476
FXUS65 KMSO 280710
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
110 AM MDT MON SEP 28 2026
DISCUSSION
KEY MESSAGES:
- NEAR-NORMAL TEMPERATURES WITH THE WEATHER PATTERN DURING THIS
WEEK, ALONG WITH MOSTLY DRY CONDITIONS.
- INCREASING WINDS TUESDAY, ESPECIALLY ACROSS NORTHWEST MONTANA AND
THE HIGHER TERRAIN.
- SCATTERED RAIN SHOWERS TUESDAY NIGHT INTO EARLY WEDNESDAY THEN
SLIGHT WARMING TREND INTO THE REMAINDER OF THE WEEK.
- CONFIDENCE INCREASING FOR A WARMER AND DRIER THAN NORMAL EARLY
OCTOBER BEYOND THE 7 DAY FORECAST.
WIDESPREAD HIGH/MID LEVEL CLOUD COVER AND A FEW LIGHT SHOWERS WILL
GRADUALLY DIMINISH THIS MORNING BY SUNRISE AS A WEAK UPPER LEVEL TROUGH
PASSES THROUGH. THEN MOSTLY SUNNY TO PARTLY CLOUDY SKIES WILL
PROMOTE SOLAR HEATING AND NEAR- NORMAL AFTERNOON TEMPERATURES.
WEST WINDS WILL BECOME LOCALLY BREEZY DURING THE AFTERNOON ACROSS
NORTHWEST MONTANA, GENERALLY REMAINING BELOW 20 MPH.
BY TUESDAY, A DECAYING MOISTURE PLUME FROM BRITISH COLUMBIA AND
NORTHWEST WASHINGTON WILL REACH NORTHWEST MONTANA. EXPECT
INCREASING CLOUD COVER ALONG WITH GUSTY WEST-TO-SOUTHWEST WINDS
RANGING FROM 10 TO 20 MPH, WITH PEAK GUSTS AROUND 30 MPH. HIGH-
RESOLUTION GUIDANCE HIGHLIGHTS A 60% PROBABILITY OF GUSTS
EXCEEDING 30 MPH ALONG THE US-2 CORRIDOR BETWEEN HAPPY'S INN AND
KALISPELL. ACROSS FLATHEAD LAKE, SUSTAINED WINDS NEAR 20 MPH ARE
ONLY EXPECTED IN A FEW PLACES SUCH AS AROUND WILD HORSE ISLAND,
CENTRAL LAKE ZONES, AND SOUTHERN POLSON BAY, PRODUCING CHOPPY
WATER CONDITIONS.
THE PRIMARY MOISTURE AXIS SHIFTS OVER NORTHWEST MONTANA LATE
TUESDAY NIGHT THROUGH WEDNESDAY MORNING, FOCUSING LIGHT RAINFALL
MAINLY OVER MOUNTAIN TERRAIN. VALLEYS EXTENDING FROM LOWELL,
IDAHO, NORTHEASTWARD THROUGH THE SEELEY-SWAN VALLEY TO GLACIER
NATIONAL PARK HAVE A 40% TO 60% CHANCE OF RECEIVING MEASURABLE
PRECIPITATION (0.01 INCHES OR GREATER) BY WEDNESDAY MORNING.
MODEL CONSENSUS POINTS TO A STABLE ZONAL FLOW PATTERN LATE IN THE
WEEK, BRINGING A SLIGHT WARMING TREND, MOSTLY DRY CONDITIONS, AND
ROUTINE AFTERNOON BREEZES.
NOT MUCH HAS CHANGED FROM THE PREVIOUS IN-DEPTH DISCUSSION ON
EARLY OCTOBER; IT CONTINUES TO LOOK WARMER AND DRIER THAN NORMAL.
HERE ARE THE DETAILS ONCE AGAIN: CONFIDENCE IS INCREASING FOR A
WARM, DRY EARLY OCTOBER BEYOND THE 7 DAY FORECAST. THE LARGE SCALE
WEATHER PATTERN IS BEING INFLUENCED BY UPSTREAM TROPICAL
ACTIVITY. WITH 2 HURRICANES AND 1 TROPICAL CYCLONE IN THE CENTRAL
AND EAST PACIFIC OCEAN FROM HAWAII TO BAJA AND A TYPHOON
APPROACHING THE EASTERN PERIPHERY OF JAPAN, IT'S BEEN A DIFFICULT
FORECAST FOR MODELS. HOWEVER, THEY'RE STARTING TO COALESCE AROUND
HIGHER CHANCES FOR A POTENT RIDGE OVER THE NORTHERN ROCKIES INTO
THE FIRST THIRD OF OCTOBER. ENSEMBLE MEAN TEMPERATURE FORECASTS
ARE COMING IN 15 DEGREES ABOVE SEASONAL AVERAGES AT ABOUT 9-12
DAYS OUT. THOSE ARE LARGE ANOMALIES FOR THAT LONG OF A LEAD TIME!
ADD IN THAT THE SIGNAL IS COMING FROM MULTIPLE ENSEMBLE SYSTEMS
INCLUDING BOTH DYNAMICAL (PHYSICS BASED) AND AI MODELING SYSTEMS,
THIS PROVIDES ABOVE NORMAL LEVELS OF CONFIDENCE FOR SUCH A LONG
LEAD TIME FORECAST. LOOKING BACK, THE LAST TIME THIS KIND OF WARM
RIDGE SET UP OVER THE NORTHWESTERN US IN EARLY OCTOBER WAS OCTOBER
9-11 AND 14, 1991. EUREKA, MONTANA HIT 86 DEGREES, GRANGEVILLE,
IDAHO 87 DEGREES, AND BUTTE 81 DEGREES! THE CENTER FOR CLIMATE
PREDICTION HAS ISSUED FORECASTS FOR THE NORTHERN ROCKIES REGION
WITH A 80-90% CHANCE OF ABOVE AVERAGE TEMPERATURES AND
PRECIPITATION FORECASTS ARE LEANING BELOW AVERAGE FOR THAT TIME
PERIOD AS WELL.
AVIATION
VFR CONDITIONS WILL DOMINATE INTO TUESDAY WITH LIGHT,
DIURNALLY DRIVEN WINDS. WESTERLY WINDS WILL PICK UP ON TUESDAY
LATE MORNING/EARLY AFTERNOON, AND A WEAKENING MOISTURE PLUME WILL
BRING SOME SHOWERS TO THE TERRAIN OF NORTHWEST MONTANA LATE IN THE
DAY.
MSO WATCHES/WARNINGS/ADVISORIES
MT...NONE.
ID...NONE.
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