Multi-State Frost Advisory on Friday, April 8th

— Written By Barclay Poling
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7daytemp.se.4Fig. 1. The minimum temp map for whole southeast on Sunday morning. The teal areas (20-25) have actually decreased since yesterday’s forecast for 4/10 (see Fig. 2). So that is good news! But, you can still see how most of NC is now in light blue (25-30), and this could be another dangerous event! Most reports I have heard from Wednesday’s outcome have been quite favorable for MID-SOUTH strawberry growers (Mid-Atlantic has been tough), BUT, just horrible on other small fruits and peaches. In blackberries, for example, there were extensive losses in Faison (NC) area where temp go below 27 F. I visited with a grower in VA yesterday who lost his entire peach crop to 23 F on Wed morning.

7daytemp.se.6Fig. 2. Yesterday’s forecast for Sunday morning – note the teal zone in Central Piedmont of NC (not there today). There was even a Piedmont area with 15-20 in yesterday’s forecast. When you get those kinds of temps, you are beginning to look like the Easter Freeze of 2007. In reality, we are NOT looking at a repeat of those terrible conditions this Sat/Sun in the Mid-South. All in all, I see this event as very manageable. One precaution I will add, is that growers MUST get covers off quickly at this time of year, as fruit will ripen very very quickly under covers (this is not like Mid-March when we are not dealing with fruit). I do not see any further cold threats this next week in Mid-South, and growers will need to get covers off Monday. Conditions could be a bit more challenging up in the Mid-Atlantic for the week ahead, and leaving covers on may be important, depending on location.

Good morning,

I’m just back in NC from a late afternoon visit in VA yesterday, and in the course of my travels since posting the noon advisory yesterday, I have had a lot of reports from growers on the phone and by email. I know time is very short today for getting ready for this Saturday night/Sunday morning’s cold event, so I will postpone sharing these Grower Reports until a little later. It is very difficult to give general recommendations on what to do for the whole region, as our conditions are so very very different across the whole area. This is why I am immediately sharing the latest AWIS forecast for  MD, VA, NC, SC and GA. One thing I can say is that winds are going to be very high on Saturday, so row covers should go on today, Friday. Perhaps you are picking today? If so, complete your picking today and then apply in late afternoon, or early evening. Even by 8 a.m. tomorrow, most locations will be dealing with pretty high winds that will only strengthen more during day.

Basically, growers are trying to figure out:

1. do I need to use covers and water overhead (igloo effect)
2. can I try to overhead frost protect only?
3. can I use covers only? (and how heavy a cover?)
Regarding No. 1 –  the answer is that row covers + irrigation may be justified if your canopy is going down to 23-24, and you only have a single cover that provides about 4 degrees protection…this technique requires a digital thermometer and thermocouple inserted in blossom to measure blossom temp. When blossoms under the cover begin to drop below 32 F, start watering on top! Typically, the row cover gives you a few extra hours of delay in start up time (compared to sprinkling alone where you must start sprinkling at wet bulb of 32 F)
One option not listed above, is row cover + drip.  I am recommending this to many growers who have called me this morning, who are in situations where they simply are not set up to irrigate, and have just a single row cover. In cases where the canopy is mid-20s, I think the dripping idea could provide that extra degree or two of warmth that will be needed in the hours just before sunrise. Dripping should start about 3-4 hours before sunrise (now at 6:55 a.m.), or around 4 a.m., and run continuously until after sunrise. Ideally, you would have a digital therm for this technique as well, so you would know when it is safe to stop running the drip (when the blossom registers 32 on digital therm).
Option 2. Overhead alone. I think this is going to be a poor choice for Sat night/Sunday morning due to much higher winds than earlier this week (Tue/Wed), when we had really still conditions. Please note in your AWIS hourly below how high winds will be on Sat/Sun and also note the lower dewpoints. Winds and low dewpoints will contribute to serious evaporative cooling problems, and I have not encountered may farms in our region who have state of the art sprinkling systems to handle more severe conditions like winds of 8-10 mph, and temps in low 20s. That is why a row cover is so critically needed in this episode on Sat/Sun – to take out the wind effect!
Option 3. In colder areas, like Central VA (where I was yesterday), growers are preparing for lower temps Sunday morning, like 23 F. And, in these more extreme conditions it can be a very good strategy to double up on covers, and some of you have been able to locate extra covers in the last day (I posted this listRow cover suppliers), and I also just now had a text from a grower in Moseley VA (Aaron Goode) who  has a fair amount of USED extra 1 ounce row covers, 26′ wide, that he is willing to take a reasonable offer on. He said they have some tears but could be very usable as a second cover…you can text him at 804-986-1573. By the way, I like the idea of putting the older, less perfect cover, underneath the newer row cover (with no holes or tears). I am happy to share info today from anyone who has extra covers. I realize that most growers have already applied their “good” covers, and the older ones will need to go on top. BUT, if you have note applied the cover yet today, and you have access to an older cover, then definitely put the older cover underneath. Winds can be a real issue with covers that are torn in places – a good reason to put the cover without tears on top. If you must put the older cover on top of the newer cover, make sure you throw down some rock or sand bags in areas where the older covers are torn. We are going to be dealing with very tough winds on Saturday.

Maryland:MD Min Temp

7daytemp.at.4

10-DAY DETAILED HOURLY WEATHER FORECASTS

Aberdeen Andrews_AFB Annapolis_Naval Baltimore_Sci_Ce
Baltimore/Wash Cambridge/Dorche College_Park_AP Cumberland_AP
Easton_MD Fort_Meade Frederick_MD Gaithersburg_AP
Hagerstown_AP Leonardtown Middle_River Oakland_MD_AP
Ocean_City_AP Patuxent_River Salisbury Stevensville_AP
St_Inigoes/Webst Washington_DC_AP Westminster_AP

Virginia:VA Min Temp

Please note how very cold it will be in some central VA locations like Farmville (20 F) on Sunday morning. Please check out the detailed hourly AWIS forecast for your location in VA. Luckily, many VA growers own a hand-held digital (Omega) from a program sponsored by VDACS in 2012 – you will find this device very handy for monitoring blossom temps under the row covers for this upcoming cold event.

In Ashland, I note that there was a minimum of 34 this morning, but there was overcast (and, rain last night, as I drove through it). Covers could  go on late today when they drop to 10 mph at 6 p.m., and then diminish a lot in the early evening. By 5 p.m. (17:00) on Sat the winds are 28 mph. Note by 10 p.m. the wet bulb will be 32 F. Be sure to insert thermocouples in the blossoms this afternoon for monitoring tonight

Ashlad 2

7daytemp.at.10I know VA and MD growers are concerned about the rest of the week, and this shows the mins for Wed, April 13. I took an extra moment to look at some of the areas in light green (35-40) to see the risk of frost on Wed. I looked at Charlottesville (below) and noted that 34 is the minimum Wed, but no frost forecast. The frost forecast in that locality, is for Friday!

charl

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

North Carolina

Min temp table for NC (many locations): NC Min Temp Table

7daytemp.nc.4 (1)Fig. 2. This map has changed some from yesterday (Fig. 3 below), and is actually a little better!

7daytemp.nc.6Fig. This was yesterday’s forecast for Sunday morning – it was more worrisome!

10-DAY DETAILED HOURLY WEATHER FORECASTS

Ahoskie-Tri-Cou Albemarle_AP Andrews Asheboro
Asheville_Munic Beaufort-Michae Boone_NC Burlington-Burl
Cape_Hatteras_AG Chapel_Hill-Hor Charlotte Cherry_Point
Clinton_NC Concord_NC Currituck_NC Edenton-Northea
Elizabeth_City Elizabethtown_NC Erwin-Harnett_C Fayetteville_AP
Fort_Bragg/Simm Franklin/Macon_C Gastonia-Gaston Goldsboro_AFB
Goldsboro_NC Greensboro Greenville_AP_NC Hickory
Jacksonville Jacksonville_(A Jefferson_AP_NC Kenansville-Dup
Kill_Devil_Hills Kinston_AP Lexington-David Lincolnton_AP
Louisburg_NC Lumberton_AP_NC Mackall_AAF Manteo/Dare_Co
Maxton Mcalf_Bogue_Fiel Monroe_AP_NC Morganton-Morga
Mount_Airy-Moun New_Bern North_Wilkesbor Oxford_NC
Piney_Island_Bom Pope_AFB Raleigh-Durham Reidsville_AP
Roanoke_Rap_AP Roanoke_Rapids_R Rockingham_NC Rocky_Mount-Wils
Roxboro_AP Rutherfordton Salisbury-Rowan Sanford_NC
Shelby_AP_NC Smithfield_AP Southern_Pines Southport_NC
Statesville-Sta Tarboro_AP Wadesboro_AP Washington-Warr
Whiteville_NC Wilmington_AP_NC Winston-Salem

SC

Minimum temps for multiple locations in SC

10-DAY DETAILED HOURLY WEATHER FORECASTS

Aiken_AP Anderson_Co_Air Barnwell_AP Beaufort_Cnty_AP
Beaufort_SC Bennettsville_Je Camden_AP Charleston_Exec_
Charleston_Muni Cheraw_AP Chester_AP Clemson-Clemson
Columbia-Columb Columbia/McEnti Columbia_Metro Conway_AP
Darlington Florence_SC Georgetown_AP_SC Greenville_Donal
Greenville_Down Greenville-Spart Greenwood-Green Hartsville_AP
Hilton_Head_AP Kingstree_AP Lancaster-McWhir Laurens_AP
Manning_AP Marion_AP_SC Moncks_Corner_AP Mount_Pleasant_A
Myrtle_Beach Newberry_AP North_Myrtle_Be Orangeburg-Oran
Pickens_AP Rock_Hill Spartanburg_Down Summerville_AP
Sumter_AP Sumter_SC Walterboro_AP Winnsboro_AP

Note from Easley, SC: (April 7th, 9:30 p.m.)

eric on april 4

Hey Dr. Poling,
What a lot at stake right now! With our crop so far ahead (we picked our first berries on the 5th, our average first picking is usually 4/20-25th), this would be very similar to having a severe cold event around the end of April. We have a tremendous load of fruit and flowers on the plants.

Our original plan was to protect using overhead irrigation this weekend, but with the pump debacle and being unsure whether it will sustain pressure, we have decided to go with row covers. Our forecasts are all over the place for Sunday morning – from 22 degrees to 30 degrees. Skybit has us at 28 and AWIS 24. I suspect these two will start to agree by tomorrow evening and probably fall somewhere around 26. We have both 1.5 oz and 1.25 oz covers. As of now we don’t plan to double cover the 1.25 oz. unless the forecast lowers for Sunday morning. We will pull covers tomorrow evening (Friday), and hopefully the wind will lessen a bit. We’ll search for tears and holes that may be in the fabric on Saturday and try to do some quick fixes with duct tape (it fixes everything, right?). One other thing that we are considering, and I wanted to get your advice on this first, is if the forecast lows get much lower, would running drip at different intervals during the night help?

Thanks,
Eric

Reply – Eric I think you are probably right about minimum being in the mid-20s, as best we can tell now (noon Fri). Good to get all those covers on today when winds subside. Those cover quick-fixes on Sat are a super idea. If the forecast lows were to go below 26, then you could consider running the drip, but the growers who have done this in Florida wait until 2-3 hours before sunrise, and this makes a lot of practical sense to me from the standpoint of not washing all the fertilizer out of your beds with longer runs, as well as timing it perfectly with when the temperatures are going to be lowest. In Rock Hill, SC, which will have 25 minimum, you will note that the temperature doesn’t even reach 30 F until 4 a.m. If you turn the drip on then, you should see a 1-2 degree bump in temps beneath the covers, and that may be all that is needed! A 1.25 oz should provide at least 4 F protection, plus 1 degree from drip, equals 5 degrees. With a canopy minimum of 25 (assuming that for your farm in Easley from Skybit), that means the row cover + drip should keep the minimum air temp beneath the cover in the area of 30 F. And, it may even be warmer. The key point is that strawberry blossoms and popcorn stage are at a critical temp at 28 F, so you are 2 degrees above that critical temp. In the final analysis, I think the row cover + drip is well suited to conditions where the minimum canopy temps will be mid-20s.

rock hill

GA

10-DAY DETAILED HOURLY WEATHER FORECASTS

Albany_Municipa Alma/Bacon_Co Americus_AP Athens_Municipa
Atlanta/DeKalb Atlanta/Fulton Atlanta_Intl_Ar Atlanta_Paulding
Augusta/Bush_Fi Augusta_Daniel_F Bainbridge_GA Blakely_AP
Brunswick_GA Brunswick/Glync Canton_GA Carrollton_AP
Cartersville_AP Claxton_AP Columbus_GA Covington_GA_AP
Dalton-Dalton_M Douglas_Muni Dublin/WHBarron Fitzgerald_AP
Fort_Benning Ft_Stewart/Wrig Gainesville_AP_G Greensboro_GA
Homerville_AP Hunter_(AAF) Jesup_AP La_Grange
Lakeland Lawrenceville_AP Macon_AP Marietta
Marietta/Cobb Milledgeville_AP Moultrie_Muni_AP Newnan-Newnan_C
Peachtree_City Rome_GA Savannah Statesboro_GA
Swainsboro_AP Sylvania_AP_GA Thomaston_AP Thomasville_AP
Thomson_GA Tifton_AP Valdosta Valdosta/Moody
Vidalia Warner_Robins_A Washington_GA Washington_GA
Waycross_AP Winder_AP