Tracking a President’s Day Weekend Snowstorm


The warm temperatures we experienced today will have a brief reprieve this weekend as a low-pressure system to our south impacts our region. A disturbance forming in the Midwest will amplify off of the mid-Atlantic coast on Saturday before moving northeast. Plenty of cold air aloft from a cold front combined with a coastal storm could bring widespread snowfall accumulation from Philadelphia to Boston.

While temperatures aloft will be cold enough to support snow, they will remain close to the freezing mark. As a result, the snow will be wet and heavy, sticking to both tree branches and power lines. Heavy precipitation will begin on Saturday night and end early Sunday morning. This is a quick mover, so a majority of the precipitation will fall within a 12-hour timeframe.

A major factor associated with this storm is the track. The further south the track, the higher chance that precipitation will fall as snow in the Delaware Valley. However, the models have been inconsistent. Shorter range models are showing colder solutions and the longer-range models are showing warmer ones. The map below is from short-range North American Model (the NAM):

nam_ptype_slp_east_18

If the NAM is correct, 4-6 inches of wet snow could accumulate along the I-95 corridor. As evidenced by the map, the rain/snow line is only 50-100 miles south of Philadelphia. Any slight shift northward of the track could have a significant impact on snow totals, especially south and east of the city.

The GFS model’s solution shows the possibility of mixing in Philadelphia and areas south:

gfs_ptype_thick_east2_11

With this solution, 1-2 inches of snow will fall with higher totals north and west of I-95.

Regardless of the precipitation type, expect a nasty Saturday night and Sunday morning, with frigid temperatures and heavy rain/snow (depending on the track of the storm).

In the longer term, a ridge in the jet stream will set up behind this system, bringing temperatures 25-30 degrees above average! A follow-up post reviewing this warmth and long-range forecast will be published this weekend.

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An Active (and Warm) Pattern Ahead


Warmer Temperatures

February is opening to an active weather pattern for our region. Over the next 7 days, we will likely be impacted by three different storm systems. During this period, temperatures will be slightly above average as shown by the European anomaly map below:

Euro 7 Day Anomaly
Euro 7 Day Anomaly

As the anomaly shows, we are currently in a transition from a negative to positive PNA. What this means is that our reprieve from the cold is likely temporary.  Additionally, the Arctic Oscillation is forecast to go negative around the 10-day timeframe. This usually indicates a colder airmass entering the continental US:

AO Forecast
AO Forecast

7-Day Pattern

Until then, we have four storms to worry about! The first is arriving tonight into tomorrow. This is a system associated with a cold front moving across the Northeast. Temperatures were in the 40s today, but will rapidly drop tonight into tomorrow morning. I expect the rain to eventually change briefly over to snow overnight before moving off the NJ coast. The map below shows the high-resolution model forecast at 3 AM Friday:

NAM high-res 3 AM Friday
NAM high-res 3 AM Friday

Tomorrow morning’s commute could be slick as wet roads freeze over once the front pulls through. Temperatures will drop during the day on Friday before plunging into the teens with wind chills into the single digits:

Temperatures Early Saturday Morning

Storm #2 will quickly follow the first, forming rapidly during the day on Sunday. This system has characteristics of a coastal, phasing with a northern piece of energy over the great lakes. Models are currently projecting a quick phase, which would push the storm further west and keep our temperatures above freezing. Super Bowl Sunday will likely be a drencher as this storm barrels through the region Sunday evening. Any celebrations following the game (knock on wood!) will be cold and wet, with temperatures around 40 degrees.

Rainstorm Super Bowl Sunday
Rainstorm Super Bowl Sunday

Storm #3 is looking like a classic “Appalachian runner.” The storm will form over Missouri next Tuesday before moving Northeast along the Appalachian mountain range. This atmospheric setup will steer the storm to the west and warm up our region. Temperatures could reach the 50s on Wednesday as the storm pulls through.

Storm #3

Our pattern continues to be active following this storm, with another system impacting the region next Saturday.

Stay dry over the coming week! Go Eagles!