An area of low pressure several hundred miles southwest of Mexico is becoming better organized and will likely become a tropical depression within the next 24 hours.
If this potential tropical system obtains tropical storm status, it would be given the name Sandra.
A continued track toward the west is expected through Wednesday before a large storm moving across the western United States pulls the tropical system northward during the second half of the week.
This sharp turn northward will bring a strengthening storm toward the southern Baja California Peninsula on Friday and Saturday.
The storm track over the western half of the United States will pull tropical moisture northward, resulting in downpours across southern Baja California and northern Mexico from Friday into Saturday.
While the tropical system will likely be weakening as it approaches the southern tip of Baja California Friday night and Saturday, locally damaging winds are a concern from La Paz and Cabo San Lucas to Culiacan and Mazatlan.
The biggest concern will be heavy rainfall that can cause flash flooding and mudslides. Areas at greatest risk for flooding include southern Baja California, Sinaloa, northern Durango and Chihuahua states.
Rainfall amounts of 75-150 mm (3-6 inches) are possible in these areas with local amounts up to 250 mm (10 inches).
After reaching the Mexico coastline, the weakening tropical cyclone will dissipate over the higher terrain of northern Mexico, while the heaviest rainfall shifts into the southern Plains of the United States where there will be a high threat for flooding early next week.