Thunderstorms began rolling through Massachusetts Friday afternoon as Tropical Storm Fay began sweeping into the region.
By midafternoon, the National Weather Service was warning of strong thunderstorms rolling through parts of Central and Western Massachusetts. The forecasters warned of brief torrential downpours, lightning, and wind gusts up 30 miles per hour.
The chance of rain is 50 percent in Boston Friday afternoon, while it is 90 percent in Springfield and other parts of Western Massachusetts, the forecasters said.
“Tropical Storm Fay will bring heavy rain to the region later today and especially tonight,” forecasters said in a Web posting. The forecasters warned of the potential for flooding mainly across Western Massachusetts and northern Connecticut. Most of the rain is expected to be over by mid-morning Saturday. But more thunderstorms could return Saturday afternoon.
There is also a very small chance that a tornado could touch down in Western or Central Massachusetts during the storm, weather service meteorologist Andrew Loconto said.
A flash flood watch is in effect for Western Massachusetts and Connecticut during the storm, which is expected to drop between 0.5 and 1 inches of rain in Boston, up to 1.5 inches of rainfall in Springfield, and up to 2 inches in Greenfield overnight, according to the weather service.
“The heavier rain in our area will be western MA/CT, and the best chance of flooding issues may remain west of southern New England,” the weather service tweeted Friday morning.
A small craft advisory has been issued for the coast of Massachusetts and Rhode Island from 6 p.m. Friday to 8 p.m. Saturday, the weather service said.
The bulk of the storm will move slowly through Eastern New York and Western New England before it pushes into Canada Saturday afternoon.
Sunday’s weather should be better. Meteorologists said Massachusetts will be mostly sunny and reach highs in the upper 80s.
Caroline Enos can be reached at caroline.enos@globe.com. Follow her on Twitter @CarolineEnos.