171
FXUS65 KTFX 041010
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
410 AM MDT SUN MAY 4 2025
KEY MESSAGES
- ACTIVE WEATHER THROUGH TUESDAY WITH WIDESPREAD SOAKING RAIN
AND SOME MOUNTAIN SNOW.
- WARMER AND DRIER FOR MIDWEEK AS UPPER LEVEL RIDGING BUILDS
INTO THE AREA.
- ADDITIONAL LIGHT RAINFALL POSSIBLE LATE THURSDAY OR FRIDAY.
DISCUSSION
- METEOROLOGICAL OVERVIEW:
UPPER LEVEL RIDGING THAT WAS PRESENT OVER THE NORTHERN ROCKIES
LATE LAST WEEK WILL CONTINUE ITS TREK TO THE EAST TODAY, ALLOWING
A DEEP UPPER LEVEL TROUGH TO TAKE ITS PLACE. AS IT DOES SO,
TEMPERATURES WILL FALL FROM THE 80S YESTERDAY TO THE 50S ALONG THE
DIVIDE, WITH 60S AND LOW 70S FOR MOST OF THE REST OF THE AREA
TODAY. IN ADDITION TO THE COOLER TEMPERATURES TODAY, A FEW SHOWERS
AND THUNDERSTORMS ARE EXPECTED TO DEVELOP DURING THE AFTERNOON,
FIRST ACROSS SOUTHWESTERN MONTANA BEFORE SPREADING FURTHER NORTH
AND SPREADING ACROSS THE PLAINS DURING THE EVENING HOURS. RAIN
WILL CONTINUE INTO THE DAY ON MONDAY AS DIFLUENCE SETS UP ALOFT,
POTENTIALLY ALLOWING FOR A BAND OF HEAVIER PRECIPITATION TO SET UP
IN AN SW TO NE LINE.
AS THE RAIN CONTINUES TO FALL ON MONDAY, COOLER AIR WILL CONTINUE
TO POUR INTO THE NORTHERN ROCKIES, WHICH WILL CAUSE SNOW LEVELS
TO GRADUALLY LOWER, EVENTUALLY REACHING AS LOW AS 5000 FEET OR SO.
THIS WILL BRING SOME LATE SEASON SNOWFALL TO THE MID AND UPPER
ELEVATIONS. WHILE ACCUMULATIONS WILL GENERALLY BE ON THE LIGHTER
SIDE (1-2 INCHES OUTSIDE OF THE LITTLE BELTS), THE HEAVY, WET
NATURE OF THE SNOWFALL MAY STILL RESULT IN SOME DAMAGE TO
VULNERABLE TREES.
UPPER LEVEL RIDGING WILL RETURN TO THE AREA FOR THE SECOND HALF
OF THE WEEK, ALLOWING TEMPERATURES TO CLIMB BACK TO ABOVE AVERAGE
FOR THE SECOND HALF OF THE WEEK. WHILE MOST OF THE SECOND HALF OF
THE WEEK WILL BE DRY, A PASSING DISTURBANCE MAY ALLOW FOR A FEW
SHOWERS TO DEVELOP AROUND THURSDAY AS THE RIDGE BUILDS.
- FORECAST CONFIDENCE & SCENARIOS:
THE MAIN AREA OF UNCERTAINTY REMAINS WITH THE UPCOMING RAIN EVENT
EARLY THIS WEEK. OVERALL, THERE SEEMS TO BE GOOD AGREEMENT IN A
WIDESPREAD SOAKING RAINFALL ACROSS NORTH CENTRAL AND SOUTHWESTERN
MONTANA. HOWEVER, THE PLACEMENT OF THE HEAVIEST RAINFALL REMAINS A
POINT OF CONTENTION BETWEEN DIFFERING SOLUTIONS. ON ONE HAND, A
FEW MODELS HAVE BEEN SUGGESTING A WIDESPREAD LIGHT RAINFALL ACROSS
THE AREA, WITH PRECIPITATION TOTALS GENERALLY FALLING UNDER A HALF
INCH FOR MOST. ON THE OTHER, A FEW MODELS (INCLUDING SOME HIGHER
RESOLUTION GUIDANCE) HAVE SEEMED TO HINT IN DIVERGENCE ALOFT
RESULTING IN A WIDESPREAD AREA OF LIGHT RAINFALL, WITH A MORE
FOCUSED AREA OF MORE INTENSE RAINFALL ALONG A SW TO NE ORIENTED
AXIS. THIS LATTER IDEA SEEMS TO FIT BETTER WITH THE CONCEPTUAL
MODEL (WHAT MAKES SENSE METEOROLOGICALLY) WITH AN UPPER LEVEL LOW
SETTING UP TO THE SOUTH, AND THE NBM SEEMS TO DO A DECENT JOB OF
CAPTURING THIS POSSIBILITY, PUTTING THE AREA OF HEAVIEST
PRECIPITATION ALONG A LINE ROUGHLY FROM HELENA TO GREAT FALLS TO
HAVRE, WHERE A HALF INCH TO AN INCH OF PRECIPITATION SEEMS LIKELY,
WITH LESSER (BUT STILL HIGHLY BENEFICIAL) AMOUNTS OF RAINFALL
ELSEWHERE ACROSS THE AREA. FOR NOW, I LIKE THE AMOUNTS I HAVE IN
THE FORECAST GRIDS, THOUGH I WOULDN’T BE OVERLY SURPRISED IF WE
SEE A FEW REPORTS OF 1-1.5 INCHES OF RAINFALL COME IN ALONG THIS
LINE, WHEREVER IT SETS UP. LUDWIG
AVIATION
04/06Z TAF PERIOD
WHILE VFR CONDITIONS ARE EXPECTED TO PREVAIL THROUGH THE OVERNIGHT
HOURS, EXPECT CONDITIONS TO GRADUALLY DEGRADE THROUGH THE DAY ON
SUNDAY AS CLOUDS LOWER AND RAIN SHOWERS (AND A FEW THUNDERSTORMS)
DEVELOP, STARTING IN SOUTHWESTERN MONTANA BEFORE SPREADING
NORTHWARD TO NORTH CENTRAL MONTANA. BEST CHANCES FOR THUNDERSTORMS
WILL BE AROUND KEKS, KBZN, AND KWYS, WHERE SOME HAIL TO A HALF
INCH IN DIAMETER WILL BE POSSIBLE. LUDWIG
REFER TO WEATHER.GOV/ZLC FOR MORE DETAILED REGIONAL AVIATION
WEATHER AND HAZARD INFORMATION.
PRELIMINARY POINT TEMPS/POPS
GTF 67 39 50 32 / 30 100 100 10
CTB 55 37 54 30 / 60 80 40 0
HLN 68 40 50 33 / 60 100 100 20
BZN 73 38 46 30 / 60 90 90 40
WYS 70 35 49 27 / 30 60 60 40
DLN 71 37 47 31 / 70 90 60 20
HVR 71 39 57 32 / 10 100 100 0
LWT 69 36 43 31 / 10 80 100 40
TFX WATCHES/WARNINGS/ADVISORIES
WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO NOON MDT
MONDAY FOR LITTLE BELT AND HIGHWOOD MOUNTAINS.
HTTP://WWW.WEATHER.GOV/GREATFALLS
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page