Frost in the Valleys First

Farmers and gardeners are always interested in the timing of the first frost. Every year we publish some medians dates for the first day with freezing temperatures and the first day with temperatures below 28 degrees. The 32 degree data roughly approximates the date for the first frost and the temperatures of less than or equal to 28 degrees would reflect the first hard freeze.  

 

32 Degree Median Date

28 Degree Median Date

Barbourville

Oct 22nd

Nov 4th

Baxter

Oct 23rd

Nov 6th

Cave Run Lake

Oct 17th

Oct 25th

Grayhawk

Oct 7th

Oct 18th

Heidelberg

Oct 19th

Oct 29th

Hyden

Oct 22nd

Nov 4th

Manchester

Oct 14th

Oct 24th

Middlesboro

Oct 18th

Nov 3rd

Monticello

Oct 19th

Oct 28th

Mt Sterling

Oct 21st

Nov 3rd

Mount Vernon

Oct 13th

Nov 3rd

Paintsville

Oct 22nd

Nov 3rd

Somerset

Oct 15th

Oct 25th

Stearns

Oct 7th

Oct 24th

West Liberty

Oct 6th

Oct 20th

Williamsburg

Oct 19th

Oct 27th

NWS Jackson

Oct 26th

Nov 7th

London-Corbin Arpt

Oct 13rd

Oct 28th

One of the things that jumps right off the page is the relatively large difference in the median date for freezing temperatures for some locations. For example, West Liberty has the earliest date of Oct 6th and nearby NWS Jackson has the latest date, Oct 26th. When looking at the range of dates, the differences are best explained by the complex terrain and differences in elevation in eastern Kentucky. As the sun starts to set, direct heating continues on the ridge tops and mid slopes, while the valleys begin to cool down, especially those that are oriented from north to south. This causes an inversion to form as the temperatures aloft remain warm.  As this inversion forms, this in essence, disconnects the lowest levels of the atmosphere from above. This then allows the lowest levels to radiate heat out, causing the temperatures to continue to drop in the lowest layers.
 
In addition to the median dates for the temperatures of less than or equal to 32 degrees, the climate data was reviewed to come up with the earliest and latest dates for these temperatures. Just as in the median, there is quite a big difference in the ranges. Part of these differences are due to differing lengths of climate records.  
 
Station ID
Temp =< 32
Temp =< 32
Elevation
 
Earliest
Latest
(FT)
Barbourville
3-Oct
13-Nov
990
Beattyville 4N
3-Oct
9-Nov
1080
Baxter
30-Sep
13-Nov
1164
Booneville 1SE
3-Oct
2-Nov
760
Booneville 12SW
14-Sep
2-Nov
880
Buckhorn
8-Oct
9-Nov
780
Closplint 4ESE
3-Oct
29-Oct
1800
Farmers 2S
10-Sep
9-Nov
680
Gray Hawk 2SE
22-Sep
22-Oct
1250
Julian-Carroll AP
4-Oct
25-Nov
1382
London-Corbin AP
24-Sep
13-Nov
1212
Manchester
23-Sep
6-Nov
870
Middlesboro
21-Sep
14-Nov
1180
Monticello 3NE
3-Oct
13-Nov
979
Mount Sterling
30-Sep
12-Nov
960
Mount Vernon
2-Oct
9-Nov
1160
Quicksand
26-Sep
6-Nov
740
Paintsville
2-Oct
18-Nov
630
Skyline
8-Oct
2-Nov
1200
Somerset 2N
27-Sep
9-Nov
1020
Stearns 2S
22-Sep
7-Nov
1220
West Liberty 3NW
14-Sep
11-Nov
780
Williamsburg
24-Sep
13-Nov
1000
 
It is evident that there are climatological differences in temperatures across our area due to the complex terrain and differences in elevation across Eastern Kentucky. The National Weather Service in Jackson has recognized many of these patterns and temperature trends through local research and experience. As a result, the National Weather Service has been able to apply this knowledge in issuing more detailed and accurate local forecasts. In fact, this forecast detail can be obtained very easily in some of our text and web based forecast products, the most detailed being the point forecast matrix. This product, along with other elements, gives a specific temperature forecast for about 60 to 65 locations across Eastern Kentucky. With a more detailed and accurate temperature forecast, residents across Eastern Kentucky will be able to plan outdoor events with more confidence, and make more informed decisions regarding agricultural issues. To see this and more, please visit our web site at www.weather.gov/jkl, and review our Point Forecast Matrix to find a specific forecast for your location, and/or use our point and click map to bring up forecasts for your area.

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