814
FXUS65 KTFX 171728
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1128 AM MDT SUN MAY 17 2026
AVIATION SECTION UPDATED.
KEY MESSAGES
- LIGHT MOUNTAIN SNOW AND LOWER ELEVATION RAIN WILL CONTINUE
THROUGH THE DAY.
- COOLER TEMPERATURES WILL PERSIST THROUGH TUESDAY MORNING BEFORE
MORE SEASONAL TEMPERATURES RETURN MID-WEEK.
- ANOTHER SYSTEM ARRIVES ON WEDNESDAY BRINGING ANOTHER ROUND OF
LIGHT MOUNTAIN SNOW AND LOWER ELEVATION RAIN AS WELL AS A
CHANCE FOR AFTERNOON THUNDERSTORMS.
UPDATE
/ISSUED 600 AM MDT SUN MAY 17 2026/
EARLY MORNING UPDATE HAS BEEN PUBLISHED, WITH THE PRIMARY
ADJUSTMENTS BEING TO LOWER HIGH TEMPERATURES BY SEVERAL DEGREES
WHERE PRECIPITATION WILL BE THE MOST PERSISTENT THROUGH THE DAY
AND TO INCREASE POPS BASED UPON LATEST RADAR AND HI-RES MODEL
TRENDS. OVERNIGHT LOW TEMPERATURES HAVE COOLED OFF SEVERAL DEGREES
COLDER THAN FORECASTED WHERE PRECIPITATION HAS/HAD FALLEN, WHICH
HAS INCREASED CONFIDENCE THAT ALONG WITH STRONG COLD AIR
ADVECTION BEHIND THE SOUTHWARD SURGING COLD FRONT THIS MORNING,
AND DYNAMIC COOLING PROCESSES, THAT HIGH TEMPERATURES WILL
STRUGGLE TO WARM TODAY WHERE PRECIPITATION FALLS MOST
PERSISTENTLY. OTHERWISE THE REMAINDER OF THE FORECAST REMAINS ON
TRACK AND NO OTHER ADJUSTMENTS WERE MADE. - MOLDAN
DISCUSSION
/ISSUED 600 AM MDT SUN MAY 17 2026/
- METEOROLOGICAL OVERVIEW:
AN UPPER LEVEL TROUGH WILL CONTINUE ITS WAY ACROSS THE REGION
BRINGING A CHANCE FOR LIGHT MOUNTAIN SNOW AND LOWER ELEVATION RAIN
THROUGHOUT THE DAY. AS THE TROUGH STARTS TO DEPART, NORTHERLY FLOW
BEHIND IT WILL KEEP TEMPERATURES WELL BELOW NORMAL THROUGH
MONDAY. MORE ZONAL FLOW RETURNS ON TUESDAY, ALLOWING FOR SEASONAL
TEMPERATURES TO RETURN. JUST AS TEMPERATURES START TO GRADUALLY
WARM UP, A SHORTWAVE TROUGH IS EXPECTED TO MOVE INTO THE REGION ON
WEDNESDAY BRINGING ANOTHER CHANCE FOR SHOWERS AND THUNDERSTORMS.
MOUNTAIN SNOW WILL GENERALLY STAY ABOVE PASS LEVEL FOR THIS STORM
WITH ONLY SLIGHT PROBABILITIES OF SNOW LEVELS DROPPING LOW ENOUGH
TO PROVIDE IMPACTS AT PASS LEVEL.
TOWARDS THE END OF THE WEEK CLUSTER GUIDANCE POINTS TOWARDS UPPER-
LEVEL RIDGING BUILDING ALONG THE WEST COAST BRINGING A RETURN TO
NORTHWESTERLY FLOW OVER MONTANA. THE RESULT WILL BE MORE SEASONAL TO
ABOVE-NORMAL TEMPERATURES WITH GENERALLY DRY CONDITIONS PERSISTING
ACROSS THE REGION.
- FORECAST CONFIDENCE & SCENARIOS:
SUNDAY SNOW:
OVERALL, SNOWFALL AMOUNTS HAVE DECREASED COMPARED TO PREVIOUS MODEL
RUNS WITH THE MOUNTAINS AND VALLEYS OF SOUTHWEST MONTANA EXPECTED TO
SEE AN ADDITIONAL 1 TO 3 INCHES WITH ISOLATED HIGHER AMOUNTS
POSSIBLE ALONG THE PEAKS. FOR THE NORTHERN ROCKY MOUNTAINS AND THE
LITTLE BELTS, 2 TO 4 INCHES ARE POSSIBLE AT PASS LEVEL WITH HIGHER
AMOUNTS EXPECTED ALONG THE PEAKS. BUT GENERALLY, THE MODELS HAVE
MOVED AWAY FROM THE PREVIOUSLY FORECASTED 6 TO 12 INCHES ALONG THE
PEAKS. THIS IS NOT TO SAY IT IS COMPLETELY OUT OF THE RANGE OF
POSSIBILITIES. BUT THE PROBABILITY OF OCCURRENCE NOW SITS AT AROUND
10-20%.
WHILE THERE IS STILL SOME POTENTIAL FOR ENHANCED SNOWFALL ALONG
NORTH-FACING SLOPES, THE MODELS HAVE BACKED OFF SIGNIFICANTLY
COMPARED TO PREVIOUS RUNS. IN PARTICULAR, THE PROBABILITIES FOR
SNOWFALL AMOUNTS GREATER THAN 6 INCHES HAVE DECREASED SIGNIFICANTLY
ACROSS THE REGION. THAT BEING SAID, THERE IS STILL ENOUGH SNOWFALL
EXPECTED TO PRODUCE IMPACTS THAT ARE WORTHY OF THE CURRENT SUITE OF
WINTER WEATHER ADVISORIES. SO NO CHANGES ADDITIONS OR SUBTRACTIONS
WERE MADE TO THE ADVISORIES WITH THIS FORECAST PACKAGE.
WEDNESDAY PRECIPITATION:
GIVEN THAT THIS SHORTWAVE TROUGH IS NOT EXPECTED TO BE AS COLD AS
THE CURRENT SYSTEM MOVING THROUGH, LIGHT SNOW WILL BE PRIMARILY
CONFINED TO THE HIGHER PEAKS OF THE MOUNTAINS. LOCATIONS AT AND
BELOW PASS LEVEL MAY PICK UP A FEW FLAKES BUT NOTHING LOOKS
PARTICULARLY IMPACTFUL AT THIS TIME. LOWER ELEVATIONS WILL SEE A
CHANCE FOR RAIN THROUGHOUT THE DAY WITH A CHANCE FOR THUNDERSTORMS
IN THE AFTERNOON/EVENING HOURS. CURRENTLY, THE EURO FOCUSES MORE OF
THE INSTABILITY IN CENTRAL MONTANA WHEREAS THE GFS PUSHES IT TOWARDS
SOUTHWEST MONTANA AND THE EASTERN HI-LINE. SO THE GENERALIZED 15-20%
CHANCE FOR A THUNDERSTORM ACROSS A LARGE PORTION OF THE REGION
MATCHES THE CURRENT CONFIDENCE OF SUGGESTING THERE COULD BE
SOMETHING BUT THERE IS STILL A BIT OF UNCERTAINTY AS TO WHERE IT
WILL HAPPEN. -THOR
AVIATION
17/18Z TAF PERIOD
VFR CONDITIONS WILL PREVAIL AT THE KBZN, KEKS, AND KWYS TERMINALS
DURING THIS TAF PERIOD. AT THE KBZN AND KEKS TERMINALS BETWEEN
17/18Z AND 18/02Z THERE IS A 15 - 20% CHANCE FOR RAIN AND SNOW
SHOWERS AND THUNDERSTORMS. A THE KHLN TERMINAL THERE IS A 30 - 40%
CHANCE FOR RAIN AND SNOW SHOWERS AND A 15 - 20% CHANCE FOR
THUNDER BETWEEN 17/18Z AND 17/24Z. AT THE KGTF AND KCTB TERMINALS
THERE IS A 15 - 40% CHANCE FOR RAIN AND SNOW SHOWERS BETWEEN
18/00Z AND 18/06Z. AT THE KLWT TERMINAL DURING THE MAJORITY OF
THIS TAF PERIOD THERE IS AT LEAST A 15 - 40% FOR RAIN AND SNOW
SHOWERS. ANY THUNDERSTORMS WILL PRODUCE GUSTY, ERRATIC WINDS AND
FREQUENT LIGHTNING. AT ANY SITES THAT CLEAR THERE IS A VERY LOW
CHANCE FOR PATCHY FOG TO FORM WHICH IS TOO LOW TO INCLUDE IN ANY
TAF AT THIS TIME. DURING THE MAJORITY OF THIS TAF PERIOD THERE
WILL BE MOUNTAIN OBSCURATION ACROSS NORTH-CENTRAL, CENTRAL, AND
SOUTHWESTERN MONTANA. -IG
PRELIMINARY POINT TEMPS/POPS
GTF 44 30 53 29 / 80 20 10 0
CTB 43 25 55 30 / 70 10 0 0
HLN 46 32 55 32 / 60 10 10 0
BZN 48 27 51 26 / 30 20 20 0
WYS 38 22 44 19 / 10 20 0 0
DLN 47 25 51 26 / 30 20 0 0
HVR 46 29 54 28 / 80 40 10 0
LWT 42 27 45 25 / 80 60 40 0
TFX WATCHES/WARNINGS/ADVISORIES
WINTER WEATHER ADVISORY UNTIL MIDNIGHT MDT TONIGHT FOR BIG BELT,
BRIDGER AND CASTLE MOUNTAINS-EAST GLACIER PARK REGION-ELKHORN
AND BOULDER MOUNTAINS-LITTLE BELT AND HIGHWOOD MOUNTAINS-
SOUTHERN ROCKY MOUNTAIN FRONT-UPPER BLACKFOOT AND MACDONALD PASS.
HTTP://WWW.WEATHER.GOV/GREATFALLS
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