Premium Weekly Outlook: A Look into Christmas and Hanukah Weekend

After brief mild surge in the 50s over much of the region yesterday, another artic airmass has moved back over the region today. Despite only some high cirrus filtering sunshine, temperatures for the rest of this afternoon will likely only reach the lower 30s. This is airmass is not cold as last week. But it’s another reminder that we are still only in December.

Another very cold night is store for tonight. High pressure building over the region, will result in mostly clear skies and calmer winds later tonight. This will allow for more radiational cooling, especially for the suburbs.  The only cavet for ideal radiation cooling conditions will be with more high clouds early tonight with a weak shortwave trough passing through. But these clouds should move out overnight.  Temperatures will likely drop well down into the teens and lower 20s over the much of the region. Some of the interior valleys and the Pine Barrens may drop into the signal digits, if skies clear out enough.

High pressure will begin sliding offshore on Tuesday. After a very cold morning, light southerly during the afternoon hours will temperatures rise a little higher into middle to upper 30s on Tuesday. Some spots may even touch 40 degrees. Then a weak cold front accompanied by shortwave trough moving through Southeast Canada, will move through region Tuesday night. A slightly colder airmass behind this front, may cause temperatures to drop again into 20s over much of the region for lows overnight.

NAM model low temperatures fin the 20s for Wednesday morning.

NAM model showing temperatures in the 20s for much of the region Wednesday morning

But more moderation is likely Wednesday and Thursday, as mid-level heights rise over the Northeast and Mid-Atlantic regions. ahead of the next shortwave trough from the west. High temperatures both days will likely be in the middle 40s, which is slightly above normal. This shortwave trough digs deeper over Great Lakes and Ohio Valley, resulting low pressure developing just north of this regions. However, the pattern this week,  is more progressive with a lack of high-latitude blocking. So low pressure tracks still well north and west of the local region. It’s warm and cold frontal boundaries will still be moving through region on Thursday.

The best forcing dynamics will be with the surface low and shortwave energy passing near Eastern Great Lakes and Northern England. Moisture will also be limited with this system, until it reaches the Canadian Maritimes.  So significant precipitation and impacts with this system, no longer appear likely. An upper-level jet streak with some divergence may still be able help produce a few showers, as passes the local region.  Temperatures should warm enough in the lower levels for any precipitation that falls to be mainly in the form of rain. Some parts of the Interior New York and New England may see some more frozen precipitation.

GFS showing a mostly dry frontal passage with shortwave trough on Thursday.

The GFS model showing a mainly dry weather with frontal system associated with shortwave trough moving through Northeast  on Thursday.

Then as the low deepens over the Canadian Maritimes, another colder, drier air mass will move behind it Thursday night and Friday morning. Temperatures will drop back into 20s and 30s over the region with a tighter pressure gradient causing some northwest gusty winds.  But as high pressure begins moving off the Mid-Atlantic coast, a more west-southwesterly flow will cause to the airmass the moderate quickly again over the region. Temperatures will likely raise back well into the 40s or to near 50 on Friday afternoon. Temperatures may remain slightly above normal into Saturday and Christmas Eve.

However, the atmospheric pattern will be more convoluted much of the nation, over the weekend. Currently model guidance today shows Pacific energy embedded with in trough will digging and carving out larger trough over Western US. As this energy phases, the trough will be amplifying into negative tilt. This will cause low pressure system to form over the Central Rockies, and then  intensify as it tracks northeastward into the Midwest or Western Great Lakes by Sunday night. A warm front extending from this system, will be approaching from the southwest on Christmas day. Isentropic lift associated with mid-level warm-air advection, may cause some precipitation to break out ahead of this front by the end of the day.

GFS showing shortwave energy along trough amplifying over the Midwest, associated with the next potential storm system for Christmas

The GFS model showing 500mb shortwave energy along trough amplifying over the Midwest, and weak shortwave and wave of low pressure running along frontal boundary over Mid-Alantic region on Christmas Day.

Meanwhile somewhat of a split-flow out over West Coast, results in more confluence underneath large area of troughiness over parts of Eastern Canada. This will support strong surface high pressure with much colder air over Ontario and Quebec. However, without high-latitude blocking, a strong southeast ridge will be building ahead of the storm system. This will likely the keep more cold air to our north. So at this time, we don’t anticipated much snow or ice out this system, for the local region. If fact,some model guidance such as the ECMWF, shows mostly dry conditions here on Sunday, with most of the dynamics staying over Midwest and Great Lakes regions.

But often during these setups, high pressure tends to nose into Northeast with more cold-air damming, especially at the lower levels. This might also lead to some another wave developing along warm front with more wintry mix, especially for the Interior locations. Currently the model and ensemble guidance doesn’t show these solutions. But these are outside chance scenarios, that we will be looking out for with new model guidance coming during this week.

For those celebrating Christmas or Hanukkah this weekend, it currently looks chilly and dry for travel, shopping and religious proceedings during Saturday, Saturday night and perhaps Sunday morning as well. Sunday afternoon onward in up in the air. But this could change, as we get closer and more details become clearer with new data. So stay tuned for more updates throughout the week!