FNUS75 KBYZ 172031
FWSBYZ

SPOT FORECAST FOR BIG PRYOR BURN...CUSTER NATIONAL FOREST
NATIONAL WEATHER SERVICE BILLINGS MT
231 PM MDT SUN MAY 17 2009

FORECAST IS BASED ON IGNITION TIME OF 1200 MDT ON MAY 18.
IF CONDITIONS BECOME UNREPRESENTATIVE...CONTACT THE NATIONAL WEATHER
SERVICE.

.DISCUSSION...

MONDAY WILL BE WARM WITH RH VALUES DROPPING INTO THE TEENS.
RELATIVE HUMIDITIES SHOULD DROP BELOW 30 PERCENT AS THE MORNING
INVERSION BREAKS AROUND 11 AM. AT THIS TIME DOWN SLOPE/VALLEY
WINDS SHOULD BECOME SOUTHWESTERLY AND INCREASE TO 10 TO 15 MPH.
THERE IS A SLIGHT CHANCE OF A WIND SHIFT TO THE NORTHEAST BY LATE
IN THE AFTERNOON...BUT GIVEN THE SLOPE OF THE TERRAIN ITS MORE
LIKELY WINDS WILL DIMINISH LATE IN THE DAY TO LIGHT SLOPE
DOMINANT. A WEAK DISTURBANCE COMBINED WITH THE WARM TEMPERATURES
WILL KEEP A SLIGHT CHANCE OF THUNDERSTORMS IN THE FORECAST AFTER 2
PM. RH WILL SLOWLY RECOVER TO AROUND 30 PERCENT BY 10 PM AND 60-65
PERCENT BY 3 AM MONDAY NIGHT.

.MONDAY...

SKY/WEATHER.........PARTLY CLOUDY. ISOLATED SHOWERS AND
                    THUNDERSTORMS IN THE AFTERNOON.
CWR.................20 PERCENT.
LAL.................2...1 TO 8 STRIKES/15 MIN/CELL.
MAX TEMPERATURE.....68-73.
MIN HUMIDITY........17-22 PERCENT.
WIND (20 FT)........
 SLOPE/VALLEY.......LIGHT DOWN SLOPE/VALLEY IN THE MORNING BECOMING
                    SOUTHWEST 10 TO 15 MPH BY 11 AM. GUSTY AND
                    ERRATIC WINDS EXPECTED NEAR THUNDERSTORMS
                    IN THE AFTERNOON.
 RIDGETOP...........SOUTHWEST 10 TO 20 MPH.
MIXING HEIGHT.......7800 FT AGL.
MIXING WINDS........WEST 10 TO 20 MPH.

$$
FORECASTER...CHAMBERS
REQUESTED BY...TIM BUMGARNER
TYPE OF REQUEST...PRESCRIBED
.TAG 20090518.BIGPR.01/BYZ