741  
FNUS75 KBYZ 251213  
FWSBYZ  
 
SPOT FORECAST FOR PORCUPINE ASPEN PROJECT RX...USFS  
NATIONAL WEATHER SERVICE BILLINGS MT  
613 AM MDT FRI MAY 25 2018  
 
FORECAST IS BASED ON IGNITION TIME OF 0800 MDT ON MAY 25.  
IF CONDITIONS BECOME UNREPRESENTATIVE...CONTACT THE NATIONAL WEATHER  
SERVICE.  
 
PLEASE CONTACT OUR OFFICE IF YOU HAVE QUESTIONS  
OR CONCERNS WITH THIS FORECAST.  
   
DISCUSSION
 
 
A RIDGE OF HIGH PRESSURE WILL BUILD OVER THE BURN SITE TODAY. WEAK  
DISTURBANCES WILL BRING ISOLATED SHOWERS AND THUNDERSTORMS IN THE  
AFTERNOON. IT WILL BE PARTLY CLOUDY TONIGHT. A STORM SYSTEM OVER NEVADA  
WILL BRING SCATTERED AFTERNOON SHOWERS AND THUNDERSTORMS TO THE BURN SITE  
SATURDAY AFTERNOON. SOME THUNDERSTORMS MAY PRODUCE GUSTY WINDS AND SMALL HAIL.  
THE SYSTEM WILL CONTINUE AFFECTING THE AREA SATURDAY NIGHT. HIGH TEMPERATURES EACH  
DAY WILL BE 65 TO 70 DEGREES, WITH HUMIDITIES IN THE 30S. LOWS TONIGHT WILL BE IN  
THE UPPER 30S TO LOWER 40S WITH GOOD HUMIDITY RECOVERIES. EXPECT LIGHT TERRAIN-DRIVEN  
WINDS TODAY AND TONIGHT, WITH SOUTH WINDS AT 5 TO 10 MPH ON SATURDAY.  
   
TODAY
 
 
SKY/WEATHER.........MOSTLY SUNNY. ISOLATED RAIN SHOWERS AND  
THUNDERSTORMS IN THE AFTERNOON.  
MAX TEMPERATURE.....65-70.  
MIN HUMIDITY........30-35 PERCENT.  
WIND (20 FT)........  
SLOPE/VALLEY.......DOWNSLOPE/DOWN-VALLEY WINDS AT 5 MPH EARLY,  
BECOMING UPSLOPE/UP-VALLEY WINDS 5 TO 10 MPH BY LATE MORNING.  
GUSTY AND ERRATIC WINDS EXPECTED NEAR THUNDERSTORMS IN THE  
AFTERNOON.  
RIDGETOP...........SOUTHWEST 5 TO 15 MPH.  
MIXING HEIGHT.......800 FT AGL IN THE MORNING...INCREASING TO 7900  
FT AGL IN THE AFTERNOON.  
TRANSPORT WINDS.....SOUTHWEST 5 TO 15 MPH.  
HAINES INDEX........3.  
CWR.................10 PERCENT.  
   
TONIGHT
 
 
SKY/WEATHER.........PARTLY CLOUDY.  
MIN TEMPERATURE.....38-43.  
MAX HUMIDITY........81-86 PERCENT.  
WIND (20 FT)........  
SLOPE/VALLEY.......UPSLOPE/UP-VALLEY WINDS 5 TO 10 MPH EARLY,  
BECOMING DOWNSLOPE/DOWN-VALLEY WINDS AROUND 5 MPH BY LATE  
EVENING.  
RIDGETOP...........SOUTH 15 TO 25 MPH.  
MIXING HEIGHT.......7900 FT AGL IN THE EVENING...DECREASING TO 700  
FT AGL OVERNIGHT.  
TRANSPORT WINDS.....SOUTH 5 TO 15 MPH.  
CWR.................0 PERCENT.  
   
SATURDAY
 
 
SKY/WEATHER.........PARTLY SUNNY. SCATTERED THUNDERSTORMS IN THE  
AFTERNOON. SOME THUNDERSTORMS MAY PRODUCE GUSTY  
WINDS AND SMALL HAIL IN THE AFTERNOON.  
MAX TEMPERATURE.....65-70.  
MIN HUMIDITY........33-38 PERCENT.  
WIND (20 FT)........  
SLOPE/VALLEY.......SOUTH WINDS 5 TO 10 MPH. GUSTY AND ERRATIC  
WINDS EXPECTED NEAR THUNDERSTORMS IN THE  
AFTERNOON.  
RIDGETOP...........SOUTHWEST 5 TO 15 MPH.  
MIXING HEIGHT.......700 FT AGL IN THE MORNING...INCREASING TO 6600  
FT AGL IN THE AFTERNOON.  
TRANSPORT WINDS.....SOUTH 5 TO 10 MPH.  
HAINES INDEX........4.  
CWR.................31 PERCENT.  
   
SATURDAY NIGHT
 
 
 
RIDGETOP...........NORTH 5 TO 15 MPH.  
MIXING HEIGHT.......6600 FT AGL IN THE EVENING...DECREASING TO 1500 FT  
FT AGL OVERNIGHT.  
TRANSPORT WINDS.....NORTHEAST 10 TO 15 MPH.  
HAINES INDEX........2.  
 

 
FORECASTER...ARTHUR  
REQUESTED BY...CRISTI HEANEY  
TYPE OF REQUEST...PRESCRIBED  
.TAG 1810621.0/BYZ  
.DELDT 05/25/18  
.EMAIL MTBZC@FS.FED.US  
 
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