Winter Weather Threat for Tuesday 2/24/15

Hey Everyone,

I know a lot of you guys have been wondering what our chances are at seeing some winter weather on Tuesday. Some of the major media outlets have put chances of winter weather on their 5 day forecasts.

Im gonna be blunt and to the point from what I have seen today in every possible weather map and model there is in existence.

Facts
There is a chance of Winter Precipitation on Tuesday morning and through the afternoon.
There is a ton of model uncertainty in regards to the amount of moisture and temperatures during the day on Tuesday.
The only model that is depicting any kind of significant event for Tuesday is the current 18Z NCEP NAM Model.

Not a Forecast! Model Guidance Only!

Above you see the NAM simulated radar for 4AM Tuesday Morning. It is depicting a large area of Snow across most of the State. I am very, very suspect of this for a multitude of reasons. I will list out below as we go below. See the next Photo and below for a description.

This is whats called a SREF Plume. SREF stands for a Short Range Ensemble Forecast. Each color is representative here of precipitation type in Columbia. (Green-Rain, Red-Freezing Rain, Blue-Snow, Pink-Ice,Sleet) At the bottom you will see a date and time stamp in Z time. You will notice around 12Z on Tuesday which is 7AM the snow chances jump to 44.89%. then later in the day the freezing rain chances increase to 59.6%.

Now most of you are thinking wow, looks like really good chances right ? Wrong.


Even though the chances are there, I will go to the next SREF Plume which is showing the amount of QPF (Quantitative Precipitation Forecast) which is measured in inches.

 
As you can see above on Tuesday the total QPF is forecasted to only be around .06" which isn't hardly anything.



With all of this being said, yes there is a legitimate chance of snow on Tuesday however my confidence for tonight will remain quite low given everything that I have looked at. Below I will show the official Snowfall and Freezing Rain Forecasts from the National Weather Service.

Both of these maps are showing the probability of each between tomorrow night and Wednesday at 7:00 PM

This will have to be monitored very closely over the next 12-16Hrs to see if any kind of model agreement can come into place. That would make me a lot more confident in seeing Winter Weather in South Carolina.

Hope everyone has a good night! Expect something tomorrow !


- Chris

Winter Storm Octavia

Hey Everyone,

Im back here on my blog format for tonight to lay out everything in a much better format versus Facebook. First off, I wanna say thank you everyone for all the positive feedback I have gotten. I have managed to get almost 20,000 page views on my Facebook Page in the last 4 days.

Getting on with the Nuts and Bolts of this impending Winter Storm.

It looks very likely that most of South Carolina will experience Winter Weather.

When: Monday Evening through Wednesday Mid Day.

Where: Will cover that below but areas North and West of I-95 should pay close attention.

What will Fall? A little bit of everything. Rain, Freezing Rain, Sleet, and Snow.

Impacts : Hard to say for now but there could be significant impacts such as dangerous slick roads, extended power outages, falling trees, And ice on everything imaginable.

Setup:

During the day tomorrow an area of Low Pressure is expected to begin to develop over Eastern Texas and Louisiana this area of Low Pressure is then expected to move ENE over the Deep South and by Monday afternoon will make its approach on South Carolina. 

I am not expecting anything significant until after 7PM Monday for any portion of South Carolina and Western North Carolina. It appears that moisture will move into the area before then but, due to low dew points and some really dry air in place, it will take a few hours to get the atmosphere wet enough to support precipitation falling to the ground. 

There has been some uncertainties in regards to the exact track of the Low Pressure. This is going to be pretty important. A jog 75 miles each way could mean a Winter Wonderland or just a soggy, raw day. I am hoping that the models come into better agreement over the next 18-24Hrs so I can have a better idea of what to expect. 

Miller A or Miller B ?

Below this paragraph is the 18z GFS Model Run from today and it has hinted at this storm phasing and becoming whats called a Miller Type B Storm. There is also a Miller Type A Storm which has one centered area of Low Pressure that usually remains offshore. Im sure you all are asking yourselves What is a Miller Type B Storm ? Miller Type B storms usually involve the following during Cyclogenisis. (An area of Low Pressure Forming and Strengthening)

• 2 Low Pressures Involved (One Primary Low, and a Secondary Low)
• The Secondary Low develops along the coast as the Primary Low over Land weakens.
• Usually occurs in situations where CAD is in place. (Cold Air Damming or "The Wedge)
• The Secondary Low can become quite intense, quickly. 

Again this only a model run and not a Forecast. 

What to Expect over the duration of the event:

This will likely start out as all snow on Monday evening after 7PM and as Isentropic Lift increases we will see a "nose" of warm air overrun the cold air at the surface. This will result in a change over to Sleet and/or Freezing Rain on Tuesday morning. During the day on Tuesday as temps warm I would expect a changeover to all rain for a few hours before once again, turning back over to freezing rain. This will remain the same until early Wednesday as the system strengthens off the Coast. If this happens, we would see cold air wrap around the Low Pressure and have yet another changeover to all snow. With the Cyclogenisis of the storm there could be a band of heavy snow that sets up somewhere in North and South Carolina.


Other Models: 

All of the other models are in agreement in Winter Precipitation but there a few differences in position, timing, and Precip Type. 

Locations:

For now, I have listed below the official National Weather Service's map of Freezing Rain accumulating greater than .01" see your area with the corresponding percentages.

Until models come into better agreement I am not going to throw any specifics out there. We will save that for tomorrow. 

 

Accumulations:

Given the model uncertainty as of now I cant say for sure who is going to get what and how much of it. Areas that do get the winter precipitation could get upwards of .10" of Ice and 1" of Snow.

In Closing:

I wouldn't be surprised at all for the National Weather Service to issue a Winter Weather Advisory or Winter Storm watch by 7PM tomorrow given the current information. I will be watching this like a hawk tomorrow and will do another write up tomorrow evening. Hope everyone has a great evening and be sure to check back tomorrow!


- Chris