Ready for This? Very Good Chance of Damaging Frost Across Much of NC Tomorrow Morning! (Issued 8am, Friday, April 7, 2017)

— Written By

Figs 1a – 1c. 1a) Impressive looking strawberry field in Sanford NC; 1b) this is the farm of John and Tina Gross – photo by David Dycus, Salesman/Agronomist, FCI (ddycus@fciag.com). David informs me that John and Tina will be covering up this field later today with row covers. 1c) The forecast for North Carolina HAS NOT IMPROVED, and almost the entire state is now going to have temperatures tomorrow morning of 38 F, or lower! This is quite a contrast to the minimum temperature map that was first posted last weekend for April 8th (Fig 2).

Below is the map posted last Sunday, 4/2 for Sat 4/8:

Fig. 2. Note how areas like Greensboro and Raleigh-Durham were in the powder blue zone (38-40) in the forecast made last Sunday, 4/2/17, by AWIS. What a difference 5 days can make! These same areas will likely experience 34-36 (Fig. 1), and that’s getting too close for comfort! With winds becoming much calmer later today and tonight, clear skies, and these colder temperatures, we can anticipate a radiational frost event Saturday morning that could be very damaging to open blossoms (Fig. 3)

Good morning,

Today is the 10th Anniversary of Easter Freeze 2007! Fortunately, we do not have anything like the Easter Freeze of April 7-8, 2007, on tap for tomorrow morning (Sat., April 8), but temperatures might get cold enough in some areas at ground level tomorrow morning to trigger “ice crystal” formation on strawberry blossoms, and that is something you will want to prevent from happening. But, will you be ready to deal with this? Everyone is understandably focused on harvesting and marketing, and chances are excellent you probably took your row covers out of the field and stored them? If not, good for you! I am definitely going to recommend for smaller and medium size growers in areas where frost is likely to apply row covers in the late afternoon today. I am also recommending drip irrigation beneath the row covers for a couple of hours before sunrise – this will “hopefully” keep things just warm enough under the covers to AVOID getting a FROST beneath the row cover! It turns out that we will have some very high dew points tonight — high enough to actually generate “ice crystals” (frost) to form on blossoms beneath the covers.

If you glance at the Georgia advisory of earlier this morning, https://strawberries.ces.ncsu.edu/2017/04/georgia-frost-update-and-suggestion-on-using-drip-beneath-row-cover-525-am-friday-april-7-2017/, you will note the suggestion of running drip irrigation beneath row covers to avoid the possibility of a frost forming beneath the cover because of very moist air conditions in the lower atmosphere. For example, in Kinston, NC, there will be an air temperature minimum of 37 F (5 ft) at 5am Kinston AND the dew point will be 32 F at the same hour. With dew points this high, frost is easily formed if winds are relatively calm.  AWIS is showing winds of 5 mph at 5 am, and that is calm enough for frost to form on open blossoms. Sprinkler irrigation would be an option if we were dealing with just the bloom stage, but we are now harvesting in many areas (we have been harvesting our research plots in Faison, NC, Twilight Tour April 20 2017.rev 1 since early last week).

So, if you are already harvesting, row covers would be an excellent way to handle this cold event, except there is this crazy chance that we could get frost forming under the covers in the early morning before sunrise on Saturday morning. And, frost under a cover is never a good thing! If frost forms on blossoms that are underneath a row cover we get the same kind of damage as we do from frost forming on blossoms outside the cover!

When to run drip?

Under conditions with dew points this high (near freezing point), I would recommend running drip for 2-3 hours before sunrise. Believe it or not, just that 1-2 F of extra heat that is generated by running the drip can keep the air temperature beneath the row cover above 32 F, and that is our goal. We do not want to let the air temperature BENEATH the row cover drop below the freezing point with such “moist air.”

Concern about Sunday morning as well!

Yes, this cold event is basically going to interrupt your whole weekend! I read in The Old Farmer’s Almanac for 2017 a short poem, “Foolish and Coolish, Spring is Cruelish,” and that sort of sums it up! See the Sunday minimums in the figure below.

Fig. 3. Minimum temperature map for Sun 4/9.

As I promised yesterday, here is the latest AWIS Frost/Freeze forecast for NC (immediately below), but don’t forget to review the DETAILED HOURLY FORECAST that AWIS provides for multiple locations in NC at the bottom of this advisory, and GOOD LUCK!

AWIS Weather Services, Inc. North Carolina Frost/Freeze Forecast
Produced at  504 AM CDT on Fri Apr  7 2017

... Forecast for Tonight ... Northeast NC Coast                      
Currituck/Camden/Pasquotank/Tyrrell Counties      
**** LITTLE IF ANY FROST DUE TO WIND **** 

Lowest Temperatures:      38 - 45
Elizabeth_City Min          38 
Range Dewpoint Temps:     28 - 39
Range Wetbulb  Temps:     36 - 45
AVG Wind Direction/Speed:  NW 14                          
AVG Sky Condition:     Partly 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)

  04/09/17  04/10/17  04/11/17  04/12/17  04/13/17  04/14/17
  --------  --------  --------  --------  --------  --------
   41 - 48   49 - 56   54 - 60   56 - 63   53 - 60   51 - 58
--------

East Central/SE NC Coast                
Carteret/Pamlico Counties                         
**** LITTLE IF ANY FROST DUE TO WIND **** 

Lowest Temperatures:      38 - 40
Morehead_City Min           40 
Range Dewpoint Temps:     31 - 37
Range Wetbulb  Temps:     36 - 43
AVG Wind Direction/Speed:  NW 13                          
AVG Sky Condition:         Clear    

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)

  04/09/17  04/10/17  04/11/17  04/12/17  04/13/17  04/14/17
  --------  --------  --------  --------  --------  --------
   40 - 43   48 - 52   54 - 56   57 - 59   55 - 58   56 - 58
--------

Southeast NC                            
NWS FORECAST ZONES 87-90,96-101                   
** PATCHY FROST COLDEST PROTECTED AREAS **

Lowest Temperatures:      36 - 40
Elizabethtown Min           38 
Range Dewpoint Temps:     26 - 37
Range Wetbulb  Temps:     37 - 45
AVG Wind Direction/Speed:  NW 10                          
AVG Sky Condition:         Clear    

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)

  04/09/17  04/10/17  04/11/17  04/12/17  04/13/17  04/14/17
  --------  --------  --------  --------  --------  --------
   38 - 42   46 - 51   52 - 57   55 - 59   53 - 59   54 - 59
--------

North-Central NC                        
Franklin County Area                              

**** FREEZE COLD LOCATIONS  ****
****  FROST LIKELY ****

Lowest Temperatures:      31 - 38
Louisburg Min               31 
Durations at/below 32:     0 -  2
Range Dewpoint Temps:     25 - 34
Range Wetbulb  Temps:     32 - 40
AVG Wind Direction/Speed:  NW  8                          
AVG Sky Condition:         Clear    

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)

  04/09/17  04/10/17  04/11/17  04/12/17  04/13/17  04/14/17
  --------  --------  --------  --------  --------  --------
   34 - 42   44 - 50   49 - 54   52 - 58   48 - 54   52 - 57
--------

North/Central NC                        
Alamance County Area                              

**** FREEZE COLD LOCATIONS  ****
****  FROST LIKELY ****

Lowest Temperatures:      32 - 37
Graham_AG Min               36 
Durations at/below 32:     0 -  0
Range Dewpoint Temps:     22 - 34
Range Wetbulb  Temps:     32 - 40
AVG Wind Direction/Speed:  NW  8                          
AVG Sky Condition:         Clear    

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)

  04/09/17  04/10/17  04/11/17  04/12/17  04/13/17  04/14/17
  --------  --------  --------  --------  --------  --------
   37 - 42   44 - 51   49 - 55   53 - 58   48 - 55   52 - 58
--------

South/Central NC                        
Richmond County Area                              

**** NEAR FREEZING COLD LOCATIONS  ****
****  WIDESPREAD FROST   ****

Lowest Temperatures:      35 - 38
Ellerbe Min                 38 
Range Dewpoint Temps:     24 - 33
Range Wetbulb  Temps:     35 - 41
AVG Wind Direction/Speed:  NW  8                          
AVG Sky Condition:         Clear    

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)

  04/09/17  04/10/17  04/11/17  04/12/17  04/13/17  04/14/17
  --------  --------  --------  --------  --------  --------
   38 - 42   46 - 49   50 - 55   53 - 57   48 - 55   54 - 57
--------

Interior/EC-SE NC                       
Wayne County Area                                 

**** NEAR FREEZING COLD LOCATIONS  ****
**** LITTLE IF ANY FROST DUE TO WIND **** 

Lowest Temperatures:      35 - 38
Goldsboro_AG Min            38 
Range Dewpoint Temps:     31 - 33
Range Wetbulb  Temps:     34 - 42
AVG Wind Direction/Speed:  NW  9                          
AVG Sky Condition:         Clear    

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)

  04/09/17  04/10/17  04/11/17  04/12/17  04/13/17  04/14/17
  --------  --------  --------  --------  --------  --------
   38 - 41   47 - 49   51 - 54   54 - 57   52 - 56   52 - 57
--------

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

For more detailed hourly information for NC growers, please check out the AWIS city/town closest to your farm:

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

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 Apr 7, 2017
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