Significant Snow Likely - But How Significant?

Things are still not as clear as I'd like them to be.

The Euro is still the westernmost track and the Canadian model (CMC) has come into line with that   Their tracks are quite close to the coast which create precipitation type issues in the forecast even west of DC and cuts down on the overall amounts.

The NAM, on the other hand, is a much colder solution and keeps us in the heavy precipitation but now it seems like the outlier.    The GFS is somewhere in between.

Here's the ECMWF deterministic output:

ECMWF Deterministic FORECAST FOR: DCA    LAT=  38.85 LON=  -77.03 ELE=    16

TUE 12Z 11-FEB  -7.6   -12.6    1030      60       9    0.00     546     523  
TUE 18Z 11-FEB  -2.0   -12.8    1030      43       9    0.00     547     524  
WED 00Z 12-FEB  -4.6   -11.8    1031      58      13    0.00     547     523  
WED 06Z 12-FEB  -6.3   -11.3    1033      51       4    0.00     549     523  
WED 12Z 12-FEB  -7.4    -9.5    1034      53       3    0.00     553     527  
WED 18Z 12-FEB  -1.8    -7.7    1032      39       3    0.00     555     530  
THU 00Z 13-FEB  -2.9    -6.7    1028      57      44    0.00     556     534  
THU 06Z 13-FEB  -3.2    -3.9    1021      88      98    0.18     554     537  
THU 12Z 13-FEB  -0.5     0.0    1010      93      99    0.55     552     544  
THU 18Z 13-FEB   0.9     2.8     998      91      76    0.21     546     547    
FRI 00Z 14-FEB   1.2    -1.2     992      89      53    0.15     533     540  
FRI 06Z 14-FEB   1.8    -2.7     996      87      90    0.25     532     536

 The same two highlighted times are still problematic - maybe even a bit more than they were last night.  The surface temperatures rise above freezing in the afternoon Thursday (0.9) and the thicknesses go well above the 540 benchmark (544, 547) meaning that mixing issues will almost certainly be present for areas east of I-95, DC included.

Looking at the GFS, I don't see as many issues.  This frame from the GFS shows heavy snow in our area Thursday afternoon:

The NAM shows a similar story but the precipitation is heavier.  However, this is a common bias with the NAM model so we can't take it too literally.

I'll be looking carefully at the upper level low as it moves into position over the next 12 hours.  If the storm "wraps up" too quickly it will make for a more potent storm but a more westward track.  The further west the track, the more mixing issues we have.  You really get a sense here of the precision necessary to produce big snows in the DC area.  The model data supports this.  There are SREF members forecasting everything from 2 inches to 20 inches for the DC area.  Clearly, that's not useful basis for a forecast.

I think we're in for some snow.  I think 4 or more inches is a good bet areawide with the first 3-5 accumulating overnight Wednesday into Thursday morning.  After that, it gets tricky.  Where will the storm track?  How close to the coast?  Does banding set up in our region?  Does the amount of lift in the atmosphere counter warming temperatures?

I think all of those questions are left to be answered still and will make the difference between a good storm, a big storm and a major storm.