Wednesday, 11:55 a.m.
The bitter blast of the past few days, the attack of the polar vortex as it is being hyped in the media, is now beginning to fade. The worst of the cold is behind it. At the very least, the strong surface pressure gradient that added to the bitter cold over the past 48 hours is now greatly relaxed. High pressure sits over the Southeast, and the intense storm that blew through the eastern Great Lakes Sunday night is now on the northeast shore of Canada. Arctic air is heavy by nature, so the low levels of the atmosphere remain very cold, but the air aloft is steadily warming. It's only a matter of time before the low levels warm as well, and that's going to take place late this week and this weekend.
The road to the full-fledged January thaw is a bumpy one, though, and there will be some weak features that will eat away at the arctic air that will generate clouds and some areas of rather light precipitation. The first of these is streaking out of the central Plains and across the mid-Mississippi Valley into the Ohio Valley today. So far, the precipitation has been limited to snow across southern and southeastern Nebraska, with a thin zone of snow across extreme southern Iowa and extreme northern Missouri. None of it is heavy, but there can be an inch or two in some locations.
As this feature streaks eastward, the snow will become more spotty in nature, basically ending up as little more than flurries across the Ohio Valley into Pennsylvania. Some places will pick up a covering of snow or so, but not much more. There's just not a lot of forcing with the feature, and even less water to work with as it tries to moisten a bone-dry air mass.
A weak upper-level trough will zip eastward across the Great Lakes toward New England late this afternoon and tonight to stretch this moisture out. It won't be a strong trough, but if you look at the surface pressure pattern and 1000-500mb thickness pattern, you can see the placement of that feature tomorrow morning:
As high pressure moves off the Southeast coast in the next 24 hours, the return flow on the southern side of it will bring moisture and increasing warmth back across the state of Florida. Again, none of the rain there will be particularly heavy, but some scattered showers are clearly on tap for much of the Peninsula before the atmosphere tends to dry out more on Friday.
Another upper-level disturbance will come across the southern Plains tonight. It's already pulling low-level moisture up into Texas, resulting in an expanding area of clouds and some very light rain and drizzle. Almost all of this through tomorrow and tomorrow night will be along and east of the I-35 corridor, extending up into southeastern Oklahoma and Arkansas. Here's the 12z Jan. 8 GFS total precipitation through Friday morning:
As this moisture moves into northern Arkansas and Missouri later tonight and tomorrow, there can be some light snow and freezing rain or freezing drizzle, enough to cause some travel issues for a time. This will then move into the Ohio Valley tomorrow night and Friday - again, some of it initially will be in the frozen form, but as temperatures aloft, then at the surface, inch their way over the freezing mark, what little remains on Friday ends up as spotty showers or a touch of rain or drizzle.
The net effect of these features is to bring the clouds in, largely keep them in place, and in the process, send temperatures steadily upward by day and hold steady or continue rising at night. Meanwhile, a much strong trough darting through the Northwest tonight will slip southeastward across the central Rockies tomorrow into early tomorrow night, producing rain showers in the Northwest and some snow in the Rockies.
As it reaches the southern Plains late tomorrow night and Friday, it will pull a lot more moisture out of the Gulf of Mexico, and a cold front will develop that will help to focus the rain. There may even be some strong thunderstorms late Friday and Friday night as this all translates across the Mississippi Valley, and there will certainly be some pockets of much heavier rain.
This will all move eastward Friday night and Saturday in a much more orchestrated procession. Suddenly the winds will be aligned, and there will be a much broader surge of very mild air up into the Ohio Valley as well as the East. Look at the projected anomalies for Saturday now:
Just like that, a lot of places that were below zero will suddenly be in the 50s! From more than 30 below normal to more than 20 above it between Tuesday and Saturday! Even then the road to the thaw will still be bumpy, but it may be a result of all the potholes that show up because of all the thawing going on on the area highways and byways combined with the heavy rain that is coming with the cold front!
Even though there's some snow on the ground over the interior Northeast today, the pattern going forward shows little sign of the winter season to come in most of the nation.
The record warmth of recent days will be replaced by a much colder air mass following a cold front moving from the Ohio Valley to the East. Rain will change to snow in the higher ground of upstate New York and northern New England.
Nicole crossed Bermuda Thursday morning as a major hurricane. Two storms will blast the Northwest with high winds and heavy rains in the next 72 hours, forcing warmer air out into the nation's midsection.
Matthew is a dangerous hurricane bearing down on the east coast of Florida. While it ravages Florida and parts of the Southeast into the weekend, it will spare the Northeast of its fury.
Major Hurricane Matthew is now a significant threat to the entire Eastern Seaboard Thursday through the weekend with with potentially destructive winds and excessive rains.
Heavy rain will soak drought-stricken areas of the mid-Atlantic over the next couple of days. Focus will then shift to Matthew and its potential to impact the Eastern Seaboard with more heavy rain later next week.