Temperatures will be much cooler this week then they were the last few days. After December finished as the 4thcoldest on record in Raleigh, January has gotten off to a very mild start with the first 2 days 11 and 9 degrees above normal. A front passed through the area yesterday evening and temps will likely stay in the 40s today for most areas.
A re-enforcing cold front will swing through the state tomorrow afternoon and ahead of this front winds will turn southwest for a brief time and temps will warm into the 50s. This front will pass through knocking temps back into the 40s again for Wednesday.
A weak s/w will pass through the state Wednesday night and this could bring a chance of light rain or snow flurries Wednesday night into Thursday morning. Right now it does not look like a big deal and in reality it is possible most will not see anything.
A potentially stronger upper level system will drop down from Canada on Friday and this could bring another round of flurries or light snow with it. The 00z ECMWF model is much more aggressive with this then the other models wringing out around 0.1 inches all snow which would be at least a dusting if not more considering the very cold temperatures in the dendritic growth region. The model then bombs the system out creating another northeast snowstorm. The other models are much less aggressive and even the ECMWF Ensemble looks more like the GFS and GFS Ensemble than the operational ECMWF. For now I will mention a chance of flurries Friday, but we will monitor the situation. Very cold air will push in behind this system as our Greenland Block continues to push colder air into the southeast US. We will likely struggle to get out of the 30s on Saturday if not above freezing.
Some interesting things begin to happen in the weather pattern by this weekend. We will see for the first time this Winter, a dual block configuration begin to take shape with a strong closed upper high over Alaska and into the Beaufort Sea while at the same time we will likely see our Greenland Block retrograde to Nunavut, Canada. This extreme high latitude blocking pattern will produce very strong high pressure in Northwest Canada, perhaps reaching 1060-1070mb. This is a foreboding sign that very cold arctic air will pour into the US during the coldest time of the year.
As this process is beginning we will also see a closed upper low in the southwest US get kicked out and move east into the southwest US and into Texas by this weekend. This will promote the development of a surface low in the northern Gulf of Mexico. At the same time we see a 50/50 or Newfoundland Low in place. This argues that this system will take a suppressed (at least initially) track through the Gulf Coast and Deep South and if the system has a enough room to amplify we will see precipitation break out across the southeast. With the 50/50 low in place this argues for upper level confluence across the Lakes region and a high pressure ridging into the northeast US and an ample supply of cold air ridging down east of the mountains.
I think there is a good chance of a significant winter storm in the 1/10-1/13 period. Right now the model seem to be zeroing in on the 1/10-1/11 time frame. This is the time frame I have been going with since last week. There is still considerable spread among the ensemble members on the exact timing, which is related to when they kick out the southwest upper low. However, I am bullish on this time frame.
Beyond this, as mentioned above, the dual block configuration will send a major arctic air mass into the country next week with the coldest air of the season for many areas. IT looks like it will be most concentrated in the interior Northwest, Front Range, Plains, and Midwest but it will spread east and south. I think we will see a tendency for energy to slide down the Front Range and dig into the southwest US, which could blunt the extreme cold from taking residence in the southeast, but at the same time it could increase our wintery precip chances it could create a persistent overrunning pattern aloft.
Either way, it looks to stay generally colder than normal likely through the month of January with no shortage of chances for wintry precip.