155  
FNUS71 KBOX 180842  
FWSBOX  
 
SPOT FORECAST FOR LEYDEN WMA RX FIRE 20250417...MASSWILDLIFE  
NATIONAL WEATHER SERVICE BOSTON/NORTON MA  
442 AM EDT FRI APR 18 2025  
 
FORECAST IS BASED ON IGNITION TIME OF 0600 EDT ON APRIL 18.  
IF CONDITIONS BECOME UNREPRESENTATIVE, CONTACT THE NATIONAL  
WEATHER SERVICE.  
   
DISCUSSION
 
 
DRY TODAY WITH AN INCREASING SOUTH TO SOUTHWEST WIND THIS MORNING.  
WIND GUSTS UP TO 30 MPH THIS AFTERNOON. MINIMUM RELATIVE HUMIDITY  
AROUND 25 PERCENT. LOW RISK FOR A SPOT SHOWER LATE IN THE DAY INTO  
TONIGHT, BUT NOT A WETTING RAINFALL.  
   
TODAY
 
 
SKY/WEATHER.........SUNNY THEN BECOMING MOSTLY CLOUDY.  
CWR.................0 PERCENT.  
MAX TEMPERATURE.....AROUND 63.  
MIN HUMIDITY........29 PERCENT.  
DEWPOINT............24 INCREASING TO 33.  
MIN APPARENT TEMP...29.  
SURFACE WINDS (MPH).LIGHT WINDS BECOMING SOUTH 5 TO 10 MPH WITH  
GUSTS TO AROUND 24 MPH IN THE LATE MORNING AND  
AFTERNOON.  
WIND (20 FT)........LIGHT WINDS BECOMING SOUTH 5 TO 10 MPH WITH  
GUSTS TO AROUND 24 MPH IN THE LATE MORNING AND  
AFTERNOON.  
MIXING HEIGHT.......4500 FT AGL.  
TRANSPORT WINDS.....SOUTHWEST 3 TO 12 MPH INCREASING TO 24 TO 25  
MPH.  
SMOKE DISPERSAL.....POOR (1000 KNOT-FT) EARLY IN THE MORNING  
INCREASING TO EXCELLENT (93400 KNOT-FT) IN THE  
AFTERNOON.  
LVORI...............3.  
ADI.................4 TO 6 INCREASING TO 14 LATE IN THE MORNING,  
THEN INCREASING TO 31 INCREASING TO 50 EARLY  
INCREASING TO 78 INCREASING TO 101 EARLY IN THE  
AFTERNOON DECREASING TO 87 TO 94 INCREASING TO  
97 LATE IN THE AFTERNOON DECREASING TO 82.  
CEILING (KFT).......25 DECREASING TO 11.  
 
TIME (EDT) 6AM 7AM 8AM 9AM 10A 11A 12P 1PM 2PM 3PM 4PM 5PM  
SKY (%).........5 6 8 10 14 26 27 23 31 55 72 84  
WEATHER COV.....  
WEATHER TYPE....  
TSTM COV........  
CWR.............0 0 0 0 0 0 0 0 0 0 0 0  
TEMP............29 32 38 43 48 52 55 58 60 61 62 61  
DEWPOINT........22 23 23 24 25 26 27 28 28 30 31 33  
RH..............75 69 54 47 40 36 34 32 29 31 31 35  
HEAT INDEX (F)..29 32 38 43 46 52 55 58 60 61 62 61  
20 FT WIND DIR..SW SW SW S S S S S S S S S  
20 FT WIND SPD..2 1 1 2 5 6 6 8 9 9 10 10  
20 FT WIND GUST.3 3 5 8 12 15 17 20 22 22 23 24  
SURFACE WND DIR.SW SW SW S S S S S S S S S  
SURFACE WND SPD.2 1 1 2 5 6 6 8 9 9 10 10  
SURFACE WND GST.3 3 5 8 12 15 17 20 22 22 23 24  
MIX HGT (KFT)...0.3 0.4 0.6 1.4 2.1 2.9 3.5 4.1 4.5 4.4 4.2 3.3  
TRANSP WIND DIR.SW SW SW SW SW SW SW SW SW SW SW S  
TRANSP WIND SPD.3 5 6 8 12 14 18 21 22 24 25 24  
LVORI...........4 3 2 2 1 1 1 1 1 1 1 1  
ADI.............4 4 6 14 31 50 78 101 87 94 97 82  
VRATE KT-FT/1K..1 2 3 10 21 35 56 74 86 92 93 70  
VENTRATE CAT....PR PR PR PR PR PR FR GD GD GD GD GD  
CEILING (KFT)...25 25 25 25 25 25 25 25 25 20 14 11  
   
TONIGHT
 
 
SKY/WEATHER.........MOSTLY CLOUDY.  
CWR.................0 PERCENT.  
MIN TEMPERATURE.....AROUND 49.  
MAX HUMIDITY........86 PERCENT.  
DEWPOINT............35 INCREASING TO 45.  
MAX APPARENT TEMP...59.  
SURFACE WINDS (MPH).SOUTH WINDS 8 TO 10 MPH. GUSTS UP TO 24 MPH IN  
THE EVENING.  
WIND (20 FT)........SOUTH WINDS 8 TO 10 MPH. GUSTS UP TO 24 MPH IN  
THE EVENING.  
MIXING HEIGHT.......400 FT AGL.  
TRANSPORT WINDS.....SOUTH 12 TO 21 MPH.  
SMOKE DISPERSAL.....GOOD (42400 KNOT-FT) EARLY IN THE EVENING  
DECREASING TO POOR (3800 KNOT-FT) LATE IN THE  
NIGHT.  
LVORI...............3.  
ADI.................57 DECREASING TO 10 TO 19.  
CEILING (KFT).......13 DECREASING TO 10 LATE IN THE EVENING, THEN  
DECREASING TO 9.0 INCREASING TO 10 AFTER  
MIDNIGHT INCREASING TO 15.  
 
TIME (EDT) 6PM 7PM 8PM 9PM 10P 11P MID 1AM 2AM 3AM 4AM 5AM  
SKY (%).........84 81 73 71 72 75 79 83 87 84 82 80  
WEATHER COV.....  
WEATHER TYPE....  
TSTM COV........  
CWR.............0 0 0 0 0 0 0 0 0 0 0 0  
TEMP............59 57 54 52 51 50 51 50 50 51 51 50  
DEWPOINT........34 35 36 37 37 39 40 41 42 44 45 46  
RH..............39 43 50 56 59 66 66 71 74 77 80 86  
HEAT INDEX (F)..59 57 54 52 51 46 51 46 46 51 51 47  
20 FT WIND DIR..S S S S S S S S S S S S  
20 FT WIND SPD..9 10 10 10 10 10 9 9 9 9 9 8  
20 FT WIND GUST.24 24 21 20 20 20 18 18 17 17 17 17  
SURFACE WND DIR.S S S S S S S S S S S S  
SURFACE WND SPD.9 10 10 10 10 10 9 9 9 9 9 8  
SURFACE WND GST.24 24 21 20 20 20 18 18 17 17 17 17  
MIX HGT (KFT)...2.4 1.4 0.5 0.5 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4  
TRANSP WIND DIR.S S S S S S S S S S S S  
TRANSP WIND SPD.21 17 17 15 14 14 13 13 13 13 12 13  
LVORI...........1 2 2 2 2 3 3 3 3 4 4 5  
ADI.............57 19 15 13 12 12 11 11 11 11 10 11  
VRATE KT-FT/1K..42 21 8 6 5 5 5 5 4 4 4 4  
VENTRATE CAT....FR PR PR PR PR PR PR PR PR PR PR PR  
CEILING (KFT)...13 14 13 10 9.0 9.0 10 10 11 11 15 15  
   
SATURDAY
 
 
SKY/WEATHER.........MOSTLY CLOUDY. SLIGHT CHANCE OF RAIN SHOWERS  
EARLY IN THE AFTERNOON. CHANCE OF RAIN SHOWERS  
LATE IN THE AFTERNOON.  
CWR.................0 PERCENT.  
MAX TEMPERATURE.....AROUND 76.  
MIN HUMIDITY........51 PERCENT.  
DEWPOINT............49 INCREASING TO 53 EARLY.  
MAX APPARENT TEMP...74.  
SURFACE WINDS (MPH).SOUTHWEST WINDS 8 TO 9 MPH WITH GUSTS TO AROUND  
22 MPH INCREASING TO 9 TO 10 MPH WITH GUSTS TO  
AROUND 26 MPH IN THE AFTERNOON.  
WIND (20 FT)........SOUTH WINDS AROUND 8 MPH SHIFTING TO THE  
SOUTHWEST 9 TO 10 MPH WITH GUSTS TO AROUND 26  
MPH IN THE AFTERNOON.  
MIXING HEIGHT.......5400 FT AGL.  
TRANSPORT WINDS.....SOUTHWEST 12 TO 20 MPH INCREASING TO WEST 22 TO  
31 MPH EARLY.  
SMOKE DISPERSAL.....POOR (4000 KNOT-FT) EARLY IN THE MORNING  
INCREASING TO EXCELLENT (100200 KNOT-FT) IN THE  
AFTERNOON INCREASING TO EXCELLENT (113100  
KNOT-FT) LATE IN THE AFTERNOON.  
LVORI...............3.  
ADI.................9 TO 11 INCREASING TO 103 TO 105.  
CEILING (KFT).......15 DECREASING TO 10 EARLY IN THE MORNING, THEN  
DECREASING TO 8.0 LATE IN THE MORNING  
DECREASING TO 7.0 DECREASING TO 5.0 INCREASING  
TO 8.0 EARLY IN THE AFTERNOON INCREASING TO 9.0  
DECREASING TO 7.0 LATE IN THE AFTERNOON  
INCREASING TO 8.0.  
 
TIME (EDT) 6 AM 8 AM 10 AM NOON 2 PM 4 PM  
SKY (%).........78 73 73 70 62 64  
WEATHER COV..... S CHC CHANCE  
WEATHER TYPE....NONE NONE NONE NONE RNSHWR RNSHWR  
TSTM COV........  
CWR.............0 0 0 0 0 0  
TEMP............51 54 60 67 72 74  
DEWPOINT........47 49 51 53 55 55  
RH..............86 83 72 61 55 51  
HEAT INDEX (F)..51 54 60 67 72 74  
20 FT WIND......S 8 S 8 SW 8 SW 9 SW 9 W 9  
20 FT WIND GUST.16 16 20 22 23 25  
SURFACE WIND....S 8 S 8 SW 8 SW 9 SW 9 W 9  
SURFACE WND GST.16 16 20 22 23 25  
MIX HGT (FT)....400 500 1700 2700 4400 5100  
TRANSPORT WIND..S 12 S 14 SW 20 W 23 W 26 W 30  
LVORI...........5 4 3 1 1 1  
ADI.............9 11 42 70 103 105  
VRATE KT-FT/1K..4 7 29 55 100 132  
VENTRATE CAT....POOR POOR POOR FAIR VYGD VYGD  
CEILING (KFT)...15 10 7.0 8.0 8.0 7.0  
 

 
FORECASTER...BELK  
REQUESTED BY...BEN MAZZEI  
TYPE OF REQUEST...PRESCRIBED  
.TAG 2510789.2/BOX  
.DELDT 04/18/25  
.FORMATTERVERSION 2.0.0  
.EMAIL BEN.MAZZEI@MASS.GOV  
 
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