NC: Easter Morning Frost Forecast (11:39am, Sat., April 4, 2015)
go.ncsu.edu/readext?350286
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!
Table 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).
Table 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!
Figure 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.
Table 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.
Table 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.):
Fig. 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?
Fig. 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.
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.
Table 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
Raleigh, NC 27695-7609
Sidney J. Harris, In: Reclaiming a Lost Heritage – Land-Grant & Other Higher Education Initiatives for the Twenty-first Century