I’ve gotten a number of emails and phone calls asking about frost and freeze conditions for this weekend. I think it is likely that many of the northern counties in Georgia are going to see temperatures of 32 F or lower on Saturday and Sunday morning based on current forecast models. The freezing temperatures may go as far south as Athens or even farther south if you are in an area that is prone to cold temperatures, so you should be prepared to deal with what is coming.
The pattern that has set up is a classic pattern for spring frosts in Georgia. A strong cold front has passed through the area, and cold and dry air is moving into the state from the northwest. Tonight, temperatures in NE Georgia could get down to 32 F for several hours. The forecasts are given for 2 meters above the ground, and air closer to the ground could be colder since it sinks because it is dense. The air is still fairly moist and there is a chance of some light precipitation in the NE, so dewpoint and wet bulb temperatures should stay in the mid- to upper 20s. Winds tonight will be in the range of 5-10 mph. This means that frost protection by irrigation will be difficult, and no inversion is expected, which will also make the use of fans to stir up the air less effective than in light wind conditions. This is an advective freeze, and you can read about them in Vineyard Frost Protection and in Commercial Freeze Protection for Fruits and Vegetables. Note that climatology says we can expect a frost this week in one out of ten years in northeast Georgia, but the warm conditions in recent weeks have brought things out of dormancy more quickly than usual, making the vines more vulnerable than usual. The links above also give some guidance about what kinds of frost protection can be used in various types of freezing weather, including chemical sprays and other methods.
On Sunday, April 10, I expect to see another round of cold conditions, this time in the form of a radiation freeze due to light winds and clear skies. The temperature could again get down to 32 F for several hours. The graphical forecast from the NWS indicates that the cold temperatures could be a little more widespread than on Saturday the 9th, so do not let your guard down if you squeak by the first night.
Freeze conditions in northern Georgia are very hard to predict accurately because of the hilly terrain. You know your own vineyards better than anyone else so should use that knowledge according to determine where the coldest conditions are likely to be. Low-lying areas will tend to collect the coldest air, and the lower parts of the vines may also experience worse conditions than vines that are more elevated.
The US map below shows one model prediction of where freezing temperatures will occur on Saturday morning. There is quite a bit of variability in the model predictions, so frost could be more or less widespread than what this shows. The second map showing the graphic temperature forecast on Sunday morning has a little wider coverage of cold temperatures than on Saturday but is based on a different model.
