561
FXUS65 KTFX 182339
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
539 PM MDT MON MAY 18 2026
AVIATION SECTION UPDATED.
KEY MESSAGES
- IT WILL BE COLD THROUGH TUESDAY MORNING.
- ISOLATED RAIN AND SNOW SHOWERS WILL AFFECT NORTH-CENTRAL,
CENTRAL, AND SOUTHWESTERN MONTANA THROUGH FRIDAY WITH THE
HEAVIEST AND MOST WIDESPREAD PRECIPITATION WEDNESDAY THROUGH
THURSDAY.
- IT WILL GRADUALLY WARM UP TUESDAY AFTERNOON THROUGH THE
WEEKEND.
DISCUSSION
- METEOROLOGICAL OVERVIEW:
THIS AFTERNOON AN UPPER-LEVEL TROUGH REMAINS OVER NORTH-CENTRAL,
CENTRAL, AND SOUTHWESTERN MONTANA. AS A RESULT RAIN/SNOW SHOWERS AND
COLD TEMPERATURES (WELL-BELOW) SEASONAL AVERAGES WILL LINGER ACROSS
THE AREA. THIS AFTERNOON RAIN/SNOW SHOWERS WILL PRIMARILY BE
CONFINED TO THE CONTINENTAL DIVIDE WITH A FEW ISOLATED RAIN SHOWERS
SPREADING EASTWARD TO THE PLAINS OF NORTH-CENTRAL MONTANA. ON
TUESDAY THE UPPER-LEVEL TROUGH REMAINS OVER NORTH-CENTRAL, CENTRAL,
AND SOUTHWESTERN MONTANA IN THE MORNING BEFORE NORTHWEST FLOW ALOFT
MOVES OVER THE AREA BY THE AFTERNOOON. THIS WILL KEEP COLD
TEMPERATURES ACROSS NORTH-CENTRAL, CENTRAL, AND SOUTHWESTERN MONTANA
TUESDAY MORNING BEFORE THEY GRADUALLY WARM UP BY TUESDAY AFTERNOON.
TUESDAY AFTERNOON THERE WILL BE ISOLATED LOWER-ELEVATION RAIN
SHOWERS AND MOUNTAIN SNOW SHOWERS DUE TO THE NORTHWEST FLOW ALOFT.
ADDITIONALLY THERE WILL BE ENOUGH INSTABILITY AROUND IN THE
AFTERNOON THAT THERE IS THE POTENTIAL FOR A FEW RUMBLES OF THUNDER.
ON WEDNESDAY AN UPPER-LEVEL TROUGH, ASSOCIATED WITH A CANADIAN COLD
FRONT, MOVES OVER NORTH-CENTRAL, CENTRAL, AND SOUTHWESTERN MONTANA.
THIS WILL BRING RAIN TO LOWER-ELEVATIONS AND SNOW TO MOUNTAIN
LOCATIONS ON WEDNESDAY. ON WEDNESDAY TEMPERATURES WILL COOL DOWN TO
SLIGHTLY BELOW SEASONAL AVERAGES. WEDNESDAY AFTERNOON SOME
INSTABILITY WILL BUILD AND ALLOW A FEW RUMBLES OF THUNDER TO OCCUR
ACROSS NORTH-CENTRAL, CENTRAL, AND SOUTHWESTERN MONTANA. ON THURSDAY
THE UPPER-LEVEL TROUGH REMAINS OVER NORTH-CENTRAL, CENTRAL, AND
SOUTHWESTERN MONTANA. THIS WILL ALLOW COOLER TEMPERATURES WITH
WIDESPREAD PRECIPITATION TO LINGER OVER THE AREA ON THURSDAY. ON
FRIDAY NORTHWEST FLOW ALOFT MOVES OVER NORTH-CENTRAL, CENTRAL, AND
SOUTHWESTERN MONTANA. THIS WILL ALLOW TEMPERATURES TO WARM UP TO
NEAR SEASONAL AVERAGES WITH ISOLATED SHOWERS AND THUNDERSTORMS
FRIDAY AFTERNOON. ON SATURDAY AND SUNDAY AN UPPER-LEVEL RIDGE/ZONAL
FLOW BUILDS IN OVER NORTH-CENTRAL, CENTRAL, AND SOUTHWESTERN
MONTANA. THIS WILL BRING WARM, MOSTLY DRY, AND WINDY WEATHER TO THE
AREA FOR MEMORIAL DAY WEEKEND. -IG
- FORECAST CONFIDENCE & SCENARIOS:
ON TUESDAY MORNING THERE IS A 30 - 70% CHANCE FOR LOW TEMPERATURES
OF 28 DEGREES OR COLDER ACROSS THE LOWER-ELEVATIONS OF NORTH-
CENTRAL, CENTRAL, AND SOUTHWESTERN MONTANA. ON TUESDAY THERE IS A
20% CHANCE FOR THUNDER ACROSS NORTH-CENTRAL MONTANA. ON WEDNESDAY
THERE IS A 15 - 30% CHANCE FOR THUNDER ACROSS NORTH-CENTRAL,
CENTRAL, AND SOUTHWESTERN MONTANA. ON WEDNESDAY ALONG THE ROCKY
MOUNTAIN FRONT THERE IS GREATER THAN A 50 - 70% CHANCE FOR A HALF
INCH OF LIQUID PRECIPITATION. ON WEDNESDAY ALONG THE HIGHWAY 200
CORRIDOR BETWEEN GREAT FALLS AND LEWISTOWN THERE IS 25 - 40%
CHANCE FOR A HALF INCH OF LIQUID PRECIPITATION OR GREATER.
ELSEWHERE ACROSS NORTH-CENTRAL, CENTRAL, AND SOUTHWESTERN MONTANA
THERE IS A 10 - 40% CHANCE FOR A QUARTER INCH OF LIQUID
PRECIPITATION OR GREATER ON WEDNESDAY. WEDNESDAY THROUGH THURSDAY
THERE IS GREATER THAN A 50% CHANCE FOR 2 INCHES OF SNOW OR GREATER
ACROSS THE MOUNTAINS OF NORTH-CENTRAL, CENTRAL, AND SOUTHWESTERN
MONTANA. ON SATURDAY AND SUNDAY THERE IS A 20 - 50% CHANCE FOR
WIND GUSTS OF 40 MPH OR GREATER. -IG
AVIATION
19/00Z TAF PERIOD
A FEW LIGHT RAIN SHOWERS WILL AFFECT THE CWA THROUGH THE EARLY
EVENING HOURS, BEFORE DIMINISHING IN COVERAGE BY 03Z. GENERALLY
VFR CONDITIONS ARE EXPECTED OVERNIGHT, BUT SOME PATCHY FOG IS
POSSIBLE. ANOTHER ROUND OF LIGHT SHOWERS IS POSSIBLE ON TUESDAY.
THERE IS JUST ENOUGH INSTABILITY THAT A THUNDERSTORM WILL BE
POSSIBLE ON TUE AFTERNOON OVER NORTH CENTRAL MT, BUT THE
PROBABILITY IS TO LOW TO INCLUDE AT A TERMINAL SITE AT THIS TIME.
MOUNTAINS/PASSES WILL BE OBSCURED AT TIMES ACROSS THE CWA BY
CLOUDS/PRECIP. BRUSDA
PRELIMINARY POINT TEMPS/POPS
GTF 30 64 40 56 / 0 40 20 70
CTB 29 63 37 53 / 30 20 30 90
HLN 30 65 38 60 / 10 30 30 40
BZN 24 62 33 60 / 0 0 30 20
WYS 15 54 25 54 / 0 10 20 20
DLN 25 61 33 61 / 0 10 20 10
HVR 28 68 40 60 / 0 40 60 50
LWT 26 60 36 56 / 0 20 30 70
TFX WATCHES/WARNINGS/ADVISORIES
NONE.
HTTP://WWW.WEATHER.GOV/GREATFALLS
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