Very active day:
mostly clear skies at the start led to it being down to 30F, followed up a warm
up to 35F after it clouded up, before falling back down to 30F after snow
started. Maximum wind has been only 7 kt. Snow,, then ice pellets, then freezing
rain has fallen all day long and will continue this evening. The precipitation
type change is driven by warm advection aloft. Actually, the heaviest
precipitation is upon Lynchburg now for the next few hours, with 0.48” so far. With
marginal temperature and weak winds, the precipitation is actually being
recorded by the station properly, unlike for Erie and New Orleans!
While warm advection
will continue aloft, cold air damming with weak northeasterly winds at the
low-levels will lead to steady temperatures staying at around 32F tonight into
tomorrow, with weak low-level cold advection balancing any latent heat released
by the freezing of raindrops onto surfaces. On the other hand, if it tries to
warm up above 32F, the melting of ice will absorb latent heat and keep the air
temperature at 32F until all the ice melts. I think it will cool slightly
tonight but only slightly, and then warm up slightly but only slightly tomorrow.
Might be the lowest high to low temperature difference in WxChallenge history! The
freezing rain will lighten and become more intermittent as today’s low-pressure
system moves off to the east, but another stronger storm will then track much
farther to the northwest into the eastern Great Lakes tomorrow evening. This
means that the best dynamics will go off to the north, but a secondary coastal
low will form and bring more freezing rain tomorrow afternoon and evening
before getting dry slotted. Without any downsloping wind and any dynamic
descent, the cold air damming will remain strong through the entire period with
almost constant temperature!
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