The case is analyzed using a traditional synoptic/mesoscale framework in order to place the subsequent potential vorticity (PV) based diagnosis in context. Dynamic tropopause features and their associated coupling index patterns are used to show that numerical models are able to hint at the correct solution despite the lack skill in QPF. Moist component PV, a moisture-sensitive PV variable previously employed in the study of tropical systems, is used to highlight the source region of the moisture released over New England on 6-7 January. Modifications to the initial moisture fields of a numerical model, well within the bounds of observational uncertainty in the radiosonde network, show strong sensitivity of the snow band to moisture over Tennessee at 0000 UTC 6 January.
The results of this study indicate that the application of state-of-the-art diagnostics can add value to operational forecasts since precipitation indicators and forcings are often better predicted in models than is QPF itself. As well, the application of moist component PV in a winter storm context shows that this quantity may be useful in tracking moisture anomalies in real time.