389
FXUS65 KTFX 150839
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
239 AM MDT MON SEP 15 2025
KEY MESSAGES
- UNSETTLED CONDITIONS WITH DAILY CHANCES FOR SHOWER AND
THUNDERSTORMS WILL CONTINUE INTO THE DAY ON TUESDAY.
- NEAR NORMAL TEMPERATURES THROUGH TUESDAY WILL WARM BACK ABOVE
NORMAL THROUGH THE REMAINDER OF THE WORK WEEK AND THEN WELL
ABOVE NORMAL FOR THE WEEKEND.
- WINDS BEGIN TO INCREASE FROM SUNDAY INTO NEXT MONDAY.
DISCUSSION
- METEOROLOGICAL OVERVIEW:
DAILY CHANCES FOR SHOWERS AND THUNDERSTORMS WILL CONTINUE THROUGH
THE DAY ON TUESDAY AS A SLOW MOVING UPPER LEVEL DISTURBANCE MOVES
OVER THE NORTHERN ROCKIES. HIGH TEMPERATURES THROUGH THIS UNSETTLED
TIMEFRAME WILL BE NEAR NORMAL ACROSS ALL OF SOUTHWEST THROUGH NORTH
CENTRAL MONTANA, WITH OVERALL LIGHT WINDS OUTSIDE OF SHOWER AND
THUNDERSTORM ACTIVITY. UPPER LEVEL RIDGING WILL THEN BEGIN TO BUILD-
IN OVER THE NORTHERN ROCKIES FROM THE MIDDLE THROUGH THE END OF THE
WORK WEEK, WHICH WILL IN-TURN BRING PREDOMINATELY DRY CONDITIONS AND
WARMING TEMPERATURES. HIGH TEMPERATURES BENEATH THIS RIDGE WILL WARM
BACK ABOVE NORMAL ON THURSDAY AND FRIDAY, WITH READINGS WARMING
FURTHER TO WELL ABOVE NORMAL FOR THE UPCOMING WEEKEND AS THE UPPER
LEVEL RIDGE BEGINS TO FLATTEN. THIS FLATTENING OF THE UPPER LEVEL
RIDGE WILL NOT ONLY BRING INCREASING TEMPERATURES FOR THE WEEKEND,
BUT ALSO INCREASING WINDS TO MUCH OF THE NORTHERN ROCKIES. -
MOLDAN
- FORECAST CONFIDENCE & SCENARIOS:
BRIEF HEAVY DOWNPOURS THROUGH TUESDAY :
SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS ARE EXPECTED ACROSS
PORTIONS OF SOUTHWEST THROUGH NORTH CENTRAL MONTANA AS A SLOW MOVING
UPPER LEVEL DISTURBANCE DRIFTS EAST OVER THE NORTHERN ROCKIES, MOST
NOTABLY ACROSS CENTRAL MONTANA BETWEEN THE MONTANA HWY 200 AND US
HWY 12 CORRIDORS AND THEN WEST OF THE I-15 CORRIDOR UP TO THE ROCKY
MOUNTAIN FRONT. WITH PWATS RUNNING BETWEEN 1 TO 2 STANDARD
DEVIATIONS ABOVE NORMAL AND STORM MOTIONS OF BETWEEN 10-30 MPH SOME
BRIEF PERIODS OF HEAVY RAIN ARE POSSIBLE BENEATH THE STRONGEST
SHOWERS AND THUNDERSTORMS. WITH THE LATEST 75TH PERCENTILE HREF
GUIDANCE SUPPORTING HOURLY RAINFALL RATES OF BETWEEN 0.1-0.25" IT IS
NOT OUT OF THE REALM OF POSSIBILITIES (25% CHANCE FOR HOURLY
RAINFALL AMOUNTS TO BE IN EXCESS OF 0.1-0.25") FOR SOME PONDING OF
WATER IN POOR DRAINAGE OR URBAN AREAS OVER THIS TIMEFRAME IF A
STRONG SHOWER OR STORM MOVES OVERHEAD.
GUSTY WINDS FROM SATURDAY NIGHT THROUGH NEXT MONDAY :
INCREASING CROSS BARRIER FLOW WITHIN A QUASI-ZONAL PATTERN ALOFT
WILL LEAD TO INCREASING SOUTH TO WEST SURFACE WINDS ACROSS SOUTHWEST
THROUGH NORTH CENTRAL MONTANA, MOST NOTABLY ALONG THE ROCKY MOUNTAIN
FRONT AND THE IMMEDIATE PLAINS OUT TO THE I-15 CORRIDOR. WHILE
CLIMATE ANOMALY INDICATORS SUCH AS THE ECMWF EFIS AND NAEFS DO NOT
CURRENTLY SUPPORT ANY UNUSUAL OR EXTREME WINDS VALUES THROUGHOUT THE
PERIOD, SEVERAL INDIVIDUAL ENSEMBLE MEMBERS WITHIN THE ECMWF AND
GEFS DO SUPPORT WIND GUSTS IN EXCESS OF 45 MPH ACROSS THE
AFOREMENTIONED AREAS. ADDITIONALLY, LATEST NBM PROBABILISTIC DATA
FOR WIND GUSTS IN EXCESS OF 45 MPH RANGE FROM A 30-55% CHANCE ON
BOTH SUNDAY AND MONDAY, WITH GENERALLY A 10-30% CHANCE FOR WIND
GUSTS IN EXCESS OF 55 MPH ON EACH RESPECTIVE DAY. WHILE THESE WIND
GUSTS (I.E. 45 AND 55 MPH) ARE NOT ATYPICAL FOR SEPTEMBER THEY WILL
MARK A CHANGE FROM THE RELATIVELY LIGHT WINDS AS OF LATE. - MOLDAN
AVIATION
15/06Z TAF PERIOD.
INITIAL CONCERN THIS TAF PERIOD WILL BE FOR GUSTY OUTFLOW WINDS,
MOSTLY ACROSS THE PLAINS OF NORTH-CENTRAL MONTANA. THESE WINDS
SHOULD SLOWLY SUBSIDE THROUGH 09Z OR SO. ATTENTION THEN TURNS TO
INTERMITTENT SHOWERS THROUGH THE REMAINDER OF THE TAF PERIOD, WITH A
FEW THUNDERSTORMS POSSIBLE IN THE AFTERNOON AND EARLY EVENING
MONDAY. -AM
PRELIMINARY POINT TEMPS/POPS
GTF 72 52 73 49 / 40 60 20 0
CTB 68 49 73 43 / 30 30 20 0
HLN 69 50 73 49 / 30 30 30 0
BZN 66 44 67 43 / 60 50 50 10
WYS 59 31 62 31 / 70 30 30 0
DLN 63 40 67 41 / 50 40 20 0
HVR 76 52 77 47 / 10 20 20 0
LWT 71 48 69 47 / 30 60 60 20
TFX WATCHES/WARNINGS/ADVISORIES
NONE.
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