A fairly big pattern change is underway that will likely end up in a tropical system that threatens the US mainland the week of Sept 20-27th. This week warmer than normal conditions will continue thru mid week for most of the west and Texas, However, by Wednesday, a strong cold will drop south from Canada into the northern Plains and plunge south and east, extending its influence over most of the eastern half of the country by Friday, resulting in below average temperatures that will persist well into next week, although for Texas their reprieve from excessive warmth will be brief; just a few days toward the end of this week before temperatures start to rebound there by the weekend.
Tropical Storm Maria is likely to pose a risk only to Newfoundland on Friday and later the UK and Ireland late Sunday and Monday.

The early fall pattern with strong high pressure over the NE is one that encourages the development of often strong tropical systems in the western Carribean and Gulf of Mexico; the type that track toward Florida or the Northern Gulf coast. This is something to anticipate for mid next week.