The graphic linked here shows the multi-day progression of Storm Prediction Center forecasts and how the tornado outbreak aligned with it in the Plains states on Saturday. The SPC had the region outlined with a risk of severe storms 7 days in advance, covered with a moderate risk of severe storms 3 days out and a high risk 2 days out. While identifying where exactly tornadoes will touch down remains difficult until within minutes, this early notification of a high-end severe weather threat was a tremendous forecasting success for the SPC and the weather service offices in the region, and it undoubtedly contributed to the low fatality count of five deaths. Click here to see several videos of tornadoes from the outbreak both Friday and Saturday.
Roanoke’s high temperature of 86 on Sunday was the hottest so far this season, 18 degrees above the normal for April 15 and only 3 degrees below the record of 89 for the date set in 1936. Blacksburg’s high of 81 only missed the standing record by a degree, set in 2006. Monday will be a similar day of temperatures, perhaps a couple of degrees cooler with some additional clouds as moisture builds slightly. The problem for anyone wanting rain this week is that the main energy of the Plains storm will move into the Great Lakes region and into Canada, taking away the dynamics, lift and some of the moisture flow from the Gulf of Mexico that could potentially trigger more rain and storms. As a weak cold front slides into the region Tuesday, some showers and storms could develop. On Wednesday, a weak wave of low pressure moving along the front may slightly increase shower activity. But as you can tell by Sunday night’s 5-day rainfall projection from the Hydrometeorological Prediction Center, amounts in our region are expected to be meager, a quarter-inch or less in most cases. That won’t be enough to head off any developing dryness or provide serious relief for the ongoing wildfires in the higher elevations north of Roanoke. Thankfully, those fires are considered about two-thirds contained as of Sunday.
The midweek system won’t hugely drop temperatures, just pull the mercury back from the summerlike highs of Sunday and Monday. But there are growing signals of a punch of colder air with frost/freeze implications possible by the weekend or early next week. This pattern of alternating warm and cold periods is fairly typical for April. Historic “normal” temperatures in the 60s for highs and 40s for lows this time of year are really the average between up-and-down extremes, not so much an expectation of steady temperatures through the month. Unless and until low-pressure systems dig farther south toward the Gulf of Mexico, Southwest Virginia will not see much rainfall or very many severe storms.