7:15 PM | ****Accumulating snow on Friday begins early in the day in the DC-to-Philly-to-NYC corridor…Arctic blast to follow for the weekend…a warming trend next week****
Paul Dorian
A strengthening upper-level jet streak (shown in purple) will slide across southern Virginia on Friday and it will play a big role in the accumulating snow coming to the Mid-Atlantic region. Upward motion will be enhanced in the left exit region of the jet streak (circled region on the forecast map) likely resulting in small-scale heavier snow bands. Map courtesy NOAA, tropicaltidbits.com
Overview
Another round of accumulating snow is headed to the Mid-Atlantic region on Friday and it should get underway early in the day in the DC-to-Philly-to-NYC corridor. This is a dynamic storm system that will have strong upper-level support and complicating factors will include small-scale heavier snow bands that are likely to develop and an inverted (aka “norlun”) trough that will extend northwestward back to the Mid-Atlantic region from the low pressure center out over the western Atlantic. On the heels of the snow, another Arctic air mass will plunge into the eastern US for the weekend and lower teens or even upper single digit overnight lows will be possible in many suburban locations. Looking ahead, the Arctic chill will dissipate early next week and we’ll turn warmer-than-normal for the middle and latter parts with rain likely back into the forecast.
An interesting feature with this storm system on Friday will be an inverted (aka “norlun”) trough that will extend northwestward to the Mid-Atlantic region from the low pressure center out over the western Atlantic. As with the upper-level jet streak, this inverted trough can also add to the possibility of heavier snow bands in those same specific areas that I outlined in the posting. Map courtesy NOAA, tropicatidbits.com
Details
A complex storm system will bring accumulating snow to the Mid-Atlantic region on Friday at varying intensities and an early day starting time in the I-95 corridor (see snow arrival times listed below for DC, Philly, NYC). This surface low pressure system will be supported by a powerful upper-level jet streak that will produce strong upward motion in its “left exit” region over much of the Mid-Atlantic. The jet streak will slide west-to-east into southern Virginia and areas just to the north of it will likely experience “meso-scale” or small-scale heavier snow bands enhancing overall accumulation amounts. The trick is to predict where these heavier snow bands will actually set up tomorrow and the following areas are where I believe this indeed will take place: southeastern Pennsylvania including the Philly metro region, northeastern Maryland, Delaware, southern and central New Jersey.
The surface low pressure system will push in an east-to-northeast direction as it amplifies during the day and should be positioned well off the east coast by late in the day (i.e., a fairly quick mover). However, there will be an inverted (aka “norlun”) trough of low pressure that will extend back to the coast in a northwest fashion from the surface center and this feature will also increase the chance for heavier snow bands to form in those same areas as outlined above.
This forecast map of total snowfall amounts is from a high-resolution computer forecast model known as the HRRR and it follows quite well my general thinking on this upcoming event. Specifically, I believe that small-scale heavier snow bands will develop across places like southeastern PA, northeastern MD, Delaware, southern and central NJ leading to higher accumulation amounts in those specific regions. Map courtesy NOAA, tropicaltidbits.com
Snow should begin early in the day on Friday in the I-95 corridor and continue through much of the day. Here is my thinking on the arrival times and snowfall accumulations in the DC, Philly, and NYC metro regions:
Philly metro region:
Arrival time: 3-7 AM
Snowfall: 3-6 inches with highest amounts to the south and east of Philly metro
DC metro region:
Arrival time: 2-6 AM
Snowfall: 2-5 inches with with highest amounts to the north and east of DC metro
NYC metro region:
Arrival time: 4-8 AM
Snowfall: 2-4 inches with isolated higher amounts possible
Another Arctic blast will dive into the eastern US for the weekend on the backside of tomorrow’s snow event. The core of this next cold shot in terms of differences relative-to-normal will be centered over the Tennessee Valley and southern Mid-Atlantic region where temperatures can drop to as much as 25 degrees normal. Map courtesy NOAA, tropicaltidbits.com
On the heels of the storm, another Arctic air mass will plunge into the central and eastern US from Canada and temperatures this weekend can bottom out in the lower teens or even in upper single digits in many suburban locations of the Mid-Atlantic region. The Arctic chill will begin to ease on Monday in the Mid-Atlantic region and warmer-than-normal conditions will intensity across the central US. The warmer-than-normal weather will then spread to the eastern seaboard later next week and rain is even likely to return to the forecast during the second half. This unfolding “January thaw” next week will likely take us to the end of the month, but February is destined to feature additional cold air outbreaks and snow threats in the central and eastern states.
Temperatures will climb to well above-normal levels later next week across much of the eastern two-thirds of the nation. This “January thaw” may take us right to the end of the month before colder air outbreaks return in February across the central and eastern states. Map courtesy NOAA, tropicaltidbits.com
Meteorologist Paul Dorian
Arcfield
arcfieldweather.com
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