Almanack Weather Prognosticator Chad Merrill
The Heat is On!
We are closing out June with a warm and humid spell. Now the question is: Will the hot weather persevere or will rain and cold fronts knock down the heat on occasion? Let’s examine the factors at play going through summer’s second month in Western Maryland and the Potomac Highlands of West Virginia.
Two patterns will work together in tandem to bring the heat to the region. Large high pressure will likely anchor itself over western Scandinavia and the North Sea. In this pattern, Europe sees very hot weather while northeast Canada and Greenland get locked into a cooler pattern. Farther south, a high pressure, known this time of the year as a “Bermuda High” because of its semi-permanent position near Bermuda, produces a warm, humid air mass for much of the East. There is also a strong signal for the West Pacific Oscillation to stay negative through the month. In July, a negative West Pacific Oscillation brings warmer than average temperatures to the Ohio Valley, mid-Atlantic and Northeast.
Let’s closely examine the pattern that will unfold in the region. July’s first week will bring warm and humid weather with only isolated thunderstorms. These storms will be driven by mountain-valley breezes that develop with help from morning sunshine. The most favored spots for these storms are along Keyser’s Ridge, Savage and Dan’s Mountain and east of the plateau over Martin’s Mountain. These storms last 15-20 minutes and usually dissipate very close to where they develop due to lack of strong winds aloft to carry them downwind of the higher terrain.
The Hagerstown Town and Country Almanack believes these isolated storms will occur on July 4, Independence Day, between 1:30-5 p.m. and then dissipate before fireworks celebrations. Our fireworks forecast has temperatures in the lower 80s in Cumberland and middle 70s along and west of the Allegheny Plateau with dry weather!
A diffuse frontal system will bring thunderstorms between July 7 and 9 followed by a drop in humidity levels to make the outdoors feel more tolerable. The slightly cooler and less muggy conditions will be short-lived as hot and humid weather returns between July 10-15. We anticipate the hottest weather occurring between July 16 and 21 with lower to middle 90s in places like Cumberland, Keyser, Romney and Petersburg, West Virginia, and lower to middle 80s in the Alleghenies. During this heat wave, isolated thunderstorms will be triggered on the ridgetops between 1-4 p.m., but have very little coverage across the region, so not everyone will see heat relief and needed rainfall.
The majority of the month’s rain will fall during a stormy period between July 27 and 31, however none of July’s rain will be attributed to tropical systems. July 27 to 31 will offer the most lightning and heaviest rain of the month. This stormy period coincides with the week of the year where the air reaches its maximum capacity to hold moisture. Therefore, flash flooding is likely to occur in a few of the thunderstorms. Remember, when you approach a flooded roadway, “Turn Around, Don’t Drown.” The water is likely deeper than what it appears. A foot of standing water on a roadway is enough to float many vehicles.
Now, let’s talk numbers. Cumberland averages 3.73 inches of rain in July and the Alleghenies see about 4.5 inches. We do feel that most of the region will see less rain than average. Unfortunately, because of the imbalance of rainfall with the most widespread amounts occurring towards the end of the month, there will be pockets of abnormally dry conditions that develop. The dry periods from July 1-6, 10-20 and 22-26 could cause stress on crops, but none of the area will transition into a drought since overall yearly rainfall departures are less than 5 inches below average.
Have a safe and prosperous July and stay cool! We’ll look ahead to the weather pattern in August in just a couple of weeks. One final note: Look for the 2022 Hagerstown Almanack to be published later in July, so if you are interested in ordering a copy, feel free to contact me at email@example.com or 240-285-8476.
Almanack Weather Prognosticator
Chad Merrill is a Cumberland native and meteorologist who serves as the Hagerstown Town and Country Almanack weather prognosticator and senior meteorologist at Earth Networks in Germantown. Merrill previously was a meteorologist with WDVM (formerly known as NBC25) in Hagerstown and WJAC-TV in Johnstown, Pennsylvania.