Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 040315
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
915 PM MDT THU SEP 3 2015

.DISCUSSION...
UPDATE FORTHCOMING. HAVE ADJUSTED POP AND WEATHER GRIDS TO BETTER
ALIGN WITH RADAR RETURNS. BAND OF PRECIPITATION FROM GREAT FALLS
NORTH TO THE CANADIAN BORDER IS FAIRLY WELL DEPICTED BY RAP13 DATA
WHICH KEEPS THE BAND IN PLACE FOR MOST OF THE NIGHT. CURRENT
FORECAST OF RAIN MOST OF THE NIGHT LOOKS ON TRACK AS DO THE
TEMPERATURES.

&&

.AVIATION...
UPDATED 0010Z.
SOUTHWEST FLOW ALOFT WILL CONTINUE TO BRING MOISTURE
TO THE AREA. SHOWERS WILL BECOME WIDESPREAD OVER NORTH AND CENTRAL
MONTANA OVERNIGHT AND CONTINUE THROUGH FRIDAY. VFR CONDITIONS
PREVAIL WITH AREAS OF MVFR DUE TO LOW CEILINGS AND RAIN. CONDITIONS
WILL BECOME INCREASINGLY MVFR AFTER 12Z. SOUTHWEST MONTANA WILL SEE
ONLY SCATTERED SHOWERS WITH VFR CONDITIONS PREVAILING THERE.
MOUNTAINS OBSCURED AT TIMES.

&&

.PREV DISCUSSION...ISSUED 252 PM MDT THU SEP 3 2015

TONIGHT THROUGH SATURDAY...AN UPPER LOW IS EXPECTED TO DEVELOP
OVER WESTERN OREGON BY LATE FRIDAY AFTERNOON OR EARLY FRIDAY
EVENING. THE UPPER LOW IS THEN FORECAST TO MOVE EAST THROUGH THE
PACIFIC NORTHWEST FRIDAY NIGHT AND SATURDAY. MOIST SOUTHWEST FLOW
AHEAD OF THE UPPER LOW HAS ALREADY DEVELOPED OVER THE FORECAST
AREA EXCEPT NEAR AND EAST OF A LINE FROM FROM BOZEMAN TO
LEWISTOWN. BANDS OF SHOWERS/RAIN WILL CONTINUE TO AFFECT AREAS
WEST OF THE AFOREMENTIONED LINE THROUGH FRIDAY WITH PRECIPITATION
EVENTUALLY MOVING INTO THE AREA FROM BOZEMAN TO LEWISTOWN BY
FRIDAY NIGHT. A QUASISTATIONARY FRONT WILL BE NEAR A BOZEMAN TO
DILLON LINE THROUGH THE PERIOD WITH HIGHS IN THE UPPER 60S TO
LOWER 70S SOUTH OF THE FRONT AND COOL READINGS IN THE MID 50S TO
MID 60S NORTH OF THE FRONT. SNOW LEVELS THROUGH SATURDAY ARE
EXPECTED TO BE GENERALLY WELL ABOVE 8000 FEET. BLANK

SATURDAY NIGHT THROUGH THURSDAY...AN UPPER LEVEL LOW PRESSURE TROF
WILL BE OVER THE REGION SATURDAY NIGHT WHICH WILL BROADEN DURING THE
NIGHT AS A PAIR OF SHORTWAVES MOVE THROUGH THE FLOW. WIDESPREAD
PRECIPITATION WILL RESULT FROM THE FIRST SHORTWAVE. IT WILL BE OVER
THE ROCKIES AND MOVE INTO CENTRAL MONTANA SUNDAY. THE SECOND
SHORTWAVE WALL BE MOVING OVER THE WEST COAST AND KEEP CYCLONIC FLOW
ALOFT ACROSS THE WESTERN US. A BREAK OR LESSENING OF PRECIPITATION
IS POSSIBLE SUNDAY AS THE FORECAST AREA LIES BETWEEN THE TWO
SHORTWAVES. THIS WILL BE A SHORT PERIOD AS THE SECOND SHORTWAVE
WILL APPROACH THE ROCKIES SUNDAY AFTERNOON. MODELS ARE IN GOOD
AGREEMENT UNTIL THEY BEGIN TO DIVERGE MONDAY MORNING. BY TUESDAY,
THE GFS HAS DEVELOPED A SHORTWAVE OVER THE ZONES WHILE THE ECMWF
IS NEARLY ZONAL. CONSEQUENTLY, THE GFS PRODUCES PRECIP WHILE THE
ECMWF REMAINS DRY. THE GEM DEVELOPS A WEAK SHORTWAVE BUT REMAINS
DRY...SO WILL LEAN TO THE DRYER SOLUTIONS. THE AIR MASS WILL
REMAIN UNSETTLED TUESDAY BUT HEIGHTS ALOFT WILL BE RISING AND THE
AIR MASS WARMING AND DRYING. A WEAK SHORTWAVE WILL CROSS THE ZONES
WEDNESDAY. BEST CHANCE FOR PRECIP WILL BE ALONG THE HI-LINE ALTHOUGH
MOISTURE WILL BE LIMITED. ZELZER

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  48  58  47  60 /  90  60  80  80
CTB  44  53  43  54 /  60  80 100  90
HLN  46  64  44  66 /  80  60 100  80
BZN  44  70  44  69 /  30  30  70  70
WEY  36  70  36  66 /  20  20  30  30
DLN  45  67  42  65 /  40  50  80  60
HVR  49  64  48  63 /  60  60  70  60
LWT  46  65  47  66 /  30  30  50  40

&&

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

$$

WEATHER.GOV/GREATFALLS


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