613  
FNUS74 KHUN 201220  
FWSHUN  
 
SPOT FORECAST FOR WALSTON RIDGE SITE PREP...USFS  
NATIONAL WEATHER SERVICE HUNTSVILLE AL  
720 AM CDT THU SEP 20 2018  
 
FORECAST IS BASED ON IGNITION TIME OF 1000 CDT ON SEPTEMBER 20.  
IF CONDITIONS BECOME UNREPRESENTATIVE...CONTACT THE NATIONAL WEATHER  
SERVICE.  
   
DISCUSSION
 
 
MOSTLY CLEAR SKIES ARE EXPECTED AT THE SITE TODAY, AS HIGH  
PRESSURE MAINTAINS ITS HOLD ON THE WEATHER PATTERN. TEMPERATURES  
WILL SOAR INTO THE MID 90S THIS AFTERNOON, WITH BOUNDARY LAYER  
WINDS MIXING DRIER AIR TO THE SURFACE. THIS WILL CREATE MINIMUM RH  
VALUES BOTTOMING OUT IN THE UPPER 30 PERCENT RANGE THIS  
AFTERNOON. WINDS AT THE 20 FOOT WIND LEVEL WILL GENERALLY REMAIN  
LIGHT AND MIXING HEIGHTS WILL REMAIN ABOVE 4000 FEET THROUGH THE  
DAY. THESE WILL COMBINE WITH SOUTHERLY TRANSPORT WINDS AROUND 9  
MPH TO CREATE GOOD DISPERSION TODAY.  
 
MOISTURE WILL RETURN TO THE AREA ON FRIDAY, WITH MINIMUM RH  
VALUES REMAINING IN THE MID 40 PERCENT RANGE. MIXING HEIGHTS AND  
TRANSPORT WINDS WILL BE SIMILAR TO THOSE OBSERVED TODAY AND  
DISPERISON CONDITIONS WILL BE GOOD ONCE AGAIN. WITH MORE MOISTURE  
IN PLACE, SCATTERED THUNDERSTORMS WILL BE POSSIBLE BUT TIMING AND  
LOCATION ARE UNCERTAIN.  
   
REST OF TODAY
 
 
SKY/WEATHER.........SUNNY (10-20 PERCENT).  
MAX TEMPERATURE.....AROUND 94.  
MIN HUMIDITY........39 PERCENT.  
WIND (20 FT)........LIGHT WINDS.  
CWR.................10 PERCENT.  
CHANCE OF PCPN......10 PERCENT.  
MIXING HEIGHT.......4300-6200 FT AGL INCREASING TO 8000-9200 FT AGL  
EARLY IN THE AFTERNOON, THEN INCREASING TO  
9100-10100 FT AGL EARLY IN THE AFTERNOON  
DECREASING TO 6400 FT AGL LATE IN THE  
AFTERNOON.  
TRANSPORT WINDS.....SOUTH 8 TO 9 MPH.  
LVORI...............1.  
 
TIME (CDT) 10 AM NOON 2 PM 4 PM  
SKY (%).........CLEAR MCLEAR MCLEAR PCLDY  
WEATHER COV.....  
WEATHER TYPE....NONE NONE NONE NONE  
TEMP............86 91 93 94  
RH..............57 45 40 39  
20 FT WIND DIR..160 160 170 170  
20 FT WIND SPD..3 3 3 3  
20 FT WIND GUST.4 5 5 5  
MIX HGT (FT)....4300 8000 10100 9100  
TRANSPORT WIND..S 9 S 9 S 8 S 9  
DISPERSION IDX..4 76 77 82  
LVORI...........1 1 1 1  
CWR.............0 10 10 10  
CHC OF PCPN (%).0 10 10 10  
   
TONIGHT
 
 
SKY/WEATHER.........MOSTLY CLEAR (20-30 PERCENT).  
MIN TEMPERATURE.....AROUND 73.  
MAX HUMIDITY........81 PERCENT.  
WIND (20 FT)........LIGHT WINDS.  
CWR.................10 PERCENT.  
CHANCE OF PCPN......10 PERCENT.  
MIXING HEIGHT.......3000 FT AGL DECREASING TO 0-300 FT AGL.  
TRANSPORT WINDS.....SOUTH 5 TO 6 MPH.  
LVORI...............3.  
 
TIME (CDT) 6 PM 8 PM 10 PM MIDNGT 2 AM 4 AM  
SKY (%).........PCLDY MCLEAR MCLEAR MCLEAR MCLEAR PCLDY  
WEATHER COV.....  
WEATHER TYPE....NONE NONE NONE NONE NONE NONE  
TEMP............89 84 80 78 77 75  
RH..............47 57 65 69 71 76  
20 FT WIND DIR..170 170 170 160 160 170  
20 FT WIND SPD..3 2 2 2 2 3  
20 FT WIND GUST.4 4  
MIX HGT (FT)....3000 BLW100 200 100 100 200  
TRANSPORT WIND..S 6 S 5 S 5 S 5 S 5 S 5  
DISPERSION IDX..21 1 1 2 2 2  
LVORI...........1 3 3 3 3 4  
CWR.............0 0 0 0 10 10  
CHC OF PCPN (%).0 0 0 0 10 10  
   
FRIDAY
 
 
SKY/WEATHER.........MOSTLY SUNNY (40-50 PERCENT). SLIGHT CHANCE OF  
SHOWERS AND THUNDERSTORMS LATE IN THE MORNING.  
CHANCE OF SHOWERS AND THUNDERSTORMS IN THE  
AFTERNOON.  
MAX TEMPERATURE.....AROUND 92.  
MIN HUMIDITY........47 PERCENT.  
WIND (20 FT)........LIGHT WINDS. GUSTY AND ERRATIC WINDS EXPECTED  
NEAR THUNDERSTORMS IN THE LATE MORNING AND  
AFTERNOON.  
CWR.................10 PERCENT INCREASING TO 30 PERCENT.  
CHANCE OF PCPN......30 PERCENT.  
MIXING HEIGHT.......0-1200 FT AGL INCREASING TO 2700-4300 FT AGL  
LATE IN THE MORNING, THEN INCREASING TO  
5500-7300 FT AGL LATE IN THE MORNING DECREASING  
TO 3800 FT AGL LATE IN THE AFTERNOON.  
TRANSPORT WINDS.....SOUTH 5 TO 12 MPH.  
LVORI...............3.  
 
TIME (CDT) 6 AM 8 AM 10 AM NOON 2 PM 4 PM  
SKY (%).........PCLDY PCLDY PCLDY PCLDY MCLDY MCLDY  
WEATHER COV..... S CHC S CHC CHANCE CHANCE  
WEATHER TYPE....NONE NONE RNSHWR RNSHWR RNSHWR RNSHWR  
TEMP............73 77 85 90 92 91  
RH..............81 74 59 50 47 49  
20 FT WIND DIR..160 160 170 180 190 190  
20 FT WIND SPD..3 3 3 3 3 3  
20 FT WIND GUST.4 4 5 5 5 4  
MIX HGT (FT)....BLW100 1200 4300 6800 7300 5500  
TRANSPORT WIND..SE 5 S 7 S 12 S 10 S 9 S 8  
DISPERSION IDX..2 3 8 76 71 50  
LVORI...........4 3 1 1 1 1  
CWR.............10 10 20 20 30 30  
CHC OF PCPN (%).10 10 20 20 30 30  
 

 
FORECASTER...CHACE  
REQUESTED BY...KERRY CLARK  
TYPE OF REQUEST...PRESCRIBED  
.TAG 1815987.1/HUN  
.DELDT 09/20/18  
.EMAIL KERRYCLARK@FS  
 
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