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2013

Winter Storm Threat: Mar 24-25 (Initial Call)

The DC-Baltimore-Philly areas are expected to miss out on the more significant accumulations yet again as bothersome low-level temperatures above freezing and March climo. rear their ugly heads.

One of the saving graces with this event is the onset of snow will be overnight, though this did not really help the I-95 corridor and points east during the last event back in the first week of March. Surface temperatures will generally be above freezing in the lower elevations, so these areas will need good rates to make up for it. A large chunk of the precipitation is expected during the daytime hours, where we will have the March Sun to contend with in addition to the temperatures. Higher elevations that stay at or below freezing will fare much better with accumulation.

Forecast confidence is normal to slightly below normal.

Winter Storm Threat: Mar 5-7 (Final Call)

There were some detail changes due to adjustments in the storm track, which mostly affected central/northern PA, southern VA and the Delmarva Peninsula. Higher confidence in the higher snow totals brought some upscale changes to northern VA.

It’s still a low confidence forecast overall, with both upside and downside risks across most of the impacted region.

Winter Storm Threat: Mar 5-7 (Initial Call)

So here we are with another complicated setup and poor model agreement leading to a low confidence forecast. The good news is it looks like DC is finally going to get a decent storm! It only took until March…

Anyway, right now it looks like the biggest risks are along the coast and in PA and southern VA. I’ll save some of the more intricate details for the final forecast, but there is going to be some serious issues with the rain/snow line in the lower-total areas to the south, with precip. shield concerns across PA, NJ and southern NY.

There is also some upside risk west and a little north of DC, where strong banding will likely occur somewhere in there. The other big question is with the coastal low track and whether or not the more northerly GFS and bring higher snow totals to PA/NJ northward or if the more conservative Euro wins out in those areas. In that case, I decided to lean a bit more towards the Euro with the lower totals.

Some strong, gusty winds are possible east of the mountains north of the VA/NC border.

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.

Winter Storm Threat: Feb 7-8 (Final Call)

Much more aggressive with the totals this time around, but there is still more upside risk than downside to the forecast.

I went with a rough 50/50 blend of the GFS and Euro, with some personal touches here and there. NAM’s still out to lunch with it’s QPF and snow totals, so I didn’t even bother with it. There’s going to be some winners and losers in the low-end/mix areas as the details work themselves out. The bulk of the snow across northern MD, southern PA and southern NJ will be during the back part of the storm. The front-end could start off as snow/mix/rain in these same areas and could/should flip to rain at some point before transitioning to snow to end the storm.

Winter Storm Threat: Feb 7-8 (Initial Call)

Just going to start off by saying that forecast confidence is lower than normal. Miller B type storm will form up late tomorrow into Friday and will initially cause mixing/temp issues across the more southern areas. As the coastal intensifies, banding on the back edge of the system could bring locally higher totals from central PA to NJ, NY and maybe even down into northeast MD and northern DE. There’s plenty of risk in either direction, especially across central PA into NJ and NYC/LI.

I didn’t try too hard to figure out contouring based on strict temperature and boundary layer issue areas since there is not enough certainty to really go into that much detail yet. That’s a job that is best saved for tomorrow’s update.

First severe threat of 2013 in the Mid-Atlantic

While the severe weather outbreak will be more focused on the southern states, I did this write-up just for folks in the Mid-Atlantic.

A widespread strong to severe wind event appears to be unfolding over the eastern half of the U.S. Tuesday into Wednesday, with isolated tornadoes also a threat, which is mostly across parts of the Southeast. The Mid-Atlantic has some opportunity for both on Wednesday, with the main threat obviously being a line of strong to severe winds.

We will be battling marginal lapse rates and pre-frontal clouds/rain, as we normally do in these early year setups. Very strong winds aloft (50-60 kt jet at 925mb!) suggests any sort of convection will bring down strong to severe level winds. With the strong forcing associated with the cold front, I don’t see much of a problem getting those winds to the surface. The only issue would be if a stable layer at the surface can linger ahead of the front, but that appears to be just a minor problem as the lift from the front should overcome the stable layer (if there is indeed a stable layer).

With dewpoints climbing into the lower 60s ahead of the front, we should be able to see a fairly strong frontal passage with widespread strong to severe winds. The main thing I’m watching now is the potential of a secondary low formation, which the NAM has (though that can’t be relied upon at this point). The Euro also develops a secondary low, but it comes later and further north than the NAM. If this secondary low develops before the front comes through, and if it’s far enough south, it will be able to back the winds more at the surface and would provide a greater risk for tornadoes in the Mid-Atlantic.