A big coastal storm will be ramping up in the Southeast Tuesday into Wednesday and will deepen along the Mid-Atlantic Coast Wednesday into Thursday, bringing significant snowfall to a large portion of the East Coast. My initial forecast leans mostly towards the Euro model, but there is some compromise with the GFS solution, which is also keeping confidence moderate at best. The Euro has been holding steady while the GFS keeps trending towards it, but the Euro may be over-amplified as it can be with these big coastal storms.
Sleet and rain mixing in along the coast should cut into totals, though how far inland the changeover goes is still up for debate. Likewise, the western edge could still see some notable shifts if the Euro track is way off (which I don’t believe to be the case). A strong area of banding is expected on the northwestern and western side of the storm, which could significantly boost totals if it can stall over an area for several hours.
I’m fairly confident that I will need to add a 12-18 inch contour in the next update, but I don’t have enough certainty in the forecast to place it at this time.
Heavy snow is expected across the northernmost parts of the forecast region, with lesser amounts the further south you go as snow at the onset of the storm battles with warming mid-levels as the storm pushes through the Mid-Atlantic. Timing of the changeover to sleet/freezing rain/rain will be critical from central PA roughly from I-80 (or even a little north of that) southward… so yeah, that’s a large area to watch for the changeover. After the storm passes, some residual moisture playing the upslope on the west side of the Appalachians could bring 1-2 inches of snow into the higher elevations of WV and the WV/MD panhandles.
Significant (damaging) icing is possible in southern OH, southern PA, WV, VA, western MD and western NJ, which is not shown on the map. For the DC area, places around I-95 and points east should have little to no icing, but west of I-95 up to 0.25-0.5 inches of ice is possible. Further north into PA/NJ, more notable ice is possible east of I-95. My forecast map includes snow+sleet accumulation, but not ice from freezing rain.
NEW! I added a confidence bar to my map, with a scale of 1 (low) to 5 (high). I almost always write out my forecast confidence in these blog posts, but those who just look at the forecast image will miss it, so I figured I would fill in some of the negative space with some useful information. The confidence in this forecast is 2 out of 5 (low-medium).
Here is the latest ice accumulation forecast from the NWS for the LWX forecast region:
Brought things northward with this update due to that pesky “warm” layer aloft. This is a considerably tough forecast across the southern areas near the 1″ line as the models generally have isothermal temperatures along the freezing line between about 850mb-750mb. Temperatures at the surface are also around freezing, with sub-freezing temperatures in most of the layer just above the surface to about 850mb. So yeah, a lot of potential for the southern areas to either bust high or low with this event.
I included the “locally 8-12″ because it’s really hard to pinpoint where the places that get it might be. My best guess for spots of 8-12″ would be in the MD/WV panhandles into south-central PA, and if the European model is correct, possibly into central NJ.
This is one of the more classic snow storms that we’re used to in the Mid-Atlantic: Temperature issues, wet (low ratio) snow and a mostly N+W of DC event. And of course there’s Philly getting in on the good stuff again like they have been basically all season.
The most uncertainty with this forecast lies in the southern edge of the accumulation zones where surface temperatures at or slightly above freezing will battle against the snow rates at least at the onset of precipitation. Most of the snow is expected to fall during 12z-18z, so it will have that pesky Sun to deal with as well. Despite what’s working against the storm, the snow rates look pretty good between 12z-18z, with the areas in and around D.C. currently expected to get about 0.5″ of QPF just within that six hour window. The northern edge of the higher totals is also a concern given the amount of disagreement and shifting the models are still doing at this juncture.
There’s still plenty of time for all this to shift north or south, and the gradient between snow totals may be tighter than what I have now across the southern areas. I’ll do some fine-tuning around this time tomorrow, but the overall theme of a nice 2-8″ swath across a good chunk of the region seems likely to hold.
Well, I *was* going to be lazy and sit this storm out, but today I decided what the heck, let’s make a forecast. It’s a little late… I hate to make a forecast when the event is already underway, but it is what it is.
Totals include any sleet that may fall near the coast.
I was actually considering going to chase this on the Outer Banks because there would be some awesome scenery with this Carolina special, but my time and budget constraints are just a bit too tight at the moment. I’ve actually never been to the Outer Banks, so it would have been a fun, new experience. I’ll just have to wait for something else to come along, I guess.
I strongly believe there will at least be a band (if not continuous then broken) of 8-12″ somewhere from this storm. In this update, I placed it where I think it will be most likely, but would not be surprised if it shifted north or south. It is really hard to pin down the area of best banding, so I won’t be too hard on myself if it doesn’t end up where I have it.
I tweaked the northern and southern edges as well now that I have higher confidence in the forecast where these gradients are. Basically everyone has the same to higher snowfall compared to my initial map. Add the cold and wind to this event and it’s gonna be a fun day to be outside. Areas around DC northward should stay below freezing through Saturday morning, so this snow pack should have some real staying power!
This storm has really come together on the models in the last 12-18 hours. The vort max has just enough of a dig and neutral/negative tilt to pop a surface low and draw some moisture into the disturbance, which is something these past clippers were missing.
There should be some nice snowfall ratios around DC and points north… certainly better than 10:1. Cold air will be moving into the region tonight, and most areas from southern VA northward will be below freezing at the onset of snowfall. Further south into North Carolina, surface temps may be above freezing at the onset of precipitation, which could hurt snow totals. There is still a fair amount of disagreement with what area gets hit with the heaviest snow, with some models highlighting just south and east of D.C. as others track the best snow over the northern suburbs. That will be something that I will try to iron out with my final update tonight in addition to the northern and southern cut-offs for the 1″+ area.