904
FXUS65 KTFX 180147
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
747 PM MDT SUN MAY 17 2026
KEY MESSAGES
- PRECIPITATION LARGELY SUBSIDE LATER THIS EVENING.
- TWO COLD NIGHTS AHEAD, WITH LOWS IN THE 20S FOR MANY AREAS.
- SLOWLY TRENDING WARMER THROUGH THE WEEK, WITH A FEW ROUNDS OF
PRECIPITATION AT TIMES.
UPDATE
UPDATED FORECAST IS OUT. MAIN CHANGE WAS TO END THE WINTER WEATHER
ADVISORY OVER THE FAR NORTHERN AND SOUTHER PORTIONS OF THE AREA,
ALONG WITH INCREASING POPS OVER CENTRAL MT THIS EVENING. A BAND OF
LIGHT RAIN/SNOW CONTINUES TO MOVE SOUTHWARD THROUGH THE FORT
BENTON/GREAT FALLS/SIEBEN FLATS AREA. ADDITIONAL SNOWFALL THROUGH
THIS EVENING OF AN INCH OR TWO IS POSSIBLE IN THE REMAINING
ADVISORY AREA THAT GOES THROUGH MIDNIGHT. OTHERWISE, ANY SNOW AT
LOWER ELEVATIONS WILL MOSTLY JUST MELT ON CONTACT. SOME PATCHY FOG
IS POSSIBLE BY MORNING IN AREAS THAT HAD RAIN/SNOW TODAY.
OVERNIGHT LOWS LOOK ON TRACK, WITH A POTENTIAL FROST FOR SOME
AREAS AS WELL MON MORNING. A FEW ISOLATED STORMS MON/TUE ALONG THE
DIVIDE FROM LINCOLN NORTH TO THE ST. MARY AND ACROSS THE HI-LINE
AREA ON TUE, OTHERWISE, THE NEXT MORE WIDESPREAD LOWER ELEVATION
RAIN AND MOUNTAIN SNOW ARRIVES ON WED. BRUSDA
DISCUSSION
/ISSUED 553 PM MDT SUN MAY 17 2026/
- METEOROLOGICAL OVERVIEW:
THE CORE OF THE UPPER LEVEL TROUGHING IS BEGINNING TO TRACK EAST OF
THE REGION THIS AFTERNOON, RESULTING IN A NORTHERLY FLOW ALOFT.
NORTHERLY/NORTHWESTERLY UPSLOPE PRECIPITATION CONTINUES THIS
AFTERNOON, WITH ADDITIONAL PRECIPITATION DEVELOPING IN THE FORM OF
SHOWERS, MAINLY ACROSS SOUTHWEST MT AND VICINITY.
LOSS OF DAYTIME HEATING AND UPSLOPE FLOW WILL ALLOW FOR
PRECIPITATION TO COME TO AN END THIS EVENING. LIGHTER NORTHERLY
FLOW ALOFT CONTINUES INTO TONIGHT THOUGH, WHICH WILL ALLOW FOR
QUITE A COLD NIGHT ACROSS THE REGION. MOST LOCATIONS LOOK TO FALL
INTO THE 20S, WITH A FEW COLD PRONE LOCATIONS DIPPING INTO THE
TEENS. SOME PATCHY FOG CANNOT BE RULED OUT TONIGHT, THOUGH
COVERAGE WILL DEPEND ON WHERE MOST PRECIPITATION FALLS THROUGH THE
REMAINDER OF THE DAY TODAY.
COOL AIR ALOFT PERSISTS INTO MONDAY, WHICH WILL COMBINE WITH DAYTIME
HEATING TO RESULT IN A MIX OF RAIN AND SNOW SHOWERS ACROSS THE
REGION. SLIGHTLY WARMER AIR ALOFT BEGINS TO MOVE IN MONDAY NIGHT,
THOUGH LINGERING COOLER AIR AT THE SURFACE WILL RESULT IN ANOTHER
COLD NIGHT BEFORE TEMPERATURES TREND CLOSER TO AVERAGE DURING THE
DAY TUESDAY. A FEW AFTERNOON SHOWERS WILL BE AROUND TUESDAY, BUT
OVERALL COVERAGE OF THE SHOWERS IS QUESTIONABLE AT THIS TIME.
SEVERAL DISTURBANCES PASS ACROSS THE REGION WITHIN A NORTHWEST FLOW
ALOFT WEDNESDAY ONWARD, WHICH WILL ALLOW FOR A COUPLE STRETCHES OF
PRECIPITATION. TEMPERATURES OVER THIS TIMEFRAME SLOWLY TREND WARMER,
THOUGH THIS TREND WILL BE BRIEFLY INTERRUPTED BY THE SHOWERY
CONDITIONS AT TIMES. -AM
- FORECAST CONFIDENCE & SCENARIOS:
COLD TEMPERATURES TONIGHT AND MONDAY NIGHT:
THE PROBABILITY FOR AN OVERNIGHT LOW BELOW 32F IS NEARLY 100% IN ALL
AREAS TONIGHT. THAT PROBABILITY ISN'T QUITE AS HIGH FOR MONDAY NIGHT,
BUT IS AT OR GREATER THAN 50% IN THE OVERWHELMING MAJORITY OF AREAS.
PRECIPITATION WEDNESDAY:
A SHARPER TROUGH LOOKS TO PASS ACROSS THE REGION WEDNESDAY INTO
WEDNESDAY NIGHT. THIS TROUGH LOOKS COOL ENOUGH TO RESULT IN SOME
MOUNTAIN SNOW, BUT MOST PRECIPITATION LOOKS TO FALL AS RAIN. AREAS
ALONG THE ROCKY MOUNTIAN FRONT AND ACROSS CENTRAL MONTANA TERRAIN
HAVE A ROUGHLY 30% PROBABILITY FOR 0.25" LIQUID FROM THIS SYSTEM. -AM
AVIATION
18/00Z TAF PERIOD
SOUTHWEST MONTANA (KBZN, KEKS, KWYS): VFR CONDITIONS WILL
GENERALLY PREVAIL THROUGH THE TAF PERIOD. LOW CLOUDS TO MID-LEVEL
CLOUDS ARE EXPECTED TO STICK AROUND THROUGH THE NIGHT WITH
MOUNTAIN OBSCURATION REMAINING A CONCERN THROUGH MONDAY MORNING.
THERE MAY BE PERIODS WHERE CIGS DIP DOWN INTO MVFR TERRITORY AT
KBZN AND KEKS BUT CONFIDENCE WAS TOO LOW TO INCLUDE IT IN THE TAF.
WHILE LOW CLOUDS ARE EXPECTED TO STICK AROUND ACROSS SOUTHWEST
MONTANA, THERE IS A CHANCE FOR SOME ISOLATED CLEARING AND ANY
LOCATION THAT IS ABLE TO CLEAR OUT MAY DEVELOP FOG. RIGHT NOW
THERE IS A 40% CHANCE FOR FOG DEVELOPING AT KWYS DURING THE NIGHT
PRIMARILY BETWEEN 18/06Z AND 18/15Z. KBZN AND KEKS BOTH HAVE A 20%
CHANCE OF FOG DEVELOPMENT DURING THIS TIME.
CENTRAL/NORTH-CENTRAL MONTANA: SCATTERED SNOW SHOWERS WILL
CONTINUE ACROSS THE REGION FOR AT LEAST THE NEXT 3 TO 4 HOURS
BEFORE GRADUALLY TAPERING OFF DURING THE OVERNIGHT HOURS. MVFR TO
IFR CIGS AND VIS ARE EXPECTED UNDER HEAVIER SNOW SHOWERS WITH LOW
CLOUDS EXPECTED TO STICK AROUND THROUGH THE REMAINDER OF THE NIGHT
BEFORE MOVING OUT OF THE AREA MONDAY AFTERNOON. DURING THIS TIME,
MOUNTAIN OBSCURATION WILL REMAIN A CONCERN THROUGH AT LEAST THE
FIRST HALF OF THE TAF PERIOD. -THOR
PRELIMINARY POINT TEMPS/POPS
GTF 28 53 30 65 / 90 10 0 10
CTB 24 54 30 63 / 20 10 10 20
HLN 31 56 32 65 / 30 10 0 0
BZN 25 51 25 61 / 20 20 10 0
WYS 21 44 18 54 / 10 10 10 0
DLN 25 51 26 60 / 20 10 0 0
HVR 27 55 28 68 / 40 10 0 0
LWT 27 47 25 60 / 60 30 10 10
TFX WATCHES/WARNINGS/ADVISORIES
WINTER WEATHER ADVISORY UNTIL MIDNIGHT MDT TONIGHT FOR LITTLE
BELT AND HIGHWOOD MOUNTAINS-SOUTHERN ROCKY MOUNTAIN FRONT-UPPER
BLACKFOOT AND MACDONALD PASS.
HTTP://WWW.WEATHER.GOV/GREATFALLS
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