FNUS75 KRIW 252113
FWSRIW

SPOT FORECAST FOR ARNICA FIRE...NPS YNP
NATIONAL WEATHER SERVICE RIVERTON WY
313 PM MDT FRI SEP 25 2009

FORECAST IS BASED ON REQUEST TIME OF 1455 MDT ON SEPTEMBER 25.
IF CONDITIONS BECOME UNREPRESENTATIVE...CONTACT THE NATIONAL WEATHER
SERVICE.

.DISCUSSION...

HIGH PRESSURE AT THE SURFACE AND ALOFT WILL PRODUCE ANOTHER DRY AFTERNOON
WITH ABOVE NORMAL TEMPERATURES...LIGHT NORTH WINDS AND AFTERNOON
RELATIVE HUMIDITY AROUND 20 PERCENT. A WEAK LOW PRESSURE SYSTEM
WILL MOVE ACROSS MONTANA SATURDAY. THIS SYSTEM WILL CAUSE WINDS TO
INCREASE SATURDAY AFTERNOON WITH WEST WIND GUSTING UP TO 25 MPH.
SATURDAY WILL ALSO BE DRY AND WARM.

...THUNDERSTORMS IMPLY STRONG GUSTY AND ERRATIC WINDS...
...HAINES INDEX IS HIGH LEVEL HAINES BOTH DAY AND NIGHT...

FORECASTER...SMITH

.TODAY...
SKY/WEATHER.........SUNNY (5-10 PERCENT). AREAS OF SMOKE IN THE
                    AFTERNOON.
MAX TEMPERATURE.....69-72.
MIN HUMIDITY........18-21 PERCENT.
20 FOOT WINDS.......NORTH 5-9 MPH.
RIDGE TOP WINDS.....NORTH AROUND 10 TO 15 MPH.
LAL.................1.
CHC OF WETTING RAIN.ZERO PERCENT.
HAINES INDEX........5 OR MODERATE POTENTIAL FOR LARGE PLUME
                    DOMINATED FIRE GROWTH.
MIXING HEIGHT.......9000 FT AGL.
TRANSPORT WINDS.....NORTH AROUND 15 MPH.
SMOKE DISPERSAL.....GOOD (86700 KNOT-FT).

.TONIGHT...
SKY/WEATHER.........MOSTLY CLEAR (5-10 PERCENT). AREAS OF SMOKE
                    EARLY IN THE EVENING...THEN PATCHY SMOKE IN THE
                    LATE EVENING AND OVERNIGHT.
MIN TEMPERATURE.....AROUND 30.
MAX HUMIDITY........70-73 PERCENT.
20 FOOT WINDS.......NORTHWEST WINDS AROUND 10 MPH...BECOMING
                    DOWNSLOPE/DOWNVALLEY 4-7 MPH AFTER 2200.
RIDGE TOP WINDS.....NORTHWEST 10 TO 15 MPH.
LAL.................1.
CHC OF WETTING RAIN.ZERO PERCENT.
HAINES INDEX........4 OR LOW POTENTIAL FOR LARGE PLUME DOMINATED
                    FIRE GROWTH.
MIXING HEIGHT.......4500 FT AGL DECREASING TO 700 FT AGL AFTER
                    MIDNIGHT.
TRANSPORT WINDS.....NORTHWEST AROUND 15 MPH.
SMOKE DISPERSAL.....GOOD (63200 KNOT-FT) DECREASING TO POOR (7700
                    KNOT-FT) AFTER MIDNIGHT.

.SATURDAY...
SKY/WEATHER.........SUNNY (0-10 PERCENT). PATCHY SMOKE IN THE
                    MORNING.
MAX TEMPERATURE.....AROUND 70.
MIN HUMIDITY........14-17 PERCENT.
20 FOOT WINDS.......UPSLOPE/UPVALLEY 5-9 MPH BECOMING WEST AROUND
                    15 MPH WITH GUSTS TO AROUND 25 MPH IN THE
                    AFTERNOON.
RIDGE TOP WINDS.....NORTHWEST AROUND 10 MPH SHIFTING...INCREASING
                    TO WEST 20 TO 25 MPH IN THE AFTERNOON.
LAL.................1.
CHC OF WETTING RAIN.ZERO PERCENT.
HAINES INDEX........4 OR LOW POTENTIAL FOR LARGE PLUME DOMINATED
                    FIRE GROWTH.
MIXING HEIGHT.......3500 FT AGL INCREASING TO 8500 FT AGL IN THE
                    AFTERNOON.
TRANSPORT WINDS.....NORTHWEST AROUND 15 MPH...THEN INCREASING
                    TO WEST AROUND 25 MPH IN THE AFTERNOON.
SMOKE DISPERSAL.....POOR (1200 KNOT-FT) INCREASING TO EXCELLENT
                    (163700 KNOT-FT) IN THE AFTERNOON.

.FORECAST DAYS 3 THROUGH 5...
.SATURDAY NIGHT...CLEAR. LOWS IN THE LOWER 30S. WINDS GENERALLY
LESS THAN 10 MPH.
.SUNDAY...CLEAR. LOWS IN THE UPPER 20S. HIGHS IN THE MID 60S.
WINDS GENERALLY LESS THAN 10 MPH.
.MONDAY...MOSTLY CLEAR. LOWS IN THE MID 30S. HIGHS IN THE LOWER
70S. WINDS GENERALLY LESS THAN 10 MPH.
.TUESDAY...COOLER. PARTLY CLOUDY. CHANCE OF SHOWERS...
THUNDERSTORMS AND SNOW SHOWERS. LOWS IN THE MID 20S. HIGHS IN THE
MID 50S. WINDS GENERALLY LESS THAN 10 MPH.

$$

FORECASTER...SMITH
REQUESTED BY...ED FOLTS
REASON FOR REQUEST...WILDFIRE
.TAG 20090925.ARNIC.01/RIW