870  
FNUS74 KHUN 131137  
FWSHUN  
 
SPOT FORECAST FOR GRINDSTONE...USFS  
NATIONAL WEATHER SERVICE HUNTSVILLE AL  
637 AM CDT TUE APR 13 2021  
 
FORECAST IS BASED ON IGNITION TIME OF 0900 CDT ON APRIL 13. IF  
CONDITIONS BECOME UNREPRESENTATIVE...CONTACT THE NATIONAL WEATHER  
SERVICE.  
   
DISCUSSION
 
 
A RIDGE OF HIGH PRESSURE CENTERED IMMEDIATELY EAST OF THE TN  
VALLEY WILL PROVIDE LIGHT SOUTHWESTERLY WINDS IN THE VICINITY OF  
THE PRESCRIBED BURN SITE TODAY. ALTHOUGH PERIODS OF BROKEN-  
OVERCAST HIGH CLOUDS CAN BE EXPECTED, DRY WEATHER CONDITIONS WILL  
PREVAIL, WITH CHANCES FOR RAIN HOLDING OFF UNTIL THE PREDAWN HOURS  
ON WEDNESDAY. SMOKE DISPERSION WILL BE IN THE GENERALLY GOOD  
CATEGORY, DUE TO SOUTHWESTERLY TRANSPORT FLOW OF 6-12 MPH AND  
MIXING HEIGHTS AROUND 4800 FT BETWEEN 1-4 PM CDT. TEMPERATURES  
WILL RISE INTO THE UPPER 70S BY EARLY AFTERNOON, PEAKING IN THE  
81-83 DEGREE RANGE BETWEEN 2-3 PM CDT. AS THIS OCCURS, RH VALUES  
WILL FALL INTO THE 26-30% RANGE. THE OVERALL THREAT FOR NOCTURNAL  
FOG DEVELOPMENT EARLY WEDNESDAY MORNING APPEARS RATHER LOW AT THIS  
TIME.  
   
REST OF TODAY
 
 
SKY/WEATHER.........PARTLY SUNNY (45-55 PERCENT).  
MAX TEMPERATURE.....AROUND 82.  
MIN HUMIDITY........28 PERCENT.  
WIND (20 FT)........LIGHT WINDS BECOMING SOUTHWEST AROUND 5 MPH  
LATE IN THE AFTERNOON, THEN BECOMING LIGHT LATE  
IN THE AFTERNOON.  
CWR.................10 PERCENT.  
CHANCE OF PCPN......10 PERCENT.  
MIXING HEIGHT.......4800 FT AGL.  
TRANSPORT WINDS.....SOUTHWEST 6 TO 12 MPH.  
LVORI...............3.  
 
TIME (CDT) 9AM 10A 11A 12P 1PM 2PM 3PM 4PM 5PM  
SKY (%).........PC MC PC MC PC PC MC MC PC  
WEATHER COV.....  
WEATHER TYPE....  
TEMP............65 71 75 78 81 82 82 82 80  
RH..............65 55 48 40 34 31 29 28 31  
20 FT WIND DIR..190 200 210 210 220 220 210 210 210  
20 FT WIND SPD..2 2 3 3 3 5 5 5 3  
20 FT WIND GUST. 4 5 6 6 6 6  
MIX HGT (KFT)...2.2 2.7 3.2 3.8 4.8 4.8 4.8 3.8 3.3  
TRANSP WIND DIR.170 180 190 210 220 220 220 220 210  
TRANSP WIND SPD.6 7 8 9 12 12 12 10 9  
DISPERSION IDX..2 3 33 43 61 61 61 47 38  
LVORI...........4 2 2 2 1 1 1 1 1  
CWR.............10 0 0 0 0 0 0 0 0  
CHC OF PCPN (%).10 0 0 0 0 0 0 0 0  
   
TONIGHT
 
 
SKY/WEATHER.........PARTLY CLOUDY (25-35 PERCENT).  
MIN TEMPERATURE.....AROUND 56.  
MAX HUMIDITY........86 PERCENT.  
WIND (20 FT)........LIGHT WINDS.  
CWR.................20 PERCENT.  
CHANCE OF PCPN......20 PERCENT.  
MIXING HEIGHT.......100 FT AGL.  
TRANSPORT WINDS.....SOUTHWEST 7 TO 9 MPH.  
LVORI...............3.  
 
TIME (CDT) 6PM 7PM 8PM 9PM 10P 11P MID 1AM 2AM 3AM 4AM 5AM  
SKY (%).........PC PC PC PC PC PC MCR MCR MCR PC PC PC  
WEATHER COV.....  
WEATHER TYPE....  
TEMP............78 75 72 69 66 64 62 61 60 60 59 57  
RH..............33 41 46 51 56 58 65 70 72 72 75 83  
20 FT WIND DIR..210 200 220 320 320 330 330 340 340 330 070 330  
20 FT WIND SPD..2 2 1 1 1 1 1 1 1 1 1 1  
20 FT WIND GUST. 2 2  
MIX HGT (KFT)...2.7 2.2 1.7 1.1 0.1 0.1 0.1 0.1 0.1 0.1 0.3 0.3  
TRANSP WIND DIR.210 210 210 210 210 220 220 220 220 220 230 240  
TRANSP WIND SPD.9 7 7 7 7 7 7 8 8 8 7 7  
DISPERSION IDX..29 20 16 10 0 0 3 3 3 3 3 3  
LVORI...........1 2 2 2 3 3 3 3 3 3 5 5  
CWR.............0 0 0 10 10 10 10 10 10 20 20 20  
CHC OF PCPN (%).0 0 0 10 10 10 10 10 10 20 20 20  
   
WEDNESDAY
 
 
SKY/WEATHER.........PARTLY SUNNY (65-75 PERCENT) THEN BECOMING  
CLOUDY (85-95 PERCENT).  
MAX TEMPERATURE.....AROUND 68.  
MIN HUMIDITY........63 PERCENT.  
WIND (20 FT)........LIGHT WINDS.  
CWR.................90 PERCENT.  
CHANCE OF PCPN......90 PERCENT.  
MIXING HEIGHT.......2600 FT AGL.  
TRANSPORT WINDS.....WEST 7 TO 9 MPH.  
LVORI...............4.  
 
TIME (CDT) 6AM 7AM 8AM 9AM 10A 11A 12P 1PM 2PM 3PM 4PM 5PM  
SKY (%).........MC MC MC MC MC MC CDY CDY CDY CDY MC MC  
WEATHER COV.....  
WEATHER TYPE....  
TEMP............56 57 60 64 67 68 68 67 67 66 66 65  
RH..............86 83 81 73 68 65 63 65 68 70 68 70  
20 FT WIND DIR..340 340 340 340 320 270 290 260 250 280 320 340  
20 FT WIND SPD..1 1 2 2 2 3 3 3 3 3 3 3  
20 FT WIND GUST. 4 5 5 5 4 4 5  
MIX HGT (KFT)...0.3 0.8 1.1 1.3 1.6 1.8 2.1 2.6 2.6 2.6 2.1 1.9  
TRANSP WIND DIR.250 260 260 260 250 240 230 220 220 220 240 280  
TRANSP WIND SPD.7 7 7 7 7 7 7 7 7 7 9 9  
DISPERSION IDX..3 3 3 3 3 15 17 16 16 21 23 18  
LVORI...........5 4 4 4 3 3 3 3 3 3 3 3  
CWR.............20 80 80 80 80 80 80 90 90 90 90 90  
CHC OF PCPN (%).20 80 80 80 80 80 80 90 90 90 90 90  
 

 
 
FORECASTER...DIXON  
REQUESTED BY...CRAIG MOORE  
TYPE OF REQUEST...PRESCRIBED  
.TAG 2108825.0/HUN  
.DELDT 04/13/21  
.FORMATTERVERSION 1.0.26  
.EMAIL GARY.C.MOORE@USDA.GOV  
 
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