NC: Easter Morning Frost Forecast (11:39am, Sat., April 4, 2015)

— Written By Barclay Poling

Good morning!

It is very windy at present (11:39 a.m.), and because of these winds it may be difficult to apply row covers in areas where some form of frost protection may be needed  tomorrow morning. The good news is that these winds will be subsiding later in the day, and conditions will be very calm tonight (and perfect for sprinkling). For growers who depend on row covers, you will hopefully get your opportunity to apply them before sunset? I just noted that in Chapel HIll area, winds will be pretty high until 1900 (7 p.m.). Sunset is 7:40 p.m., so that will give you a little window of time before dark (maybe?). But, even if you are  late in applying them (we always like to get them on by about 2-3 p.m.), I strongly recommend putting them on if your area in is going to be prone to FROST Easter morning. You really do not need “that much” protection as we are NOT dealing with temperature minimums anything like what happened last weekend – thank goodness!

ChapelTable 1. High winds all day will make row covers harder to apply. But, even a late afternoon/early evening application will still be beneficial in areas where frost is likely, and frost is likely in the Chapel Hill area (see next table).

chapel 2Table 2. Chapel HIll  is a very representative of the kind of conditions expected in Central Piedmont Easter morning – note the low winds, relatively high dewpoints near the freezing mark (32), which make forming frost “very easy,” clear skies for perfect radiational cooling (when it is overcast, you don’t get radiation frosts), and an air temperature minimum of 34 F, which is the temperature at weather shelter height. Unless you get SkyBit’s forecast (like my one for Clayton at bottom of advisory), it is hard to know what the minimum canopy temperature may be?

So, let’s take a quick look at statewide minimum temps (AWIS NC Apr 4-11), and what you need to do is see if your area will have a minimum temperature of 34-35, or lower? If you do, then I would recommend getting ready  frost  frost tomorrow morning. Even if you have to pull row covers at sunset, or after dark, it could still be worth it to save those “open blossoms” from an Easter morning black eye!

van meter under double coverFigure 1. The upper two open blossoms got a “black (brown) eye” from last weekend’s extreme cold. On Easter morning 2015, growers will only need a few degrees of protection to keep “ice crystals” from forming and injuring open blossoms. (Photo from Danny VanMeter, Clarkson, KY).

A. The official AWIS Frost/Freeze Forecast for NC (this product is only available from AWIS for NC and KY). In the interest of your time, I have quickly summarized the entire report with these bullets:

  • Along the Northeast NC Coast “patchy frost in coldest protected areas” is anticipated (see full report below). A similar forecast is being made by AWIS for the East Central/ SE NC Coast (Morehead).
  • In the Elizabethtown area (Southeast NC) there is a “freeze in cold locations” and “patchy frost in coldest protected areas.”
  • In the Louisburg/Franklin County area there is a “freeze in cold locations” and “widespread frost”;
  • In the North Central/Alamance area there is a  “freeze in cold locations” and “patchy frost” forecast;
  • The final area of coverage by this forecast for NC is in the Wayne County/Goldsboro area, and there is a  forecast of “near freezing coldest locations” and “frost likely”

Full forecast:

AWIS Weather Services, Inc. North Carolina Frost/Freeze Forecast
Produced at  504 a.m. CDT on Sat Apr  4 2015

... Forecast for Tonight ... Northeast NC Coast                      
Currituck/Camden/Pasquotank/Tyrrell Counties      
** PATCHY FROST COLDEST PROTECTED AREAS **

Lowest Temperatures:      36 - 43
Elizabeth_City Min          37 
Range Dewpoint Temps:     31 - 44
Range Wetbulb  Temps:     36 - 49
AVG Wind Direction/Speed:  NE  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)

  04/06/15  04/07/15  04/08/15  04/09/15  04/10/15  04/11/15
  --------  --------  --------  --------  --------  --------
   44 - 51   53 - 59   57 - 64   56 - 63   53 - 60   59 - 65
--------

East Central/SE NC Coast                
Carteret/Pamlico Counties                         
** PATCHY FROST COLDEST PROTECTED AREAS **

Lowest Temperatures:      39 - 40
Morehead_City Min           40 
Range Dewpoint Temps:     33 - 40
Range Wetbulb  Temps:     37 - 48
AVG Wind Direction/Speed:  NE  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)

  04/06/15  04/07/15  04/08/15  04/09/15  04/10/15  04/11/15
  --------  --------  --------  --------  --------  --------
   45 - 49   58 - 59   60 - 62   63 - 63   57 - 59   62 - 64
--------

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

**** FREEZE COLD LOCATIONS  ****
** PATCHY FROST COLDEST PROTECTED AREAS **

Lowest Temperatures:      32 - 40
Elizabethtown Min           38 
Durations at/below 32:     0 -  1
Range Dewpoint Temps:     27 - 40
Range Wetbulb  Temps:     33 - 48
AVG Wind Direction/Speed:   N  7                          
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)

  04/06/15  04/07/15  04/08/15  04/09/15  04/10/15  04/11/15
  --------  --------  --------  --------  --------  --------
   44 - 49   56 - 60   59 - 64   59 - 64   55 - 60   60 - 65
--------

North-Central NC                        
Franklin County Area                              

**** FREEZE COLD LOCATIONS  ****
****  WIDESPREAD FROST   ****

Lowest Temperatures:      30 - 37
Louisburg Min               30 
Durations at/below 32:     0 -  2
Range Dewpoint Temps:     23 - 30
Range Wetbulb  Temps:     31 - 42
AVG Wind Direction/Speed:  NW  3     Long Periods of Calm 
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)

  04/06/15  04/07/15  04/08/15  04/09/15  04/10/15  04/11/15
  --------  --------  --------  --------  --------  --------
   41 - 46   51 - 56   54 - 60   52 - 60   47 - 55   54 - 61
--------

North/Central NC                        
Alamance County Area                              

**** FREEZE COLD LOCATIONS  ****
****    PATCHY FROST  ****

Lowest Temperatures:      32 - 37
Graham_AG Min               35 
Durations at/below 32:     0 -  1
Range Dewpoint Temps:     18 - 30
Range Wetbulb  Temps:     30 - 42
AVG Wind Direction/Speed:  NW  3     Long Periods of Calm 
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)

  04/06/15  04/07/15  04/08/15  04/09/15  04/10/15  04/11/15
  --------  --------  --------  --------  --------  --------
   40 - 47   52 - 57   55 - 60   54 - 59   49 - 54   54 - 60
--------

South/Central NC                        
Richmond County Area                              
**** LITTLE/NO FROST DUE TO DRY AIR **** 

Lowest Temperatures:      36 - 38
Ellerbe Min                 38 
Range Dewpoint Temps:     21 - 35
Range Wetbulb  Temps:     33 - 44
AVG Wind Direction/Speed:  NW  6                          
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)

  04/06/15  04/07/15  04/08/15  04/09/15  04/10/15  04/11/15
  --------  --------  --------  --------  --------  --------
   45 - 46   54 - 58   56 - 61   56 - 61   54 - 57   56 - 63
--------

Interior/EC-SE NC                       
Wayne County Area                                 

**** NEAR FREEZING COLD LOCATIONS  ****
****  FROST LIKELY ****

Lowest Temperatures:      35 - 38
Goldsboro_AG Min            38 
Range Dewpoint Temps:     27 - 34
Range Wetbulb  Temps:     36 - 41
AVG Wind Direction/Speed:  NW  5     Long Periods of Calm 
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)

  04/06/15  04/07/15  04/08/15  04/09/15  04/10/15  04/11/15
  --------  --------  --------  --------  --------  --------
   44 - 47   54 - 57   57 - 62   58 - 62   54 - 57   59 - 62
--------

Let’s back up and quickly study this comment for areas like Ellerbe in Sandhills where AWIS is calling for:

**** LITTLE/NO FROST DUE TO DRY AIR ****

What exactly does this mean? Well, I went to another AWIS product for hourly temperatures, and the air temp minimum is going to be 38. That would seem to be fairly safe. But, if you get SkyBit’s E-Weather Strawberry Canopy Forecast, you may wish to take special note of the dew points in your forecast.

EllerbeTable 4. The forecast for minimum temp on Easter morning is  38 in Ellerbe. This should be warm enough to keep from having a frost?

I was able to look at a more complete hourly forecast for Southern Pines (closest location for AWIS towns/cities), and I saw that the dew points are in the mid-20s. It is true that with DPs in this middle range (25), it is somewhat harder to “make frost” than with higher DPs (like Chapel Hill at 27), but I don’t think this is worth splitting hairs over! The best I can say is that if the Ellerbe area has mid-20s DPS, and air temps stay in in upper 30s, there would be less chance of frost formation than if DPs were closer to 32 F.

southern pinesTable 5. Frost is expected in Southern Pines at 5 a.m., and note the minimum temp of 32. Dewpoints are in sort of a middle range:   25-26. However, these dew points are not “that low” and nothing like what we had last weekend when dew points fell into single digits.

This would be a great time for all NC growers to glance at the latest AWIS minimum temperature map (11 a.m.):

11am7daytemp.nc.2Fig. 2. Minimum temperature forecast for Easter morning. A potentially damaging  “frost” is in the forecast for many areas in NC on Easter morning. Please note that in all blue and navy blue areas, as well as pink, purple and gray, there could be very high risk of frost in the morning.

Over night changes in AWIS minimum forecast?

7daytemp.nc.4Fig. 3. Last night’s forecast for Easter morning. The main change today is that the Charlotte area and directly east through Sandhills will not be quite as cold tomorrow morning as was originally expected. If you now look at Fig. 2 note that this whole area is now in the teal color (36-38). But, there is a small area in Sandhills in blue (34-36), and I would be more careful in this area.

Clayton area:

AWIS is showing a minimum air temperature of 37 F for the Clayton area in this morning’s Easter forecast (below). One of the coldest spots in Central NC will be Lousiburg (no surprise) at 30 F; Danbury will be 31 F; Durham 32 F; Henderson 32 F. Any location with 32 F or lower, is  high risk for frost tomorrow morning.

CENTRAL NC

Skybit for Clayton:  In my  morning SkyBit for Clayton, I got the  good news  that the minimum canopy temperature did come up “a little” from last night’s forecast of 33 F — we are now looking at 35 F (below). Even so, there is STILL potential for an Easter  morning WHITE frost with CLEAR SKIES, NO WIND,  DEWPOINT NEAR 32 F.sky 8 a.m. satTable 1. This is the E-Weather Strawberry Canopy Forecast issued at 8 a.m. for Clayton. There will be an evening update as well. The air temperature minimum for Easter morning is 35, and the canopy minimum is 35. Usually, we see a slightly low canopy temperature.

What you need to do now if you don’t get SkyBit forecast that is specific to your farm, is take a good look at these Detailed Hourly Forecasts from AWIS products for a city or town near your farm. Just click the live AWIS link to the location nearest you, and then look to see if there is an  “F” (FROST) indicated on the DEWF line, like the F you see in the Southern Pines detailed forecast in Table 5.

Final recommendation:  Even if you don’t see an AWIS forecast of “F”  for your area, it is ALWAYS VIP TO SET YOUR FROST ALARM BEFORE GOING TO BED, AND WITH THE CROP BEING IN SUCH HEAVY BLOOM, I WOULD PROBABLY SET IT AS HIGH AS  37- 38 F.

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

IGood luck!

Dr. E. Barclay Poling
Professor Emeritus (Strawberry Plasticulture Researcher)
Department of Horticultural Science
Campus Box 7609, 162A Kilgore Hall
NC State University
Raleigh, NC 27695-7609
“An idealist believes the short run does not count. A cynic believes the long run does not matter. A realist believes that what is done or left undone in the short run determines the long run.”

Sidney J. Harris, In: Reclaiming a Lost Heritage – Land-Grant & Other Higher Education Initiatives for the Twenty-first Century