quick update on tonight's snow.

A fast moving very strong upper level disturbance will move through the region after sunset tonight. Upper level dynamics and thermodynamics suggest enough lift to cause moderate and even heavy at times precip in a relatively small south to north band of about 50 miles somewhere near the US 64 corridor. 2-4 inches of snow will be possible w/n this relatively thin band of heavy precip. This is an extremely rare event for this type of system therefore past climate data is virtually non existent. The big question is exactly where does this band of heavier precip set up and will there be any rain mixed in. Ground temps are also an issue right now, which normally you'd expect about an inch of snow wasted to cool the ground. Also, if the precip arrives before sunset, boundary layer conditions would likely mean more rain at the start. Will update more after lunch time on this one.

Updates on 2 winter systems

Chance of snow/rain mix Friday night as an unusually strong clipper systems moves through the region. This type of system rarely causes issues for the triangle due to a lack of moisture however, the location and intensity of this clipper system will likely lead to precipitation for the triangle. A surprise 1-2 inches is possible with this system.

Snow and ice are likely for Monday and especially Monday night. Will wait to pin down predominant precip type, but models are in good agreement that a major winter storm will impact the deep south. Will wait a wee bit longer before I make posts in regards to precip type and amounts for the triangle. As of now it appears the biggest impact will be in Northern and parts of central Alabama, Mississippi, Georgia and South Carolina. But a significant even is possible in North Carolina as well.

1/05 Update on 2 potential winter weather systems

Up to an inch of snow is possible in the triangle region as a weak surface features] moves into the western Atlantic through the deep south. Scattered snow showers, associated with this system's deformation zone, are likely and up to an inch of snow is possible. qpf of about .1 on both the NAM and GFS with decent ratios could cause some problems for rush hour commute. Expect the heaviest snow to fall between 5 AM and 9 AM in the triangle. The precip will start as light rain before mixing with and likely changing to all snow. Surface temps will likely stay above freezing through the even which should help to dampen accumulation. Therefore while an inch of snow is possible, it is quite unlikely that more than a dusting will occur. Also, warming just above the surface is likely due to a weak low pressure forming on the Lee side of the Apps in response to the upper level feature. This could keep precip mixed throughout the event.

A winter weather advisory still may be issued tonight by the NWS.


The next system will arrive in the 6-7 day period. This system has the potential to produce signficant snowfall for the triangle. But with it being this far out it is only worth keeping an eye on at this time. Very cold air will follow behind this storm system.

Post Christmas storm analysis

Forecast looked pretty good with a general 3-7 inches in the triangle with potential for higher accumulations. Accumulation was close to that conservative estimate with just a couple more inches on the high side. So a 4- 10 inch prediction with more toward the NE would've been perfect for the triangle. But still not bad at all. Timing was good as well with the significant snow arriving after midnight and arriving by lunch. I should've mentioned that NE sections of the triangle would do better than west sections, but I just didn't mention it. The NE sections and just to the east of the triangle did very well with 10 - 13 inches, so the intensity there was unexpected and aided by the fact that there were very little temp issues there and the storm was a wee bit stronger than anticipated.

Here's the map from RAH NWS:

11:00 AM Christmas day update`

Everything looks like a go for 3-7 inches of snow for the Triangle northeast through Williamsburg.

Some light snow may fall late this afternoon in Emporia and Williamsburg with little accumulation expect from this first batch.

The major batch of accumulating snow should come through the triangle late tonight. The RUC and the NAM first bring snow into the triangle by around 7:00 PM. This round is the snow falling in Western NC and down through northern Alabama. This band of precip should weaken as it enters the triangle... Late tonight expect a band of SE to NE oriented precip to move into the region. This will occur as the low deepens off the Georgia coast. This heavier batch of precip is well represented by the GFS and should arrive in the triangle after midnight and should last until about mid morning in the triangle. Up to 1 inch is possible in the triangle with the first batch and 1-2 inches possible north toward Emporia and Williamsburg and potentially higher amounts in Emporia. 3-7 inches is possible with the second round in the triangle. I expect the 2nd round of precip to have higher accumulation rates due to the more powdery nature of the snow. Locally higher amounts are possible.

The snow may mix with rain in the triangle if any falls this afternoon.

11:00 PM Update

Christmas night snow storm 2010:

A significant winter storm for the triangle now appears likely as a low pressure system moves across the gulf coast line tomorrow and eventually up the eastern seaboard off the North Carolina coast. 3-7 inches of snow is possible for the triangle by lunch time on Sunday with potentially higher amounts. Expect about the same amount in Emporia with potentially higher snowfall totals in Williamsburg possible but with less confidence that Williamsburg will see up to 3 inches.

While confidence is much higher at this time, things can still change and the forecast may need to be updated tomorrow morning. Expect the majority of the snow to fall after 5:00 PM Christmas night with a potential for heavy snow.

Significant winter storm appearing more and more likely

Both the GFS and the NAM continue to strengthen the southern energy associated with the storm, as well as phase the storm a bit sooner then earlier depicted. This is likely due to a small piece of energy shooting due south out of the Dakotas. This is causing the northern stream to catch up with the the stronger then earlier depicted southern energy. The RUC appears to be supporting this scenario as well. Even the NAM... which is further east and eventually out to sea... depicts warning criteria snow for the triangle. I need to see what the HPC says about any initialization errors... but right now I think at least a blending of the NAM and GFS makes sense. Will go ahead and up totals to reflect my earlier forecast. Taken literally the NAM is about 7" while the GFS is over 10"... It's the support of the RUC in keeping the southern vort strong that has me thinking the GFS may be on to something.

The snow/rain mix should start late Saturday afternoon with the bulk of accumulating snow falling at overnight/Sunday morning.

Right now I'll go with 3 - 7 inches for the triangle... maybe a bit more conservative for Emporia and Williamsburg at 2-6 inches.

Forecast confidence is still rather low and the storm has the potential to produce around a foot of snow.

I'll update again late tonight at around 11 or so after the next suite of models comes in.