Independence Day Weekend: we're on the borderline between normal and above-normal.

But there is something lurking that could play with this forecast. The National Hurricane Center is watching a system in the northwest Caribbean that has at least some chance of developing into a tropical storm as it enters the Gulf of Mexico. Something to watch, but nothing to lay a heavy bet on, yet. The storm's name would be Ana if it becomes a tropical storm.

With moisture increasing on southwesterly winds, there might be a few afternoon thunderstorms on Thursday, and likely even more on Friday as a cold front moves in. While a few spots may get soaked under the heavier thunderstorms (and some gusty winds and hail are possible, too), it does not look like there will be any widespread soaking rainfall. Beyond that ... still looks mostly dry into early next week, and pretty hot with highs hovering around 90.

Our 5-day outlook for rain potential from the Hydrometeorological Prediction Center shows only light rainfall amounts in Southwest Virginia through the weekend, and even that is probably related only to some scattered showers and thunderstorms that may develop late in the week over the mountains as some moisture returns. There are no copious supplies of Gulf moisture in sight as dry, northerly air flow only slowly gives way to west/southwest winds that will be coming from under dry high pressure to the west, so humidity values will only gradually increase as a Gulf moisture only trickles in.

Four of the Virginia Tech storm chasers ... instructor Dave Carroll and students Andrew Smith, Samantha Huddleston and Nathan Horne ... plus Maria Floyd, a South Carolina resident who helped lead the trip back in 2004 and 2005, made a sequel storm chase trip last week to capture a few days of a favorable severe weather pattern from the Northern Plains and Upper Midwest into the Ohio Valley. Some of what they found can be found by linking here to the Hokie Storm Chasers page. The original trip back in May -- that included 12 to 16 chasers at different times -- caught a lull pattern for severe weather, with only 3 storm days and really only one definitive supercell.

I didn't make this trip ... I was out of state a few days, but I was visiting family in Arkansas this time around.

We wouldn't have said this last year during the drought, but we could use a few days of dry weather. And that's what we're going to get this week as a strong low to the east circulates dry north winds into the region for the next few days. That will slowly give way to a hot, dry southwest flow which will only slowly rebuild moisture levels by mid to late week. So those of you who have been wanting dry weather after so many periods of rain ... you're very likely to get your wish.