From the MTA service tracker at 9:06 AM:
"New Haven Line customers please be advised eastbound trains will resume stopping at Larchmont, Mamaroneck and Harrison. Westbound trains will continue to operate on opposite sides. This is due to several weather related issues on the New Haven Line. Customers should anticipate delays of up to 20-30 minutes. Please listen to announcements at your station."
Looks like yesterday's storm messed up the westbound tracks (or catenary, or both) of the New Haven Line in Westchester something good.