059
FXUS65 KTFX 170501
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1001 PM MST MON DEC 16 2024
AVIATION SECTION UPDATED.
KEY MESSAGES
- SNOW CONTINUES TO MOVE INTO THE REGION TODAY, AND WILL
CONTINUE INTO TUESDAY.
- STRONG WINDS ARE EXPECTED ALONG THE ROCKY MOUNTAIN FRONT AND
THE MONTANA HIGHWAY 200 CORRIDOR WEDNESDAY.
- ANOTHER ROUND OF PRECIPITATION ARRIVES WEDNESDAY, WITH MAINLY
MOUNTAIN SNOW AND A RAIN AND SNOW MIX AT LOWER ELEVATIONS.
UPDATE
/ISSUED 928 PM MST MON DEC 16 2024/
SATELLITE IMAGERY SHOWS A SHORTWAVE DISTURBANCE IN MOIST WESTERLY
FLOW FROM THE PACIFIC MOVING ACROSS THE NORTHER ROCKIES THIS
EVENING. AREAS OF LIGHT SNOW ACROSS THE FORECAST AREA WILL
GRADUALLY DIMINISH FROM SOUTHWEST TO NORTHEAST THROUGH TUESDAY
MORNING AS THE DISTURBANCE AND DEEPER MOISTURE FIELD SHIFT EAST
OF THE AREA. ADDITIONAL SNOW ACCUMULATIONS OF AN INCH OR MORE
WILL PRIMARILY BE CONFINED THE GALLATIN, BRIDGER AND LITTLE BELT
RANGES WHERE A WINTER WEATHER ADVISORY CONTINUES INTO TUESDAY
MORNING. NO SIGNIFICANT CHANGES TO THE OVERALL FORECAST BUT DID
INCORPORATE LATEST HI-RESOLUTION MODEL GUIDANCE AND OBSERVED
TRENDS INTO UPDATED POP/QPF GRIDS THROUGH TOMORROW MORNING.
LOOKING AHEAD, THERE ARE SEVERAL FACTORS POINTING TOWARD A
POTENTIALLY MORE WIDESPREAD AND IMPACTFUL WIND EVENT ACROSS THE
AREA ON WEDNESDAY. IN ADDITION TO MID-LEVEL WIND SPEEDS ON THE
HIGHER END OF CLIMATOLOGY, THE MIDDAY/AFTERNOON TIMING OF A
FAIRLY POTENT SHORTWAVE AND SURFACE LOW TRACK ALONG THE AB/MT
BORDER IS FAVORABLE FOR ENHANCED TRANSPORT OF STRONGER WINDS
ALOFT TO THE SURFACE ACROSS MUCH OF CENTRAL MT. HOENISCH
DISCUSSION
/ISSUED 928 PM MST MON DEC 16 2024/
- METEOROLOGICAL OVERVIEW:
AND UPPER LEVEL DISTURBANCE PASSING THROUGH TODAY WILL CONTINUE
TO BRING SNOW EAST ACROSS THE REGION TODAY, EXPANDING TO THE
NORTH- CENTRAL MT PLAINS IN THE EVENING. SNOW CONTINUES ACROSS
THE PLAINS THROUGH TUESDAY AFTERNOON. THERE WILL BE A LULL IN
PRECIPITATION BEFORE ANOTHER SMALL TROUGH BRINGS IN ANOTHER ROUND
OF LIGHT MOUNTAIN SNOW/LOWER ELEVATION RAIN AND SNOW MIX
WEDNESDAY. ALONG WITH PRECIPITATION WEDNESDAY, STRONGER MID AND
LOW LEVEL WINDS MOVE IN ACROSS MUCH OF THE REGION WEDNESDAY
AFTERNOON. A SURFACE BOUNDARY DRAPED ACROSS THE ROCKY MOUNTAIN
FRONT TO CENTRAL MT COULD HELP MIX THESE STRONGER WINDS TO THE
SURFACE.
COOLER TEMPERATURES ARE EXPECTED TODAY AND TOMORROW, BEFORE
STRONGER CHINOOK WINDS BRING MILDER TEMPERATURES WEDNESDAY
THROUGH THE BEGINNING OF NEXT WEEK.
BEHIND WEDNESDAY SYSTEM, A WEAKER RIDGE BUILDS IN FOR THE LATTER
PART OF THE WEEK, WHICH WILL KEEP DRIER AND WARMER WEATHER.
ENSEMBLE MODEL CLUSTERS INDICATE A TROUGH BUILDING ALONG THE
WESTERN U.S COAST BEGINNING OF NEXT WEEK, KEEPING SOUTHWEST FLOW
ALOFT HERE. THIS MAY TRY TO BRING IN ANOTHER DISTURBANCE MONDAY,
BRINGING PRECIPITATION ALONG THE CONTINENTAL DIVIDE AND
SOUTHWEST.
- FORECAST CONFIDENCE & SCENARIOS:
THERE GOOD CONFIDENCE FOR MINOR TO MODERATE SNOWFALL IN THE
MOUNTAINS TODAY AND TUESDAY. KINGS HILL PASS HAS A 30% CHANCE FOR
4" OF SNOW, WITH HIGHER TERRAIN ABOVE 7,500FT AT GREATER
PROBABILITIES. NEWER MODEL GUIDANCE HAVE BACKED OFF OF SLIGHTLY
HIGHER AMOUNTS OF SNOW AT LOWER ELEVATIONS. THERE'S A 10-20% FOR
LOCAL AMOUNTS OF 2", WITH SNOW GENERALLY STAYING AROUND AN INCH
OR LESS AT LOWER ELEVATIONS.
SNOW WEDNESDAY LOOKS TO REMAIN MAINLY CONFINED TO THE NORTHERN
CONTINENTAL DIVIDE, WITH SOME LIGHT SNOW MIXING IN AT LOWER
ELEVATIONS. MARIAS PASS HAS A 40% FOR 3" OF SNOW. HIGHER-RES
GUIDANCE HINTS AT SOME LIGHT SNOW MIXING IN ALONG THE HI-LINE
REGION WEDNESDAY MORNING, WITH A 20% CHANCE FOR 1" NORTH OF THE
US ROUTE 2 CORRIDOR.
THERE HAS BEEN A CONSISTENT SIGNAL FOR GUSTY TO STRONG WINDS
ACROSS MUCH OF THE REGION WEDNESDAY, WITH THE ROCKY MOUNTAIN
FRONT AND THE MONTANA HIGHWAY 200 CORRIDOR WITH THE STRONGEST
WINDS. THERE'S GREATER THAN A 50% CHANCE FOR 55MPH WINDS
WEDNESDAY. THIS HAS PROMPTED THE ISSUANCE OF A HIGH WIND WATCH
FOR WEDNESDAY. AFTERNOON. THERE IS SOME UNCERTAINTY IN HOW FAR
SOUTH THIS HIGH WIND THREAT WILL GO, AS PROFILE SOUNDINGS
SUGGESTS THE HELENA VALLEY AND OTHER SOUTHWEST MT VALLEYS
STRUGGLE TO MIX DOWN THESE STRONGER MID LEVEL WINDS. IF TRENDS
CONTINUE TO UPTREND, THEN THE CURRENT WATCH MAY NEED TO BE
EXPANDED. -WILSON
AVIATION
17/06Z TAF PERIOD
A WEAK DISTURBANCE WILL CONTINUE MOSTLY BROKEN TO OVERCAST LOW VFR
AND MVFR CEILINGS, CAUSING SOME MOUNTAIN TOP OBSCURATION. LIGHT
SNOW ASSOCIATED WITH THE DISTURBANCE COULD STILL LOWER CONDITIONS
TO IFR AT TIMES, BUT THE SNOW WILL CONTINUE TO DECREASE FROM THE
WEST THROUGH 12Z. HOWEVER, BREAKS IN THE CLOUDS IN THE WAKE OF THE
DISTURBANCE MAY ALLOW LOWER CLOUDS AND FOG TO FORM, CAUSING MAINLY
IFR CONDITIONS AT TIMES THROUGH 17Z OR SO. BROKEN VFR TO MVFR
SHOULD LINGER THROUGH AT LEAST 18/00Z IN A NORTHWEST FLOW ALOFT,
BUT CEILINGS SHOULD START TO LIFT AFTER 00Z. THE PASSAGE OF THIS
DISTURBANCE WILL ALSO CAUSE SOME MOUNTAIN WAVE TURBULENCE.
-COULSTON
REFER TO WEATHER.GOV/ZLC FOR MORE DETAILED REGIONAL AVIATION
WEATHER AND HAZARD INFORMATION.
PRELIMINARY POINT TEMPS/POPS
GTF 20 30 19 52 / 60 10 30 20
CTB 14 22 11 45 / 50 10 50 40
HLN 23 40 28 52 / 70 10 20 40
BZN 20 38 22 47 / 80 10 10 30
WYS 15 30 17 32 / 90 40 60 50
DLN 20 38 24 44 / 40 10 10 10
HVR 13 22 7 39 / 50 40 50 60
LWT 20 31 16 48 / 80 20 30 30
TFX WATCHES/WARNINGS/ADVISORIES
WINTER WEATHER ADVISORY UNTIL 9 AM MST TUESDAY FOR BIG BELT,
BRIDGER AND CASTLE MOUNTAINS-EAST GLACIER PARK REGION-GALLATIN
AND MADISON COUNTY MOUNTAINS AND CENTENNIAL MOUNTAINS-LITTLE
BELT AND HIGHWOOD MOUNTAINS.
HIGH WIND WATCH FROM LATE TUESDAY NIGHT THROUGH LATE WEDNESDAY
NIGHT FOR EAST GLACIER PARK REGION-EASTERN GLACIER, WESTERN
TOOLE, AND CENTRAL PONDERA-NORTHERN HIGH PLAINS-SOUTHERN HIGH
PLAINS-SOUTHERN ROCKY MOUNTAIN FRONT.
HIGH WIND WATCH FROM WEDNESDAY MORNING THROUGH LATE WEDNESDAY
NIGHT FOR CASCADE COUNTY BELOW 5000FT-FERGUS COUNTY BELOW 4500FT-
JUDITH BASIN COUNTY AND JUDITH GAP-SNOWY AND JUDITH MOUNTAINS.
HTTP://WWW.WEATHER.GOV/GREATFALLS
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