Friday, December 24, 2010

Update on Xmas Snow

No MAJOR changes to my previous forecast, however, latest model runs of the GFS/NAM (18Z) and WRF have all placed the location of the surface low (see HPC depiction below) further west than the past 2 days or so.

Closer equals more precip here, and right now 1.5-2" call looks good when combined with the various other factors affecting accumulation. Timing call still on track with the bulk of snowfall late afternoon into the night. There is still a small chance that the energy (cold high pressure)  from the north is slower, allowing the southern low to strengthen enough to "bomb" out earlier, and it will be interesting to see what happens not only here, but along the eastern seaboard. A 50-100 mile deviation means snow or no snow for places like DC, NYC, Philly, Boston the I-95 corridor. In fact, the heaviest snowfall accumulation should be the coastal plain region in NC. More snow at the beach than here... Here is the latest NWS precipitation (QPF) forecast for the next 3 days combined:

The last factor that always wreaks havoc on operational forecasts of snowfall  is banding. This micro-scale phenomenon happens frequently in the NC Piedmont when low pressure starts to strengthen (deepen) off the coast. Any precipitation banding that does occur will make pinpoint accumulations even harder - guess we'll just have to wait and see. If you have any questions or want me to explain something use the comment section.