100
FXUS65 KRIW 190920
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
220 AM MST THU DEC 19 2024
KEY MESSAGES
- WIND DECREASES TODAY, BRING A MILD AND TRANQUIL DAY.
- DRY AND MILD WEATHER CONTINUES THROUGH SATURDAY.
- THE NEXT POTENTIAL SNOW MAKER MOVES INTO WESTERN WYOMING
SATURDAY NIGHT AND SUNDAY.
DISCUSSION
ISSUED AT 219 AM MST THU DEC 19 2024
THE FRONT AND TROUGH ARE NOW THROUGH THE AREA. WINDS HAS DECREASED
FROM EARLIER IN MOST LOCATIONS, THE EXCEPTIONS BRING AROUND THE WIND
RIVER BASIN, INCLUDING OUR OFFICE, COURTESY OF AN 140 KNOT JET
MOVING THROUGH NORTHEASTERN WYOMING, PUTTING THE AREA IN THE RIGHT
FRONT QUADRANT OF IT, BRINGING THE DOWNWARD MOMENTUM. WIND IS
BEGINNING TO DECREASE NOW THOUGH, AND I HOPE THAT TREND CONTINUES AS
I HAVE A BALLOON LAUNCH IN A COUPLE OF HOURS AND THESE ARE NO FUN IN
STRONG WIND.
WIND SHOULD CONTINUE TO DECREASE THROUGH THE MORNING AS THE JET
MOVES AWAY TO THE EAST AND THE PRESSURE GRADIENT DECREASES. RIDGING
SHOULD THEN BUILD INTO THE AREA TODAY AND BRING A RELATIVELY
TRANQUIL DAY WITH A CONTINUATION OF ABOVE NORMAL TEMPERATURES. WE
CAN'T COMPLETELY RULE OUT A SHOWER IN NORTHWESTERN WYOMING, BUT THE
CHANCE IS LESS THAN 1 OUT OF 10 SO IT WAS LEFT OUT.
THIS DRY AND MILD PATTERN WILL CONTINUE THROUGH SATURDAY. THE ONLY
CONCERNS WILL WITH THE SOUTHWEST FLOW, GUSTY WIND WILL CONTINUE
AROUND CASPER BUT MID LEVEL WIND IS NOT SUFFICIENT FOR HIGH WIND.
THE NEXT WEATHER MAKER THEN APPROACHES THE WEST LATER SATURDAY NIGHT
AND SUNDAY IN THE FORM OF ANOTHER PACIFIC TROUGH AND COLD FRONT.
WITH THE FLOW LARGELY ZONAL AND NOT WITH A DEEP TROUGH, THIS SYSTEM
WILL BE ANOTHER FAST MOVER SO SNOW FALL AMOUNTS LOOK MODERATE AT
BEST IN THE WEST, LIGHT TO NON EXISTENT ELSEWHERE WITH THE
DOWNSLOPING FLOW. SOME JET ENERGY MOVING CLOSE TO NORTHERN WYOMING
MAY BRING SOME LIGHT PRECIPITATION TO THE NORTH, BUT ANY
ACCUMULATION WOULD BE VERY SMALL. THE MAIN CONCERN EAST OF THE
DIVIDE MAY AGAIN TURN OUT TO BE STRONG WIND, BUT TOO SOON THE
SPECULATE ON POTENTIAL HIGH WIND.
THE FAST MOVING PATTERN MAY BRING ANOTHER SYSTEM ON IT'S HEELS FOR
MONDAY, BUT THIS ON LOOKS SIMILAR, A FAST MOVER WITH MOST OF ANY
SNOW CONFINED TO THE WESTERN MOUNTAINS. AS FOR THE POSSIBLE
CHRISTMAS SNOW EVENT AND A POSSIBLE WHITE CHRISTMAS, TRENDS THIS
MORNING ARE NOT GOOD FOR THIS AS MOST GUIDANCE TAKES THE THE BEST
ENERGY FURTHER SOUTH, LEAVING THE STATE WITH ONLY A GLANCING BLOW.
LOOKING FURTHER OUT, IT LOOKS THE PATTERN OF ZONAL TO FLAT RIDGING
CONTINUES. THIS MEANS NEAR TO SOMEWHAT ABOVE NORMAL TEMPERATURES,
WINDY CONDITIONS AT TIMES, SOME MINOR SNOW EVENTS FOR MAINLY WESTERN
WYOMING. NO MAJOR STORMS ARE EXPECTED FOR THE NEXT 7 DAYS.
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
NONE.
DISCUSSION...HATTINGS
AVIATION...GERHARDT/HENSLEY
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