Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 270517
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1017 PM MST MON JAN 26 2015

.SHORT TERM...TONIGHT THROUGH TUESDAY (ISSUED AT 158 PM MST)

MAINLY TRANQUIL WEATHER WILL BE THE RULE THROUGH THE SHORT TERM. BY
AS ALWAYS...THERE ARE A COUPLE OF THINGS CAUSING PROBLEMS...IT WOULD
NOT BE WYOMING WEATHER WITHOUT IT. FIRST IS IN THE WESTERN VALLEYS
WHERE SOME FOG HAS STUCK AROUND MOST OF THE MORNING. IT HAS LIFTED
IN THE JACKSON VALLEY...BUT HAS PERSISTED IN THE STAR VALLEY.
HOWEVER...IT IS RATHER PATCHY AND HARD TO PINPOINT. IN
ADDITION...INVERSIONS ARE STILL PRESENT ACROSS THE DEEPER BASINS
EAST OF THE DIVIDE. CASE IN POINT...AT NEAR NOON WE ARE SITTING AT
38 AT THE HUMBLE RIVERTON WEATHER ABODE. MEANWHILE...ABOUT 35 MILES
UP THE ROAD AT CROWHEART IT IS 61...ABOUT A DEGREE FOR EVERY MILE
AND A HALF. AROUND NOON...THERE WAS A 46 DEGREE DIFFERENCE ACROSS
THE COUNTY WARNING AREA. FOR TONIGHT...IT LOOKS LIKE A REPEAT WITH
MORE FOG IN THE WESTERN VALLEYS WITH MAINLY TRANQUIL WEATHER
ELSEWHERE. WE CAN NOT RULE OUT FOG IN SPOTS EAST OF THE DIVIDE...BUT
THIS WOULD BE THE EXCEPTION RATHER THAN THE RULE.

ON TUESDAY...A SYSTEM MOVING UP FROM ARIZONA WILL MAKE ITS WAY
TOWARD THE COWBOY STATE. CLOUDS WILL INCREASE FROM THE WEST IN THE
AFTERNOON AS IT APPROACHES. ANY CHANCE OF PRECIPITATION WOULD BE
CONFINED TO FAR WESTERN AREAS DURING THE DAYLIGHT HOURS. AND EVEN
HERE...THE MORNING LOOKS DRY WITH MOST AREAS REMAINING DRY FOR A
VAST MAJORITY OF THE DAY. THERE WILL BE MORE ON THE SNOW POTENTIAL
IN THE LONG TERM DISCUSSION FROM MY ESTEEMED COLLEAGUE.
MEANWHILE..EAST OF THE DIVIDE IT LOOKS LIKE ANOTHER DRY WITH MILD
TEMPERATURES. ONCE AGAIN...BASINS WILL BE COOLER WITH THE EVER
PRESENT INVERSIONS. THERE WILL BE AN INCREASE IN HIGH CLOUDS IN THE
AFTERNOON HOWEVER. IN ADDITION...SOUTHWEST FLOW AND THE PRESSURE
GRADIENT TIGHTENING A BIT WILL BRING GUSTY TO WINDS TO AREAS AROUND
NATRONA COUNTY. AT THIS TIME...UPPER LEVEL WINDS DO NOT LOOK STRONG
ENOUGH FOR ANY WIND HIGHLIGHTS...BUT SOMETHING TO WATCH.

.LONG TERM...TUESDAY NIGHT THROUGH MONDAY

UPPER LOW OFF THE CALIFORNIA COAST BECOMES ARE MAIN WEATHER MAKER
FOR TUESDAY NIGHT AND WEDNESDAY AS IT STARTS TO SHEAR APART AND THE
NRN PART MOVES INTO WRN WYO BY TUESDAY EVENING CONTINUING INTO
WEDNESDAY MORNING. AS THIS PIECE OF ENERGY CROSS THE DIVIDE IN NWRN
WYOMING LATE TUESDAY NIGHT IT LOOKS LIKE IT WILL TRACK THRU SERN WYO
WITH A SWATH OF LIGHT RAIN/SNOW QUITE POSSIBLE. A FRONTAL BOUNDARY
IN THE NORTH AND EAST MAY ALSO HELP TO FOCUS THIS. LIKED THE IDEA OF
SWATCH FROM THE BIGHORN BASIN AREA TO CASPER ON WEDNESDAY AND DIDN`T
CHANGE THAT. DID ADD A LITTLE NEAR THE MT BORDER EARLY WEDNESDAY.
SNOWFALL AMOUNTS STILL LOOK GENERALLY SUB-ADVISORY BUT IT DOESN`T
TAKE MUCH TO GET 3 INCHES OR MORE IN PLACES LIKE THE STAR VALLEY SO
WE`LL JUST HAVE TO WATCH THAT. A FEW OF THE MOUNTAIN LOCALES COULD SEE
ADVISORY AMOUNTS BUT OVERALL IT`LL PROBABLY BE A MORE 3 TO 6 INCH
TYPE EVENT TUESDAY NIGHT AND WEDNESDAY MORNING. NEXT SYSTEM WHICH IS
JUST A LITTLE FURTHER WEST IN THE PACIFIC FROM THE ONE JUST OFFSHORE
CALIFORNIA THEN MOVES ONSHORE THURSDAY AND INTO THE DESERT SW
THURSDAY NIGHT INTO FRIDAY. MOISTURE AHEAD OF THIS ON WEAK NEWD
MOVING RIPPLES MAY SPREAD A LITTLE LIGHT QPF INTO THE FAR S OR SW
THURSDAY NIGHT INTO FRIDAY. THE GFS IS MOST BULLISH WITH THIS IDEA
WHILE THE NAM AT 84HRS AND THE ECMWF AT 84 AND BEYOND KEEPS MOST OF
IT TO THE SOUTH. LIKE THE IDEA OF SOME LOW POPS MAINLY IN THE FAR S
AND SW THURSDAY NIGHT THROUGH FRIDAY. LATE FRIDAY OR FRIDAY NIGHT A
SHORTWAVE DROPS DOWN INTO THE NRN HIGH PLAINS WITH A COLD FRONT
PUSHING INTO AT LEAST FAR NRN OR NERN ZONES. 12Z ECMWF HAS BACKED
OFF ON A STRONGER PUSH WHICH PRODUCED A LITTLE UPSLOPE. KEEPING
PREVIOUS IDEA OF MAINLY SLIGHT CHANCES IN THE MOUNTAINS. ANOTHER
CLIPPER MAY JUST NICK THE FAR N AND NERN ZONES ABOUT SATURDAY NIGHT
SO PUT IN SOME SLIGHT CHANCES FOR JOHNSON COUNTY BESIDES KEEPING THE
MTN POPS. THE GEM IS MUCH STRONGER AND FURTHER WEST WITH THIS
SHORTWAVE AND ASSOCIATED FRONT. LOOKS LIKE FLOW STARTS TO FLATTEN AT
THE END OF THE MEDIUM RANGE PERIOD WITH POTENTIAL FOR INCREASING
WIND EAST OF THE DIVIDE AND SNOW IN THE W OR NW.

&&

.AVIATION.../06Z ISSUANCE/

VFR CONDITIONS WILL OCCUR EAST OF THE CONTINENTAL DIVIDE THROUGH
TUESDAY NIGHT.

AREAS OF FOG OR LOW CLOUDS WILL OCCUR IN THE FAR WEST VALLEYS
INCLUDING THE AFTON AND JACKSON AIRPORTS MVFR TO LIFR CONDITIONS CAN
BE EXPECTED UNTIL 19Z. OTHERWISE...VFR CONDITIONS WILL PREVAIL WEST
OF THE CONTINENTAL DIVIDE THROUGH 00Z WEDNESDAY. AFTER 00Z WED AREAS
OF SNOW WILL OCCUR IN THE MOUNTAINS WITH A MIX OR RAIN OR SNOW IN
THE WESTERN VALLEYS. EXPECT SOME MVFR CONDITIONS THROUGH 06Z WED.

&&

.FIRE WEATHER...

INVERSIONS WILL CONTINUE ACROSS THE WESTERN VALLEYS AS WELL AS SOME
OF LOWER BASINS EAST OF THE DIVIDE INTO TOMORROW...RESULTING IN LOW
MIXING HEIGHTS AND POOR SMOKE DISPERSAL. GUSTY SOUTHWEST WINDS WILL
CONTINUE FROM THE RED DESERT THROUGH NATRONA COUNTY THROUGH TUESDAY.
A SYSTEM APPROACHING FROM THE SOUTH WILL SPREAD SOME SNOW INTO THE
WESTERN MOUNTAIN ON TUESDAY NIGHT AND WEDNESDAY.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

SHORT TERM...HATTINGS
LONG TERM...SKRBAC
AVIATION...AR
FIRE WEATHER...HATTINGS








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