Wow, what a start to December! Our currently monthly temperature departure stands at whopping +10.3F through the 15th. That is *extremely* above normal by monthly average standards. We even posted an average temperature last Saturday (for the whole day) that was 29 degrees above normal. The warm December wasn’t unexpected, but the degree of the warmth has been astounding.
One of the reasons for the added bonus of warm air is an Arctic Oscillation that has been extremely positive. El Nino is probably the main underlying driver, but the +AO has been giving temps an extra nudge lately. The AO is positive when pressures are low in the Arctic and the globe’s coldest air is locked up closest to the pole. We can actually thank a very strong circumpolar vortex for this because a strong PV is more likely to lock that cold air away. As it weakens, it has a tendency to send lobes of extreme winter weather south. As of right now, it does not appear likely to weaken anytime soon.
We do have a “blip” in the pattern coming though. The AO took a brief negative dip this week, but it will return to positive next week. This little dip will help spur a fairly deep trough in the jet stream over the Great Lakes and Eastern US. The effects will be cold air being ushered into the Tri-State for the end of the week and first half of the weekend. However this will be more a taste of winter rather than a full on switch to winter.
An area of low pressure will pull through the Great Lakes today and bring a cold front into Ohio. Ahead of this front, expect temperatures to warm quickly today into the upper 50s and lower 60s. A few scattered showers will be possible after 4 p.m. and through the evening hours as the cold front moves through.
Temperatures will take a nose dive overnight and drop into the lower 40s for Thursday morning. With a stiff northwest breeze and partial cloud cover, temperatures will have a hard drive recovering much. Expect a high in the middle 40s which will feel significantly cooler than what we have become recently accustomed to.
The core of the cold air will move overhead on Friday along with the upper level low in the jet stream. This will mean two things: 1) It will be very cold on Friday with highs unlikely to get out of the 30s 2) A few afternoon flurries and snow showers may develop. No accumulation is expected.
The core of the cold will have some lingering effects on Saturday. Despite plenty of sunshine, we will once again likely remain in the 30s. A south wind will pick up Saturday night and deliver a return to warmer conditions for Sunday as we head for nearly 50 degrees.
The start of Christmas week is looking mild and dreary. Showers will develop at the start of the week but temperatures will head for the middle 50s. It appears as though several waves of low pressure may bring rain and relatively mild temperatures to the area for most of Christmas week. At this time, the odds of a white Christmas are near zero. Enjoy the flurries Friday! (If you like snow)