Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 242047
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
147 PM MST SAT JAN 24 2015

.SHORT TERM...TONIGHT THROUGH SUNDAY

ACTIVE SHORTWAVE MOVING THROUGH SWRN ND ATTM WITH CONVECTIVE
SHOWERS BUILDING AS FAR WEST AS NERN JOHNSON COUNTY. LIGHT WARM
ADVECTION PCPN IF FURTHER WEST FROM ABOUT THE BIGHORN MOUNTAINS
WWD TO THE TETONS. POWDER RIVER PASS HAS SEEN SOME PRETTY DECENT
SNOW AT TIMES TODAY AS HAS HIGHWAY 14. THE POWDER RIVER SNOTEL
REPORTED A 4 INCH SNOW DEPTH INCREASE THIS MORNING. LIGHTER SNOWS HAVE
FALLEN FURTHER WEST. LIGHT MAINLY RAIN SHOWERS HAVE FALLEN ACROSS
THE LOWER ELEVATIONS OF THE NORTH...MAINLY IN JOHNSON COUNTY A
COUPLE TIMES TODAY. PROBABLY THE MOST INTERESTING WEATHER TODAY IN
CENTRAL WYOMING HAS BEEN WATCHING THE STRONG NW WIND SLOWLY EDGING
TOWARDS THE CENTER OF THE WIND RIVER BASIN TODAY. WINDS HAVE
GUSTED OVER 35 MPH AT OUR OFFICE AND AROUND 30 MPH SO FAR AT THE
KRIW AIRPORT. TEMPS POPPED UP INTO THE LOWER TO MID 40S ONCE THE
WINDS HIT. INVERSION WAS DECENT THIS MORNING BUT IT DIDN`T MATTER
TODAY. SOME LIGHT SNOW WILL PERSIST INTO THE NIGHT ACROSS THE NRN
MOUNTAINS WITH A FEW LIGHT MAINLY RAIN SHOWERS/SPRINKLES EAST OF
THE DIVIDE FOR A FEW MORE HOURS. CLOUD COVER IS A LITTLE TRICKY
WITH ISENTROPIC UPGLIDE INTO THE NIGHT WITH THICKER CLOUDS
POTENTIALLY THINNING THIS EVENING. CENTRAL AND PARTS OF THE SWRN
SECTIONS MAY HAVE THE BEST CHANCE FOR AT LEAST PARTIAL CLEARING
THIS EVENING WITH A LITTLE MORE SPILLOVER TRYING TO WORK SOUTH
SUNDAY MORNING. LOOKS THINNER RIGHT NOW THAN TODAY`S ACTION. AFTER
A LITTLE COLD AIR ADVECTION TODAY...WE`LL RETURN TO WARMING IN THE
MID LEVELS ON SUNDAY. SOME LEE TROUGHING REDEVELOPING AFTER A
LITTLE LULL THIS WILL KEEP WINDS GOING THROUGH SUNDAY IN ABOUT THE
SAME AREAS. THE CLARK HIGHWAY 120 SENSOR HIT 60 MPH+ A COUPLE
TIMES THIS MORNING PEAKING OUT AT 68 MPH. EVEN THE SHERIFF`S
OFFICE IN CODY HIT 46 MPH THIS MORNING. BASINS AND VALLEYS WILL
REMAIN AT LEAST PARTIALLY TRAPPED TOMORROW...ESPECIALLY IN THE
WEST.

.LONG TERM...SUNDAY NIGHT THROUGH SATURDAY

THE FIRST PART OF THE LONG TERM IS FAIRLY QUIET. ANY SHOWERS FROM
THE LAST OF THE SHORTWAVES SHOULD BE ENDING BY SUNDAY NIGHT AND WITH
RIDGING BUILDING ACROSS THE AREA EXPECT MAINLY QUIET CONDITIONS. THE
MAIN CONCERN FOR SUNDAY AND MONDAY NIGHTS WILL BE THE DEVELOPMENT OF
FOG ALONG WITH THE POTENTIAL FOR INVERSIONS TO THROW A MONKEY WRENCH
INTO THE TEMPERATURE FORECASTS FOR THE BASINS AND VALLEYS. THE
CONDITIONS FOR FOG LOOK TO BE DECENT WITH A CLEAR SKY AND LIGHT
WINDS. IT MAY NOT BE A THICK AS SOME OF THE FOG EARLIER THIS
MONTH...ESPECIALLY EAST OF THE DIVIDE SINCE SNOW COVER IS MUCH LESS
WITH A LOT OF BARE SPOTS APPEARING. HOWEVER...THERE SHOULD BE SOME
AND THE PREVIOUS FORECAST HAD IT HANDLED WELL SO WE MADE FEW
CHANGES. AS FOR INVERSIONS...THERE ARE THE SAME CONCERNS. WITH GOOD
SNOWPACK WEST OF THE DIVIDE...INVERSIONS SEEM FAIRLY LIKELY THERE.
EAST OF THE DIVIDE...MAYBE NOT QUITE AS CERTAIN SINCE THE
AFOREMENTIONED LACK OF FRESH SNOW COULD LIMIT RADIATIONAL COOLING
AND ALBEDO A BIT. FOR NOW...WE KEPT THE TEMPERATURES COOLER WITH THE
THINKING THAT IF IT GETS WARMER...MOST PEOPLE WILL BE HAPPY. THE
AREAS THAT DO MIX WELL...AKA CODY...CASPER...BUFFALO...COULD GET
QUITE WARM. THE NAM MOS HIGH FOR BUFFALO ON MONDAY IS 73!  THIS IS
PROBABLY OVERDONE BUT WE DID PUT SOME 60S IN THE FORECAST FOR MONDAY
AND TUESDAY.

THE NEXT WEATHER MAKER LOOKS TO MOVE INTO THE WEST LATER ON
TUESDAY...THIS ONE COMING UP FROM THE BAJA AND FROM THE SOUTH. THE
MODELS HAVE SOME DIFFERENCES ON TIMING WITH THE GFS THE FASTEST. THE
NEW EUROPEAN HAS TRENDED A BIT SLOWER AND FURTHER WEST. FOR NOW...WE
HAVE COMPROMISED. WE REMOVED POPS FOR THE MORNING AND HAVE ONLY
SLIGHT POPS FOR THE AFTERNOON IN THE SOUTHWEST. AND EVEN HERE...THE
VAST MAJORITY OF THE DAY SHOULD BE DRY. THE BULK OF THE
PRECIPITATION...AND WE SAID PRECIPITATION NOT SNOW...WOULD BE
TUESDAY NIGHT ACROSS THE WEST. AT THIS POINT...IT DOES NOT LOOK LIKE
A MAJOR STORM. THE SOUTHERN ORIGIN KEEPS THE SYSTEM FROM HAVING A
LOT OF MOISTURE. IN ADDITION...WARMER AIR WOULD KEEP SNOW LEVELS
HIGHER. THE EUROPEAN HAS MORE PRECIPITATION THAN THE GFS AT THIS
POINT. STILL...MORE TIME TO WATCH IT. THE SYSTEM THEN SHIFTS EAST
ACROSS THE STATE. THIS DIRECTION IS NOT FAVORABLE FOR A LOT OF
PRECIPITATION EAST OF THE DIVIDE. FOR NOW...WE HAVE SLIGHT POPS IN
FOR MOST AREAS ON WEDNESDAY. TEMPERATURES WILL BE COOLER WITH MORE
CLOUD COVER BUT STILL WARM FOR JANUARY. THIS WILL LIKELY LEAD TO
MAINLY RAIN IN THE LOWER ELEVATIONS AS WELL. BY THURSDAY...THE
SYSTEM WILL BE GONE AND REPLACED WITH DRY...NORTHWEST FLOW FOR
THURSDAY.

THE MODELS THEN BECOME DIAMETRICALLY OPPOSED FOR FRIDAY. THE GFS AND
EUROPEAN HAVE A SURGE OF MOISTURE MOVING TOWARD THE AREA FROM THE
SOUTH. HOWEVER...THE OTHER INGREDIENT IS AN ALBERTA CLIPPER DROPPING
SOUTHWARD. THE GFS HAS SHIFTED FURTHER WEST OVER THE PAST 24 HOURS
AND ACTUALLY HAS A DECENT SWATH OF PRECIPITATION FOR MUCH OF THE
STATE FOR FRIDAY WITH AN ARCTIC AIR MAS DROPPING EAST OF THE
ROCKIES. MEANWHILE...THE EUROPEAN KEEPS THE CLIPPER FURTHER EAST
WITH ONLY SOME LIGHT PRECIPITATION ACROSS THE SOUTH. THE EUROPEAN
HAS BEEN MORE CONSISTENT SO FOR NOW WE WILL ADD SOME SLIGHT POPS
ACROSS THE SOUTH ONLY.

&&

.AVIATION.../00Z ISSUANCE/

A WEATHER SYSTEM WILL SPREAD SNOW ACROSS THE NORTHERN MOUNTAINS
THROUGH TONIGHT. EXPECT MOUNTAIN OBSCURATION AND MVFR TO IFR CONDITIONS.
SCATTERED AREAS OF LIGHT RAIN OR SNOW ARE POSSIBLE OVER THE LOWER
ELEVATIONS OF NORTHERN WY WITH LOCAL MVFR CONDITIONS. LIGHT RAIN
MAY GET CLOSE TO THE CASPER AIRPORT IN THE LATE AFTERNOON INTO THE
EVENING HOURS. EXPECT WINDY CONDITIONS AT KCPR AIRPORT TODAY AND
TONIGHT. A GUSTY WIND WILL DEVELOP OVER NORTHERN JOHNSON COUNTY
AFTER 17Z AND THIS WIND WILL CONTINUE THROUGH TONIGHT. THE KBYG
AIRPORT WILL LIKELY SEE WIND GUSTS OVER 40 KNOTS.

AT THE KJAC AIRPORT LIGHT SNOW WILL FALL AT TIMES THROUGH 12Z SUNDAY
WITH VFR TO MVFR CONDITIONS EXPECTED.

&&

.FIRE WEATHER...

HIGH PRESSURE LOOMS TO THE WEST WHILE ANOTHER WEAK SYSTEM RIPPLES
AROUND THE HIGH TODAY. IT WILL HAVE MINOR IMPACT ON THE AREA WITH
SOME INCREASING CLOUDS AND SOME BREEZES IN MOST AREAS...WITH STRONG
WINDS POSSIBLE IN THE BUFFALO AREA. THE MOUNTAINS MAY SEE SOME SNOW
WITH A VERY SMALL CHANCE OF A RAIN OR SNOW SHOWER IN THE LOW
ELEVATIONS OF NORTHERN CODY DISPATCH AND CASPER DISPATCH.
TEMPERATURES WILL BE MILD THROUGH THE PERIOD WITH A WARMING TREND
EXPECTED TO LAST INTO NEXT WEEK. WE STILL CAN NOT GET MIXING HEIGHTS
UP TOO MUCH...ESPECIALLY IN LESS WIND PRONE AREAS. HOWEVER THERE
WILL BE SOME HIGH END POOR TO FAIR SMOKE DISPERSAL POSSIBLE
TODAY...EVEN IN THE LESS WINDY AREAS.

&&

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

&&

$$

SHORT TERM...PS
LONG TERM...HATTINGS
AVIATION...PS
FIRE WEATHER...PS







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