Steve signing in at 7:07 AM. Under overcast skies, a band of showers and thunderstorms is slowly moving through the three counties. Radar shows the leading edge of a broken line of thunderstorms extending from Lenoir to Morganton to Forest City with steadier and occasionally heavy rains westward to Asheville and Madison County. More showers and occasional thunderstorms are streaming northward from northeast Georgia. The tornado watch for McDowell County has expired. Temperatures are currently in the mid 50s across the three-county area. The reason: the back door or wedge front I have been talking about for the past two or three days has sagged well into the SC Upstate and northern Midlands. Easterly winds are being reported as far south as Chester SC. This stabilizes the surface layer, the layer of the atmosphere we live in. According to the model information Ive looked at this morning, this layer extends up to about 2000 feet aloft, not particularly deep, but deep enough to alleviate the severe storm threat a bit. So while most of us are or have seen lightning or thunder, the only storm report Ive noted is half-inch hail around Hendersonville this morning. What were experiencing now is the same thunderstorm complex that generated 80 tornado reports from Mississippi, Alabama and Tennessee yesterday evening. So far there are reports of 3 fatalities from that system. However, once it reached our area, due to the presence of that shallow layer of maritime air near the surface, it lost a good bit of its punch. So where do we go from here? The models, especially the short range model I use most frequently, erode this cooler surface air around 3 or 4 PM today. Im not sure its going to go away that quickly but eventually, under increasing southwesterly flow aloft ahead of the approaching cold front, it is likely to retreat northward, probably later this evening into the overnight. In the meantime, ahead of the front, another round of thunderstorms, some tornadic, are likely to develop over the same areas of Mississippi and Alabama that had them yesterday. While well see off and on showers and thunderstorms throughout the day today, I think the main event is going to be this area that is supposed to develop later today to our southwest. I foresee it organizing into another line of thunderstorms, with embedded bows and lewps (these will pose a wind damage threat) and where the line fractures, a tornado threat will exist. By later tonight into early morning Wednesday, there appears to be a dramatic increase in wind shear, atmospheric turning and instability. If this all plays out as indicated, we face an overnight round of severe weather including damaging winds, hail and a possible tornado or two, say, somewhere between 11 PM and 3 AM. Again, there are several factors that could work against a severe storm episode later tonight. If the wedge holds out longer than expected as it might, we would still get plenty of lightning and heavy rain but less of a severe threat. Also, the atmosphere over Alabama and Mississippi has been pretty worked over which may delay storm development. It is possible that we could see severe weather later tonight but not a certainty at this point. Wednesday, as the front approaches and the southwesterly flow aloft strengthens to about 60 mph 5000 feet above ground level, I think our wedge will be pretty much history. There should be good atmospheric turning and in addition there is the possibility of another disturbance developing in or close to our area. This could trigger another line of thunderstorms, potentially right over top of us Wednesday afternoon. This would be our worst case scenario for severe weather because there would be nothing stopping these storms from rapidly intensifying and posing a damaging wind, hail and tornado threat. The Storm Prediction Center places us in an elevated slight risk area with a 30% chance of severe storms. Wednesday, while were by no means out of danger, I think the epicenter of the activity may lie in the Charlotte to Raleigh corridor where the storms have had sufficient time to build and intensify and where richer, moist air will have destabilized the atmosphere. By Wednesday evening, the severe storm threat should diminish for our area but by then well face a serious flooding threat after rounds and rounds of heavy rain. In addition to stream and river flooding, rock slides and mudslides are possible. In fact, I believe the most widespread hazard from this entire event will be the heavy rain/flood/landslide threat. Wind and hail damage, if it occurs, will be more isolated and localized in nature. To summarize: expect occasional showers and thunderstorms today; as the day progresses the severe thunderstorm threat increases. A line of intense storms is possible tonight and again Wednesday afternoon. Heavy rain and flooding will be our biggest problems through Thursday morning.
Posted on: Tue, 29 Apr 2014 11:45:53 +0000