1/6-1/7 major winter storm update

There are no significant changes to the forecast. Models are in better agreement now on potential accumulations for the triangle. The national weather service essentially calls for 6-10 inches for the triangle. Listed below are three most likely snow/sleet accumulation probabilities associated with this storm. 

-10% chance 1-3 inches of snow/sleet accumulation.

-80% chance 5-10 inches of snow/sleet accumulation.

-10% chance 10-12 inches of snow/sleet accumulation.

Northern sections of the triangle are more likely to see the higher end of the accumulation forecast. What could go wrong with the forecast? The changeover from sleet to snow could take longer than forecast which would significantly cut back on accumulations. However, even in that scenario the triangle should still see 1-4 inches of snow.

1/6 - 1/7 2017 Winter Storm

A significant winter storm is likely to impact the triangle Friday night through Saturday afternoon.  A mix of rain, sleet and snow will begin Friday evening and eventually changing to all snow by around midnight. The snow could be heavy at times, particularly for the far eastern portions of the triangle. Sleet could mix in a bit longer than anticipated, which could greatly cut down on accumulations. Also, the heaviest axis of snowfall is going to be relatively narrow, so if the low pressure were to travel 50-100 miles north or south of the anticipated location then the forecast could bust. As of right now there is decent agreement in the models that the heaviest accumulations will occur in a line from Charlotte through the triangle to southeast Virginia. 8-12 inches of snow is possible where the heaviest axis of snow sets up. The best chance for 12 inches will be on the east side of the heavy snow band. Here is my current forecast for the triangle:

Friday Night: rain, sleet and snow changing to all snow by midnight.  Accumulation of 2-5 inches possible.

Saturday: Snow mainly in the morning. Another 3-4 inches of snow possible. Snow will be ending from west to east.  Expect higher accumulation in the northeast portion of the triangle.

Confidence level of the triangle seeing > 4 inches of snow is 60%

1/22 - 1/23 Winter Storm update

Just a few changes to the initial forecasts for RDU increasing snow/sleet amounts and delaying the switch over to rain.

Friday:  Snow and sleet after 6:00 AM, changing to sleet/freezing rain by mid afternoon.  2-6 inches of snow/sleet possible with around .25 inches of ice accrual possible.

Friday night: Freezing rain possibly changing to rain at around 8 PM, but back to freezing rain/drizzle by 2:00 AM.  An additional .25 inches of ice accrual possible

Saturday through Saturday night:  Freezing drizzle becoming snow showers after 10 AM.  The snow showers will pick up in intensity by lunch time with another 1-3 inches of accumulation possible. Snow ends shortly after midnight.

This winter storm looks like it will be very similar to a winter storm that impacted the southeast in 1996.  Here's a look at the impacts from that storm:

Expect some differences because no two storms are the same but this should give an idea of where the heaviest snow accumulations will likely be and the areas that are most likely to see ice.  I think we might see more ice from this upcoming storm in especially the southwest parts of the light blue shading.

1/22 - 1/23 Winter Storm Update

North American models have come closer to agreement in regards to the track of this winter storm with the GFS and NAM both inching closer to the proposed path and strength of the surface and upper level features by the European model.  What this means is that my initial forecast really won't change much other than bringing in possibly a bit more snow/sleet on the outset and possibly a longer period of sleet.  There is also a possibility that the temperature never gets above freezing if the low progresses along the eastern side of the proposed tracks.  Keep in mind that there will be more impacts from ice/sleet/snow for the triangle from NW to SE.  So Chapel Hill is likely to see more of an impact than Garner with North Raleigh and Cary fitting somewhere in the middle.

Late Tursday Night/Early Friday morning:  Snow and sleet with accumulations of 1-3 inches possible. 

Friday morning till late Friday afternoon:  Sleet and freezing rain turning to all freezing rain by early afternoon.  Changing to rain late afternoon.  Significant ice and sleet accumulations possible.

Friday night through Saturday:  Rain changing to snow with light snow possible through the day on Saturday.  An additional 1-3 inches possible.

1/22 - 1/23 Winter Storm

On Friday and Saturday a potent winter storm will likely effect parts of the southeast and much of the mid-atlantic.  For the Triangle the most likely scenario at this time appears to be a mix of sleet/snow and freezing rain early Friday morning slowly transitioning to sleet/freezing rain Friday morning before changing to rain Friday afternoon.  Expect the rain to change back to sleet/snow Friday night into Saturday with the potential for some accumulation.  

The European and Canadian models were further south with the surface features than the American models.  The result is for a longer period of snow/sleet/freezing rain with potential for significant ice accrual and potential that temperatures may not actually get high enough to change the system to rain.  The American models trended toward the European model in regards to temperature, which showed a much colder forecast, which is more reasonable given the likely intensity of the cold air damming process due to the Mountains.

Because the American model has trended a bit toward the Euro/Canadian and the Euro/Canadian have trended a bit colder and stronger with the system, I will lean towards a 60/40 Euro/GFS split at this time.  The European model shows 2-3 feet of snow in Northwest and Northcentral Northcarolina into Virginia.  It also shows several inches of snow followed by significiant ice accumulations for much of Wake County.  I think that should be tempered a bit given that it isn't fully supported by the American model and climatology suggests that the chances of this being what it could be (A historic winter storm) won't actually come to fruition.

Late Thursday night/Friday Morning:  A chance of snow/sleet changing to sleet/freezing rain.

Friday:  A chance of sleet/freezing rain.  Significant ice accrual is possible

Friday night/Saturday:  Rain changing to sleet/snow.  Some light snow accumulation is possible.

The system hasn't been sampled on shore yet, therefore better sampling will be available in tonight's model runs.  So as we get closer to the storm I'll have a better understanding of how cold it will be and how strong the system itself will be.  It could still just be a mostly rain event for the triangle, but after tonight I hope to have a bit more confidence.

More wintry weather possibly the week of 2/29 - 3/6

A chance of light freezing rain is possible late sunday night through Monday morning as an in situ cold air damming event.  Cold high pressure will be sliding off the New England coast Monday morning as precip increases in the triangle region from the west.  The moisture will encounter cold dry air.  Due to the dryness of the air, much of the initial precip will fail to reach the ground.  But a light icing event for the triangle is not out of the question.  A winter weather advisory may need to be issued for Monday morning.

Another chance of wintry precip will be possible later in the week as a very cold arctic front moves very slowly east of the triangle.  It's possible that a wave of low pressure will develop along this front and bring some wintry precip to the triangle.  This storm is too far out to determine what if anything will occur, but the possibility certainly exists for another wintry storm and possibly another significant winter storm.