They're not confidence intervals, but weather.gov's forecasts include a link to the NWS office's forecast discussion (updated every few hours). This can give you a bit of insight into forecaster uncertainty and the variation between models.

To excerpt the most recent (8:14PM EDT) NYC office's discussion:

"As a result, expect most precipitation to be focused mainly during the evening hours. Hi-resolution models have been suggesting that the overnight hours could be mainly if not entirely dry. This is due to 850 hPa warm front lifting to the north by around 6z and a dry slot moving in from the SW (DC/PHI area). For now, have just lowered pops to chance. If trends in the high resolution models hold, pops will need to be lowered further if not removed for the overnight hours with future updates."