Multi-State Freeze and Frost Update (10:45am, Sat., March 11, 2017)

— Written By

“Daylight Savings Time Starts Tomorrow”

Hello again!

I was feeling a little guilty the day before yesterday in advising an Eastern NC strawberry grower to proceed ahead with a large row cover investment. As you may recall, there was a significant change in the forecast for NC that happened early Friday morning (for the better), and with the new forecast with minimum temps over the next week of 27 F and higher, you could make an argument that the covers would not be needed (for this particular 10 day period from today until March 20). In Table 1 (below), I noted that you could use row cover OR sprinkling on all of the events. In Table 2 you can see how in this morning’s forecast how things have changed (again). And, please note that on Tue/Wed, March 14-15, we are no longer looking at a minimum air temp of 31, but now 22 F. Wow! That changes everything! With a temperature that low, and sustained winds of 9 mph we are dealing with a very dangerous frost/freeze (you say, “What is a Frost/freeze? Check out: cold protection in winegrapes …the short version is that it is cold event with sub-freezing temps and winds in the range of 5-9 mph; if winds were 10 mph, it would be a windborne freeze). You can argue that sprinkler irrigation alone can handle a “frost/freeze,” but I would not risk it – there is real risk of evaporative cooling damage even when winds are above 7 mph. The best solution to keeping open blossoms safe is to run water on top of covers.

Fig. 1. This is the best solution for a frost/freeze, or windborne freeze.

Without the purchase of these new covers, the grower would have been forced to rely on sprinkling alone, and that is a VERY DANGEROUS PROPOSITION WITH SUSTAINED WINDS OF 9 MPH.

Table 1. Kenasville AWIS Hourly (3/10/17)

Kenansville Morning sky cover Min air temp (F) Time of minimum DP 6 am (F) Winds 6 am (mph) Frost potential Strategy
Fri/Sat Few clouds 34 7:00 AM 24 3 ? Row cover or H20
Sat/Sun Overcast 32 10:00 PM 29 5 Frost 10 pm Row cover or H20
Sun/Mon Scattered 30 5:00 AM 29 11 Frost midnight Row cover or H20
Mon/Tue Overcast 42 5:00 AM 40 9 NONE
Tue/Wed Broken 31 6:00 AM 22 14 Unlikely
Wed/Thur Clear 27 5:00 AM 21 7 Frost at 6 am row cover or H20
Thur/Fri Clear 35 6:00 AM 33 5 Frost at 2 am row cover or H20

Table 2. Kenasville AWIS Hourly (3/11/17)

Kenansville Morning sky cover Min air temp (F) Time of minimum DP 6 am (F) Winds 6 am (mph) Frost potential Strategy
Fri/Sat Scattered 32 7:00 AM 22 2 ? need to ask
Sat/Sun Overcast 31 7:00 AM 25 6 ? Row cover or H20
Sun/Mon Clear 30 4:00 AM 28 5 Frost midnight Row cover or H20
Mon/Tue Overcast 40 5:00 AM 37 9 NONE
Tue/Wed CLEAR 28 5:00 AM 21 14 Windborne Freeze Row cover only
Wed/Thur CLEAR 22 5:00 AM 14 9 Frost/freeze Row cover + H20
Thur/Fri CLEAR 28 5:00 AM 25 3 FROST 2 am row cover or H20
Fri/Sat Scattered 40 5:00 AM 36 9 NONE

ARE YOU TAKING ADVANTAGE OF THE AWIS HOURLY FORECAST TOOL? (I can stop producing it if it is not useful?)

<GROWER FEEDBACK ON WHETHER TO CONTINUE PUBLISHING AWIS HOURLY PRODUCT>

  • Yes, Barclay, the AWIS hourly forecast is very useful.
     
    We look at forecasts from AWIS, AccuWeather, and Weather Channel (came on my smartphone). We prepare for the “worst” forecast and hope for the “best.”
     
    We did not renew SkyBit this year. It was never that accurate for our farm(s). Too many times, as related to frost, if we had waited for the SkyBit frost time, we would have missed the start of the frost, sometimes badly. We do better looking at temps, dew points, winds, and cloud cover, all from AWIS, AW and WC, to come up with our own “frost” forecast. That and “looking at the donkey.”
  • <Editor’s comment: My philosophy on this whole subject is that the more quality weather information you can access ahead of a cold event, the more successful you will be in managing the event when it arrives.  Skybit does one thing very well — it is unique for being able to give you strawberry canopy-level, minimum temperature information, 2-3 days AHEAD of the event. And, then it continues to give you information about those canopy minimums right up until the late afternoon/early evening prior to the cold event. Having this information on what the actual canopy minimum air temperature can be is very useful in making ADVANCE preparations to protect your crop. SkyBit does not include a FROST forecast – accurate forecasts of when a (white) frost will occur are very difficult to make. As far as knowing when to initiate protective measures against a white frost situation with sprinkling, I agree with Tom about the importance of “looking at the donkey” (i.e. watching for evidence of ice crystals forming on solid objects at the crop level). But, for a potential black frost scenario, you need advance information on canopy minimums, and that is something that SkyBit excels at providing.>
    (cont’d)
  • Thankfully, 26 on Wednesday night (subject to change, of course!) looks to be our worst for this cold event. Our covers should do us fine. The biggest problem is our bees can’t work covered strawberries, but with these cold temps the bees don’t work much anyway. Plus the plants are rather “arrested” so blossoms aren’t popping out and getting past pollinating, either. Actually, I wonder if the wind-caused “flapping” of the covers (really more like rolling ocean waves than “flapping”) isn’t sufficient to shake some pollen around and get that job done? I’d like to hear your take on that.
     
    Thanks for the advisories. It’s interesting to know what others are dealing with, too.
     
    Tom Baker
  • Feedback from SC Growers:
  • Dr. Poling,

    North Augusta TODAY. Yes the advisory is helpful. We integrate 4 to decide on our strategies. Yesterday we hit 80F, could not harvest or cover for lack of labor and had to overhead protect 0500-0745 despite forecasts of 40F this morning. You SNOOZE, you LOSE!! Today we are harvesting & selling hundreds & covering. Looks like a CHALLENGING week ahead, probably requiring combination protection and PRAYERS! I’ll send some pictures later today, as the fruit is BEAUTIFUL!!
    Sincerely,
    Clyde

  •  Eric Hunter- Yes, absolutely use and appreciate the AWIS tool. I think its one of the more valuable tools we have. Coupled with Skybit makes it a must have in times like these in my opinion.
    Looking ahead, my guess last week that we would hit the 18-19 next week mark appears to be coming true. Are you of the opinion that double covers of 1.25oz and 1.50oz are adequate for protecting the blooms without overhead irrigation?
    • Reply – I feel the row cover (single cover) + sprinkling is more reliable for upper teens than double covers.   I wish we had more data on this, but we actually had a presentation at the VA Beach meeting where a grower from Kentucky indicated to us that he felt the row cover + sprinkling is better than double covering.

AWIS is covering 71 locations in NC Alone:

I personally “hope” that many of you are taking advantage of the AWIS Hourly Forecast tool that is being provided as a service to the strawberry industry this season.  It can really help you make sense of what could be happening with the weather in you farm location on an hour by hour basis for the next 10 days. One trick to using the AWIS Hourly Forecast is to select the city/town in NC that is closest to your farm. They are now covering 71 locations across the state of NC.

Create an excel spreadsheet to track changes:

Regarding the AWIS Hourly Forecast tool, I find it helpful to also create an excel spreadsheet summarizing the basic weather information derived from this forecast (that is what I just did for Tables 1 and 2), and if you click on Kenansville (below), you can see all the data that went into Table 2 this morning. AWIS updated this forecast at 8:47am this morning. What I try to do each morning (time permitting), is review the previous day’s excel spreadsheet against the new forecast for a site that I like to follow closely (like Kenansville, NC; Farmville, VA and Chesapeake, VA). And, when you come across a significant change in the weather forecast, as I did this morning for Kenansville (the new minimum of 22 on Wed/Thur), you can then make the appropriate adjustment in your Crop Protection Strategy (3rd C). If I were still teaching at NCSU (I retired in Dec 2010), I would have my students become familiar with tracking “strawberry weather during bloom” for their home location (using AWIS hourly information), and then have them make a decision on the best Strawberry Crop Protection strategy based on the changes they are seeing in the AWIS data from day to day.  Recording this data on a regular basis, and then reviewing it, can be a terrific learning tool for students and growers!

AWIS HOURLY FORECAST FOR MD, VA, NC, SC, GA and KY

Before I list all the AWIS Hourly Forecasts for MD, VA, NC, SC, GA and KY, I am also going to share the AWIS Frost/freeze forecast for tonight for the benefit of NC growers – I only wish AWIS produced these for the other states as well. What NC growers may notice tonight’s AWIS Frost/freeze forecast is the mention of little if any frost due to clouds in some areas of the state. This can be a tricky situation! All the temperature numbers for air temp and dew points are right for frost, and with long periods of calm, and just scattered clouds, it could happen!

Tonight's AWIS Frost/Freeze Forecast for NC
AWIS Weather Services, Inc. North Carolina Frost/Freeze Forecast
Produced at  504 AM CST on Sat Mar 11 2017

... Forecast for Tonight ... Northeast NC Coast                      
Currituck/Camden/Pasquotank/Tyrrell Counties      

**** FREEZE COLD LOCATIONS  ****
**** LITTLE/NO FROST DUE TO DRY AIR **** 

Lowest Temperatures:      29 - 36
Elizabeth_City Min          29 
Durations at/below 32:     0 -  8
Range Dewpoint Temps:     10 - 30
Range Wetbulb  Temps:     25 - 37
AVG Wind Direction/Speed:   N  5     Long Periods of Calm 
AVG Sky Condition:     Mostly Cloudy

Extended Forecast: Range of Lowest Min Temperatures in the Above Zones
Min Temps Valid For Morning of Given Date (May NOT include ALL cold pockets)

  03/13/17  03/14/17  03/15/17  03/16/17  03/17/17  03/18/17
  --------  --------  --------  --------  --------  --------
   31 - 37   40 - 46   32 - 38   29 - 35   36 - 42   41 - 47
--------

East Central/SE NC Coast                
Carteret/Pamlico Counties                         

**** FREEZE COLD LOCATIONS  ****
**** LITTLE/NO FROST DUE TO DRY AIR **** 

Lowest Temperatures:      32 - 35
Morehead_City Min           35 
Durations at/below 32:     0 -  1
Range Dewpoint Temps:     17 - 32
Range Wetbulb  Temps:     27 - 37
AVG Wind Direction/Speed:   N  3     Long Periods of Calm 
AVG Sky Condition:     Mostly Cloudy

Extended Forecast: Range of Lowest Min Temperatures in the Above Zones
Min Temps Valid For Morning of Given Date (May NOT include ALL cold pockets)

  03/13/17  03/14/17  03/15/17  03/16/17  03/17/17  03/18/17
  --------  --------  --------  --------  --------  --------
   31 - 35   43 - 48   31 - 33   24 - 29   30 - 34   44 - 45
--------

Southeast NC                            
NWS FORECAST ZONES 87-90,96-101                   

**** FREEZE COLD LOCATIONS  ****
**** LITTLE IF ANY FROST DUE TO CLOUDS **** 

Lowest Temperatures:      32 - 36
Elizabethtown Min           35 
Durations at/below 32:     0 -  1
Range Dewpoint Temps:     15 - 33
Range Wetbulb  Temps:     32 - 40
AVG Wind Direction/Speed:  NE  4     Long Periods of Calm 
AVG Sky Condition:         Cloudy   

Extended Forecast: Range of Lowest Min Temperatures in the Above Zones
Min Temps Valid For Morning of Given Date (May NOT include ALL cold pockets)

  03/13/17  03/14/17  03/15/17  03/16/17  03/17/17  03/18/17
  --------  --------  --------  --------  --------  --------
   29 - 35   34 - 43   27 - 33   21 - 28   26 - 33   42 - 46
--------

North-Central NC                        
Franklin County Area                              

**** FREEZING TEMPERATURES ****
**** LITTLE IF ANY FROST DUE TO CLOUDS **** 

Lowest Temperatures:      26 - 33
Louisburg Min               26 
Durations at/below 32:     0 -  9
Durations at/below 28:     0 -  4
Range Dewpoint Temps:      7 - 19
Range Wetbulb  Temps:     24 - 34
AVG Wind Direction/Speed:  NE  4     Long Periods of Calm 
AVG Sky Condition:         Cloudy   

Extended Forecast: Range of Lowest Min Temperatures in the Above Zones
Min Temps Valid For Morning of Given Date (May NOT include ALL cold pockets)

  03/13/17  03/14/17  03/15/17  03/16/17  03/17/17  03/18/17
  --------  --------  --------  --------  --------  --------
   24 - 31   31 - 40   21 - 31   18 - 28   25 - 35   36 - 42
--------

North/Central NC                        
Alamance County Area                              

**** FREEZING TEMPERATURES ****
**** LITTLE IF ANY FROST DUE TO CLOUDS **** 

Lowest Temperatures:      27 - 33
Graham_AG Min               30 
Durations at/below 32:     0 -  8
Durations at/below 28:     0 -  3
Range Dewpoint Temps:      8 - 19
Range Wetbulb  Temps:     26 - 34
AVG Wind Direction/Speed:  NE  5     Long Periods of Calm 
AVG Sky Condition:         Cloudy   

Extended Forecast: Range of Lowest Min Temperatures in the Above Zones
Min Temps Valid For Morning of Given Date (May NOT include ALL cold pockets)

  03/13/17  03/14/17  03/15/17  03/16/17  03/17/17  03/18/17
  --------  --------  --------  --------  --------  --------
   25 - 30   32 - 37   21 - 27   19 - 24   25 - 31   37 - 42
--------

South/Central NC                        
Richmond County Area                              

**** FREEZE COLD LOCATIONS  ****
**** LITTLE IF ANY FROST DUE TO CLOUDS **** 

Lowest Temperatures:      31 - 34
Ellerbe Min                 34 
Durations at/below 32:     0 -  2
Range Dewpoint Temps:     13 - 31
Range Wetbulb  Temps:     29 - 37
AVG Wind Direction/Speed:  NE  7                          
AVG Sky Condition:         Cloudy   

Extended Forecast: Range of Lowest Min Temperatures in the Above Zones
Min Temps Valid For Morning of Given Date (May NOT include ALL cold pockets)

  03/13/17  03/14/17  03/15/17  03/16/17  03/17/17  03/18/17
  --------  --------  --------  --------  --------  --------
   28 - 33   32 - 40   25 - 29   23 - 27   29 - 32   39 - 44
--------

Interior/EC-SE NC                       
Wayne County Area                                 

**** FREEZING TEMPERATURES ****
**** LITTLE IF ANY FROST DUE TO CLOUDS **** 

Lowest Temperatures:      30 - 34
Goldsboro_AG Min            33 
Durations at/below 32:     0 -  4
Range Dewpoint Temps:     17 - 30
Range Wetbulb  Temps:     30 - 35
AVG Wind Direction/Speed:  NE  3     Long Periods of Calm 
AVG Sky Condition:         Cloudy   

Extended Forecast: Range of Lowest Min Temperatures in the Above Zones
Min Temps Valid For Morning of Given Date (May NOT include ALL cold pockets)

  03/13/17  03/14/17  03/15/17  03/16/17  03/17/17  03/18/17
  --------  --------  --------  --------  --------  --------
   29 - 32   38 - 42   27 - 31   24 - 26   29 - 31   40 - 46
--------

For more detailed information visit www.awis.com or call 888-798-9955. Copyright 2017 AWIS Weather Services, Inc. All rights reserved.

Multi-state Update on Saturday, March 11th:

Note: I will not be able to produce an advisory of this sort until next weekend, so plan on referring back to this Saturday advisory to obtain current AWIS Hourly Information – these links for individual towns and cities remain updated. I try to do this as a service to the industry, and given the extreme toughness of this season so far, I am glad that I jumped in to help out some. But, I also need to attend to a number of personal things in the week ahead. Of course, the Sunday Outlook will be published tomorrow evening.

MD MD Outlook

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

Fig. 2. It was nice to take a break from all the ADVISORY WORK yesterday morning (Friday) to visit strawberry growers near our townhome in Williamsburg. Many of you may recognize Roy Flanagan in the photo – Roy is our VA Extension Agent out of VA Beach. Roy was also recipient of the Outstanding Industry Service Award of the NC Strawberry Assn. last Nov. He also hosted an outstanding Mid-Atlantic Strawberry Meeting in VA Beach at the end of February.

VA VA Outlook

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

NC NC Outlook

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 SC Outlook

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

GA GA Outlook

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

KY KY Outlook

10-DAY DETAILED HOURLY WEATHER FORECASTS

Bowling_Green Covington Danville-Powell_ Fort_Campbell
Fort_Knox/Godma Frankfort_AP Glasgow_KY Henderson_City
Jackson_KY Lexington_KY London_Corbin Louisville_AP
Louisville/Bowm Middlesboro_AP Monticello_KY_AP Murray_AP
Owensboro_AP Paducah Richmond_Madison Somerset(AWOS)

Question on botrytis (9:45 am Sat)

Eric Hunter asked me, “Over the next few days it’s gonna be wet and cool. We’d like to go ahead and spray, but my question is with it being so cool, is a botrytis spray necessary? Seems like I remember cooler temperatures not being conducive to the spread of botrytis?

Dr. Guido Schnabel, Clemson:

If temps are below 40 there is little chance of infection. But if people use row covers and don’t get them off as soon as temps rise there will be problems. 

Added info. Strawberry Disease Compendium:

The ideal temperature for sporulation is 59-72 F, and optimum at 64 F. So, I would have a look at AWIS hourly temp information for your area, and depending on sky conditions, you might be getting some very significant elevation of temperatures under the row covers!

In closing, I want to wish everyone best of luck this weekend and week ahead. Given all this cold weather headed our way again this week, I think I’d rather be back in warm-sunny Florida working with my new friend Rono in our advanced selection breeding plots!

Barclay

Fig. 3. An advanced strawberry selection – maybe we’ve gone a little too far with better berry size objective? This particular berry had a weight of 120 grams (4 1/4 ounces), and measured 10 cm (4 inches) in width.

Example SkyBit:

Written By

Photo of Dr. Barclay PolingDr. Barclay PolingFormer Professor and Extension Specialist, Strawberries and Muscadines (919) 515-5373 (Office) barclay_poling@ncsu.eduHorticultural Science - NC State University
Updated on Mar 11, 2017
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