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Rain amounts of a quarter to half inch appear to be likely across most of the Southwest Virginia overnight and into Wednesday as showers break out along a cold front advancing eastward. Thunderstorm activity near the Gulf Coast may cut off a richer flow of moisture that would cause heavier rain, but considering there is more rain likely on the way Thursday night and Friday and then again early next week, there's no need to get all of it at once.

With April beginning at midnight, these indeed with be the first of the April showers that are said to lead to May flowers.

Roanoke had four very even days of rainfall from Wednesday to Saturday: 0.28, 0.26, 0.29 and 0.28. Throw in .04 early today, and that's 1.15 inch of rain ... just about an ideal amount of rain. It only takes about .82 inch of rain a week for us to meet the annual "normal" of 42.49 inches, and getting a little more than that is well and good considering (1) 4 years of deficits totalling more than 30 inches and (2) the likelihood for lengthy dry spells in summer.

Even is a good way to describe the weather pattern ahead. It will not be very warm or very cool, with temperatures most days this week with a few degrees of the normals of highs in the low 60s and lows in the low 40s. The overall jet stream pattern will be "progressive," which means regular low-pressure troughs, or jet stream dips, pushing fronts across the nation at regular intervals. For us, that will mean solid chances of rain Tuesday night/Wednesday and Thursday night/Friday, with neither looking likely to produce torrential downpours or widespread severe thunderstorms.

Yes, spring is looking amazingly "normal" as we reach the end of March and head into April. Quite a contrast from the dizzying seesaw early in the month, with snow, lows in the single digits and teens, and highs in the 80s all within the first week.

The last round of this week's series of rainy episodes -- none of which have been terribly heavy, but collectively decent for our long-term dryness issues -- is due later tonight as the line of storms shown in the radar grab at left across Tennesse and Kentucky moves our way.  This line was triggered this afternoon as a cold front pressed into unstable, moist air where the sun managed to come out across central Tennessee north into Kentucky. But the time it gets here, this line will not be producing the severe thunderstorms it has to our west, as it will hit much more stable, cooler air. Dont' be surprised to hear a rumble or thunder and even less so to hear a brief period of heavy rain on your roof sometime overnight. Also don't expect a prolonged heavy rain, likely lasting under 2 hours. It should all be over by Sunday morning, and the sun may make a return by the afternoon. Expect at least 2 or 3 dry days after that, with seasonable temperatures (60s for highs, 30s and 40s for lows)

First, just a note about extremes with the storm system approaching us. Yes, Texas is a huge state, but the contrast across it today was stunning. While the Panhandle region was experiencing a blizzard with temperatures in the teens, Harlingen in south Texas set a record high for the date of 101 degrees. Summer and winter a few hundred miles apart. Not surprisingly, there was angry spring weather in the middle, including hail, high winds and tornadoes.

We've had three or four disturbances (I've honestly lost count) bring us a series of rounds of rain since Wednesday. On Saturday, the core system will finally affect us, as a strong low pressure system heads northeast from Texas toward the Great Lakes and drags a strong cold front into the area (strong in the sense of wind dynamics ... it's a Pacific front, so not extremely cold stuff for our region). This low will pull more Gulf of Mexico moisture than we've seen yet into our region, and we could see some heavy rain, with the Hydrometeorological Prediction Center projecting 1.5 to  2 inches of rain over much of Southwest Virginia through Sunday evening (the rain should actually end Sunday morning).

We may even hear a few rumbles of thunder on Saturday afternoon and evening. The Storm Prediction Center continues to have us at the edge of the slight risk zone for severe weather on Saturday, but it appears that the cool air wedge east of the mountains will limit severe weather in our immediate area. Without surface heating, it will be hard to build the updrafts into cooler air aloft necessary for large and powerful thunderstorms. However, because of the extreme wind energy involved in this storm, a few severe wind gusts cannot be ruled out with a few of the stronger storms in our region. It will mostly be a heavy rain event here, with a more serious severe weather threat from the Deep South into the Carolinas.

Some showers are possible during the day Friday, but we will be between disturbances. Meanwhile, a powerful low pressure system will be cranking up to our west, bringing a dangerous threat of severe weather to the lower Mississippi River Valley and heavy snow to the Texas/Oklahoma Panhandle region (the linked map is for 4-plus inch threat, but local forecasts there are calling for 1-2 feet with drifts of 10-20 feet on 55 mph winds). Moisture will again begin to surge into our area Friday night, and by Saturday, with the strong low passing just to our west and dragging through a strong cold front, there could even be a threat of the season's first strong to severe thunderstorms.

Storm Prediction Center

National Weather Service-Blacksburg

I don't often link to articles on the major weather Web sites, but this blog entry on AccuWeather.com is just too much on the money, specifically pointing out Roanoke's recent-years snow drought and noting that the Eastern snow drought is really part of an overall year-round precipitation drought -- a familiar theme of mine.

Thanks to reader Douglas Rutz for pointing this out to me.

The next several days will feature a highly active weather pattern, not just for Virginia, but across much of the central and eastern United States. The last couple of days brought severe weather to the central U.S. and a blizzard to the northern Plains, where record flooding is also occurring from both precipitation, snow melt and ice jams. Severe weather again developed in Texas today, resulting from the same disturbance that will bring our second round of rain on Thursday. A strong upper-level low pressure system will trigger severe weather in the lower Mississippi River Valley (think Arkansas, Louisiana, Mississippi) over the next couple of days, and also a large snowstorm over the southern Plains, particularly the Oklahoma and Texas panhandles. The powerhouse surface low triggered by this diving disturbance will move northeast and drag a vigorous cold front eastward, which will spread possibly heavy rain our way late Friday and through the weekend, and Saturday could even bring severe thunderstorms into Southwest Virginia (though the chances will be much better south and east of us).

On top of all this, after a brief hiatus early next week, another strong low pressure system moving from the Plains to the Great Lakes may affect the weather over much of the central and eastern U.S. about the middle of next week.

It's almost too much weather to keep up with. The good news is that several very dry areas from the Southern Plains to the Southeast to the Appalachians are getting moisture ... maybe a bit too much in some places. (Tonight's rain potential map from the Hydrometeorological Prediction Center is projecting widespread amounts over 2 inches in our area over the next 5 days). But there will also likely be some weather misery too, ranging from floods to tornadoes to car-burying snowdrifts. In our region, despite the long-term dryness preceding it, there is at least some risk of flooding problems by the weekend if some of the heavier rain bands and stronger thunderstorms move through our area.

Late Wednesday into this evening, the first of several waves of rain and showers is expected to arrive in Southwest Virginia. There will be a chance of rain each day until Sunday, when a strong cold front (Pacific origin, not Arctic, so while it may be windy it won't be extremely cold) will push through the area. The Hydrometeorological Prediction Center is currently forecasting rainfall amounts generally around 1.5 to 1.75 inches through Sunday evening in Southwest Virginia, but of course that all depends on the details of each new wave of moisture. The heaveist rain is forecast in states to our south, including especially drought-stricken regions of north Georgia and the western Carolinas. So this could be a copious spring rain for many dry areas of the Southeast, Appalachians and Middle Atlantic ... though it might be a little too much of a good thing too fast in some areas.

Several interesting weather things have been going on across the nation.

* Tonight's severe weather outbreak in the Plains has been hamstrung by a lack of moisture and limited instability, thankfully for residents out there who have a long season yet ahead, but still enough atmospheric dynamics for a handful of tornado reports and scattered large hail and high winds. Click here for a look at the Storm Prediction Center's severe weather reports.

* Mount Redoubt in Alaska has been in a series of ash-belching eruptions, the latest late Sunday. Volcanic ash injected into the atmosphere often tends to have a medium-range (several months to a year or two) cooling effect. We'll see in time if these eruptions have emitted enough ash to have a noticeable effect on North American or Northern Hemisphere climate.

* The same storm system responsible for severe weather in the central and southern Plains is blasting the western Dakotas and nearby parts of Montana and Wyoming with a massive blizzard.

* Meanwhile, eastern North Dakota is bracing for massive flooding as a winter of deep snowpack rapidly melts, with some rain on top of it.

Southwest Virginia looks cool and rainy most of the week after Tuesday. Temperatures will hover in the 40s and 50s most days. That should dampen the severe weather risk, while any rain that falls will help with continuing dryness that has improved some with March rains.

Here's a sign that spring is under way. The first Plains severe weather outbreak of the season appears likely to occur on Monday, with parts of Oklahoama and Kansas already placed under a moderate risk of severe weather, according to the Storm Prediction Center. Several of the ingredients are there as colder, drier air from the west meets warm, moist air from the Gulf of Mexico, with daytime heating and strong winds aloft. The main question is whether this erupts suddenly into a huge mass of thunderstorms, which would make hail and high winds the major concern, or whether more discrete cells can develop and be spun by upper-level winds, which would put a tornado outbreak on the plate of possibility.

This particular system is not expected to have a major impact on Southwest Virginia's weather, but could set the stage for a possibly wet and stormy period toward the week's end. That's something to keep an eye on throughout the week. Temperatures this week will not be especially warm, and may even slip back into daylong 40s by Wednesday, as cooler air wedges in from the northeast, before slowly become milder going into the weekend.