476  
FNUS75 KTFX 262000  
FWSTFX  
 
SPOT FORECAST FOR HELMVILLE RX...HELENA-LEWIS AND CLARK NATIONAL FOREST  
NATIONAL WEATHER SERVICE GREAT FALLS MT  
200 PM MDT THU APR 26 2018  
 
FORECAST IS BASED ON IGNITION TIME OF 1400 MDT ON APRIL 26.  
IF CONDITIONS BECOME UNREPRESENTATIVE...CONTACT THE NATIONAL WEATHER  
SERVICE.  
   
DISCUSSION
 
 
HIGH PRESSURE WILL KEEP THE AREA MOSTLY CLEAR AND DRY THROUGH FRIDAY  
NIGHT WITH WARMER THAN NORMAL TEMPERATURES. WINDS WILL BE LIGHT AND  
TERRAIN-DRIVEN TONIGHT, BUT AN APPROACHING PACIFIC COLD FRONT WILL  
CAUSE MORE CONSISTENT EASTERLY WINDS FRIDAY INTO FRIDAY NIGHT. THE  
COLD FRONT WILL MOVE THROUGH THE AREA ON SATURDAY, SHIFTING WINDS  
MORE WESTERLY DURING THE AFTERNOON AND CAUSING SCATTERED THUNDERSTORMS  
WITH GUSTY ERRATIC WINDS.  
   
TONIGHT
 
 
SKY/WEATHER.........CLEAR.  
CWR.................0 PERCENT.  
LAL.................1.  
MIN TEMPERATURE.....30-35.  
MAX HUMIDITY........55-60 PERCENT.  
WIND (20 FT)........  
SLOPE/VALLEY.......LIGHT AND VARIABLE WINDS INCREASING TO EAST (DOWN  
SLOPE) AT 4 TO 7 MPH BY MIDNIGHT.  
MIXING HEIGHT.......5000 FT AGL DECREASING TO 500 FT AGL AFTER  
MIDNIGHT.  
TRANSPORT WINDS.....SOUTH AROUND 5 MPH.  
   
FRIDAY
 
 
SKY/WEATHER.........SUNNY.  
CWR.................0 PERCENT.  
LAL.................1.  
MAX TEMPERATURE.....70-75.  
MIN HUMIDITY........15-20 PERCENT.  
WIND (20 FT)........  
SLOPE/VALLEY.......EAST WINDS AROUND 10 MPH. GUSTS TO 20 MPH  
POSSIBLE IN THE AFTERNOON.  
MIXING HEIGHT.......500 FT AGL INCREASING TO 4000 FT AGL IN THE  
AFTERNOON.  
TRANSPORT WINDS.....EAST AROUND 10 MPH.  
HAINES INDEX........3 VERY LOW.  
   
FRIDAY NIGHT
 
 
SKY/WEATHER.........MOSTLY CLEAR.  
CWR.................0 PERCENT.  
LAL.................1.  
MIN TEMPERATURE.....40-45.  
MAX HUMIDITY........70-75 PERCENT.  
WIND (20 FT)........  
SLOPE/VALLEY.......EAST WINDS 5 TO 10 MPH.  
MIXING HEIGHT.......4000 FT AGL DECREASING TO 500 FT AGL AFTER  
MIDNIGHT.  
TRANSPORT WINDS.....SOUTHEAST AROUND 10 MPH.  
   
SATURDAY
 
 
SKY/WEATHER.........PARTLY SUNNY. SCATTERED SHOWERS AND  
THUNDERSTORMS IN THE AFTERNOON.  
CWR.................10 PERCENT.  
LAL.................3.  
MAX TEMPERATURE.....67-72.  
MIN HUMIDITY........30-35 PERCENT.  
WIND (20 FT)........  
SLOPE/VALLEY.......SOUTHEAST WINDS AROUND 5 MPH INCREASING TO THE  
WEST AT 5 TO 10 MPH IN THE AFTERNOON WITH GUSTS  
TO 20 MPH POSSIBLE. GUSTY AND ERRATIC WINDS  
EXPECTED NEAR THUNDERSTORMS IN THE AFTERNOON.  
MIXING HEIGHT.......500 FT AGL INCREASING TO 3000 FT AGL IN THE  
AFTERNOON.  
TRANSPORT WINDS.....SOUTHWEST AROUND 5 MPH.  
HAINES INDEX........4 LOW.  
 

 
FORECASTER...COULSTON  
REQUESTED BY...JAREL KURTZ  
TYPE OF REQUEST...PRESCRIBED  
.TAG 1808009.0/TFX  
.EMAIL JKURTZ@FS.FED.US,JRUSSELL@FS.FED.US  
 
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