511 
FXUS65 KTFX 010309
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
909 PM MDT WED SEP 30 2015

.DISCUSSION...
SATELLITE IMAGERY INDICATES CONSIDERABLY MORE CLOUDINESS OVER THE
FORECAST AREA THAN IN THE INHERITED FORECAST SO HAVE INCREASED
SKY COVER FOR NOT ONLY THE REST OF THIS EVENING BUT ALSO FOR THE
AFTER MIDNIGHT PERIOD. THESE CHANGES ALSO NECESSITATED SOME
ADJUSTMENTS TO SKY COVER FORECASTS FOR THURSDAY. IN LINE WITH THE
INCREASED SKY COVER HAVE RAISED FORECAST LOWS FOR TONIGHT. RADAR
AT MID-EVENING SHOWED SOME SHOWERS APPROACHING THE BORDER WITH
IDAHO AND THEY COULD WORK THEIR WAY INTO SOUTHWEST MONTANA NEAR
AND AFTER MIDNIGHT. THIS IS WELL-COVERED IN THE INHERITED
FORECAST. BLANK

&&

.AVIATION... 
UPDATED 2333Z. 

EXPECT VFR CONDITIONS. CEILINGS ABOVE 15000 FT WILL GRADUALLY SPREAD
NORTH OVER THE AREA TONIGHT. SCATTERED SHOWERS ARE EXPECTED TO
DEVELOP OVER FAR SOUTHWEST MONTANA LATE TONIGHT OR EARLY THURSDAY
MORNING. THE SHOWERS WILL THEN SPREAD SLOWLY NORTHEAST AND REACH AS
FAR NORTH AS THE AREA FROM THE SOUTHERN ROCKY MOUNTAIN FRONT THROUGH
THE LITTLE BELT MOUNTAINS TO NEAR THE SNOWY MOUNTAINS BY LATE
AFTERNOON. THERE WILL BE A FEW THUNDERSTORMS NEAR THE IDAHO BORDER
THURSDAY AFTERNOON WITH A VERY SMALL THREAT AS FAR NORTH AS THE
LITTLE BELT THROUGH THE SNOWY MOUNTAINS BY LATE AFTERNOON. BLANK

&&

.PREV DISCUSSION...
/ISSUED 533 PM MDT WED SEP 30 2015/
TONIGHT THROUGH FRIDAY...AN UPPER LEVEL RIDGE OF HIGH PRESSURE
CURRENTLY OVER THE REGION WILL BEGIN TO BREAK DOWN OVER THE NEXT
FEW DAYS. THUS THIS AFTERNOON WILL BE THE END OF THE WARM AIR FOR
AWHILE. AFTERNOON HIGHS WILL COOL INTO THE 70S FOR THURSDAY INTO
THE 50S/60S FOR FRIDAY. THE CHANCES FOR PRECIP WILL ALSO BE ON THE
INCREASE...STARTING ON THUR AFTERNOON. EXPECT SHOWERS/ISOLATED
THUNDERSTORMS TO DEVELOP IN THE SOUTHWEST AND GRADUALLY MOVE
NORTHEASTWARD INTO CENTRAL MT BY THUR EVENING. OVERALL RAINFALL
AMOUNTS FROM THIS FIRST WAVE SHOULD GENERALLY RANGE FROM 0.10 TO
0.30 INCHES. SHOWERS CONTINUE ON FRIDAY...ESPECIALLY IN THE
HAVRE/LEWISTOWN AREAS. BRUSDA

FRIDAY NIGHT THROUGH WEDNESDAY...FORECAST MODELS HAVE COME IN TO 
BETTER AGREEMENT WITH THE SYSTEMS IMPACTING THE AREA THROUGH SUNDAY, 
BUT THEY THEN BEGIN TO DIFFER ON THE TIMING OF MOVING THE LATTER 
SYSTEM OUT OF THE AREA. THE SHORTWAVE TROUGH OVER THE CENTRAL 
ROCKIES FRIDAY NIGHT WILL WEAKEN AND LIFT NORTHEAST INTO THE 
NORTHERN GREAT PLAINS SATURDAY INTO SUNDAY, WHICH WILL KEEP 
PRECIPITATION LIKELY OVER MUCH OF THE AREA. HOWEVER, DURING THIS 
TIME, A DEEP LOW PRESSURE AREA WILL MOVE SOUTH FROM THE PACIFIC 
NORTHWEST ALONG THE PACIFIC COAST, WHICH WILL DRAG MUCH COOLER 
CANADIAN AIR INTO THE FORECAST AREA. THIS SYSTEM WILL ALSO BRING 
DEEP PACIFIC MOISTURE INTO THE AREA TO COMBINE WITH THE NORTHEAST 
UPSLOPE WINDS TO CREATE AN OVERRUNNING SITUATION, WHICH WILL ENHANCE 
PRECIPITATION AMOUNTS ALONG THE NORTH AND EAST FACING SLOPES OF 
NORTH CENTRAL MONTANA. 0.50 TO 0.75 INCHES OF RAIN MAY FALL IN THESE 
AREAS OVER THE WEEKEND, WHILE MOST OTHER AREAS WILL MAINLY RECEIVE 
0.10 TO 0.25 INCHES. SNOW LEVELS WILL ALSO FALL TO BETWEEN 5000 AND 
6000 FEET BY SUNDAY FOR MUCH OF NORTH CENTRAL MONTANA, WHICH WILL 
LIKELY BRING LIGHT MEASURABLE SNOW TO THE MOUNTAINS AND A RAIN/SNOW 
MIX TO THE PLAINS ALONG THE ROCKY MOUNTAIN FRONT. CURRENT FORECAST 
SNOW AMOUNTS ARE MAINLY 2 TO 4 INCHES ABOVE MOUNTAIN PASS LEVEL WITH 
LESS THAN 2 INCHES OF SLUSHY SNOW POSSIBLE ON MOST PASSES. HOWEVER, 
AMOUNTS MAY CHANGE AS THE EVENT GETS CLOSER. THERE WILL BE LESS OF A 
CHANCE OF PRECIPITATION OVER SOUTHWEST MONTANA AND SNOW LEVELS WILL 
REMAIN ABOVE 7000 FEET. DAYTIME TEMPERATURES WILL STRUGGLE TO GET 
OUT OF THE 40S, AS OVERNIGHT LOWS FALL WELL INTO THE 30S. FORECAST 
MODELS DIFFER ON MOVING THIS SYSTEM OUT OF THE AREA. THE ECMWF 
INDICATES THAT IT WILL MOVE FROM THE SOUTHWEST CONUS NORTHEAST INTO 
THE NORTHERN GREAT PLAINS THROUGH TUESDAY. THE GFS KEEPS IT OVER THE 
WESTERN GREAT BASIN UNTIL TUESDAY, THEN IT MOVES IT INTO THE PLAINS 
BY WEDNESDAY. UNTIL THESE COME INTO BETTER AGREEMENT, WILL CONTINUE 
TO GO WITH A CONSENSUS FORECAST AND KEEP A SLIGHT CHANCE OF SPOTTY 
SHOWERS ACROSS THE FORECAST AREA. TEMPERATURES WILL ALSO GRADUALLY 
WARM BACK TO NEAR NORMAL BY WEDNESDAY.  COULSTON

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  49  73  50  59 /   0  10  30  40 
CTB  41  70  46  65 /   0  10  20  20 
HLN  50  75  50  64 /   0  30  40  40 
BZN  49  72  44  63 /  10  30  40  40 
WEY  38  68  34  56 /  20  40  40  50 
DLN  51  71  47  61 /  20  40  50  40 
HVR  44  73  46  62 /   0  10  40  50 
LWT  48  74  47  59 /   0  10  60  70 

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

WEATHER.GOV/GREATFALLS