Monday, 11:45 A.M.
If you examine the surface and upper-level charts this morning, you'd find several features that stick out across the nation. At the surface, there's a strong surface high camped over the northern Great Lakes, a feature that has pushed drier air deep into the Southeast. On its western flank, some isobars run from Mississippi northward, well beyond Hudson Bay, transporting warmer air up into the Midwest and the Plains states.
The other surface features are relatively weak, though the storm pulling out of northeast Colorado has soaked the flood-ravaged areas of eastern Colorado with one-half inch to two inches of rain so far today. There's also an area of low pressure in the western Gulf of Mexico, the same feature we've been keeping tabs on since the middle of last week as it inched off the Yucatan Peninsula and into the southwest Gulf of Mexico. It is not well organized, and even if it were to become more so in the next 48 hours, it would likely do so in the southwest Atlantic come Thursday and Friday once east of Florida.
Aloft, though, the feature coming out of Colorado looks more impressive:
So, too, is the upper-level low forming over Maine, a feature that will be in place through tomorrow before slowly rolling eastward and passing south of Nova Scotia.
While that is happening, the seemingly innocent trough in the West morphs into a much deeper feature by Thursday afternoon:
With the first feature we're already seeing snow in the higher ground west of Denver. With the second trough, an even chillier air mass will invade the West, bringing snow levels down across the board. The snows will not be prolific by winter standards, but the mere fact it can and will snow even a few inches in the mountains just after the autumnal equinox should be a strong alert to how close we're getting to the winter season.
As the trough in the West deepens, the heights will rise downstream, promoting warmth from the southern Plains to the Midwest and Great Lakes up into Ontario and Quebec. The largest anomalies will be in the Mississippi Valley and parts of the Midwest, where there will be better mixing and and easier access to the warmth. The farther east you go, the influence of the large surface high and temperature inversions will limit the mixing potential. When combined with light night time winds and lower night time minimums, the daily averages will struggle to much above normal until late in the week or the weekend.
Despite a downturn in temperatures in the Northeast, most of the country will remain milder than normal for at least the next week.
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.
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.