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Winter Storm Threat: Feb 12-13 (Final Call)

Only real notable adjustment for the final map was the expansion of the 12-18 contour and addition of locally 12+ over northern Maryland and into Pennsylvania. Expanded the 8-12 contour eastward slightly near I-95 and bumped the higher totals in North Carolina eastward a bit. Small changes to the western cut-off of the system as well.

20140212-13_MAsnowFinal

There is more risk to the higher side west of I-95 and equal risks along and east of I-95. I will be in D.C. tonight into tomorrow to cover the storm!

Winter Storm Threat: Feb 12-13 (Second Call)

Not incredibly different from my initial forecast… still uncertainty with the low track, which could cause more/less sleet and rain along the coast and could move the western edge of accumulation west/east. Also have to watch that band on the west side of the storm for possible higher totals. Hard to tell if I should lean more GFS, Euro or just split the solutions.

20140212-13_MAsnowSecond

Notable differences are 1) eastward shift of the 4-8 and 8-12 contours from central Maryland through northern North Carolina, 2) eastward shift of the western cut-off, and 3) addition of 12-18 contour in Virginia and extreme northern North Carolina. I think there is still more upward potential than downward west of I-95, but I am unsure of which way to lean along and east of I-95, where mixing could cut down totals but banding on the back side of the storm could boost totals.

Significant icing (0.25″+) is also possible in the Carolinas with this event, which could cut down on snow totals around Raleigh and Charlotte.

Even though the event will be underway in southern North Carolina tomorrow morning, I plan on issuing a quick update in the early afternoon tomorrow because Virginia northward could still see some decent shifts and I want to leave room to adjust if needed.

Winter Storm Threat: Feb 12-13 (Initial Call)

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.

20140212-13_MAsnowInitial

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.

Winter Storm Threat: Feb 13 (Only/Final Call)

Boundary temperatures and snowfall rates will be the two main things to watch tomorrow as a nice looking vort. max passes over the region. Precipitation will start off as rain for most/all of the region tomorrow, with the back end of the system changing over to a heavy, wet snow. The strong vort. max will help dynamically cool the air as decent rates form up along the back part of the storm, but with the boundary layer temperatures remaining at or above freezing, it will be hard to get a lot of that snow to stick.

Then there is the disagreement between the models. The Euro continues to run drier and further south compared to a host of other models, which is somewhat concerning considering it has never really been on board with the snow totals that I have forecast. Given the non-consensus of the models along with the temperature issues, risks to the forecast are more to the down side throughout the region, though some of the models do still show some upward potential with this storm. All in all, it will just be something that needs to be nowcasted as the bands of snow develop and try to overcome above freezing surface temperatures.

Radar watching – snow at two levels

Just wanted to post this as it is an interesting phenomena where you can see the low-level convective snow (the long and thin features oriented west-to-east) and the comma-head snow/clouds rotating around the Radar site:

 
The low-level convective snow is created as leftover moisture takes advantage of the steep low-level lapse rates behind the cold front, which forms low-topped convective clouds and precipitates. The comma-head snow in the mid-levels is pivoting around the 700mb low. It’s interesting to see both of these features together so distinctly on radar.

Quick thoughts on tonight’s/tomorrow’s snow

This rain-changing-over-to-snow event has been the main snow event to watch over the past few days, and now it looks like it will come to fruition… at least for those from DC and points north as the tail-end of precipitation rolls through the region between 2-5am.

The latest HRRR is putting down some light accumulation east of the mountains for those north of DC:

I would be a little weary for the total amount of accumulation east of the mountains, but it certainly is possible if the “thump” of snow is strong enough.

Some isolated flurries are also possible during the day tomorrow east of the mountains if enough moisture is available.