Weekend Forecast Still On Track For ENC
Update #2: As of 10:18 PM, there are no changes needed for the forecast.
Update: As of midnight 12-15-16, no changes to this forecast are needed. Everything setting up as expected right now.
Good morning ENC! Today we begin to dry out after a couple of day of rain. Right now there are a few lingering clouds over portions of ENC and we will continue to see clouds on and off as we go through the day. High temperatures today will rise into the mid 50s with some areas potentially reaching upper 50s (especially areas where the sun will be out).
Thursday and Friday will be sunny and much colder as an Arctic air mass dives southward over the eastern US. Temperatures will drop significantly Thursday and Thursday night with lows in the lower 20s. Highs Friday only reach the mid 30s.
This weekend’s forecast has had many people across North Carolina (and surrounding states) interested in seeing what the weather will do.
Yesterday I laid out my forecast thinking on this week’s forecast and I have found no reason to change my forecast for this weekend. The cold air at the surface will be very shallow due to the northward progressing warm front and the air will be too dry for early onset precipitation into this cold layer. Below are update forecast soundings from the NAM forecast model (probably the most aggressive solution of frozen precipitation NOT the consensus solution for my forecast):
I use these particular models because they clearly show the players involved in the deciding factor of precip type this weekend.
The Arctic air mass will still be in place Saturday morning thanks to the high pressure to the north. On Friday, a coastal trough will form off the southeast coast and begin to lift inland and northward as a warm front. At this point, isentropic lift along the front will moisten and warm the air aloft. This will increase cloud cover late Friday night.
The low levels will still be cold and dry so it is unlikely that we will see precipitation overnight. As the warm front approaches at the surface, the atmosphere will begin to moisten as the temperature will begin to rise to near or above freezing. If the low levels are able to moisten quicker than the temperature rises, we could see frozen precipitation (freezing rain in this situation) at the surface.
So given how warm and deep the layer above the ground is, any precipitation will fall through this lay as a liquid and would have to re-freeze once it reaches the cold, shallow layer at the surface. If there isn’t a deep enough layer of cold temperatures, the precipitation will not have time to re-freeze until it reaches the surface. From what I have seen from the forecast data, I can conclude (at least right now) the dry air will limit precipitation onset until after the surface has warmed over 32F in ENC. The scenario is a little different for areas west of our territory.
The forecast soundings for Greensboro and Raleigh are good examples of what I am talking about when I discuss the potential for frozen precipitation at the surface. At these locations, the cold air at the surface could be deep enough to allow this level more time to moisten before temperatures rise above freezing. In these scenarios, it is possible to have a period of freezing rain before transitioning to all rain as the warm front at the surface passes.
The example I used is from one model run out of several for this time period and some models disagree with this one. The GFS shows greater low level warming before onset of precipitation leading to an all rain event east of a line from Greensboro to Charlotte. The NAM shows all rain east of I-95. The CMC shows all rain east of Raleigh. The Euro is similar to the GFS. Which gives me higher confidence in an all rain forecast for ENC. The forecast still could change over the next couple of days though I do not see that happening.
I hope everyone has a great day and I will update if needed.
