156
FXUS65 KTFX 302054
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
254 PM MDT SAT MAY 30 2026
KEY MESSAGES
- WIDESPREAD MODERATE TO LOCALLY HEAVY RAIN THROUGH SUNDAY MORNING.
- ISOLATED THUNDERSTORMS ACROSS EASTERN PORTIONS OF NORTH-CENTRAL
MONTANA THROUGH THIS EVENING.
- MINOR FLOODING POSSIBLE IN AREAS OF POOR DRAINAGE WITH ELEVATED STREAMFLOWS
ACROSS PRIMARILY WESTERN PORTIONS OF NORTH-CENTRAL MONTANA.
- UNSETTLED WEATHER WITH BELOW AVERAGE TEMPERATURES THROUGH
TUESDAY WITH WARMING TEMPERATURES AND SOME DRYING MID TO LATE
NEXT WEEK.
DISCUSSION
- METEOROLOGICAL OVERVIEW:
AN UPPER LEVEL LOW CENTERED OVER SW WY THIS AFTERNOON WILL SLOWLY
LIFT NORTHWARD INTO MT SUNDAY AND STALL FOR A PERIOD BEFORE LIFTING
NORTH OF THE BORDER EARLY NEXT WEEK AS THE LARGER SCALE OMEGA
BLOCKING PATTERN OF WHICH IT IS A PART OF WEAKENS. SHOWERS ALREADY
COVERING MUCH OF THE AREA EARLY THIS AFTERNOON WILL CONTINUE TO
TRACK NORTHWESTWARD IN MOIST SOUTHEAST TO EASTERLY MID-LEVEL FLOW
THROUGH THIS EVENING WITH A FEW EMBEDDED THUNDERSTORMS POSSIBLE
THROUGH EARLY THIS EVENING, MAINLY ACROSS EASTERN PORTIONS OF
CENTRAL/NORTH-CENTRAL MT. PRECIPITATION EVOLVES INTO A MORE TROWAL-
LIKE FEATURE LATER TONIGHT THROUGH SUNDAY MORNING AS THE UPPER LOW
LIFTS INTO THE STATE AND AN AREA OF WIDESPREAD (NON-CONVECTIVE)
PRECIPITATION PIVOTS AROUND THE LOW WITH AN AXIS CENTERED ACROSS
WESTERN PORTIONS OF NORTH-CENTRAL MT.
GUSTY NORTH TO NORTHWEST WINDS INCREASE TONIGHT AND CONTINUE THROUGH
SUNDAY AS SURFACE LOW PRESSURE LIFTS NORTH INTO SK WITH COOLER AIR
AND SURFACE HIGH PRESSURE SLIDING SOUTH ON ITS BACK SIDE OUT OF
SOUTHERN AB. THIS WILL ALSO FURTHER COOL TEMPERATURES ACROSS THE AREA
WITH MOST LOWER ELEVATION LOCATIONS HOLDING IN THE LOWER 50S THROUGH
SUNDAY. SNOW LEVELS ARE INITIALLY FAIRLY HIGH (8-10KFT) TONIGHT BUT
LOWER TO 7-8KFT ON SUNDAY, LIMITING CHANCES FOR ANY ACCUMULATION OR
IMPACTS TO THE HIGHEST TERRAIN ABOVE PASSES.
THE UPPER LEVEL LOW SLOWLY LIFTS NORTH INTO SOUTHERN AB/SK EARLY
NEXT WEEK. WHILE WIDESPREAD PRECIPITATION DIMINISHES TO SHOWERS FOR
MOST AREAS SUNDAY NIGHT, CYCLONIC FLOW AROUND THE LOW AND COOL
AIR ALOFT WILL MAINTAIN BELOW AVERAGE TEMPERATURES AND LIKELY A
DAILY RISK FOR SHOWERS AND POSSIBLY SOME AFTERNOON THUNDERSTORMS
THROUGH AT LEAST TUESDAY. TEMPERATURES WARM BACK TO NEAR SEASONAL
LEVELS MID TO LATE NEXT WEEK WITH SOME DRYING, BUT THERE IS LOWER
CONFIDENCE IN THE TIMING OF A WEAKER SHORTWAVE AROUND THURSDAY AS
WELL AS THE ARRIVAL OF THE NEXT TROUGH INTO THE PACIFIC NW NEXT
WEEKEND, BOTH OF WHICH COULD GENERATE AN INCREASED CHANCE FOR
THUNDERSTORMS. HOENISCH
- FORECAST CONFIDENCE & SCENARIOS:
AN UNSTABLE AIRMASS ACROSS NORTHEAST MT EXTENDS AS FAR WEST AS HILL
AND BLAINE COUNTIES AND MAY SUPPORT THE DEVELOPMENT OF A STRONGER
THUNDERSTORM OR TWO THERE THROUGH THIS EVENING. OTHERWISE,
THUNDERSTORM ACTIVITY TRACKING WEST/NORTHWEST OUT OF EASTERN MT
THROUGH THIS EVENING WILL WEAKEN BUT BRING THE RISK FOR EMBEDDED
INSTANCES OF HEAVIER RAINFALL/RATES.
OVERALL CONFIDENCE IN FORECAST PRECIPITATION AMOUNTS THROUGH
SUNDAY NIGHT REMAINS GOOD WITH AREAS ALONG AND WEST OF I-15 FROM
CUT BANK SOUTH TO GREAT FALLS AND THE LITTLE BELTS WEST TO THE
CONTINENTAL DIVIDE AND HELENA AND SOUTH THROUGH THE BIG BELTS AND
MUCH OF NORTHERN GALLATIN COUNTY HAVING A 90% OR HIGHER
PROBABILITY FOR 1.00" OR GREATER PRECIPITATION AMOUNTS. 2.00" OR
GREATER AMOUNTS WILL LIKELY DEPEND ON WHERE EXACTLY THE TROWAL
FEATURE SETS UP WITH AREAS FROM GLACIER COUNTY SOUTHEAST THROUGH
CASCADE COUNTY AND THE LITTLE BELTS MOST PROBABLE(40-60% CHANCE).
3.00" OR GREATER AMOUNTS WILL BE LIMITED AND MOST LIKELY TO OCCUR
WHERE UPSLOPE ENHANCEMENT OCCURS SUNDAY. THIS INCLUDES AREAS NEAR
HIGHWOODS AND NORTH SLOPES OF THE LITTLE BELTS WHERE PROBABILITIES
ARE AS HIGH AS 60%, DECREASING TO AROUND 30% AT GREAT FALLS.
HOENISCH
AVIATION
30/18Z TAF PERIOD
SHOWERS WILL CONTINUE TO FILL IN ACROSS THE REGION TODAY, LEADING
TO WIDESPREAD COVERAGE BY THE EVENING. WEAK INSTABILITY THIS
AFTERNOON WILL ALLOW FOR SOME MODERATE TO HEAVY SHOWERS/ISOLATED
THUNDERSTORMS TO DEVELOP. HOWEVER, THE THUNDERSTORM RISK IS MORE
LIKELY TOWARDS CENTRAL MT (BY KLWT). RAIN WILL TURN MORE
STRATIFORM LATER THIS EVENING THROUGH SUNDAY. MVFR TO IFR
VISIBILITIES ARE EXPECTED AT TIMES THROUGHOUT THE TAF PERIOD FROM
CEILINGS AND VISIBILITY. BREEZY WEST/NORTHWEST WINDS PICK UP LATE
SATURDAY/SUNDAY MORNING, WITH THE HIGHEST WINDS EXPECTED ALONG THE
HI-LINE. CLOUD OBSCURATION WILL BE PERSISTENT THROUGH THE TAF
PERIOD FROM PRECIPITATION AND LOW CEILINGS. -WILSON
HYDROLOGY
WIDESPREAD RAINFALL AMOUNTS OF THE MAGNITUDE EXPECTED THROUGH SUNDAY
NIGHT ARE NOT UNUSUAL FOR LATE SPRING WEATHER SYSTEMS AND CLIMATE
DATA SHOWS A RECURRENCE INTERVAL OF ABOUT EVERY 2-5 YEARS. RECENT
DRYNESS AND LOWER THAN AVERAGE STREAMFLOWS DURING WHAT WOULD
TYPICALLY BE PEAK SNOWMELT WILL HELP TO MITIGATE SOME OF THE RUNOFF
FROM THIS PRECIPITATION AS WELL. SOME MINOR FLOODING/PONDING OF WATER
IN LOW-LYING FIELDS AND URBAN AREAS WITH POOR DRAINAGE IS THE MAIN
CONCERN IN AREAS THAT RECEIVE 2" OR MORE RAINFALL THROUGH SUNDAY.
CREEKS EMANATING FROM THE ROCKY MTN FRONT, LITTLE BELTS AND
HIGHWOODS ARE LIKELY TO SEE INCREASED VOLUME AND MAY EXCEED BANKS.
THE RISK FOR INTENSE PRECIPITATION RATES IS MAINLY WITH DECAYING
CONVECTION THROUGH THIS EVENING, BUT THIS WILL BE MONITORED FOR
POTENTIAL IMPACTS TO MORE SENSITIVE AREAS INCLUDING RECENT BURN
SCARS AND AREAS OF STEEP TERRAIN. THE RISK FOR FLOODING ALONG THE
SUN RIVER AND OTHER RIVERS ORIGINATING ALONG THE ROCKY MOUNTAIN
FRONT HAS DECREASED WITH NEWER FORECAST DATA, HOWEVER A RISE TO
AROUND BANKFUL IS STILL EXPECTED AND WILL CONTINUE TO BE MONITORED
AS WELL. HOENISCH
PRELIMINARY POINT TEMPS/POPS
GTF 46 52 42 59 / 100 100 80 40
CTB 41 49 37 52 / 100 100 80 70
HLN 44 55 42 63 / 100 80 50 50
BZN 40 54 36 64 / 90 80 20 40
WYS 35 54 29 63 / 60 60 30 20
DLN 41 59 37 63 / 90 50 20 50
HVR 45 58 39 59 / 80 80 70 50
LWT 42 52 37 59 / 80 90 60 40
TFX WATCHES/WARNINGS/ADVISORIES
FLOOD WATCH THROUGH MONDAY AFTERNOON FOR CASCADE COUNTY BELOW
5000FT-EAST GLACIER PARK REGION-EASTERN GLACIER, WESTERN TOOLE,
AND CENTRAL PONDERA-EASTERN PONDERA AND EASTERN TETON-GATES OF
THE MOUNTAINS-NORTHERN HIGH PLAINS-SOUTHERN HIGH PLAINS-SOUTHERN
ROCKY MOUNTAIN FRONT.
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