The image above shows the latest Sea Surface temperature anomalies (departure from average). NOAA has issued an El Nino Watch and the latest global forecast models indicate that weak El Nino conditions will likely develop as we head into the latter half of Summer 2018 and continuing into the upcoming winter of 2018-2019.
High Pressure will be strengthening aloft producing sinking air and allowing for a five to seven-day stretch of temperatures at or above 90 degrees. The peak of the heat wave will likely arrive just in time for the fourth of July with temperatures rising into the mid to upper 90s Monday through Thursday.
Scattered showers and a few thunderstorms may pop up during the early afternoon hours, then attention will shift to the north as a line of severe thunderstorms may develop along the Pennsylvania-Maryland border during the afternoon rush hour. This line of storms will need to be closely monitored as the high-resolution models suggest a “bowing” segment (indicative of damaging winds) may develop and then rapidly move southeast into the Washington Metropolitan Area between 6 and 9PM. Damaging winds in excess of 60 mph and hail are the primary threat with this line, although an isolated tornado can’t be ruled out either as wind shear increases in the atmosphere.
A closer look at the line of storms that I will be watching: