Winter Storm 12/9/18

Here is a zoomed in map with 4 zones indicating most likely amounts.

Zone 1: 1-3 inches of snow possible at the onset changing to sleet and rain by late morning. Minimal impacts expected. Most counties in thiz zone are now under a winter weather advisory.

Zone 2: 2-4 inches of snow/sleet possible at onset. changing to freezing rain/sleet/snow at around noon. Changing to rain after noon. .10 inch ice accrual possible. Significant winter weather impacts expected. This area is now under a winter storm warning

Zone 3: 3-6 inches of snow mixing with sleet and freezing rain by early afternoon. Changing to rain by late afternoon.

Zone 4: 5-9 inches of snow mixing with sleet and freezing rain by the afternoon.

This is a map showing the most likely effects of the winter storm which will arrive in the triangle late Saturday night/early morning Sunday. I've broken it up into 5 distinct zones. I've mainly been concentrating on the triangle region, so pay less attention the the details further west in the state.

Zone 1: 1-3 inches of snow possible at the onset changing to sleet and rain by late morning. Minimal impacts expected.

Zone 2: 2-4 inches of snow/sleet possible at onset. changing to freezing rain/sleet at around lunch. Possibly changing to rain by late afternoon. .5 inch ice accrual possible. Significant winter weather impacts expected. The southern and western parts of this region are not part of the winter storm watch right now, but I think has a good chance to be added to the eventual winter storm warning.

Zone 3: 4-9 inches of snow mixing with sleet and freezing rain. Then back to snow.

Zone 4: 8-12 inches of snow possibly mixing with sleet and freezing rain..

Zone 5: Over 1 foot of snow possible, possibly mixing with sleet.

For the triangle expect a better chance for winter weather impacts on the Northwest part of the triangle near Chapel Hill with less impacts in southeast Wake.

1/17 snow update 4

The arctic cold front is now over Wake County and slowly moving east. The system is a bit slower and stronger than anticipated. This means a slight delay in the arrival of precip as well as a delay in the end of the precip. Expect the heaviest snow to fall between 8 AM and 2 PM in Chapel Hill/Durham and 10 AM and 4PM for Wake County.

Snowfall is now expected into tonight. Barring more rain mixing in than expected, I think the triangle can expect 5-8 inches. Expect 3-5 inches for areas where mixing lasts through the morning, more on the southeast side of the triangle.

1/17 snow update #3

This mornings' model runs show more precip and a faster change over to snow and therefore they spit out 4-6 inches of snow for RDU.  I now believe the most likely scenario is 2-5 inches of snow for the triangle with higher totals more likely on the north and west part of the triangle. I also believe there is a good chance winter storm warnings will be issued this afternoon if the European model also shows greater than 3 inches of snow. I expect the rain/snow mix to start before dawn and also change over to  snow all around dawn. The snow may be heavy at times. Expect the heaviest snow to fall mainly between 9 AM and 2 PM.  The snow should end around 4 PM. Here are the latest potential outcomes:

20% chance 1-2 inches of snow
75% chance 2-5 inches of snow
5% chance less than one inch of snow.

1/17 snow update 2

Most likely scenario at this time:

1-3 inches of snow for the triangle. Better chance for higher amounts on west and northern half of the triangle, particularly Chapel Hill and Durham. There's about a 50% chance this is the outcome. The other outcomes are:

10% chance we see zero accumulation
30% chance we get a dusting to an inch
10% chance we get 3-6 inches

The precip will mostly occur near daybreak on Wednesday and last through most of the afternoon. The snow is expected to mix with rain early on and change to snow by around noon. The duration of the mixed precip will be the greatest negating factor in regards to accumulation.

1/17 Snow event update

A quick update on the snow potential this Wednesday. The timing of the event is now focused on Wednesday morning through lunch time. About 4-6 hours of moderate snow with perhaps a short burst of heavy snow is possible. If this happens then expect 2-4 inches of snow for most of the triangle. However, there are some mitigating factors that could impact accumulation. First, the precip could fall as rain or a rain snow/mix for a good chunk of the beginning of the end. If true then expect more like an inch or less. Also, it's possible that models are currently overdoing the amount of precip as upper level events typically do not perform well east of the mountains.

My first forecast is for a dusting to 4 inches of snow possible for the triangle with areas on the west and north side of the triangle more likely to get more than an inch. I'll try to narrow down that forecast as it gets a little closer.

1/16 - 1/17 2018 Snow event

A strong upper level storm system will move into the are Tuesday night and through the day on Wednesday. The strength of the system is dependent on how strong the accompanying surface features are with the storm. It's unusual for an event that is mainly dependent on upper level disturbances to provide a lot of snow for the triangle. I am not very bullish on the amount of snow because of this fact, but it does appear likely that at least some accumulating snow will fall. I will wait until later today before I detail potential amounts.

1/3/2018 snow event update

Light to moderate snow is possible after 4pm today for the triangle region and continuing into tonight. The best chances of snow will be between 9 PM and 2 AM. 

Around a half an inch to an inch is expected in the western part of the triangle, which includes Chapel Hill, Durham and Cary while the eastern parts of the triangle could see 1-2 inches. 

There is still a small chance that the weather models are not depicting the westward expanse of precipitation well. Therefore, it is still possible for more moderate snowfall than anticipated which could dump 3-5 inches over the triangle. But that is still a remote possibility at this time.

1/3/2018 snow event

Snow accumulations look more likely for the triangle. A strong low pressure system will move NNE along the gulf stream Wednesday afternoon through the evening. Very cold dry air will be in place over central North Carolina. It is expect that warm moist air will ride up over the cold dry air potentially leading to winter weather advisor to winter storm warning snowfall possibility. The questions of the placement of the low and strength of the low will be critical in the amount of snowfall. Also, the ability of the precipitation to overcome the very dry air and actually reach the ground will play a major role in amounts.

I think as of now we're looking at .5 - 2 inches for Western Wake County, Orange County and Durham County. Eastern Wake County is more likely to get 2-3 inches. Keep in mind that the precip rate cut off will be very sharp.

This will be a very strong storm, and it's possible the models are not quite picking up on the intensity of the wrap around precip. The HiRes models are showing signficant amounts of snow for most of the triangle. This is certainly a possibility as a models don't have much data in regards to winter storms this intense at this latitude.

Any snow that falls will stick as the ground temperature is very cold.