Frigid Temperatures Tonight in VA and Mid-Atlantic Region (3/10/17)

— Written By Barclay Poling
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Fig. 1. Photograph taken at 11:45 a.m. this morning in Southern NJ – the growers at this location are planning to run water on top of the sprinklers tonight because temperature minimums could go to 20 F Saturday morning, and then teens on Sunday night as well as Monday Millville NJ Hourly Detailed Weather Forecast. If the growers do not irrigate on the covers (starting around 4-5 p.m.), they will lose emerged tight buds at these temps (see Fig. 2)  They have Sweet Charlie with blooms!

Fig. 2. Emerged tight buds can only tolerate down to 20 F at best!

Fig. 3. This photo was taken this morning by a NC grower northwest of Winston-Salem. You can see these Chandler plants are not far along. They did not apply any row covers at all this winter. The main concern here is with emerged tight flower buds (clustered around the crown below the open bloom). As far as the first C of the 3C’s, I would characterize this plant as being primarily at the tight bud stage, and I would be very cautious about taking a lot of risks to save 1-2 blooms per plant. One important marketing point:  I think a lot of growers are missing the boat by putting all of their crop under covers in winter, as this will force the crop to come in earlier, and they may regret having the crop come too early! You always want to have berries for Mother’s Day – which is May 14. I think it is much smarter to only have  a portion of the crop in row covers, but not all of it. It also makes for easier freeze and frost protection on the more delayed, non-covered portion of the crop.

Virginia minimums tonight and for the next 7 days:Va Temp Outlook at 2 p.m.

General concerns about the forecast for VA growers – if you take a quick look at the AWIS hourly for Farmville, you will see that dew points are really going to drop after 3 p.m. (from 28 to 18 F), and then going into low teens by 7 p.m. A wet bulb of just 31 F will be reached at 10 p.m. (2200). If you were going to irrigate, you would want start up before blossom temps on digital thermometer go below 32 F, or before the wet bulb gets below 33 F (so, somewhere between 9 and 10 p.m.). In Farmville Farmville – Hourly Detailed Weather Forecast it will be 25 minimum tomorrow morning, so that is potentially cold enough to even kill emerged flower buds (see Fig. 2). What is very unusual about this Cold Event (the 2nd C), is how the dewpoints are simply crashing all night long. And, in the morning, they go into single digits at 8 a.m., and finally negative at noon tomorrow. And, the wet bulb will never even reach 33 tomorrow — so, this is one of those very weird deals when you really never see the ice melt during the day. I can definitely appreciate whys some strawberry growers simply say forget it with watering, and I am going with double covers. A double cover would be the better Control Strategy with such wickedly low dew points as these! What is also discouraging about this forecast is the possibility of 23 F minimum on Sun/Mon, and 20 F on Wed/Thur (March 15-16).

Farmville Morning sky cover Min air temp (F) Time of minimum DP 6 a.m. (F) Winds 6 a.m. (mph) Frost potential
Fri/Sat clear 25 7:00 a.m. 10 3 Black Frost
Sat/Sun Overcast 27 7:00 a.m. 17 2 Marginal pot’l
Sun/Mon Clear 23 7:00 a.m. 16 7 FREEZE
Mon/Tue OVC 31 6:00 a.m. 24 6 unlikely
Tue/Wed Broken 25 6:00 a.m. 13 10 wind borneFREEZE
Wed/Thur Clear 20 5:00 a.m. 8 8 wind borneFREEZE
Thur/Fri Clear 30 6:00 a.m. 22 4 Marginal pot’l

In a visit near a strawberry farm outside Williamsburg this morning with Roy Flanagan, VA Tech Agent,  we discussed the very difficult (and somewhat discouraging) forecast for the week ahead, including the possibility of 5 nights of freeze and frost over the next 7 days in areas like Farmville.

It will not be quite so cold tonight over in Chesapeake, Chesapeake Hourly Detailed Weather Forecast,but it will be down to 25 F on Sunday morning at 1 a.m.! Normally, we see the low for the night around 6 a.m., but in Chesapeake will happen around 1-2 a.m.

So, I cannot emphasize enough that with this kind of variability in the forecast for different locations in VA, it is critical to study the forecast for your farm area, and develop your own custom strategy using the 3 C’s:

1. Crop status and condition – how far along is your crop? The more open blooms per plant, the more vulnerable you are, and more you need to go all out to save what you can. If you are only concerned with saving emerged tight buds, then this really impacts the decision-making for cold protection strategy!

2. Cold event – as we are learning, it is not just a matter of examining a forecast for a minimum temp, but you need to take into account wind speeds, dew points, and even things like % cloud cover. Some of you also take into account the stage of the moon (full moon on 3/12)

3. Cold protection strategy – In last night’s advisory (SC Grower Report), you learned Eric Hunter formulated his final cold protection strategy for the week ahead. And, he decided his best bet was to double up his row covers. In his report, note that he discussed the Crop Status (some 20 blossoms per plant — very exposed), and he talked about the Cold Event (for Easley, SC) and that he may see some low 20s (extremely dangerous to all flower stages), as well as MULTIPLE DAYS OF FROST AND FREEZES, and after taking all this into account, he decided on double row covers. Here is what he had to say in last night’s advisory:

“We have the capability to frost protect using overhead irrigation, but the older I get, the more staying up for several nights in a row becomes a dreadful thing. I’d rather spend 2-3 hours putting out and removing covers and get some sleep. I don’t mind 1-2 nights of being up, but once we get past that, no thank you.”

So much variability in VA forecast!

There is a great deal of variability in the forecast across VA tonight, and for the next week. Please study the AWIS Hourly Forecasts for the town/city closest to you, OR for the town/city that is actually as cold as where you are. I learned this morning that the area of Williamsburg where we were standing this morning is more like Richmond to the west!

10-DAY DETAILED HOURLY WEATHER FORECASTS

Abingdon Ashland_VA Charlottesville Chesapeake-Ches
Culpeper Danville Dublin/New_Riv Emporia_VA
Farmville Fentress_Naval_A Fort_Belvoir/Da Fort_Eustis/Fel
Franklin/J_B_Ro Hillsville Hot_Springs/Ing Jonesville_AP
Langley_AFB Leesburg/Godfre Louisa-Louisa_C Lynchburg
Manassas_Muni(A Marion/Wythev Martinsville Mecklenburg/Bru
Melfa/Accomack Newport_News Norfolk_Hampton_ Norfolk_NAS
Norfolk_VA Oceana Orange_VA Petersburg_(AWO
Quantico Richlands_AP Richlands_VA Richmond
Richmond_Chester Roanoke Shannon_Arpt Stafford_AP_VA
Staunton-Shenan Suffolk-Suffolk Tappahannock_AP Virginia_Tech_A
Wakefield_AP Wallops_Island Warrenton_Fauqui Washington_Dulle
West_Point_VA Williamsburg_VA Winchester_Rgnl Wise/Lonesome_P