763
FXUS65 KRIW 190504
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1004 PM MST WED DEC 18 2024
KEY MESSAGES
- HIGH WINDS ARE EXPECTED THIS AFTERNOON AND EVENING OVER THE
ABSAROKA MOUNTAINS AND CODY FOOTHILLS AS WELL AS FROM SOUTH
PASS EASTWARD INTO NATRONA COUNTY. WIND GUSTS 55-65 MPH CAN BE
EXPECTED WITH LOCALLY HIGHER GUSTS. BREEZY AND GUSTY WIND WILL
OCCUR IN OTHER AREAS FOR THIS TIME FRAME AS WELL.
- LIGHT SNOW SHOWERS OVER THE NORTHWEST WY MOUNTAINS WILL
DIMINISH AFTER MIDNIGHT, WITH HIGH PRESSURE SETTLING IN
THURSDAY THROUGH SATURDAY. ABOVE NORMAL TEMPERATURES WITH
GENERALLY SLIGHT WINDS AND PARTLY CLOUDY SKIES ARE EXPECTED.
- WEAK STORM SYSTEMS RETURN TO WESTERN WY EARLY SUNDAY MORNING,
MONDAY, AND CHRISTMAS DAY. NO MAJOR IMPACTS ARE EXPECTED AT
THIS TIME, THOUGH LIGHT TO MODERATE SNOWFALL MAY IMPACT
HOLIDAY TRAVEL.
DISCUSSION
ISSUED AT 100 PM MST WED DEC 18 2024
THE CURRENT WEATHER PATTERN INDICATES A SHORTWAVE TROUGH MOVING
IN WESTERLY FLOW THROUGH MONTANA AND NORTHERN WYOMING THIS
AFTERNOON AND EVENING. THE RESULTING TIGHTENED PRESSURE
GRADIENTS IN THE MID- AND LOWER-LEVELS ARE LEADING TO AN
INCREASE IN HIGH WIND POTENTIAL FOR THE ABSAROKA MOUNTAINS AND
CODY FOOTHILLS AS WELL AS ACROSS PORTIONS OF CENTRAL WYOMING.
THE EXISTING HIGH WIND WARNING IS HIGHLIGHTING THE POTENTIAL FOR
60-75 MPH WIND GUSTS IN THE HIGHER TERRAIN, WITH 55-65 GUSTS IN
THE LOWER ELEVATIONS OF THOSE AREAS. AS LIKE MUCH OF WYOMING,
LOCALLY AREAS NAY SEE ENHANCEMENTS, SUCH AS RED CANYON, CHIEF
JOSEPH PASS, OUTER DRIVE, ETC. BREEZY AND GUSTY WINDS ARE
EXPECTED ELSEWHERE, AND SHOULD CREATE BLOWING SNOW IN THE AREAS
WITH RECENT SNOWFALL. TEMPERATURES REMAIN ABOVE NORMAL AND LOOK
TO STAY ABOVE NORMAL FOR THE NEXT 7 DAYS AT LEAST.
AS THIS TROUGH MOVES INTO THE NORTHERN PLAINS EARLY THURSDAY
MORNING, COOL AND BREEZY NORTHWEST FLOW ON THE DOWNSTREAM BACK
EDGE OF A RIDGE WILL BE OVER THE FORECAST AREA. SHOWERS WILL
DIMINISH QUICKLY THU MORNING, THOUGH BREEZY AND GUSTY WEST-
NORTHWEST WINDS WILL MAKE IT FEEL COOL. OF NOTE AS WELL EARLY
THURSDAY MORNING IS THE POSSIBILITY OF FOG IN SOME WESTERN
VALLEYS. THE MOST LIKELY LOCATIONS ARE STAR VALLEY AND
COKEVILLE, WITH LESSER CHANCES AROUND JACKSON AND BIG
PINEY/PINEDALE. AS THE UPPER- LEVEL HIGH PRESSURE BUILDS OVER
THE WESTERN US THURSDAY, SKIES WILL BECOME MORE CLEAR FROM WEST
TO EAST, THOUGH UPPER-LEVEL CLOUDS SHOULD CONTINUE OVER WESTERN
AND NORTHERN WY. FRIDAY WILL SEE THE RIDGE MOVE EASTWARD TO THE
WY/ID BORDER WITH MORE CLOUDINESS OVER NORTHWEST WY.
TEMPERATURES WILL REMAIN WARM AND WINDS WILL BE ON THE LIGHTER
SIDE. SATURDAY WILL THEN SEE THE RIDGE AXIS MOVE OVER WY AND
THEN TO THE EAST AS A TROUGH DIGS ALONG THE WEST COAST. WINDS
WILL INCREASE AGAIN SATURDAY AS THE SURFACE PRESSURE GRADIENT
STRENGTHENS. BREEZY AND GUSTY WINDS CAN BE EXPECTED DURING THE
DAY IN THE TYPICAL AREAS FROM SOUTHWEST INTO CENTRAL WY. CLOUDS
WILL INCREASE DURING THE AFTERNOON OVER WESTERN WY DUE TO AN
INITIAL SHORTWAVE TROUGH MOVING INTO SW IDAHO.
THE MEDIUM-RANGE MODELS ARE INDICATING THAT THIS INITIAL
SHORTWAVE TROUGH WILL EJECT EASTWARD EARLY SUNDAY MORNING. AT
THIS TIME, THE PRECIPITATION FROM THIS SYSTEM LOOKS LIKE IT
SHOULD IMPACT NORTHWEST AND NORTHERN WY, WITH THE SOUTHERN AND
CENTRAL PARTS OF THE FORECAST AREA GETTING IMPACTED BY STRONG
GUSTY WEST WINDS. TEMPERATURES WILL TAKE A DROP ON SUNDAY AS A
RESULT, BUT STILL REMAIN SLIGHTLY ABOVE NORMAL. THE NEXT
SHORTWAVE TROUGH FROM THE SYSTEM WILL THEN PUSH INTO WESTERN WY
LATE SUNDAY NIGHT INTO MONDAY. AT THIS TIME, MODERATE SNOW
SHOULD IMPACT WESTERN AND SOUTHERN WY, KEEPING TEMPERATURES ON
THE COOL SIDE. AND LIKE THE PREVIOUS SYSTEM, LITTLE TO NO
PRECIPITATION IS EXPECTED EAST OF THE DIVIDE IN THE CENTRAL AND
NORTHERN BASINS. SHORTWAVE HIGH PRESSURE THEN BUILDS IN BRIEFLY
ON TUESDAY AS A STRONGER SHORTWAVE TROUGH MOVES FROM THE WEST
COAST INTO THE GREAT BASIN. THIS SYSTEM WHICH IS POISED TO
POTENTIALLY IMPACT THE AREA ON CHRISTMAS DAY, HAS A VARIABLE
TRACK AT THIS TIME. MODELS ARE TRENDING TOWARD A MORE SOUTHERLY
TRACK THROUGH UTAH AND COLORADO, WHICH WOULD LESSEN THE CHANCES
OF SNOW FOR MUCH OF WYOMING. WILL CERTAINLY NEED TO KEEP AN EYE
ON THE POSSIBILITIES AS WE HEAD INTO THE WEEKEND. THE ACTIVE
PATTERN IS EXPECTED TO CONTINUE FOR THE LATTER HALF OF NEXT
WEEK, THOUGH DETAILS ARE UNCERTAIN AT THIS TIME.
AVIATION /06Z TAFS THROUGH 06Z FRIDAY/
ISSUED AT 1000 PM MST WED DEC 18 2024
A SHORTWAVE TROUGH PUSHES THROUGH TONIGHT, WHICH WILL TIGHTEN THE
PRESSURE GRADIENT AND ALSO BRING A JET STREAK OVER THE REGION,
RESULTING IN STRONG DOWNSLOPING WINDS ON THE LEE SIDE OF THE
ABSAROKAS, BIGHORNS, CASPER MOUNTAIN, AND THE TETONS. WINDS
REMAIN A CONCERN OVER THE NEXT FEW HOURS, ESPECIALLY AT KCOD,
KCPR, KJAC AND KRKS. WIND GUSTS UP TO 30 KNOTS ARE POSSIBLE AT
THE AFOREMENTIONED TERMINALS. LLWS AT KCOD UP TO 60 TO 65 KNOTS
IS ALSO POSSIBLE. THERE IS ALSO A 30% CHANCE THAT INCREASED
SUSTAINED DOWNVALLEY NORTHWESTERLY WINDS AROUND 15 KNOTS WILL
PUSH INTO KRIW BEFORE 12Z. WINDS WILL SIGNIFICANTLY TAPER OFF
TOWARDS SUNRISE THURSDAY AT ALL TERMINALS, WITH WINDS GENERALLY
LESS THAN 12 KNOTS EVERYWHERE BETWEEN 12Z AND 14Z.
THE OTHER NOTABLE AVIATION CONCERN IS FOG WEST OF THE DIVIDE.
BECAUSE WINDS HAVE STAYED INCREASED, THE ONSET OF FOG
DEVELOPMENT HAS BEEN PUSHED LATER. KBPI REMAINS THE TERMINAL
WITH THE MOST LIKELY CHANCE (50%) FOR FOG, STAYING AT FL001 TO
FL002 THROUGH 18/19Z THURSDAY. INDICATIONS OF FOG AT KPNA AND
KRKS ARE SIMILAR, BUT LOOKS TO BE LATER ONSET (PERHAPS CLOSER TO
06-08Z). FOR KRKS, BETTER CHANCES (80%) ARE FARTHER NORTH AND
WEST (FARSON/FONTENELLE) BUT THERE IS STILL A 30% CHANCE THAT
FOG WILL SPREAD FAR ENOUGH SOUTH AND EAST TO IMPACT THE
TERMINAL. AT KJAC, THERE IS ALSO A 30% CHANCE OF FOG, BUT
BECAUSE WINDS ARE FORECAST TO STAY INCREASED, DEVELOPMENT WOULD
BE DELAYED UNTIL AROUND 15Z. HAVE INCLUDED VCFG AND
FEW001/FEW002 GROUPS FOR WEST OF THE DIVIDE TERMINALS THROUGH
MUCH OF THE NIGHT, AS THERE IS NOT ENOUGH CONFIDENCE IN FOG FOR
A PREVAILING GROUP.
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
HIGH WIND WARNING UNTIL 2 AM MST THURSDAY FOR WYZ002-003.
HIGH WIND WARNING UNTIL 11 PM MST THIS EVENING FOR WYZ019-020.
DISCUSSION...MCDONALD
AVIATION...GERHARDT/HENSLEY
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page