NC Strawberry Weather Update (Noon, Wed., 3/18/19)
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As you can see from these several minimum temperature maps for Sunday, March 22 – Tue., March 24, we are going to be returning to some colder temperature conditions in the early part of next week. In the last advisory, the forecast was for some freezing temperatures on Monday morning (3/23), and that may still happen in northern piedmont. But, the greater concern now is with Tuesday morning, as those purple and pink areas (3rd map down) are signifying freezing temperatures.
Figs. 1-3. You can see the minimum temperature maps for Sunday (Fig 1), Monday (Fig 2) and Tuesday (Fig 3). Right now it looks like Tuesday morning will have temperatures at, or below freezing in all areas that are gray, purple and pink. It is not clear at this time that this will actually be a frost. It could be somewhat windy, and dewpoints are not that high. You need very low wind condition, clear skies and dewpoints near 32 F to set-up for a classic radiation frost. In other words, there may be no frost formation on Tuesday morning! And, unless the air temperature at the canopy level drop below 28 F (not looking likely from this forecast), there is a good probability that temperatures will not be cold enough to cause open blossom injury on Monday night/Tuesday morning.
But, take a look at this! This is the minimum temperature map for Wed., 3/25:
Fig. 4. The colder conditions will continue on Wed morning as well. What is of concern is potential for an actual frost on Wed. morning in the north central and western piedmont (as well as pink areas in upper mountains). But, the crop in piedmont is more advanced, and many growers will have open blooms to be concerned about by the middle of next week!
A more detailed forecast for a north-central piedmont area shows FROST is likely next Wed. morning! I am using Burlington, NC, as an example (from AWIS 10-day, hourly forecast product):
Burlington, NC (Alamance Co)
Table 1. Note the F (frost) for both Wed and Thursday mornings next week. These could be potentially damaging frost events, and growers will need to get ready this week, and be sure they can pull covers back over the crop, or use sprinkling.
Special benefit of this Advisory Service in Spring 2015:
As a special feature of this season’s Strawberry Weather Alerts, I am now able to include these very detailed 10-day hourly forecasts for a number of NC cities and towns (I also have access to this same information for other states that are supporting these advisories this season). This did cost “extra” but this kind of information is invaluable for figuring out what kind of cold event to expect. If you see the “F” for frost, you can generally anticipate “problems” with a radiation frost event. If frost forms on open blossoms, they can be partially damaged, or killed. Returning to the Burlington, NC , example (Table 1) – note that on Tuesday morning (3/24) the minimum temperature forecast is 30 F at 6 a.m. This temperature is getting pretty close to a truly ‘critical minimum’ for a strawberry blossom, winds will be “up” (7-8 mph in early morning), and dewpoints are in a mid-range (24 F), and in this range it is “harder” for frost to form (air is less humid). However, if you look at the very next night, you can see winds are lower (3 mph) and dewpoints are higher (28 F). Thus, you see the AWIS forecast for FROST on Wed morning for this location. You will need to set your FROST ALARM to go out and inspect the crop to see if “ice crystals are starting to form” – I would set my alarm at perhaps 37 F. If you are a SkyBit subscriber, you will be getting some excellent information on canopy minimums as well.
For NC growers please check out the city/town closest to you to see whether there is any indication of a frost (F) for next week.
Raleigh, NC 27695-7609