You knew this day would come, again.

You knew this day would come, again.

FROM THE NOAA WEATHER PREDICTION CENTER:

• "HIGH CONFIDENCE IN A MAJOR WINTER STORM INCLUDING HEAVY SNOWS FOR THE URBAN CORRIDOR EXTENDING FROM WASHINGTON DC TO NEW YORK AND BOSTON FRIDAY INTO SUNDAY...
• THE LOW'S ANTICIPATED TRACK AND SWATH OF HIGH LIQUID EQUIVALENTS SUPPORTING 1 TO 2 FEET NEAR AND NORTHWEST OF I-95. 
• FROM THE MID-ATLANTIC INTO THE NORTHEAST ARE ALSO LIKELY. COASTAL FLOODING AND OTHER SIGNIFICANT IMPACTS TO MARINE INTERESTS."

5:00 PM EST 1/19 - Our revised Storm Impact Scenarios & Map will be posted with the next update around 8:00 PM this evening. 


9:35 AM EST 1/19 (Forecaster Connor & the Winter Stormcast Team) There's no easy way to break the news. A potentially major storm may affect the entire region starting Friday into Sunday. Below we have prepared our most current scenarios based on the best available information at present. Our analysis is presented in three categories: Track, Liquid, Wind. 

TRACK & SCENARIOS - As you can see in the attached image, we have outlined 3 general scenarios of what might take place this coming weekend. We are fairly confident of a strong storm system getting its act together in the Southeast before making a run at the East coast on Friday.As is the case with most of our winter storms, the strength, track, and the proximity to the coast play crucial roles in what type of weather occurs in the Mid-Atlantic.

• In scenario A (left), the system in the southeast rapidly intensifies and takes a sharp turn to stay very close to the coast. In scenario B (middle), the system takes a bit wider of a turn and stays a bit further offshore. In Scenario C (left), the system is suppressed and takes a very wide turn which results in less snow for the northern mid-Atlantic and a focus on southern areas.

One thing guidance has been consistent with is that once the storm reaches the middle latitudes near 40 degrees North (the PA-MD line) it has the potential to meander off the coast for quite some time before weakening and moving away. Sound familiar?

LIQUID & TEMPS - Regardless of where this storm ends up, it will bring with it an enormous amount of moisture.

• In Scenarios A & B, the lows proximity to the coast combined with the very slow movement of the system results in the unleashing a massive amount of moisture. Just how close the low stays to the coast will have a lot to do with what form this liquid will fall in across the area.
• Scenario A would likely present some mixing issues east of 95 while scenario B would allow for more cold air to filter in and mostly snow to fall. Scenario C would also be a very cold solution, but the bulk of the moisture would slide to the south of the area.

WIND IMPACTS - If either Scenario A or B play out (which seems most likely at this point), we could be dealing with a very powerful winter storm that would bring strong winds of 40 mph or more to the surface along the coast, and gusts at least that high inland.

• It has been a while since we have mentioned the potential for a storm type that starts with the letter "B" but given the current projections, it’s surely possible. These gale force winds could last for over 12 hours as the powerful low takes its easy time to continue east,

We urge people to always be prepared for power outages whether an event is looming or not, but this week would be a good time to make sure you are well-prepared.

The FF Winter Stormcast Team

11:00 PM EST 1/18 - For storm fans and powder people, it has been a long time since this situation has been on the table. For Emergency managers, school district officials and those charged with making big decisions for lots of people, this day is one you may want to add to your "un-bucket list."

But, before we get any farther ahead, let's make one fact clear: The storm that everyone is starting to talk about is actually still off the California coast. Once that energy is onshore, ground-based observation stations can obtain more precise data about it's characteristics. Here's a shot of it from NOAA satellite:

WHAT WE (THINK) WE KNOW SO FAR

Energy in the northern jet stream is slated to meet up with this Pacific system once it moves into the southern U.S. Thursday is where the real action starts in upper levels. Once the upper level and surface lows interact and start marshaling the cold air in their favor, computer models show what we call a "bowling ball" type cut off Low steamrolling over the eastern U.S. 

• Long range forecasts have been showing for some time that above-normal precipitation was anticipated for this time period by NOAA in 6-10 day outlooks;
• Widespread cold air for 5-7 days ahead of the future storm means that ground surfaces from the Tennessee Valley on north and east will have been adequately chilled to support accumulation.
• Influence of El Nino on East Pacific waters has been transporting additional deep tropical moisture into developing systems in the southern U.S. The Mississippi floods of last fall are a prime example of what's possible.

WHAT DATA AND AGENCIES ARE UP TO

• The National Weather Service has assigned a moderate probability of a winter storm impacting the Mid-Atlantic region Friday into Sunday;
• Projected liquid equivalents range from 1.5" to 3.5" depending on the computer model, covering much of the northeast U.S. from the Carolinas to New York State;
• If the surface low intensifies as projected over open waters Friday night into Saturday, winds are expected to reach gale to storm force (39-55 mph) along the Delmarva and into the Chesapeake Bay. 
• Add in heavy wet snow, or rain and sleet and this would become untenable for travel. In fact, there's a technical term used to describe weather of that kind. We surmise the NWS is debating on eligibility for usage of that word in the current situation.  

WHAT IT MEANS FOR YOU NOW TO FRIDAY

• A long duration high precipitation event seems probable at this time. Whether it is all snow, a mix of snow/sleet or rain will depend on your location. If computer model trends continue in the manner they have shown since Friday 1/15, there is potential to see impacts that could equal that of events in January 1996 and February 2010.  

• Significant uncertainty remains regarding track, due to the future storms still being several thousand miles away from the east coast at present. A one hundred mile shift in track five days out is miniscule to a global model, although it would affect millions of real people. 

• Once a good 12 hours of data from ground stations in the west has been ingested by the models, if this results in any big changes in the setup -- starting late Tuesday into Wednesday you will begin to see weather agencies and emergency management ramp up language & preparations. If there is one item we suggest having on hand, it's road salt.  

• We know you'll need on-going access to weather intelligence, but don't have a lot of time to hunt for it. One resource to stay more directly informed without having to check this site or Facebook is to join our Insider's service. This way we can deliver reports, snowfall maps and storm timing directly to you by text, email and (shhh! An app, on Tuesday.) 

So if that day truly comes again, 

you're in the know before the snow.