Less rain was seen than previously expected during the day but current radar trends indicate that we will make up for it tonight. Rainfall will overspread the state tonight ahead of a cold front moving through the state. Rain should be mostly light but up to an inch is possible south. Rain will exit from northwest to southeast Friday morning with clouds slowly eroding thought he day. Canadian high pressure will settle into the state Friday night, and with clear skies and calm winds, we will see a very cold night for the state with a growing season ending freeze likely. Most will see 20s to near freezing but the northwest corner of the state will be close enough to the snow pack in the Plains to see a few teens there. This is pipe freezing cold. Remember to protect your pipes, bring pets in and make sure the people around you stay warm. Cold air sticks around for the weekend. We may see some slight warming on Sunday but with increasing clouds temps look to stay cold. Moisture will increase ahead of our next storm system and there are a lot of questions surrounding it. That will be addressed in the next period. Sunday night, with increasing moisture, rainfall will start to increase especially central and southern sections. Across the north, cold air will be slower to erode. Here we could see rainfall mix with a few snowflakes late Sunday night as the rain moves in. Temps will be very marginal with this and the atmospheric profiles will have a slight warm layer so not expecting an all snow event but this will be monitored. With the warm ground temps, no impacts are expected.
Temps will be well below average for November for the period.
Snow or no snow that is the biggest question surrounding the Monday forecast, even though cold air is a larger threat. Here is where I will take it with this forecast.
Guidance is sold on a snow event as of the afternoon runs. What its not sold on is placement. GFS is south, Euro north, CMC in between and various others have similar setups. This is a very unique setup with a very strong 500mb trough swinging through overhead and a strengthening surface low near the Gulf coast. Data is insistent on keeping moisture around as the coldest air enters the state. In fact, some bring it in sooner. However, there are a few things that work against this forecast.
One is WAA or warm air advection. This is moisture transport over cold air. This happens a lot in the winter months and tends to work against our snowfall setups. It helps to warm the mid levels just enough to keep precip liquid. Another thing is called a Dry slot. Typically when you get Arctic air moving in and a deepening low, they work to create a dry slot somewhere within either the lower or mid levels, preventing moisture to reach the ground,. This happens a lot with these arctic air masses and tend to not be seen by data. This is when the human aspect to forecasting comes in. This setup is unique and similar to the one in November 2014 when we saw a bit more snow than expected. I do not expect that this time, however experience tells me not discount either solution.
There are basically 3 ways this can go. We warm up, no snow at all just a cold rain. Dry slot moves in cuts off precip with coldest air moving in or last, things end up colder than expected and we see more snow than currently forecast. Here is my thinking on Monday:
With cold air typically slower to erode have gone with a blend of guidance as well as the setup. Have left mention of a mix of rain and snow, especially in the higher elevations of northern Arkansas through at least mid-day. For central and south, mainly a cold rain is expected. However, with a northeast surface wind, cold air tends to go around the mountains and get here sooner. Have gone below guidance for highs Monday because of this and this may be to warm. Even with the WAA over the state there may be just enough CAA or cold air advection to keep us colder than current thinking. This will need to be watched closely. As we head into Monday night, there does look to be a dry slot working towards the state. Where this sets up is key. Colder air will be working into the state as the moisture is leaving. There is a small window of opportunity for flakes to fly, especially in the north. Even with dry air in place, arctic air tends to squeeze out even the smallest amount of moisture. So with this, have opted to leave mention of a few flakes for the north with rain central and south. If dry slot is slower and cold air is faster than the forecast would require snow mention further south. Will keep it for the most favored area for now. Even if we do see any snowfall, no accumulation is expected due to the warm ground and limited time for snow to fall. This also will be watched closely.
Beyond Monday, things dry out. We will be cold on Tuesday but sunny. Warming trend commences starting on Wednesday with sunny skies seen. Temps near average by the end of the period.
North: Rain and snow mix north changing to rain during the day. Small chance of a changeover in the evening before dry air works in.
Central and south: Cold rain expected however future trends and atmospheric profiling may warrant other headlines.
Stay tuned to future updates as this forecast continues to be fine tuned in the coming days.