WINTER STORM THURSDAY-FRIDAY
/**This post will be a detailed update in an attempt to answer all your questions, what we are expecting to happen and the “red flags” we see that could potentially “bust” the forecast either direction. Please read the post thoroughly and it should answer all of your questions! We will not be answering any questions about “how much for x city” as we simply do not have the resources to answer all of those questions!**
SETUP
Our storm system will be moving into the area Thursday morning from the southwest. Areas in Western NC/SC will feel the affects from it first and then precipitation will gradually spread across the rest of the area. It will initially take some time for the atmosphere to moisten up as there will be some dry air in place, especially a few thousand feet up!
A weak low pressure will develop off the coast of NC and as it intensifies could bring some gusty winds to coastal areas. Pictured below is the NAM for late Thursday night as the coastal low starts to strengthen. The pressure gradient between it and a strong high will funnel some gusty winds along the coastal areas.
TIMING
Precipitation will begin moving into NC and SC at these rough intervals below. The last bit of precipitation will be moving off the coast Friday morning around 7-10am.
Western NC and most of SC - 8-11am Thursday morning
Central NC - Around noon
Eastern NC - 1-3pm
TRANSITION ZONE
As all of you know by now the “warm nose” is almost ALWAYS an issue we have to deal with in NC, especially Central and Eastern NC. This storm will also have issues with a warm nose. Below is a picture from the 3km NAM for where it thinks the main transition zone will be early on in the storm.
The “battle zone” appears to be right along the highway 264 corridor from Washington to Greenville to Raleigh. Oftentimes the heaviest snow in a setup like this will be JUST north of the transition zone where things stay all or mostly all snow.
Later on as the storm really begins to intensify off the coast, cold air will wrap around and change over much of Eastern NC to snow. Here is the depiction shown by the 3km NAM later on Thursday evening and into the early morning hours on Friday.
Notice also some very dark blue in there? The NAM is hinting at some convective elements to this storm, it’s possible there could be some thunder snow or thunder sleet if any of these bands are strong enough (rare but it has happened before in NC).
OUR FORECAST MAP
Here is our forecast map. Keep in mind in a storm like this with a warm nose it is VERY easy for things to go wrong. We will outline those in a separate section later but this is our best blend with a heavy reliance on the 3km NAM, RGEM and experience.
Light Blue - There are three of these areas on the map. One in the mountains, another in Western NC and one more along the coast. We anticipate lighter amounts of 1-3” for these areas (lower elevations in the mountains could be rain) but some areas could locally see 4” or so in some of the heavier bands, primarily near the Greensboro to Durham area.
Pink - This will be the battle zone as the warm nose fights against the colder air. Right now the best model for warm noses has the battle right along the highway 264 corridor for a good portion of the storm. Snowfall amounts here could be 2-5” with higher amounts in the areas that stay snow longer (further north) and lesser amounts to the south where more rain/sleet will mix in.
Dark Blue - This area will have the best combination of colder temps and precipitation to maximize snowfall amounts. A general 4-8” is possible across this area and some of the banding could drop 9-10” in a few lucky locations.
Green - Mostly rain with some snow on the backside of the storm. Anything from flurries to an inch of snow is possible in this area, some areas near the pink/blue zones could see locally higher amounts.
**We chose to leave a small blank area on our map in Western NC and most of SC. In Western NC it’s anticipated this small area will have the least amount of precipitation to work with and the cold air may be too late for much more than a few flurries. In SC there may be some snow showers further south near the light blue and green zones but no accumulation is expected.**
WHAT COULD GO WRONG?
The warm nose is stronger than forecast. This would push everything on our map to the north and is a possibility but we won’t know until the event gets going how this will play out. The science can only take us so far and these exact details of where the transition zone will be, how long it stays there, etc. are impossible to nail down exactly with current technology.
Less precipitation than forecast and warmer surface temperatures. The higher resolution models drop temperatures in the snowier zones on the map down to 30-32F during the peak of the storm. Warmer temperatures of 33-35F would cut down on snow accumulations and less precipitation to work with also would. This is always a possibility as the low pressure develops and energy shifts to the coastal areas.
Warm ground can be an issue in areas that have seen a good amount of rain and where temperatures are above freezing. If the snowfall rates are light these all make a bad combination for snow to accumulate. The snowier zones on the map on forecast to be near or below freezing with moderate to heavy snow which will negate the warm ground but if the precipitation is lighter than modeled this would cut down on accumulations.
Well, that’s about all we have to offer for tonight! We will post another update in the morning with any changes. Overall we feel like a good portion of NC will see snow from this system if everything plays out as modeled. Have a good night everyone and we will provide additional information tomorrow morning!