902
FXUS65 KRIW 171714
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1014 AM MST TUE DEC 17 2024
KEY MESSAGES
- SNOW CONTINUES WEST OF THE DIVIDE FOR MUCH OF TUESDAY WITH THE
HEAVIEST RATES ALREADY OCCURRED.
- GUSTY WINDS TUESDAY AND WEDNESDAY AFTERNOONS AS THE SYSTEM
EXITS EAST, ESPECIALLY ACROSS THE CODY FOOTHILLS.
- WARMING TREND AND DRY CONDITIONS EXPECTED FOR THE REMAINDER OF
THE WEEK AND INTO THE WEEKEND WITH THE NEXT SYSTEM EARLY NEXT
WEEK.
DISCUSSION
ISSUED AT 1218 AM MST TUE DEC 17 2024
IR CURRENTLY DEPICTS THE MAIN SYSTEM ACROSS THE NORTHERN ROCKIES
AND THE CWA WITH THE NEXT PVA MAX PUSHING ACROSS FROM IDAHO.
ADDITIONAL SNOWFALL FOR THE REMAINDER OF THE MORNING WEST OF THE
DIVIDE LINGERING INTO THE AFTERNOON HOURS. POINTS EAST OF THE
DIVIDE WILL REMAIN DRY WITH THE ZONAL WEST FLOW ALOFT IN THE MID
AND UPPER LEVELS. LOWER VALLEYS OUT WEST HAVE BEEN VERIFYING
QUITE WELL WITH 30-40 PERCENT PROBABILITIES FOR AN ADDITIONAL 2
INCHES OR MORE TUESDAY. HIGHER ELEVATIONS HAVE UNDERPERFORMED IN
ALIGNMENT WITH WPC SNOWFALL TOTALS BUT REGARDLESS, ADDITIONAL
SNOWFALL WILL CONTINUE THROUGH MUCH OF THE DAY. 60-70 PERCENT
PROBS FOR 6 INCHES OR MORE FOR THE SALTS, 30-40 PERCENT FOR THE
WESTERN WINDS AND GROS VENTRES, AND 50-60 PERCENT FOR UP TO A
FOOT ACROSS THE TETONS. AS THE TROUGH SHIFTS EASTWARD BY EARLY
AFTERNOON, NORTHWEST FLOW STARTS TO PUSH INTO THE CWA THAT WILL
START TO DIMINISH SNOWFALL SIGNIFICANTLY SOUTH TO NORTH WITH
LINGERING FLURRIES TO LITTLE ACCUMULATION INTO THE OVERNIGHT
HOURS THROUGH WEDNESDAY MORNING.
AS THIS MAIN TROUGH PIVOTS EAST, THE PFJ WILL MIGRATE BACK
NORTHWARD INTO MONTANA WITH MINOR MID LEVEL TROUGHS TO PUSH
ACROSS NORTHERN SECTIONS OF THE CWA. THIS WILL KEEP WINDS
ELEVATED TO BREEZY CONDITIONS WITH SOME HI-RES MODELS PICKING UP
ON A MOUNTAIN WAVE ANOMALY ACROSS THE CODY FOOTHILLS FOR
WEDNESDAY AFTERNOON. WIND GUSTS UP TO 60 MPH PLUS POSSIBLE AT
THIS POINT IN TIME BUT NOT HIGH IN CONFIDENCE AS ALL DEPENDENT
ON HOW FAR SOUTH THESE MINOR SHORTWAVES EXTEND. THIS WILL BE
SOMETHING TO KEEP AN EYE ON IN COMING MODEL RUNS TO SHOW
CONSISTENCY. FOR NOW, NO HIGHLIGHTS BUT EMPHASIZED IN OTHER
REALMS. THIS WILL ALSO GIVE SOME LOW POPS ACROSS THE
NORTHWESTERN HIGHER ELEVATIONS FOR MINOR SNOW ACCUMULATIONS AS
WELL WEDNESDAY AFTERNOON AND EVENING BUT NOTHING TO WRITE HOME
ABOUT BEHIND THESE PAST COUPLE OF SYSTEMS.
ONCE THIS PASSES, THE PFJ RETREATS FURTHER NORTHEAST TO THE
NORTHERN GREAT PLAINS GIVING WAY TO A WEAKER NORTHWEST FLOW FOR
THE CWA AND NORTHERN ROCKIES. AS A RESULT, UPPER LEVEL RIDGING
WITH AMPLE CONVERGENCE ALOFT WILL BUILD IN FROM THE SOUTHWEST
BECOMING MORE ENTRANCED THROUGH THE AREA BY WEEK'S END. THIS
WILL GIVE WAY TO DRY CONDITIONS AND A WARMING TREND THROUGH THE
WEEKEND. SEASONABLE TEMPERATURES TODAY AND TOMORROW WILL GIVE
WAY TO WELL ABOVE AVERAGE DURING THIS TIMEFRAME AS WELL.
THE AFOREMENTIONED RIDGING LOOKS TO BREAK DOWN BY SUNDAY THAT
WILL START TO ALL THE JET TO DIP SOUTHWARD ACROSS THE PACIFIC
NORTHWEST TO SUPER THE NEXT UPPER LEVEL SYSTEM THAT WILL START
TO HAVE SOME AFFECTS FOR WESTERN MOUNTAINS BY LATE SUNDAY. FOR
NOW, IMPACTS LOOK TO BE MINIMAL INTO EARLY NEXT WEEK CONSTRAINED
TO NORTHERN PARTS OF THE CWA AHEAD OF THE MAIN TROUGH BY
TUESDAY NIGHT INTO WEDNESDAY. MORE RELIABLE LONGER TERM MODELS
INDICATE A FURTHER SOUTH TRAJECTORY AS SOME PREVIOUS STORMS HAVE
TAKEN, AND IF SO, IMPACTS WILL BE MINOR. HOWEVER, THIS WILL
MONITORED IN THE COMING DAYS AS THIS WILL BE DURING HEAVY
HOLIDAY TRAVEL ON CHRISTMAS EVE AND CHRISTMAS DAY.
AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/
ISSUED AT 1014 AM MST TUE DEC 17 2024
WEST OF THE DIVIDE...KBPI/KJAC/KPNA/KRKS TERMINALS
LINGERING SNOW SHOWERS TAPER OFF LATER THIS AFTERNOON. CONDITIONS
WILL IMPROVE FROM MVFR/IFR TO VFR BY MID-AFTERNOON AT ALL TERMINALS
AS SNOW ENDS AND CIGS RISE. FROM THIS AFTERNOON ONWARD CONDITIONS
WILL REMAIN VFR THROUGH THE TAF PERIOD. MOUNTAIN OBSCURATION WILL
CONTINUE EARLY THIS AFTERNOON, WITH MODEST IMPROVEMENT AROUND KJAC.
AT OTHER TERMINALS MOUNTAIN OBSCURATION WILL END THIS AFTERNOON. IT
WILL BE WINDY THIS AFTERNOON AT KRKS, WITH GUSTS OF 30-35 KNOTS
SLOWLY SUBSIDING THIS EVENING.
EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL TERMINALS
VFR CONDITIONS WILL PREVAIL THROUGH THE TAF PERIOD. A WEATHER SYSTEM
DEPARTS THE AREA TODAY, BUT THE JET STREAM WILL REMAIN ANCHORED OVER
THE REGION, WHICH WILL RESULT IN BREEZY TO WINDY CONDITIONS FOR
SEVERAL TERMINALS BY WEDNESDAY MORNING THROUGH THE AFTERNOON. THERE
IS POTENTIAL FOR A HIGH WIND EVENT IN THE CODY FOOTHILLS THAT WOULD
IMPACT KCOD LATE WEDNESDAY, BUT CONFIDENCE IN THE STRONGEST WIND
REACHING THE SURFACE IS LOW (20-30% CHANCE). TERMINALS THAT WILL BE
WINDY ARE KCPR/KCOD, OTHERWISE WIND WILL REMAIN BELOW 10 KNOTS. SOME
MOUNTAIN OBSCURATION WILL OCCUR THIS AFTERNOON, BUT WILL IMPROVE
THIS EVENING.
PLEASE SEE THE AVIATION WEATHER CENTER AND/OR CWSU ZDV AND ZLC FOR
THE LATEST INFORMATION ON ICING AND TURBULENCE FORECASTS.
RIW WATCHES/WARNINGS/ADVISORIES
WINTER WEATHER ADVISORY UNTIL 5 PM MST THIS AFTERNOON FOR
WYZ001-013-023.
WINTER STORM WARNING UNTIL 5 PM MST THIS AFTERNOON FOR WYZ012-
014-024.
DISCUSSION...LOWE
AVIATION...ROWE
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