I was referring more to the fact seasonal normals are much warmer out here in early December, such that -20°F departures aren’t really noteworthy in terms of raw temps (averages are roughly the same as early March). As for the PV, what you said can be true (see 1988/89) however it is also complicated. The coldest airmasses develop under arctic highs, where the lack of cloud cover/wind allows uninhibited radiative cooling to space under the polar night. And when the PV is strong/well coupled to the troposphere, it inhibits the development of arctic highs. But you are correct in that when a strong PV is disrupted/destroyed, exceptionally cold airmasses often develop because high pressure/surface cooling surrounds the frigid airmass(es) contained within the TPVs/daughter vortices, insulating them from warm advection/dilution. So the resultant airmasses can be exceptionally cold. And because these TPVs/daughter vortices are now mobile, unchained from the parent PV, they often end up plowing into the middle latitudes, producing extreme cold anomalies wherever they end up.

Hmm. 6 members drop to at least -10C on the 12z GEFS

0.27" yesterday, 0.08" today, 10.68" for the month. 42.2˚F.

Another good snow band is moving through, probably have 8" on the ground at this point. The mesoscale models have this winding down shortly.

Low of 34F and currently 35F with dense fog. No matter the circumstances, one thing we can always count on during the fall and winter months around here is fog. Additionally, a wind advisory is in effect until 8 PM today.