Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 010611
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1111 PM MST SUN JAN 31 2016

.SHORT TERM...TONIGHT THROUGH MONDAY

ISSUED WINTER WEATHER ADVISORY FROM MONDAY MORNING THROUGH
TUESDAY MORNING FOR SNOW AND BLOWING SNOW ACROSS NATRONA...
FREMONT...SWEETWATER AND SOUTHERN LINCOLN COUNTIES.
CENTRAL AND SOUTHERN WYOMING WILL BE ON THE NORTHWEST EDGE OF A
LARGE WINTER STORM THAT WILL BE MOVING THROUGH THE SOUTHERN AND
CENTRAL ROCKIES MONDAY AND MONDAY NIGHT. NATRONA...FREMONT...
SWEETWATER AND SOUTHERN LINCOLN COUNTIES ARE EXPECTED TO SEE SNOW
DEVELOP MONDAY MORNING WITH BRISK NORTHEAST WINDS. BY MONDAY
AFTERNOON SIGNIFICANT SNOW AND BLOWING SNOW IS EXPECTED. THE SNOW
AND BLOWING SNOW SHOULD CONTINUE THROUGH MONDAY NIGHT AND TAPER
OFF TUESDAY MORNING. TO THE NORTH SCATTERED SNOW SHOWERS ARE
EXPECTED WITH COLDER TEMPERATURES.

.LONG TERM...MONDAY NIGHT THROUGH SUNDAY

BY EARLY MONDAY EVENING THE SNOWFALL WILL CONTINUE MAINLY SOUTH OF A
LINE FROM KMM TO FT WASHAKIE...RIW AND TO KAYCEE AS THE ISENTROPIC
LIFT CONTINUES TO PENETRATE NORTH TO THIS LINE ALONG WITH SOME Q
VECTOR FORCING. THESE DYNAMICS WILL SEED THE LOWER DECK OF STRATOCU
IN PLACE THAT WILL BE ASCT WITH THE LOW LEVEL UPSLOPE FLOW AFFECTING
THE AREA FROM LND TO CPR. BY 00Z TUE...THE MAIN LOW WILL BE
UNDERGOING CYCLOGENESIS OVER SE COLORADO AND WILL BECOME MORE OR
LESS VERTICALLY STACKED. THE INFLUENCE OF THE STRONG CYCLONIC FLOW
AROUND THE BACKSIDE OF THE LOW WILL STILL BE ENCOMPASSING THESE
AFOREMENTIONED AREAS. SNOW AND BLOWING SNOW WILL CONTINUE IN THESE
REGIONS IN THE ADVISORY THROUGH MONDAY NIGHT WITH SNOW TOTALS OF UP
TO 4 INCHES IN LANDER AND CASPER BY 15Z TUESDAY ALONG WITH 1 TO 2
INCHES IN RIVERTON...UP TO 6 INCHES ON THE EAST SLOPE OF THE WIND
RVR MTNS AND 8 INCHES ON CASPER MTN. AREAS JUST TO THE NORTH OF
RIVERTON SHOULD SEE VERY LITTLE IN THE WAY OF SNOWFALL DUE TO BEING
TOO FAR NORTH OF THE DYNAMICS AND THE OWL CREEK MTN SNOW SHADOW
EFFECT. THE UPPER GREEN RVR BASIN WILL GET SHADOWED BY THE WIND RVR
MTNS AS WELL. WINTER WEATHER ADVISORIES WILL BE IN EFFECT TIL 15Z
TUESDAY. BY 15Z TUE...THE LOW WILL BE WAY OUT OVER CENTRAL KANSAS
BUT THERE SHOULD BE ENOUGH LIGHT SNOWFALL AND LINGERING BLOWING SNOW
TO WARRANT HAVING THE ADVISORY EXTEND THROUGH THE RUSH HOUR FOR
THOSE SOUTH AND SOUTHEAST ZONES. THEN BY TUESDAY AFTERNOON...OUR
ATTENTION WILL SHIFT TO WESTERN WY WHERE A SHORTWAVE TROUGH RIDING
DOWN THE BACK SIDE OF THE MAIN EXITING TROUGH WILL CAUSE THE FLOW TO
BECOME INCREASINGLY DIFLUENT FROM THE NNW WITH SNOWFALL INCREASING
IN FAR WESTERN WY BY LATE TUESDAY AFTERNOON. SNOWFALL WILL CONTINUE
TUESDAY NIGHT THROUGH WEDNESDAY IN THE WEST. A BIT TOO EARLY TO
FINE TUNE SNOW AMNTS WITH THIS FEATURE FOR NOW. THEN BEHIND THIS
SHORTWAVE...TEMPS WILL BEGIN TO WARM AS THE JET STREAM SHIFTS TO OUR
NORTHEAST. A TEMPERATURE INVERSION SHOULD BE IN PLACE BY 12Z WED IN
THE VALLEYS AND BASINS BUT ELECTED TO HOLD OFF ON MENTION OF PATCHY
FOG IN THE WIND RIVER BASIN FOR NOW IN SPITE OF THE FRESH SNOW COVER
AS FCST SOUNDINGS ARE NOT IDEAL FOR THAT TIME FRAME. THE NEXT
SHORTWAVE IN THE NW FLOW WILL GIVE THE FAR WEST MORE SNOWFALL
THURSDAY THROUGH FRIDAY. THEN ANOTHER...MORE VIGOROUS SHORTWAVE
TROUGH...THAT WILL BE ASCT WITH A STRONG NW DIFLUENT FLOW...WILL
SWING A 700MB COLD FRONT NOSING RIGHT INTO CENTRAL WY LATER
SATURDAY...WHICH TENDS TO BE AN INDICATION THAT CENTRAL WY EAST OF
THE DVD COULD GET SOME PRECIP ACDG TO THE GFS BUT WE WILL HAVE TO
WAIT FOR MORE RUN TO RUN CONSISTENCY. THE ECMWF TAKES THIS FEATURE
FARTHER SOUTH. THE GFS HAS THE TROUGHPA SAY NT AND THE ECMWF
SUNDAY...SO AGAIN...WE WILL WAIT FOR A BIT MORE CONSISTENCY TO MAKE
ANY WHOLE SALE CHANGES TO THE POP/SNOWFALL GRIDS FOR NEXT WEEKEND.

&&

.AVIATION.../06Z ISSUANCE/

RAPIDLY DETERIORATING CONDITIONS FROM SOUTH TO NORTH MONDAY MORNING
AS A LARGE WINTER STORM IMPACTS THE CENTRAL AND SOUTHERN ROCKIES.
WIDESPREAD IFR CONDITIONS IN VSBY REDUCTIONS IN SNOW ARE EXPECTED TO
DEVELOP MONDAY MORNING...AND REMAIN FOR MUCH OF THE TAF FORECAST
PERIOD ALONG AND SOUTHEAST OF KEMM-KLND-KBYG LINE. ALSO STRONG NORTH
TO NORTHEAST WINDS WILL OCCUR IN MUCH OF THE SAME AREA CAUSING
CONSIDERABLE BLOWING SNOW. AIRFIELD MINIMUMS COULD OCCUR FOR SEVERAL
HOURS AT KRKS DUE TO VSBY RESTRICTIONS IN SN AND BLSN WITH THE BEST
CHANCE BETWEEN 19Z AND 01Z. ALSO CPR COULD ALSO SEE AIRFIELD
MINIMUMS...BUT CONFIDENCE IS NOT AS HIGH AS KRKS. HAVE KEPT BOTH
TERMINALS JUST ABOVE AIRFIELD MINIMUMS FOR NOW. KPNA MAIN ISSUE WILL
BE LOW LEVEL WIND SHEAR FROM THE NORTHEAST TODAY...AS DOWNSLOPING
SHOULD KEEP THEM DRY. KJAC TERMINAL WILL BE LEAST IMPACTED FROM THIS
SYSTEM WITH ONLY SOME SNOW SHOWERS IMPACTING THE AREA...WITH VFR
CONDITIONS EXPECTED WITH A BREEZY FROM THE NORTH.

PLEASE SEE THE AVIATION WEATHER CENTER FOR THE LATEST INFORMATION ON
ICING AND TURBULENCE FORECASTS.

&&

.FIRE WEATHER...

ISSUED WINTER WEATHER ADVISORY FROM MONDAY MORNING THROUGH
TUESDAY MORNING FOR SNOW AND BLOWING SNOW ACROSS NATRONA...
FREMONT...SWEETWATER AND SOUTHERN LINCOLN COUNTIES.
CENTRAL AND SOUTHERN WYOMING WILL BE ON THE NORTHWEST EDGE OF A
LARGE WINTER STORM THAT WILL BE MOVING THROUGH THE SOUTHERN AND
CENTRAL ROCKIES MONDAY AND MONDAY NIGHT. NATRONA...FREMONT...
SWEETWATER AND SOUTHERN LINCOLN COUNTIES ARE EXPECTED TO SEE SNOW
DEVELOP MONDAY MORNING WITH BRISK NORTHEAST WINDS. BY MONDAY
AFTERNOON SIGNIFICANT SNOW AND BLOWING SNOW IS EXPECTED. THE SNOW
AND BLOWING SNOW SHOULD CONTINUE THROUGH MONDAY NIGHT AND TAPER
OFF TUESDAY MORNING. TO THE NORTH SCATTERED SNOW SHOWERS ARE
EXPECTED WITH COLDER TEMPERATURES. HIGH RELATIVE HUMIDITY WITH
LOW MIXING HEIGHTS AND POOR SMOKE DISPERSAL IS EXPECTED THROUGH
TUESDAY.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM 9 AM MONDAY TO 9 AM MST TUESDAY FOR
WYZ015-018>020-022-027>030.

&&

$$

SHORT TERM...C.BAKER
LONG TERM...LIPSON
AVIATION...WM
FIRE WEATHER...C.BAKER


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