340
FXUS65 KMSO 300628
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
1228 AM MDT WED SEP 30 2026
DISCUSSION
KEY MESSAGES:
- SCATTERED RAIN SHOWERS AND SLIGHTLY COOLER TODAY, THEN WARMING
TREND BEGINNING FRIDAY.
- HIGH CONFIDENCE IN WARMER AND DRIER CONDITIONS THIS WEEKEND
THROUGH MUCH OF NEXT WEEK (AND MAYBE BEYOND).
TODAY-FRIDAY: A WEAK MOISTURE PLUME EMBEDDED WITHIN ZONAL FLOW
WILL BRING LIGHT, MOUNTAIN-FOCUSED SHOWERS TODAY, MAINLY NORTH OF
I-90. RAIN TOTALS WILL BE LIGHT: UP TO A FEW HUNDREDTHS IN VALLEYS
AND 0.10-0.30 INCHES OVER THE HIGHER TERRAIN OF NORTHWEST
MONTANA. LIGHT SPRINKLES REMAIN POSSIBLE OVER THE MOUNTAINS
THURSDAY AND FRIDAY, BUT MEASURABLE RAIN WILL BE SPARSE. EXPECT
NEAR-NORMAL DAYTIME TEMPERATURES AND LIGHT WINDS THROUGH FRIDAY.
EXTENDED PATTERN & CLIMATE OUTLOOK (THIS WEEKEND THROUGH MID-
OCTOBER):
CONFIDENCE IS HIGH (80-90%) THAT A ROBUST UPPER-LEVEL RIDGE WILL
BUILD OVER THE NORTHERN ROCKIES THIS WEEKEND AND PERSIST INTO NEXT
WEEK.
-DAYTIME TEMPERATURES: ANOMALOUSLY WARM AIR ALOFT (10-20
DEGREES F ABOVE NORMAL AT 850MB) WILL TRANSLATE TO MILD DAYS,
THOUGH VALLEY INVERSIONS MAY CAP MAXIMUM WARMING POTENTIAL IN
LOWER ELEVATIONS.
-OVERNIGHT TEMPERATURES: VALLEY LOWS WILL TREND COOLER THAN
STANDARD NBM GUIDANCE DUE TO STRONG RADIATIONAL COOLING (CLEAR
SKIES, LIGHT WINDS, DRY AIR). MID-SLOPES AND THERMAL BELTS
WILL REMAIN SIGNIFICANTLY WARMER AND DRIER OVERNIGHT.
-LONG-RANGE TREND: ENSEMBLE CLUSTERS AND CPC OUTLOOKS FAVOR A
EXTENDED PERIOD OF WARMER AND DRIER-THAN-NORMAL CONDITIONS
THROUGH MID-OCTOBER. BRIEF, MINOR DISTURBANCES REMAIN
POSSIBLE, BUT NO SIGNIFICANT PRECIPITATION EVENTS ARE
INDICATED.
AVIATION
PERIODIC MOUNTAIN OBSCURATIONS WILL PRESENT THE PRIMARY
AVIATION HAZARD NORTH OF I-90 TODAY AS A WEAK MOISTURE PLUME SAGS
SOUTHWARD. LIGHT, TERRAIN-DRIVEN SHOWERS WILL CONCENTRATE OVER
THE HIGHER ELEVATIONS, OCCASIONALLY EXTENDING INTO ADJACENT
VALLEYS. BROAD VFR CONDITIONS WILL PREVAIL ACROSS THE NORTHERN
ROCKIES, THOUGH LOCALIZED MVFR CEILINGS REMAIN POSSIBLE IN
MOUNTAIN SHOWERS AND ALONG PASS LEVEL. ELEVATED RIDGETOP WINDS
WILL GUST 20-30 KT THROUGH THE AFTERNOON, WHILE VALLEY TERMINALS
WILL SEE LIGHTER GUSTS OF 10-20 KT. WINDS WILL DECOUPLE AND
SLACKEN RAPIDLY AROUND SUNSET. NO CONVECTIVE HAZARDS OR WIDESPREAD
LOW-LEVEL WIND SHEAR ARE EXPECTED.
MSO WATCHES/WARNINGS/ADVISORIES
MT...NONE.
ID...NONE.
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