La Nina, the flip side of El Nino, is the cooling of the central Pacific Ocean that affects weather patterns worldwide.
In the United States, La Nina conditions usually means wetter winters in the northern Rockies, Pacific Northwest and Ohio Valley. Warmer, drier conditions in the southern portions of the United States.
La Nina and El Nino years vary in terms of impact for the Brazos Valley. Typically Texas sees drier and warmer winters during La Nina. During a weak La Nina, that impact may not be as large or may have little effect at all on Texas weather.
A 55-60% chance of La Niña equates to a 40-45% chance of an El Niño or "neutral" (neither dominant pattern) over the coming months. In other words, while we're trending to a more likely La Niña, this isn't a foregone conclusion that we'll see those conditions occurring in the coming fall/winter season.
Our last, weak, La Niña season was short lived, but it may have contributed to a warmer than normal winter 2016-2017.