April showers bring May flowers. But April showers may be in short supply.
We are entering what is likely to be a prolonged bone-dry period in Virginia, following what has already been several months of below-normal precipitation that has left the majority of the commonwealth in moderate to severe drought on the latest U.S. Drought Monitor.
This dry spell is developing because of a significant re-shuffling of the prevailing atmospheric pattern over North America.
For much of winter, the western U.S. has been dominated by high pressure, leading to unusually warm and dry weather, while a jet stream trough has brought frequent cold shots and some substantial rounds of snow and ice to the eastern U.S.
The pattern is shifting to one in which high pressure is centered over the southeast U.S. while the jet stream dips southward over the western half of the nation. This is going to allow cooler and wetter weather into a large area that has been hot and dry, and will probably bring rounds of heavy rain, severe storms and some tornadoes to the central U.S.
But high pressure will keep most of that to our north and west, probably for 10 days or more. In time, a cold front or two may slide far enough southeast to kick up some showers and storms, but widespread soaking rain looks to be unlikely, with a strong chance April becomes another in a string of below-normal rainfall months in our region.
Long dry spell
Most locations in our region have been below normal in rainfall (includes melted snow and sleet) by varying levels each month from September to March. Some places also had dry summer months, but sporadic downpours in thunderstorms occurred in other locations.
The seven-month September to March period rates as the driest such period in 53 years of records at South Boston, with only 14.62 inches of rain, nearly two inches less than the same stretch of the previous driest September to March period in late 1980 and early 1981.
Even at several sites in our region with many more years of weather records, the September to March period ranks among the driest.
· Roanoke, 13.05 inches, third driest of 104.
· Danville, 13.80 inches, fourth driest of 94.
· Blacksburg, 14.93 inches, seventh driest of 100.
· Burke’s Garden, 17.34 inches, seventh driest of 103.
· Wytheville, 13.50 inches, eighth driest of 95.
· Lynchburg, 15.54 inches, 16th driest of 132.
This persistent lack of rainfall has left most of Virginia in moderate to severe drought, according to the latest U.S. Drought Monitor issued last week (a new one posts Thursday with little improvement anticipated).
In Cardinal News’ Southwest and Southside Virginia region, Roanoke and most places east of the Blue Ridge are considered to be in severe drought, with moderate drought covering the rest of the region except a thin sliver near the West Virginia border that is still in the less onerous “abnormally dry” category.
During March, the western high has expanded in a few pulses to include all of the contiguous 48 states except for the Northeast corner. We, in Virginia, have had a lot of warm and mostly dry weather in March, with few brief spells of rain and storms followed by windy cold and, in a couple of cases, quick-hitting snow.
Easter Sunday brought the latest round of widespread showers followed by windy cold, with some scattered frost Wednesday morning. The rest of the week, however, will see warming temperatures, with 80s highs again by the weekend — and, most likely, no rain.
Sooner or later, it gets wet again
Impacts of potential drought are likely to increase as we enter the growing season, when newly greening plants are competing for whatever little ground moisture may exist.
Spring is a notable time for an increase in wildfires even during a year that is fairly moist, more so when surface fuels are dried out and the occasional windy weather systems fan sparks.
Sooner or later, the dry pattern will pass, either for a somewhat wetter spell or a much longer wet pattern. How much sooner or later that is will determine how impactful this drought becomes, as summer heat and drought often feed on each other in a vicious cycle.
Long term, there is much discussion about the likely ongoing changes from a weak La Niña during the winter to a strong and possibly “super” El Niño by the latter half of this year. Such a shift from cold to warm equatorial Pacific sea surface temperatures is often connected to a substantial increase in rainfall across the southern half of the United States as a subtropical branch of the jet stream becomes more active.
In our region’s recent weather history, dry Aprils have often morphed into wet Mays since the start of the 21st century, as discussed in this Cardinal Weather article two years ago.
You will notice that article starts with the same “April showers” theme that this one did, but says instead that they have often led to “May torrents.” We’ll see where this spring flows.
Journalist Kevin Myatt has been writing about weather for 20 years. His weekly column, appearing on Wednesdays, is sponsored by Oakey’s, a family-run, locally-owned funeral home with locations throughout the Roanoke Valley.
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