Gorgeous Friday, Heavy Rain/Wind This Weekend

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~A FANTASTIC end to the work week with high pressure centered over the region. This brought widespread sunshine to the state with low humidity. Temperatures Wednesday through Friday topped out in the middle 80s for most locations with low humidity leading to cool mornings! Once again, it was in the mid to upper 50s in spots for the mainland, especially the Pine Barrens Thursday and Friday morning thanks to low dew points. The best radiational cooling nights are those where skies are clear, winds are calm, and the air is dry. 

~If you were lucky enough to get down to the beach one of these days, it was amazing beach weather! I was lucky enough to spend a day at Ocean City on Thursday. Water temperatures were in the lower 70s and air temperatures were in the upper 70s to low 80s with a refreshing breeze. Unfortunately, this is all about to change this weekend!

~An upper level trough will deepen and move eastward over the Great Lakes/Ohio Valley region Friday into this weekend. This is the same disturbance that lead to an unusual tornado outbreak across Iowa Thursday afternoon. No, there won't be much of a tornado threat here in NJ, but we can't rule out the possibility. This upper level trough will help to trigger a surface low pressure in the Carolina's as strong mid and upper level winds diverge aloft, creating lift at the surface. This is pretty atypical for late July, a setup more prominent in the late fall and winter months where the jet stream is strong and variable. This system won't become a tropical storm of any sorts because it is forming in a way that conflicts the definition. Tropical systems of any kind, including depressions and hurricanes, form and intensify with warm ocean surface waters and very weak wind shear aloft. They thrive in a very warm, tropical environment and derive their energy from latent heat release in thunderstorm convection as well as the warm ocean waters. Mid-latitude cyclones, nor'easter's, and sub/post-tropical storms derive their energy from the collision of two different air masses and strong jet stream winds. Mid and upper level dynamics come into play for the formation of these systems. Again, tropical systems form with high pressure aloft and no wind shear, the opposite of a non-tropical system. Another thing to notice is tropical systems have NO fronts (warm fronts, cold fronts, etc) the air mass is barotropic, meaning uniform temperature distribution. 

~With that being said, Saturday and early Sunday will be raw. As the coastal low moves northward up the coast, heavy rain and thunderstorms will be likely as well as strong winds. Saturday will become cloudy with a few showers possible in the morning, then by mid and especially late afternoon heavy rain will overspread the area as the storm approaches. Given the warm, humid environment with wind shear aloft and extra spin at the surface due to our low pressure, an isolated tornado threat exists with any stronger storms that develop. 

~The heaviest rain will occur from Saturday afternoon into EARLY Sunday morning. 1-3" amounts will be common with up to 4"+ in localized cases. This may lead to flooding in some areas. Sunday will be cloudy with on and off showers/thunderstorms. 

~Another hazard with this storm will be strong winds. Winds gusting 20-40mph Saturday afternoon into Saturday night with the strongest gusts, perhaps up to 50mph at the coast. Sporadic power outages possible. Minor coastal flooding and high surf is also expected. 

~As the system pulls well north later Sunday, our upper level trough will be with us much of next week. This will bring chances for rain/thunderstorms virtually every day next week as well as very humid conditions. Our long awaited pattern chance is here. At least a week of unsettled weather is expected, but how long it lasts is still uncertain. The overall pattern heading into late July and early August suggests a cooler and wetter regime. 

Alexander Bronsky, Meteorology Intern SNj News