Rain can be expected later tonight (Sunday Mar 15) and throughout Monday (Mar 16), accompanied by gusty winds. A cold front bringing cold air from the North will follow shortly after the rain, causing a temperature drop between 20-30F in less than 24 hours before Tuesday (Mar 17). These are dangerous conditions for many of our fruit crops.
Min predicted air temperatures for Tuesday, Mar 17:
- NC Coastal areas: 35-40.
- Eastern NC: 30-35.
- Central NC (Triangle/Triad area): 25-30.
- Foothills/Yadkin Valley: 20-25.
- Asheville/Hendersonville: 20-25.
- Boone/Northern Mountain Ranges: 15-20.
Min predicted air temperatures for Wednesday, Mar 18:
- NC Coastal areas: 30-35.
- Eastern NC: 25-30.
- Central NC (Triangle/Triad area): 20-25.
- Foothills/Yadkin Valley: 20-25.
- Asheville/Hendersonville: 15-25.
- Boone/Northern Mountain Ranges: 10-15.
These air temperatures can be threatening not just to open blossoms (strawberry) or young tender shoots (grapes), but also to flower buds that have not opened yet.
Most growers could not cover over the Thursday/Friday frost event, due to wet covers. They potentially lost already open blossoms in the field due to the temperatures.
However, the upcoming event pushes temperatures a lot lower. You might be under the impression that protecting for the upcoming event might not be as important, because blossoms were already lost.
Triangle/Triad and further West:
In the Triad/Triangle area and further West, temperatures might drop into dangerous conditions. Please consult your local weather forecast (see tables below!)
Those conditions, if unprotected, have the potential to threaten even unopened blossoms.
The upcoming rain and wind will make the deployment of row-covers unfeasible if deployed too late. If row-cover are used, you should put them out today before the rain.
Be aware that wet and frozen covers can also cause damage to your plants! However, they might cause enough protection for closed and not fully open blossoms.
If you use sprinklers for protection, the nights of Monday-Tuesday and Tuesday-Wednesday should have not a lot wind and might warrant sprinkler protection.
Eastern NC:
Generally, conditions will mostly threaten open blossoms, but not closed buds. If you haven't lost flowers in the last event (Thursday-Friday), you will be well advised to protect either with row-covers or sprinklers through the nights of Monday-Tuesday and Tuesday-Wednesday.
In most European style wine-grape growing areas, we are looking at min air temperatures in the 20s on Tuesday morning. Early bud breaking varieties are at heightened risk for extensive damage. Primary buds in tender bud tissue (budswell) can be damaged, as well emerging leafs or shoots will most likely suffer cold damage.
Especially Chardonnay and Merlot are at high risk. However, time of bud swell depends not just on grape variety, but also on training system, management, vine health and specific location.
If you want to estimate potential damages, it is important to know your site and document vine phenology across your vineyard, as it can differ from site to site.
If you have a sprinkler system in place that is in working condition, you can try to use it for protection during the cold nights. Make sure you start the sprinklers before the dew point! reaches critical values that can cause bud damage.
Wind machines most likely will not help, since we are not looking at an inversion weather, but a cold front.
