320 
FXUS65 KTFX 162338
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
438 PM MST MON JAN 16 2012

UPDATED AVIATION

.DISCUSSION...
TONIGHT THROUGH WEDNESDAY...OVERALL...AN ACTIVE WEATHER PATTERN
WILL RESIDE OVER THE REGION FOR THE NEXT FEW DAYS. EXPECT
SCATTERED SHOWERS OVER THE ROCKY MOUNTAIN FRONT...TO BECOME MORE
WIDESPREAD AND HEAVIER TOWARDS MORNING. THERE IS THE POTENTIAL FOR
HEAVY SNOW OVER THIS REGION AT TIMES THEN FROM TUESDAY THROUGH
THURSDAY NIGHT...SO THIS REGION HAS BEEN PLACED UNDER A WINTER
STORM WATCH. ELSEWHERE OVER THE REGION TONIGHT...EXPECT SOME
PASSING EVENING FLURRIES...WITH ISOLATED SNOW SHOWERS AFTER
MIDNIGHT...MAINLY OVER THE NORTHERN TIER OF THE REGION. FOR
TUESDAY...EXPECT THE SNOW TO CONTINUE ALONG THE FRONT
RANGE...WHILE THE SNOW SHOWERS START TO SPREAD A BIT FURTHER
EASTWARD OVER NORTH CENTRAL MONTANA DURING THE AFTERNOON HOURS.
TEMPERATURES WILL GENERALLY REMAIN COLD. FOR TUESDAY NIGHT THE
SNOW BECOMES LIKELY ACROSS MUCH OF NORTH CENTRAL/SOUTHWEST MONTANA
AS THE MAIN WARM FRONT BEGINS TO DEVELOP OVER SOUTHWEST MONTANA.
THIS WARM FRONT WILL BEGIN TO SLOWLY PUSH NORTHWARD
WEDNESDAY...AND LOCATIONS NEAR THE MAIN FRONTAL BOUNDARY SHOULD
RECEIVE THE HEAVIEST SNOWFALL. TEMPERATURES WILL REMAIN COLD OVER
MUCH OF NORTH CENTRAL MONTANA...AS SEASONABLE TEMPERATURES START
TO MOVE BACK INTO FAR SOUTHWEST MONTANA. BRUSDA

WEDNESDAY NIGHT THROUGH MONDAY NIGHT...MEDIUM RANGE MODELS AGREE 
THAT THE BITTERLY COLD AIRMASS WILL BEGIN TO MODERATE WEDNESDAY 
NIGHT INTO THURSDAY AS THE FLOW ALOFT BECOMES MORE WESTERLY. 
HOWEVER...THERE ARE STILL DIFFERENCES AMONG THE MODELS IN THE EXACT 
POSITIONING OF THE SURFACE BOUNDARY DIVIDING THE WARM AND COLD 
AIRMASSES...WHICH IS RESULTING IN MODEL FORECAST TEMPERATURE 
DIFFERENCES OF GENERALLY 10 TO 20 DEGREES THROUGH THE END OF THIS 
WEEK. THEREFORE...AM ELECTING TO GO WITH MORE OF A GRADUAL MOVEMENT 
OF THE BOUNDARY THROUGH THE PERIOD...RESULTING IN A GRADUAL WARMING 
OF TEMPERATURES. HOWEVER...SNOW WILL REMAIN LIKELY FOR THE WEDNESDAY 
NIGHT AND THURSDAY PERIODS DUE TO CONTINUED SIGNIFICANT MOISTURE 
OVERRUNNING THE COLD AIRMASS STILL IN PLACE. AS HAS BEEN MENTIONED 
IN THE HAZARDOUS WEATHER OUTLOOK...WINTER WEATHER HIGHLIGHTS MAY BE 
NECESSARY FOR THIS EVENT...AS SNOWFALL WILL BE LIGHT BUT PERSISTENT. 
THE SURFACE BOUNDARY WILL LIFT NORTHEAST DURING THIS 
PERIOD...ALLOWING TEMPERATURES IN SOUTHWEST MONTANA TO WARM TO ABOVE 
NORMAL...CAUSING VALLEY PRECIPITATION TO LIKELY BE A RAIN/SNOW MIX. 
CENTRAL MONTANA (INCLUDING GREAT FALLS AND LEWISTOWN) WILL LIKELY 
ONLY REACH NEAR NORMAL. 

AS THE FLOW ALOFT BECOMES MORE WESTERLY FRIDAY AND SATURDAY...THE
BOUNDARY WILL CONTINUE TO MOVE NORTHEAST...ALLOWING ABOVE NORMAL
TEMPERATURES TO REACH INTO CENTRAL MONTANA WITH NEAR NORMAL
TEMPERATURES AS FAR NORTH AS THE CANADIAN BORDER. THERE WILL LESS
OF A THREAT OF OVERRUNNING PRECIPITATION AS THE SURFACE BOUNDARY
LIFTS NORTH...BUT A DISTURBANCE IN THE FLOW ALOFT WILL CONTINUE
MOUNTAIN SHOWERS AND KEEP A CHANCE OF SHOWERS OVER THE PLAINS.
HOWEVER...STRONG WESTERLY WINDS BLOWING OVER RIDGE TOPS WILL CAUSE
AREAS OF BLOWING SNOW THERE. THE MORE PROGRESSIVE WESTERLY FLOW
ALOFT WILL BECOME LESS MOIST OVER THE WEEKEND AND KEEP
TEMPERATURES CLOSE TO NORMAL...BUT DISTURBANCES IN THE FLOW WILL
GENERALLY KEEP AT LEAST A SLIGHT CHANCE OF SHOWERS AROUND THROUGH
THE REMAINDER OF THE PERIOD. COULSTON

&&

.AVIATION...
UPDATED 0000Z.
LOW CLOUDS WILL LINGER OVER PORTIONS OF CENTRAL AND SOUTHWEST 
MONTANA THOUGH CLOUDS WILL GRADUALLY LIFT FROM KGTF TO KLWT AND 
AREAS SOUTH OF THIS LINE AS WINDS SHIFT SOUTHWEST. A COLD FRONT WILL 
DESCEND FROM CANADA AND BRING LIGHT SNOW TO AREAS ALONG THE HI-LINE 
INCLUDING KCTB AND KHVR. WINDS WILL SHIFT TO THE NORTHEAST BEHIND 
THE FRONT FOR KCTB AND KHVR. MVFR AND OCCASIONAL IFR CONDITIONS ARE 
POSSIBLE FOR THESE LOCATIONS AND WIDESPREAD MOUNTAIN OBSCURATION IS 
ALSO EXPECTED THROUGH TUESDAY MORNING. THE FRONT WILL GRADUALLY 
APPROACH CENTRAL MONTANA TOWARDS THE END OF THE CURRENT FORECAST 
PERIOD. MLV 

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  -3  13 -10  -2 /  10  30  80  90 
CTB -16  -6 -21 -10 /  20  70  80  90 
HLN   1  21   8  16 /  10  30  70  90 
BZN   1  22  10  21 /  10  20  70  80 
WEY -16  11   3  20 /  20  40  60  80 
DLN  -4  18  11  21 /  10  20  60  80 
HVR -13   2 -18  -9 /  20  40  60  60 
LWT  -4  19  -8   0 /  10  20  70  80 

&&

.TFX WATCHES/WARNINGS/ADVISORIES...

WINTER STORM WATCH FROM LATE TONIGHT THROUGH LATE THURSDAY NIGHT 
NORTHERN ROCKY MOUNTAIN FRONT...SOUTHERN ROCKY MOUNTAIN FRONT.

&&

$$

WEATHER.GOV/GREATFALLS