785  
FNUS75 KBOI 180313  
FWSBOI  
 
SPOT FORECAST FOR LEGGIT...FOREST SERVICE  
NATIONAL WEATHER SERVICE BOISE ID  
913 PM MDT THU SEP 17 2020  
 
FORECAST IS BASED ON FORECAST START TIME OF 2200 MDT ON SEPTEMBER 17.  
IF CONDITIONS BECOME UNREPRESENTATIVE...CONTACT THE NATIONAL WEATHER  
SERVICE.  
   
..RED FLAG WARNING IN EFFECT UNTIL 9 PM MDT FRIDAY
 
 
...THUNDERSTORMS WITH GUSTY WIND POSSIBLE BEGINNING FRIDAY  
AFTERNOON...  
   
DISCUSSION
 
 
HAINES VALUES OF 6 WILL BE PRESENT ON FRIDAY, AHEAD OF AN  
APPROACHING AREA OF LOW PRESSURE. THIS SYSTEM WILL SEND INCREASED  
MOISTURE OVER THE FIRE TO PROMOTE SHOWER AND THUNDERSTORM  
DEVELOPMENT DURING THE AFTERNOON. SOME STORMS WILL PRODUCE ERRATIC  
AND GUSTY WIND. AN ASSOCIATED COLD FRONT IS EXPECTED TO MOVE  
THROUGH THE AREA ON FRIDAY EVENING, SOMETIME BETWEEN 2000 AND  
2200. SHOWERS AND THUNDERSTORMS ASSOCIATED WITH THIS SYSTEM WILL  
CONTINUE INTO SATURDAY, WITH CONTINUED THREATS OF GUSTY WIND.  
   
TONIGHT
 
 
SKY/WEATHER.........SMOKE.  
MIN TEMPERATURE.....49 TO 54.  
MAX HUMIDITY........27 TO 33 PERCENT.  
CWR /0.10 INCH/.....0 PERCENT.  
LAL.................1.  
WIND - EYE LEVEL....SOUTHEAST 5 TO 10 MPH. OCCASIONAL GUSTS TO  
16 MPH POSSIBLE, ESPECIALLY AFTER 2100.  
MIXING HEIGHT.......400 FT AGL.  
TRANSPORT WINDS.....SOUTHEAST AROUND 10 MPH.  
HAINES INDEX........6 HIGH.  
VENTILATION INDEX...40 POOR.  
   
FRIDAY
 
 
SKY/WEATHER.........SMOKE. A 20 PERCENT CHANCE OF SHOWERS  
AND THUNDERSTORMS AFTER 0900. SOME  
THUNDERSTORMS MAY PRODUCE GUSTY WINDS TO  
40 MPH AFTER 1200.  
MAX TEMPERATURE.....61 TO 70.  
MIN HUMIDITY........20 TO 25 PERCENT.  
CWR /0.10 INCH/.....0 PERCENT.  
LAL.................1 IN THE MORNING, INCREASING TO 2 IN THE  
AFTER 1100.  
WIND - EYE LEVEL....SOUTH 5 TO 11 MPH. GUSTS UP TO 18 MPH IN THE  
AFTERNOON. THUNDERSTORMS COULD PRODUCE ERRATIC  
AND GUSTY WIND TO 40 MPH.  
MIXING HEIGHT.......11000 FT AGL.  
TRANSPORT WINDS.....SOUTH AROUND 20 MPH.  
HAINES INDEX........6 HIGH.  
VENTILATION INDEX...2200 EXCELLENT.  
   
FRIDAY NIGHT
 
 
SKY/WEATHER.........A SLIGHT CHANCE OF THUNDERSTORMS. RAIN SHOWERS  
LIKELY IN THE EVENING, THEN RAIN SHOWERS AFTER  
MIDNIGHT. SOME THUNDERSTORMS MAY PRODUCE GUSTY  
WINDS. CHANCE OF PRECIPITATION 80 PERCENT.  
MIN TEMPERATURE.....37 TO 44.  
MAX HUMIDITY........83 TO 91 PERCENT.  
CWR /0.10 INCH/.....50 PERCENT.  
LAL.................2.  
WIND - EYE LEVEL....SOUTH 3 TO 7 MPH. GUSTS TO 35 MPH POSSIBLE WITH  
THUNDERSTORM ACTIVITY.  
MIXING HEIGHT.......400 FT AGL.  
TRANSPORT WINDS.....SOUTHEAST AROUND 5 MPH.  
HAINES INDEX........3 VERY LOW.  
VENTILATION INDEX...20 POOR.  
 

 
FORECASTER...BRANHAM  
REQUESTED BY...MICHELLE ERDIE  
TYPE OF REQUEST...WILDFIRE  
.TAG 2012633.4/BOI  
 
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