Here we go! There's the conveyor belt I mentioned. The 2nd to 4th images are for 8 PM, 11 PM, & 6AM:

This is from the Weather Prediction Center:

Mesoscale Precipitation Discussion 1195 NWS Weather Prediction Center College Park MD 341 PM EST Sun Dec 10 2023

Areas affected...southeastern New York State into southern New England and Boston Metropolitan

Concerning...Heavy rainfall...Flash flooding possible

Summary...Areas of moderate to heavy rainfall are spreading north-northeastward across the discussion area and should continue to do so through much of the evening. Flash flood potential is low initially, but should ramp up with time.

Discussion...A robust warm conveyor extends along and ahead of a frontal boundary extending from the Carolinas north-northeastward toward New England. Within this warm conveyor, seasonably warm/moist air was streaming northward toward a warm front located over central Vermont/New Hampshire. South of this boundary, 50s and 60s temperatures/dewpoints were contributing to anomalously high moisture content (1-1.5 inch PW) and modest instability (around 500 J/kg MUCAPE), which was resulting in areas of moderate to heavy rainfall and occasional thunder. Latest radar mosaic imagery shows a cluster of convection extending from south of Long Island into far southern Massachusetts. This cluster was oriented parallel to deep south-southwesterly flow aloft, enabling occasional 0.5 inch/hr and 1-1.25 inch/3-hr rain rates (highest in Delaware). Continued warm advection and modest destabilization should allow for these rain rates to continue into southeastern New York State and areas of southern New England through at least 01Z.

As these areas of rainfall stream north-northeastward, they will occur across populated, urbanized areas along and east of the I-95 corridor, suggesting that at least minor impacts from flash flooding are possible. FFG thresholds are in the 2 inch/3-hr range, and while they should not be exceeded on a widespread basis, indications are that multiple rounds of rainfall should wet soils and lower FFGs enough to increase the flash flood potential over time. Models/CAMs also support this notion, with several hours of 0.5+ inch/hr rain rates potentially occurring across the discussion area through well beyond 02Z tonight. Flash flood potential is marginal in the short term, but should continue to increase through the overnight hours.