Area Forecast Discussion
Issued by NWS Riverton, WY

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS65 KRIW 260555
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1055 PM MST THU DEC 25 2014

UPDATE...ALLOWED THE REMAINDER OF THE HIGHLIGHTS TO EXPIRE.
STILL SOME UPSLOPE FLOW WITH EMBEDDED COOLER TOPS BUT BECOMING
MORE AND MORE FRAGMENTED SO AREAS OF ACCUMULATING SNOW ARE
SHRINKING. WIND STILL BLOWING SOME SNOW AROUND IN SWEETWATER
COUNTY BUT WEBCAMS SHOWING DECENT VISIBILITY.

.SHORT TERM...TONIGHT THROUGH FRIDAY
SNOWFALL IS GRADUALLY TAPERING OFF FROM NORTH TO SOUTH AFTER SOME
AREAS OF THE CWA LIKELY EXPERIENCED THE SNOWIEST CHRISTMAS ON
RECORD. ALPINE RECEIVED 12 INCHES OVERNIGHT. THE MAIN CIRCULATION
NOW APPEARS TO BE JUST SOUTH OF THE GREAT SALT LAKE. THE MID LEVEL
CIRCULATION WAS PROGGED TO TRACK SSE ACROSS SW WY TODAY. THE
COMBINATION OF THE CLOSE PROXIMITY OF THE MID LEVEL
CIRCULATION...QG FORCING DIRECTLY ASSOCIATED WITH THE MAIN
LOW...ISENTROPIC LIFT AROUND THE BACKSIDE OF THE LOW AS WELL AS
THE SURFACE CONVERGENCE WITH THE ASCT STRONG CANADIAN FRONT THAT
TRACKED SOUTH THIS MORNING ALL CONTRIBUTED TO THE SUBSTANTIAL
SNOWFALL ACROSS MUCH OF THE AREA...EAST AND WEST OF THE DIVIDE. IN
ADDITION...AREAS FROM THE LANDER FOOTHILLS AND THE NEARBY EAST
SLOPE OF THE WIND RIVERS TO THE GREEN MTNS TO CASPER HAVE BEEN
RECEIVING ADDITIONAL SNOWFALL FROM THE POST FRONTAL LOW LEVEL
UPSLOPE COMPONENT WITH LANDER RECEIVING AROUND HALF A FOOT OF SNOW
SO FAR. WITH THE MAIN LOW TRACKING FROM IDAHO LAST NIGHT TO UTAH
TODAY AND ON INTO THE FOUR CORNERS AREA FRIDAY HAS BEEN A FAVORABLE
TRACK FOR LND TO RECEIVE SIGNIFICANT SNOWFALL. AREAS IN THE FAVORED
UPSLOPE AREAS FROM LND TO CPR SHOULD SEE SEVERAL MORE INCHES OF
SNOWFALL THIS EVENING AS THE UPSLOPE DEEPENS ONCE THE MID LEVEL
CIRCULATION TRAVELS TO OUR SOUTH OVER THE UTAH/CO BORDER...EVEN AS
THE AFOREMENTIONED ENDING OF THE SNOW CONTINUES THIS EVENING FROM
NORTH TO SOUTH. THE SNOWFALL WILL CONTINUE TO TAPER OFF OVER CENTRAL
AND SOUTHERN WY AFTER MIDNIGHT TONIGHT WITH DRY CONDITIONS ACROSS
MOST OF THE NORTH. SOME LIGHT UPSLOPE SNOWFALL WILL LIKELY LINGER
THROUGH SUNRISE ABOVE CPR AND LANDER. OTHERWISE...JUST SOME ISOLATED
HIGH MTN FLURRIES WILL OCCUR FRIDAY WITH MOSTLY CLOUDY SKIES SLATED
FOR FRIDAY IN MOST AREAS AS THE EAST SIDE OF THE MAIN TROUGH
CONTINUES TO SLOWLY EXIT TO THE SOUTHEAST. AS SKIES CLEAR AND WINDS
CONTINUE TO TAPER OFF THROUGH LATE TONIGHT AND WITH FRESH SNOW COVER
ON THE GROUND...LOWS TONIGHT WILL HAVE NO TROUBLE DROPPING TO THE
SINGLE DIGITS MOST AREAS AND BELOW ZERO IN THE NORTHWEST. FRIDAYS
HIGH TEMPS WILL BE A FEW DEGREES COLDER FRIDAY BEHIND THIS EXITING
SNOWSTORM.

.LONG TERM...FRIDAY NIGHT THROUGH THURSDAY
WESTERN AND CENTRAL WYOMING WILL BE ON THE NORTHWEST FRINGE OF
THE LOW PRESSURE CIRCULATION WHICH WILL BE EXITING THE AREA.
MOUNTAIN AND EASTERN AREAS COULD SEE SOME VERY LIGHT SNOW.  COLD
NORTH FLOW WILL BE OVER THE AREA.  ADDED AREAS OF FOG IN THE VALLEYS
AND BASINS  WITH PARTIAL CLEARING OVER FRESH SNOW COVER.  SATURDAY
SHOULD BE DRY WITH LITTLE WARMING EXCEPT IN THE SOUTHWEST WHERE
WINDS WILL MIX THE LOWER AIR MASS.  BASIN COLD POOLS SHOULD RESIST
WARMING WITH WARM AIR ADVECTION IN THE MID LEVELS INCREASING SURFACE
BASED INVERSIONS.  AN APPROACHING PACIFIC LOW PRESSURE TROUGH WILL
BEGIN TO BRING SOME LIGHT SNOW TO THE NORTHWEST MOUNTAINS SATURDAY
AFTERNOON INCREASING THROUGH THE NIGHT.  INCREASED CLOUD COVER AND
WIND WILL ERODE AREAS OF COLD AIR ALONG THE EDGES OF THE BASINS.
THE WIND CORRIDOR ACROSS SWEETWATER...SOUTHERN FREMONT AND NATRONA
COUNTIES AND THE CODY FOOTHILLS WILL BECOME WINDY SATURDAY NIGHT AS
SNOW BECOMES MORE WIDESPREAD ACROSS THE WEST SPREADING INTO THE
SOUTHWEST.  SNOW WILL CONTINUE ACROSS THE WEST AND SOUTHWEST
DEVELOPING IN THE NORTH ON SUNDAY AS A COLD FRONT WORKS ITS WAY INTO
THE NORTH. SUNDAY NIGHT AND MONDAY ANOTHER LOW PRESSURE STORM SYSTEM
WILL WRAP UP AND DEEPEN OVER THE AREA WITH POTENTIAL WIDESPREAD
SNOWFALL ACROSS WESTERN AND CENTRAL WYOMING.  THIS WILL BE SUPPORTED
BY AN UPPER LEVEL LOW PRESSURE CENTER OVER NORTHEAST UTAH AND
NORTHWEST COLORADO PROVIDING UPPER AIR SUPPORT WITH UPPER LEVEL
DIVERGENCE AND MID LEVEL INSTABILITY OVER AN INTENSIFYING COLD
FRONT ALONG THE CONTINENTAL DIVIDE. MUCH OF THE AREA WILL SEE SNOW
THROUGH MONDAY AND MONDAY EVENING BEFORE THE LOW MOVES SOUTH AND
EAST THROUGH THE NIGHT WITH SNOWFALL ENDING FROM NORTHWEST TO
SOUTHEAST ACROSS THE AREA. CLEARING WILL OCCUR ON TUESDAY. A
CANADIAN COLD FRONT WILL BRING SOME ARCTIC AIR SOUTH LATE
WEDNESDAY AND WEDNESDAY NIGHT WITH A BETTER PUSH SOUTH ON
THURSDAY.

.AVIATION.../06Z ISSUANCE/

EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL ROUTES

EXPECT MVFR TO LCL IFR IN -SN AND LOW CLOUDS TO CONTINUE OVERNIGHT
WITH FQT MTN OBSCURATIONS IN THE SOUTH HALF. NORTH OF KRIW AND
KCPR...EXPECT GRADUALLY IMPROVING CONDITIONS FROM THE NORTH TONIGHT
WITH VFR TO LCL MVFR IN MAINLY LOW CLOUDS AND LCL -SN. AREAS OF GUSTY
NORTHEAST WINDS 15-25KTS WITH GUSTS TO 35KTS AND AREAS OF BLSN CAN
ALSO BE EXPECTED INTO THE EARLY MORNING ALONG I80. LCL MVFR
CONDITIONS DUE TO CIGS ARE EXPECTED THROUGH FRIDAY WITH WIDELY SCT
SNOW SHOWERS FRIDAY EVENING.

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

CONDITIONS WILL CONTINUE TO IMPROVE OVERNIGHT WITH GENERALLY VFR TO
LCL MVFR CONDS OVERNIGHT AND INTO FRIDAY. HOWEVER...CIGS AROUND 040
WILL LIKELY CONTINUE FRIDAY WITH HYR MTN OBSCURATIONS. PATCHY FOG
MAY CREATE LCL IFR CONDS EARLY SATURDAY.

.FIRE WEATHER...

WIDESPREAD SNOW AND GUSTY WIND THROUGH TONIGHT SOUTH OF A CASPER
TO LANDER TO WESTERN SWEETWATER COUNTY LINE. EXPECT IMPROVING
CONDITIONS FROM NORTH TO SOUTH TONIGHT NORTH OF THIS AREAS. MOSTLY
DRY CONDITIONS ARE EXPECTED FRIDAY. BASINS AND VALLEYS WILL
DEVELOP INVERSIONS FOR FRIDAY NIGHT THAT WILL LEAD TO POOR MIXING
AND SMOKE DISPERSAL. ON SATURDAY...MILDER AIR MOVES IN ALONG WITH
SOME STRONGER WINDS THAT WILL ENCOURAGE SOME MIXING. ANOTHER SNOW
STORM IS POSSIBLE ON SATURDAY NIGHT IN THE WEST AND SPREADING EAST
OF THE DIVIDE SUNDAY.

&&

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

&&

$$

SHORT TERM...HATTINGS/SKRBAC
LONG TERM...C.BAKER
AVIATION...SKRBAC
FIRE WEATHER...LIPSON








USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.