Big changes are currently taking place in the weather pattern over the US , we have a developing El Nino episode in the Pacific which is beginning to effect the pattern.
As we all know July was brutal as a heat ridge centered itself over the Mississippi River Valley and just sat there until recently. Now as we begin to head into a El Nino episode, an upper level low is forming over the Aleutian Islands which in turn is leading to ridge in the west and the heat ridge to shift west into the Western US.
That ridge in the west will lead to a dominant trough in the east with a Northwesterly flow right out of the Northern Plains and Canada, this trough will over take the Midwest and the Northeast US .
Our storm system responsible for 3 days of scattered to widespread thunderstorms has started this pattern change and is now exiting, our next storm system is already moving into the Midwest and will progress through the area Tuesday into Wednesday, you can see the strong trough following this system, which will lead to a very comfortable end to this upcoming week. The cold front will bring scattered to widespread showers and thunderstorms Tuesday afternoon through Wednesday.
Highs from today through Tuesday will be in the low 80s interior to mid to upper 80s elsewhere with pretty humid conditions although not oppressive , especially today and Monday. Tuesday will have increasing humidity and winds turn SSW ahead of the cold front. Lows each night will be in the mid 60s to low 70s
Below is Tuesday into Wednesday you can see the cold front is coming through and a nice trough is coming southbound, also note the developing ridge in the western US
Wednesday afternoon the front will come through , with dropping humidity and highs in the mid 80s and lows dropping into the upper 50s over NE PA to upper 60s along the coast.
Thursday (above) will be very comfortable with low humidity and highs in the upper 70s to mid 80s, lows in the upper 50s to mid 60s
Friday again will have increasing humidity as a secondary but much weaker cold front comes through with highs in the upper 70s to mid 80s with a slight chance of showers and thunderstorms through Saturday morning
Here is Friday into Saturday you can see the cold front coming SE with a big trough incoming behind it
By Sunday the front slowly drops south of us and a deep trough moves in, which will lead to very comfortable conditions next weekend with highs in the mid 70s to lower 80s and dropping humidity
Looking longer range into early next week I expect a trough to remain over the eastern half of the nation with comfortable conditions , highs in the low 70s over NE PA to mid 70s to around 80 for the rest of the forecast area,with of course low humidity, lows in the lower to mid 50s over NE PA to lower 60s along the coast as a very autumn like pattern takes hold
I expect this overall pattern to remain in place through the rest of August and into September, a dominant trough over the east with overall comfortable conditions , with occasional cold fronts and shots for thunderstorms, along with brief spikes in humidity along and ahead of these fronts. So basically expect average to below average temperatures and a pretty active pattern from this week on. A ridge over the Atlantic will keep the coolest conditions over the Midwest but the Northeast will still be on the cooler side just with some shots of humidity with cold fronts