334
FXUS65 KGJT 181539 CCA
AFDGJT
AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
839 AM MST SAT JAN 18 2025
KEY MESSAGES
- A PATTERN CHANGE IS UPON US AS AN ARCTIC FRONT TRAVERSES THE
AREA THIS MORNING WITH GUSTY NORTHERLY WINDS AND AN ARCTIC AIR
MASS SETTLING IN BEHIND IT TODAY. PERIODS OF MODERATE TO HEAVY
SNOW WILL OCCUR OVER THE NORTHWEST COLORADO MOUNTAINS AS WELL
AS NORTHWEST SAN JUANS IN ADDITION TO VERY COLD TEMPERATURES.
- A STRONG ARCTIC OUTBREAK IS EXPECTED TO CLOSE OUT THE WEEKEND
INTO EARLY NEXT WEEK ACROSS THE CENTRAL CONUS. THE COLDEST AIR
SHOULD REMAIN EAST OF THE DIVIDE BUT TEMPERATURES ON THIS SIDE
ARE FORECAST TO BE WELL-BELOW NORMAL. OVERNIGHT LOWS HAVE A
HIGH PROBABILITY OF DROPPING WELL-BELOW ZERO IN MANY MOUNTAIN
AND HIGH VALLEY/BASIN AREAS. AS A RESULT, COLD WEATHER
ADVISORIES HAVE BEEN ISSUED FOR THE GUNNISON AND UPPER YAMPA
RIVER BASINS TONIGHT AND SUNDAY NIGHT WITH AN EXTREME COLD
WATCH FOR MONDAY NIGHT.
SHORT TERM /THROUGH SUNDAY/
ISSUED AT 314 AM MST SAT JAN 18 2025
THE ARCTIC FRONT ON THE LEADING EDGE OF A DEEP UPPER LEVEL TROUGH
IS PUSHING SOUTHWARD ACROSS THE CWA WITH SNOW FALLING OVER THE
NORTHERN AND CENTRAL MOUNTAINS AND EVEN DOWN TO THE NORTHWEST SAN
JUANS AT THIS TIME. THE FLOW WAS STILL PRIMARILY WESTERLY BUT
THIS SHOULD SHIFT TO A NORTHERLY FLOW BEHIND THE ARCTIC FRONT AS
THE COLD AIR SETTLES IN. CLOUD COVER IS HELPING KEEP TEMPERATURES
FROM BOTTOMING OUT TOO DRASTICALLY THIS MORNING, BUT EXPECT THIS
TO CHANGE TONIGHT WHEN MANY AREAS WILL FEEL THE EFFECT OF THIS
ARCTIC AIR MASS.
H7 TEMPERATURES WILL DROP AS LOW AS -20 C BY SUNRISE THIS MORNING
SO ANTICIPATE SNOW DENSITIES TO BE VERY LOW WITH SNOW TO LIQUID
RATIOS (SLRS) NEAR 20:1 RESULTING IN A VERY FLUFFY, POWDERY SNOW.
THERE MAY BE A BIT OF A REPRIEVE IN SNOW RATES AND ACCUMULATIONS
OVER THE NORTHERN MOUNTAINS THIS MORNING BUT RATES SHOULD PICK
BACK UP THIS AFTERNOON AS INSTABILITY AND VERY STEEP LAPSE RATES
LEND THEMSELVES TO AN UPTICK IN SNOW PRODUCTION AND POTENTIAL SNOW
BANDS. ONE PARTICULAR AREA THAT LOOKS TO SEE AN INCREASE IN
SNOWFALL THIS MORNING THOUGH APPEARS TO BE THE UNCOMPAHGRE GORGE
IN THE NORTHWEST SAN JUANS FROM OURAY TO RED MOUNTAIN PASS, WHICH
DOES VERY WELL IN LIGHT NORTHERLY FLOW. WITH TEMPERATURES IN THE
DENDRITIC GROWTH RANGE, SNOW CAN POTENTIALLY PILE UP HERE THIS
MORNING THROUGH THE AFTERNOON BEFORE COMING TO AN END LATE IN THE
DAY AS THE TROUGH MOVES EASTWARD.
WINTER WEATHER ADVISORIES REMAIN ON TRACK FOR THE PARK RANGE,
FLATTOPS, GORE AND ELK MOUNTAINS AS WELL AS THE NORTHWEST SAN
JUANS THROUGH 5 PM MST TODAY AND WILL MAKE NO ADJUSTMENTS HERE. IN
TOTAL, 5 TO 12 INCHES LOOKS LIKELY FOR THE PARK RANGE WITH 4 TO 8
INCHES IN THE REMAINING NORTHWEST COLORADO MOUNTAINS UNDER THE
ADVISORY AND 5 TO 10 INCHES IN THE NORTHWEST SAN JUANS,
PARTICULARLY THE GORGE AREA.
ANOTHER WEATHER IMPACT TODAY, IN ADDITION TO THE MOUNTAIN SNOW,
IS THE WIND AS BREEZY NORTHWEST WINDS WILL FOLLOW THE TROUGH AND
ARCTIC FRONTAL PASSAGE ACROSS SOUTHWEST COLORADO. THE NORTHWEST
FLOW IN THESE TYPES OF EVENTS IS PARTICULARLY STRONG AND AS A
RESULT, WINDS COULD GUST IN THE 35 TO 50 MPH RANGE. THEREFORE, A
WIND ADVISORY REMAINS IN EFFECT FROM 9 AM THIS MORNING THROUGH 5
PM TODAY FOR OUR SOUTHWEST COLORADO VALLEYS, INCLUDING CORTEZ AND
DURANGO IN THE UPPER DOLORES AND ANIMAS RIVER BASINS.
SKIES GENERALLY CLEAR OVERNIGHT TONIGHT AND THE EFFECTS OF THE
ARCTIC AIR MASS WILL BE FELT MOST INTENSELY IN THE COLD POOL
BASINS. DECIDED TO ISSUE A COLD WEATHER ADVISORY FOR THE GUNNISON
BASIN (COZ014) AND UPPER YAMPA RIVER BASIN (COZ005) FROM 10 PM
THIS EVENING THROUGH 11 AM SUNDAY MORNING AS LOW TEMPERATURES ARE
EXPECTED TO BOTTOM OUT INTO THE -25 F TO -30 F RANGE UNDER THESE
DEEP STRONG INVERSIONS. THE ARCTIC AIR MASS WILL ONLY REINFORCE
THESE STRONG INVERSIONS RESULTING IN MUCH COLDER TEMPERATURES IN
THE PREVIOUSLY MENTIONED BASINS. ELSEWHERE, IT WILL BE COLD, BUT
NOT COLD ENOUGH TO CONSIDER ANY COLD WEATHER PRODUCTS. SINCE THE
ARCTIC AIR WILL BE STAYING, ANOTHER COLD WEATHER ADVISORY HAS BEEN
ISSUED FOR THE GUNNISON BASIN SUNDAY NIGHT INTO MONDAY MORNING.
IN ADDITION, WENT AHEAD AND ISSUED AN EXTREME COLD WATCH FOR THE
GUNNISON AND UPPER YAMPA RIVER BASINS FOR MONDAY NIGHT INTO
TUESDAY MORNING IN WHAT PROJECTS TO BE OUR COLDEST NIGHT IN A LONG
TIME. MORE DETAILS ON THE EXTREME COLD POTENTIAL BEYOND SUNDAY IS
IN THE LONG TERM DISCUSSION.
ON SUNDAY, ANOTHER SHORT WAVE DIVES THROUGH THE AREA AS WE REMAIN
ON THE BACKSIDE OF THE WESTERN FRINGES OF THIS DEEP ARCTIC TROUGH,
RESULTING IN SOME SCATTERED LIGHT SNOW SHOWERS PARTICULARLY OVER
THE MOUNTAINS ALONG THE DIVIDE. NOT EXPECTING A LOT WITH THIS WAVE
BUT TEMPERATURES WILL BE PLENTY COLD WITH H7 TEMPS STILL AROUND
-20 C SO SLRS WILL BE HIGHER UNDER THIS VERY COLD REGIME. THE
PARK RANGE LOOKS TO RECEIVE ANOTHER 2 TO 4 INCHES OF SNOW ON
SUNDAY WHILE OTHER MOUNTAIN AREAS SEE 1 TO 3 INCHES OR LESS.
LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/
ISSUED AT 314 AM MST SAT JAN 18 2025
THERE HAS BEEN A SLIGHT UPTICK IN THE NBM PROBABILITY OF SNOW
ACCUMULATION ACROSS THE NORTHERN AND CENTRAL COLORADO MOUNTAINS
SUNDAY NIGHT AS A SHORTWAVE TROUGH PASSES THROUGH THE REGION.
THIS DOES APPEAR TO BE A RATHER DRY SYSTEM, AND AS A RESULT,
FORECASTS ARE CALLING FOR LITTLE MORE THAN 1-4 INCHES ACROSS THE
PARK RANGE AND LIKELY LESS EVERYWHERE ELSE WHERE FLURRIES DO
FALL. INSTEAD, AS HAS BEEN A STRONG FOCAL POINT IN PRIOR
DISCUSSIONS, WE'RE CONCERNED MOSTLY WITH THE COLD TEMPERATURES
ACCOMPANYING THIS LINGERING TROUGH. SUNDAY SHOULD EXPERIENCE
SOMEWHAT WARMER OVERNIGHT LOWS THAN SATURDAY, THOUGH THIS ISN'T
SAYING A WHOLE LOT CONSIDERING THE EXTENT OF THE FRIGID PATTERN.
TEMPERATURES IN THE UPPER YAMPA RIVER BASIN AND GUNNISON VALLEY
ARE ON TRACK FOR -15 TO -25F SUNDAY NIGHT. WITH THIS, WE HAVE
ISSUED A COLD WEATHER ADVISORY FOR THE GUNNISON VALLEY SUNDAY
NIGHT INTO MONDAY MORNING, AND THE UPPER YAMPA RIVER VALLEY
COULD POTENTIALLY DIP INTO THAT CRITERIA SHOULD TEMPERATURES
TREND DOWNWARDS AT ALL. PURELY NORTHERN UPPER-LEVEL FLOW THEN
SETTLES ACROSS THE ROCKIES LATE MONDAY, ADVECTING ARCTIC AIR
INTO OUR CWA. BY TUESDAY MORNING WE SHOULD EXPECT TO SEE
TEMPERATURES HIT THEIR LOWEST OF THIS COLD SPELL. WIND CHILLS
ARE LIKELY TO BE IN THE -20 TO -40F RANGE FOR UPPER VALLEYS,
THOUGH SOME LOCALLY COLDER VALUES ARE POSSIBLE AS WELL. AN
EXTREME COLD WATCH HAS BEEN ISSUED FOR THE UPPER YAMPA RIVER
BASIN AND GUNNISON VALLEY MONDAY NIGHT INTO TUESDAY MORNING AS A
RESULT WITH OVERNIGHT LOWS POTENTIALLY AS LOW AS -35F IN
STEAMBOAT SPRINGS AND -40F IN GUNNISON BY TUESDAY MORNING.
MODELS ARE BEGINNING TO CONVERGE SOMEWHAT ON THE ENSUING
PATTERN BEGINNING TUESDAY AFTERNOON AS THE TROUGH BEGINS TO
BREAK DOWN, THOUGH RIDGING SEEMS TO REMAIN OVER THE PACIFIC
COAST FOR A COUPLE MORE DAYS, KEEPING US IN RELATIVELY WEAK
NORTH TO NORTHWESTERLY FLOW. SO, THE MID-TO-LATE-WEEK WARM-UP IN
TEMPERATURES IS TRENDING TOWARDS BEING MORE GRADUAL. AGREEMENT
IS MINIMAL AMONG MODELS BY FRIDAY, AND CLUSTER ANALYSIS IS
SUGGESTING WE WILL NOT HAVE EVEN SEEN THE RIDGE AXIS PASS US BY
THIS POINT. THESE DETAILS ARE CERTAINLY STILL UP IN THE AIR
THOUGH, SO WHEN (AND IF) WE DO EXPECT TO SEE SEASONALLY WARMER
WEATHER ROLL IN COULD CHANGE DRASTICALLY OVER THE COMING DAYS.
AVIATION /12Z TAFS THROUGH 12Z SUNDAY/
ISSUED AT 422 AM MST SAT JAN 18 2025
SNOW CONTINUES TO FALL ACROSS THE REGION EARLY THIS MORNING,
DROPPING VISIBILITY AND CEILINGS AT MANY TERMINALS. KASE, KEGE,
KMTJ, KTEX, AND KGUC ARE CURRENTLY BELOW ILS BREAKPOINTS AS A
RESULT. TO ADD TO THIS, GUSTY WINDS ARE BEGINNING TO SHOW UP
AROUND THE CWA, AND MOST, IF NOT ALL TERMINALS ARE LIKELY TO
EXPERIENCE STRONG GUSTS BY NOON TODAY, LASTING THROUGHOUT THE
AFTERNOON. NEAR SUNSET THOUGH, WINDS ARE EXPECTED TO CALM DOWN
AND LINGERING SNOW SHOWERS SHOULD CAUSE MINIMAL IMPACTS AS VFR
CONDITIONS WILL ONCE AGAIN DOMINATE THE AREA.
GJT WATCHES/WARNINGS/ADVISORIES
CO...WINTER WEATHER ADVISORY UNTIL 5 PM MST THIS AFTERNOON FOR
COZ004-010-013-018.
COLD WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 9 AM MST SUNDAY
FOR COZ005.
EXTREME COLD WATCH FROM MONDAY EVENING THROUGH TUESDAY MORNING
FOR COZ005-014.
COLD WEATHER ADVISORY FROM 10 PM THIS EVENING TO 11 AM MST
SUNDAY FOR COZ014.
COLD WEATHER ADVISORY FROM 10 PM SUNDAY TO 11 AM MST MONDAY
FOR COZ014.
WIND ADVISORY FROM 9 AM THIS MORNING TO 5 PM MST THIS
AFTERNOON FOR COZ021-022.
UT...NONE.
SHORT TERM...MDA
LONG TERM...BW
AVIATION...TGJT
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