Gradual cold
advection from the northeast led to a low of 37F last night, warmer than
modeled. I suppose the cold air is coming in slower than modeled. Surprisingly,
a few breaks in the clouds led to a warmup to a high of 44F during the early
afternoon. A few showers are possible this evening, which would lead to
evaporative cooling and it getting colder than it did last night. Heavier
showers are expected later tonight into tomorrow as well, which will eventually
cool down the low-levels until fully saturated (a substantial cooling given the
dry low-level air now with dew point of 22F), which will lead to the true cold
air damming will take place as an elongated trough of low-pressure leads to
warm advection aloft, but the weak winds will dam the low-level cold air
against the Appalachians, especially in the foothills like Lynchburg, leading
to steady temperatures after rain saturates the atmosphere tonight (clouds and
saturation will also prevent any radiational cooling). I don't expect
temperatures to continue to be warmer than modeled after the rain starts. There
appears to be significant model disagreement on rainfall amounts, likely
relating to exactly where the axis of train of showers sets up.
As the
low-pressure passes to the north tomorrow, winds will eventually turn to the
southwest, accompanied by the entrance into the warm sector and more sunshine
and rapidly warming temperatures, but exactly when this happens will be
critical for the high temperature. Models tend to scour out the low-level cold
air and clouds too soon, and this is a feedback loop given that the longer the
low-level cold air stays, the longer the low-levels will be saturated, leading
to more cloudiness and less sunshine to heat up the low-levels. For now, all
indications are that the cold air will eventually erode by late afternoon,
though it might not get as warm as areas farther south that will experience a
longer period of sunshine. The lack of vertical mixing will also preclude
strong winds from reaching down to the surface, with winds possibly weaker than
most model guidance. A few showers ahead of a cold front are possible tomorrow
evening, but with the dynamics all to the north and downsloping drying out the
low-levels and providing low-level descent, it appears unlikely that there will
be any measurable rain during this time.
Plenty of uncertainty and
doesn't seem like a good day for confident risk taking!
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| Source: Meteogram Generator |
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| Source: PivotalWeather |
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| Source: PivotalWeather |
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| Source: PivotalWeather |
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