Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 010655 CCA
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1149 PM MST SAT JAN 31 2015

.SHORT TERM...TONIGHT THROUGH SUNDAY (ISSUED AT 242 PM MST)

LOW CLOUDS AND FOG TOOK UNTIL EARLY AFTERNOON TO LIFT IN THE CENTRAL
VALLEYS AS WELL AS IN THE STAR VALLEY. OTHERWISE A MOSTLY SUNNY DAY
WITH MILD TEMPS FOR THE MOST PART. A COLD FRONT HAS ENTERED NORTHERN
WY AS OF 19Z. PRECIP IS BREAKING OUT IN SOUTHERN MONTANA AS A
WEATHER SYSTEM DIVES SOUTHEAST THROUGH MONTANA AND HEADS TOWARD WY
FOR THE TONIGHT PERIOD. THIS SYSTEM WILL MAINLY IMPACT THE AREAS
EAST OF THE CONTINENTAL DIVIDE TONIGHT INTO EARLY SUNDAY WITH SOME
SNOW AND WIND AND COLDER TEMPS. THE BEST CHANCE OF SNOW WILL BE FROM
THE BIGHORN MOUNTAINS SOUTH TO CASPER MOUNTAIN...INCLUDING BUFFALO
TO CASPER. HAVE WENT HIGHER WITH THE CHANCE OF SNOW WITH
ACCUMULATIONS AROUND AN INCH IN PLACES. THE BIG HORN BASIN SHOULD
SEE SOME LIGHT SNOW TONIGHT...ENDING BY SUNDAY MORNING. THE WIND
RIVER BASIN SHOULD SEE SOME LIGHT SNOW AT TIMES LATE THIS EVENING TO
AROUND SUNRISE SUNDAY. LESS THAN AN INCH IS EXPECTED FOR THE MOST
PARTS IN THE THOSE BASINS. OUT WEST NOT MUCH EXPECTED ASIDE FROM
SOME MOUNTAIN SNOW SHOWERS OVER THE NORTHWEST MOUNTAINS AND WIND
RIVER MOUNTAINS. WILL HAVE TO DEAL WITH THE FOG AND LOW CLOUDS IN
THE STAR VALLEY AGAIN TONIGHT INTO SUNDAY MORNING. COLDER LOWS EAST
OF THE DIVIDE AS THE BRUNT OF THE COLD AIR WILL REMAIN EAST OF THE
DIVIDE TONIGHT AND SUNDAY. CLOUDS WILL BE ON THE DECREASE SUNDAY
EAST OF THE DIVIDE AS THE SYSTEM DEPARTS. SOME HIGH CLOUDS WILL
FILTER IN SUNDAY PM IN THE NORTHWEST FLOW ALOFT. OUT WEST...SUNDAY
WILL BE DRY FOR MOST OF THE DAY. INCREASING CLOUDS SUNDAY AFTERNOON
WITH SCATTERED LIGHT SNOW FOR THE NORTHWEST WY MOUNTAINS AS MOISTURE
INCREASES IN THE NW FLOW ALOFT. IT SHOULD STAY DRY IN THE WESTERN
VALLEYS THROUGH 00Z MONDAY. HIGHS ON SUNDAY WILL BE 5 TO 10 DEGREES
COLDER THAN SATURDAY EAST OF THE DIVIDE AND SLIGHTLY COLDER WEST OF
THE DIVIDE.

.LONG TERM...SUNDAY NIGHT THROUGH SATURDAY

THROUGH THE FIRST PORTION OF THE LONG TERM FORECAST...MAINLY THROUGH
TUESDAY...REMAINS OF AN OLD SHOW ON PBS MANY YEARS AGO. THE SHOW IS
UPSTAIRS DOWNSTAIRS. EXCEPT...THIS IS THE WEATHER VERSION CALLED
UPSLOPE DOWNSLOPE. IN AREAS WEST OF THE DIVIDE...THEY WILL BE IN THE
UPSLOPE PORTION OF THE FORECAST. THE FIRST SHORTWAVE APPROACHES FROM
THE WEST FOR SUNDAY NIGHT WITH THE FIRST SHOT OF POTENTIAL
ACCUMULATING SNOW. THE NEXT WAVE THEN ARRIVES SOMETIME ON MONDAY.
THE MODELS DO HAVE A FEW TIMING DIFFERENCES WITH THE NAM HAVING A
BIT OF A BREAK ON MONDAY AND THE GFS KEEPING THE PRECIPITATION GOING
THROUGH MUCH OF THE DAY. AT THIS POINT...CONTINUITY LOOKED
REASONABLE SO WE MADE FEW CHANGES. MEANWHILE...EAST OF THE DIVIDE IS
ON THE DOWNSLOPE SIDE. THIS MEANS MAINLY DRY CONDITIONS FOR MOST
LOCATIONS EXPECT FOR THE BIGHORN RANGE AND POSSIBLY THE NORTHERN BIG
HORN BASIN WHERE SOME JET ENERGY COULD BRING SOME LIGHT
PRECIPITATION. WITH THE DOWNSLOPING FLOW...EXPECT TEMPERATURES TO BE
NEAR TO ABOVE NORMAL FOR MOST LOCATIONS. THERE MAY BE THE POTENTIAL
FOR SOME HIGH WINDS...ESPECIALLY MONDAY NIGHT WITH A COUPLE OF
MODELS SHOWING 700 MILLIBAR WINDS AT OR OVER 50 KNOTS...ESPECIALLY
NEAR THE FAVORED AREAS LIKE NEAR CLARK AND PORTIONS OF NATRONA
COUNTY.

THE NEXT DECENT CHANCE FOR PRECIPITATION ACROSS THE AREA WOULD BE
TUESDAY NIGHT INTO WEDNESDAY. BOTH THE GFS AND EUROPEAN SHOW SOME
PRECIPITATION GETTING KICKED ACROSS THE DIVIDE AS A COLD FRONT AND
ASSOCIATED SHORT WAVE DROPS SOUTHWARD OUT OF CANADA AND INTO WYOMING
WITH MAYBE SOME LIGHT UPSLOPE EAST OF THE DIVIDE. AT THIS
POINT...THIS DOES NOT LOOK LIKE A BIG EVENT BUT THERE WILL BE THE
POTENTIAL FOR SOME PRECIPITATION EVERYWHERE. THERE ARE SOME
DIFFERENCES IN THE MODELS TIMING THE SYSTEMS WITH THE GFS MOVING
PRECIPITATION OUT FASTER THAN THE GFS AT THIS POINT.

BOTH THE GFS AND EUROPEAN NOW BUILD RIDGING ACROSS THE AREA FOR LATE
NEXT WEEK WITH MAINLY DRY CONDITIONS DOMINATING FOR THURSDAY AND
EVEN INTO FRIDAY. WE STILL HAVE SOME LIGHT POPS ACROSS THE WEST BUT
FUTURE SHIFTS MAY WANT TO REMOVE IT. WITH THE RIDGING...THE PATTERN
OF ABOVE NORMAL TEMPERATURES WILL CONTINUE WITH SOME 50S POSSIBLE BY
FRIDAY IN WARMER AREAS EAST OF THE DIVIDE. THEN BOTH MODELS SHOW THE
NEXT SYSTEM MOVING IN FOR NEXT WEEKEND.

&&

.AVIATION.../06Z ISSUANCE/

SNOW...MAINLY CONVECTIVE SNOWBANDS IN THE VCNTY OF KRIW...WILL
MOSTLY END BY 09Z.  AREAS OF MVFR...LCL IFR CIGS AND MTN
OBSCURATIONS WILL LINGER OVER MUCH OF THE AREA THROUGH
14Z...ESPECIALLY ALONG THE EAST SLOPES OF THE DIVIDE...AND NORTH
FACING SLOPES.  THESE CIGS WILL DISSIPATE LEAVING PREVAILING VFR
CONDITIONS BY 18Z SUNDAY AND THROUGH THE REST OF THE PERIOD.
SOUTHWEST WINDS WILL PICK UP THROUGH THE WIND CORRIDOR KRKS-KCPR AND
ALONG THE EASTERN FOOTHILLS OF THE DIVIDE LATE SUNDAY AFTERNOON
THROUGH SUNDAY NIGHT.

WEST OF THE DIVIDE...KBPI/KJAC/KPNA/KRKS ROUTES

PATCHY FOG WILL FORM OVER THE FAR WEST VALLEYS OVERNIGHT WITH FOG
MORE WIDESPREAD ACROSS THE STAR VALLEY...VCNTY KAFO.  SOME LOWER
MVFR/IFR CIGS WILL ALSO BE ENCOUNTERED VCNTY AND NE-E OF KRKS
THROUGH AROUND 15Z SUNDAY.  VFR CONDITIONS WILL PREVAIL ACROSS THE
AREA BY 18Z SUNDAY.  HOWEVER...CIGS ARE EXPECTED TO LOWER ACROSS THE
FAR WEST BY 00Z MONDAY WITH MVFR/IFR CIGS AND -SN PREVAILING ACROSS
MUCH OF THE WEST...VCNTY AND NORTH OF A KPNA-KAFO LINE...BY 03Z
MONDAY.  LCL MVFR/IFR -SN WILL BE ENCOUNTERED FURTHER SOUTH ALONG
KBPI-KRKS ROUTES SUNDAY NIGHT.

&&

.FIRE WEATHER...

A WEATHER SYSTEM WILL BRING SOME LIGHT SNOW EAST OF THE DIVIDE
TONIGHT AND SUNDAY MORNING. THEN MOSTLY DRY SUNDAY AFTERNOON
THROUGH MONDAY EAST OF THE DIVIDE. WEST OF THE DIVIDE WILL BE DRY
TONIGHT AND SUNDAY MORNING. LIGHT SNOW DEVELOPS OVER THE NORTHWEST
MOUNTAINS SUNDAY AFTERNOON. PERIODS OF SNOW FOR THE WESTERN
MOUNTAINS AND FAR WEST VALLEYS SUNDAY NIGHT THROUGH MONDAY NIGHT.

&&

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

&&

$$

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











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