The upper level ridge of high pressure which is responsible for the ongoing heat wave across much of the nation produces sinking air from the upper levels of our atmosphere all the way to the surface. Ever wonder why it isn’t storming with such ample heat and humidity? The answer is because it is too warm aloft underneath these upper-level ridges of high pressure. However, along the edges of these ridges the jet stream is very active and cooler air aloft allows for large-scale thunderstorm development along the northern periphery of these high pressure systems. This is where the term “Ring of Fire” is coined from in meteorology.
-Watching an MCS (Mesoscale Convective System/large complex of thunderstorms) over Ohio and how it evolves as it makes the trip toward the spine of the West Virginia Appalachians. If this system survives, the southwestern portion of the Washington Region would be in the most favored location for thunderstorms that could produce damaging winds this afternoon. Something to watch (if the MCS survives the trip).
Even if this system begins to weaken, its outflow boundaries may be able to produce some isolated thunderstorms across our region, some of which could become severe with damaging winds being the main threat.
On Saturday, the Storm Prediction Center has placed the northern half of the DC Region under a Slight Risk for Severe Thunderstorms. The strongest upper-level energy will be passing just north of the PA/MD border, however, Northern Virginia on northward needs to be on guard during the late afternoon and evening hours as the next MCS moves into the northern Mid-Atlantic and we will have to watch for bowing thunderstorms, indicative of damaging winds.
SPC has placed the northern half of the Washington Region under a Slight Risk for Severe Thunderstorms on Saturday (Image courtesy NOAA/SPC)
On Sunday the upper-level ridge of high pressure will have shifted a bit to the south and east allowing for more divergence aloft across the Washington Area. Divergence aloft simply means that there will be better lift (upward movement) in our atmosphere allowing for convection to initiate. Storms on Sunday again will be capable of producing straight-line damaging wind gusts and even some hail as lapse rates will be a bit steeper (with cooler air in the mid to upper levels).
A break from the heat wave as a cold front is currently forecast to cross our region on Monday afternoon
A cold front is currently forecast to pass through our region on Monday afternoon, possibly accompanied by a few scattered thunderstorms (westerly flow may prevent deep moist convection/numerous thunderstorms). Behind this boundary noticeably dryer will infiltrate the region with lower humidity levels and high temperatures holding in the middle 80s on Tuesday and Wednesday of next week. In fact, Washington’s suburbs may wake up on Wednesday morning in the lower to middle 60s! How refreshing (thank you Canada!)
Temperature Departure from Average Wednesday pre-dawn:
GFS Forecast Temperatures pre-dawn Wednesday:
50s outside the urban heat islands of DC, Baltimore, Philadelphia & New York!