1:00 PM | *Arctic blast arrives Monday and storm threat(s) to monitor around 10-15 days out*

Overview

We’ve talked for several days about several signals (“teleconnections”, stratospheric warming, MJO) that pointed to an important change coming in the overall weather pattern that would bring us much closer-to-normal temperatures by the beginning of the New Year and more sustained cold air outbreaks during the month of January and perhaps beyond.  There is no change at all in that outlook.  In fact, there are even signs for below-normal cold air outbreaks in the Mid-Atlantic region during the next few weeks beginning with an Arctic blast set to arrive for Monday and Tuesday of next week.  Furthermore, now that the colder pattern seems to be settling into the Mid-Atlantic region, it is time to monitor potential threats for snow and indeed the period about 10-15 days from now looks quite ripe with storminess potential for the Mid-Atlantic region.

2-meter temperature anomalies for early Tuesday (courtesy tropicaltidbits.com, NOAA)

Arctic blast

Seasonably cold air is moving into the Mid-Atlantic region as we begin the New Year and high temperatures on Friday, Saturday and Sunday will be much closer-to-normal compared to the recent balmy December weather that we experienced.  A new cold front will push through the region by Sunday night and this will usher in a true Arctic air mass for the Mid-Atlantic and Northeast US for the Monday/Tuesday time period.  Temperatures on both of those days are likely to be confined to the "below-normal" 30’s for highs in the I-95 corridor – perhaps even the 20's  – and a stiff NW wind will produce even lower wind chills.  Nighttime lows during this Arctic blast will likely fall to the teens in much of the region.  There is even an outside chance that some snow or flurries accompanies this Arctic blast in portions of the region early next week.  The 2-meter temperature anomaly map (above) from the latest (12Z) GFS computer model forecast shows the widespread colder-than-normal temperature pattern (blues, purples) for early Tuesday morning in the Mid-Atlantic and Northeast US associated with this coming Arctic blast.

Forecast map of 500 millibar height anomalies for Wednesday, January 13th (courtesy tropicaltidbits.com, NOAA)

Days 10-15 and potential storm threat(s)

The teleconnections that we focused on in recent postings (Arctic Oscillation (AO), North Atlantic Oscillation (NAO), Pacific North America (PNA) all suggest the overall weather pattern will be ripe with potential for additional cold air outbreaks and storminess in the eastern states around 10-15 days from now (approximately January 8th -13th).  Several computer forecast models are now indicating there will be a deep trough in the upper atmosphere (at 500 millibars) before we reach the middle of the month along with a ridge along the west coasts of Canada and US.  This upper atmospheric combination will allow for cold air outbreaks in the eastern states at this time and can certainly can produce one or more surface-level storms possibly resulting in some snowfall for the region.  The forecast map (above) from the latest (12Z) operational version of the GFS computer forecast model shows a deep upper level trough (blues) centered across southeastern Canada along with ridging along the west coasts of Canada/US (oranges) on Wednesday, January 13th.   The 12Z "ensemble" version of the GFS model has a very similar-looking 500 millibar height anomaly forecast map for the same day lending support to the operational model prediction.   

Bottom line

Let the games begin - January will be quite a change from December.  Stay tuned – we’ll continue to monitor all of this over the next couple of weeks.

Meteorologist Paul Dorian

Vencore, Inc.