Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 031755
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1155 AM MDT THU SEP 3 2015

...UPDATE TO AVIATION...

.UPDATE...ADJUSTED THE COVERAGE OF SHOWERS ACROSS PARTS OF THE AREA
FOR THIS MORNING BASED ON LATEST RADAR TRENDS. THE BAND OF SHOWERS
EXTENDING FROM ID TO MT SHOULD CONTINUE TO SLOWLY MOVE NE AND EAST
INTO THIS AFTERNOON WHILE MORE SHOWERS GRADUALLY DEVELOP FROM SW TO
NE ACROSS SOUTHWEST AND CENTRAL MONTANA. INSTABILITY LOOKS
MEAGER...BUT AN ISOLATED THUNDERSTORM WILL BE POSSIBLE THROUGH THIS
AFTERNOON AS WELL. HIGHEST RAINFALL AMOUNTS THROUGH THIS AFTERNOON
WILL LIKELY BE ALONG THE ROCKY MOUNTAIN FRONT. THERE HAVE ALREADY
BEEN A FEW RAINFALL REPORTS OF 0.20"-0.30"+ IN THIS AREA WITH RADAR
ESTIMATES OF UP TO A HALF AN INCH IN A FEW SPOTS. OTHERWISE...TEMPS
AND CLOUDS LOOK GOOD.

&&

.AVIATION...
UPDATED 1755Z.

MOIST SOUTHWEST FLOW ALOFT WILL CONTINUE TO BRING AN INCREASING
CHANCE FOR SHOWERS AND POSSIBLY A FEW THUNDERSTORMS TO MONTANA THIS
AFTERNOON. VFR CONDITIONS WILL PREVAIL THROUGH 00Z FRIDAY BUT CLOUD
CEILINGS WILL LOWER WITH WIDESPREAD RAIN DEVELOPING ACROSS CENTRAL
MONTANA BY 06Z FOR A MIX OF MVFR/VFR CONDITIONS WITH AREAS IFR IN
HEAVIER RAIN. ONLY SCATTERED SHOWERS EXPECTED IN SOUTHWEST MONTANA
WITH VFR CONDITIONS PREVAILING THROUGH LATE FRIDAY MORNING. MPJ

&&

.PREV DISCUSSION...
/ISSUED 525 AM MDT THU SEP 3 2015/
THURSDAY THROUGH SATURDAY...RAINFALL AHEAD OF THE NEXT WINTER
WEATHER SYSTEM IS BEGINNING TO MOVE OVER THE AREA AND WILL
CONTINUE TO INCH EASTWARD THROUGH THE NEXT FEW DAYS AS THE UPPER
LEVEL LOW PRESSURE SYSTEM CONTINUES INLAND ACROSS THE PACIFIC
NORTHWEST. TEMPERATURES WILL BE WELL BELOW SEASONAL AVERAGES FOR
THE NEXT FEW DAYS WITH A MAJORITY OF THE AREA RECEIVING RAINFALL
TOTALS BETWEEN 1 AND 2 INCHES THROUGH THIS WEEKEND. SOME SNOWFALL
WILL BE POSSIBLE AT THE HIGHER ELEVATIONS...HOWEVER NO SIGNIFICANT
SNOWFALL IS CURRENTLY EXPECTED TO IMPACT ANY MAJOR TRANSPORTATION
PASSES. SUK

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 CWA 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 HILINE ALTHOUGH MOISTURE WILL BE LIMITED.
ZELZER

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  65  48  62  48 /  50  90  50  70
CTB  58  43  55  42 / 100  60  80 100
HLN  67  44  67  46 /  40  80  60  80
BZN  76  44  73  45 /  30  30  20  50
WEY  72  36  70  36 /  20  20  20  20
DLN  73  43  69  43 /  30  40  40  60
HVR  71  49  67  50 /  20  60  50  70
LWT  71  45  67  47 /  20  30  30  50

&&

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

$$

WEATHER.GOV/GREATFALLS



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