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

I decided to not be lazy and actually make a snow map for a Mid-Atlantic snow event this time. I may have skipped the first two of the season.

Ample cold air supply with a 1040+ mb high to the north and cold air in place preceding the event means there should not be much issue with getting the start of the snow to stick late Saturday morning through Saturday afternoon. This interesting disturbance actually has two parts, one being on Saturday and the other being a low pressure center developing over the Carolinas on Sunday.

The two big questions are 1) How much does the dry air ahead of the storm affect the snow rates/ratio, and 2) How strong is the Sunday disturbance in the Carolinas, as 1) could eat up some of the lighter snowfall and make for lower totals, and 2) will greatly influence how far north the more moderate snowfall gets on Sunday.

Mixing issues start to hit once you hit the Richmond metro to Ocean City, MD line. North of there, it should be all snow, with >10:1 ratios as you get to D.C. northward.

Winter Storm Threat: March 13-14 (Final Call)

The wintry mix of snow, sleet, and rain appears to be creeping closer to I-95 on the models, so I tightened up the gradient a bit to reflect lower totals from D.C. to Baltimore. The same is true for Long Island, and could be true for eastern New Jersey and New York City as well.

On the flip side, higher QPF across most of Pennsylvania into northern New Jersey and eastern Upstate New York increased the snow total forecast for these areas. Some small increases also occurred along the Appalachians.

Highest risk is still how far north and west the sleet/rain mixing line gets tonight, which could cut deeply into totals along I-95. Once you get far enough north and west and enter the “safe zone” where no mixing is expected, locally higher snow totals are possible.

Oh yeah, and don’t forget about those winds, especially along the coast. Gonna be fun.

Winter Storm Threat: March 13-14 (Initial Call)

As has been the pattern of recent Marches, we in the Mid-Atlantic find ourselves with a late-season snow storm that contains significant snowfall. While the storm evolution may not be classic, it seems that we will see a fairly common snowfall distribution, with the highest snow totals hitting mostly north and west of I-95 while areas south and east see more of a rain and a wintry mix.

The two main questions are where the rain/snow line ends up, and how warm will the surface temperatures be when the snow is falling. For the D.C. to Philadelphia corridor, this will mean a lot. The models differ on just how cold it is along the I-95 corridor as the precipitation is falling, which is where most of the uncertainty with this forecast lies.

The QPF is also a bit of an issue, but taking a model blend seems to be the best way to go at this point. I wouldn’t count hugely on anomalous pockets of minimal QPF, and I’m sure there will be some area that gets sweet deformation banding and ends up with more snow than expected.

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.

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