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 232130
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
230 PM MST TUE DEC 23 2014

.SHORT TERM...TONIGHT THROUGH CHRISTMAS EVE

A TRANSIENT RIDGE WILL SHIFT SOUTHEAST ACROSS THE CWA
WHICH WILL DECREASE THE WINDS BRIEFLY. A PACIFIC TROUGH WILL MAKE
LANDFALL TONIGHT. AHEAD OF THIS APPROACHING WEATHER
SYSTEM...INCREASING CLOUDS AND A FEW FLURRIES WILL TAKE PLACE IN THE
NORTHWEST MTNS LATE. AS THE TROUGH DIGS AND TRACKS EAST ACROSS THE GREAT
BASIN CHRISTMAS EVE...SNOWFALL WILL INCREASE IN COVERAGE ACROSS THE
FAR WEST. THE GRADIENT WILL TIGHTEN ON CHRISTMAS EVE AHEAD OF THIS
APPROACHING WEATHER SYSTEM WITH A RESPONDING INCREASING SOUTHWEST
WIND FROM THE GREEN MTNS TO CASPER. TEMPERATURES WILL CONTINUE
SEASONABLY COOL THROUGH CHRISTMAS EVE.

.LONG TERM...WEDNESDAY NIGHT THROUGH TUESDAY

CHRISTMAS STORM IS STILL ON TRACK TO IMPACT MUCH OF OUR AREA LATE ON
CHRISTMAS EVE THROUGH CHRISTMAS DAY AND INTO CHRISTMAS NIGHT.
CURRENT SYSTEM IS JUST OFF THE PACNW COAST AND WILL MAKE IT ONTO THE
COAST EARLY TOMORROW. SYSTEM THEN DIGS SE INTO THE NRN GREAT BASIN
CHRISTMAS EVE BEFORE CLOSING OFF AND SLOWING DOWN ON CHRISTMAS DAY
BEFORE GRADUALLY WEAKENING AND DRIFTING SOUTH INTO THE END OF THIS
PERIOD. VERY FAVORABLE UPPER LOW POSITION ON CHRISTMAS DAY WITH THE
H5 AND H7 CIRCULATIONS GENERALLY BETWEEN FAR NERN UT AND SWRN
WYOMING. SNOWFALL GETS GOING IN THE EVENING OUT WEST AND THEN QUICKLY
SPREADS INTO THE SW CORNER AFTER MIDNIGHT...THEN INTO THE FAR NORTH
AND EVENTUALLY SWEETWATER COUNTY BETWEEN 09Z AND 12Z ON THE 25TH.
FAVORABLE QG FORCING AND NOSE OF THE CYCLONICALLY CURVED JET WILL
THEN LIKELY GET THE SNOW GOING QUICKLY IN THE CENTRAL ZONES AROUND
12Z. ALL THE TIME HEIGHTS LOOK VERY FAVORABLE FOR STEADY IF NOT
HEAVY SNOW AT TIMES DURING THE DAY CHRISTMAS DAY FOR OUR CENTRAL
ZONES WITH WINDS INCREASING AND THE FRONT BACKING THROUGH SWEETWATER
COUNTY INTO SRN LINCOLN. THEY GET THE SNOW FIRST WITH THE WLY WIND
AND THEN AS THE DAY WEARS ON...ON CHRISTMAS DAY...THE FRONT WILL
MOVE WWD WITH STRONG NE WIND DEVELOPING. THE EXACT AMOUNTS ARE STILL
A LITTLE UNCERTAIN BUT AFTER LOOKING AT EVERYTHING TODAY WILL ISSUE
WINTER STORM WATCHES FOR MOST OF CENTRAL AND SWRN WYOMING FROM THP
AND CPR SWWD TO RIW...LND...RKS AND KMM. GENERALLY GOING ADVISORY
AMOUNTS OR LESS IN THE NRN THIRD WHERE A FEW ADVISORIES WILL
EVENTUALLY BE NEEDED MOST LIKELY FOR COD AND BYG WITH WRL ON THE
EDGE. THP LOOKS LIKE A SOLID ADVISORY TO POTENTIAL WARNING SO WATCH
IS WARRANTED THERE. RIW TO CPR LOOKS LIKE 3-6 RIGHT NOW WITH THE
POTENTIAL STILL OF WARNING AMOUNTS DEPENDING A FEW DETAILS AND SNOW
RATIOS. FOR EXAMPLE THE LCL WRF...NAM12 AND THE PARALLEL GFS ALL
HAVE BETWEEN .40 AND .50 INCHES OF LIQUID BETWEEN RIW AND CPR. LND
SHOULD BE AN EASY WARNING VERIFICATION. IF RATIOS ARE 15-1 OR
GREATER AS WPC IS FORECASTING...THAT WILL END UP TO OVER 6 INCHES
FOR PLACES LIKE RIW AND CPR. THUS...THE WINTER STORM WATCH FOR
CHRISTMAS DAY THROUGH THROUGH 06Z ON THE 26TH. THE FAR SOUTH AND
SOUTHWEST SHOULD SEE SOLID ADVISORY AMOUNTS WITH STRONG WIND. SOME
HIGHER TERRAIN AND UPSLOPE FAVORED AREAS OF SOUTHERN LINCOLN COULD
SEE WARNING AMOUNTS. LATER SHIFTS CAN FINE TUNE EVERYTHING BUT
LOOKS LIKE A DECENT WINTER STORM THAT JUST HAPPENS TO OCCUR ON
CHRISTMAS. SLOW IMPROVEMENT LATE ON CHRISTMAS NIGHT BUT STILL SOME
LIGHT ACCUMULATION AND BLOWING SNOW AROUND. DIDN`T MENTION THE
BLOWING SNOW BUT THAT WILL BE A PROBLEM IN JOHNSON COUNT AND THE
OPEN AREAS OF THE FAR NORTH AND THEN EVENTUALLY ON CHRISTMAS IN
THE OPEN AND EXPOSED AREAS OF CENTRAL AND SWRN WYOMING.

QUITE COLD BEHIND THIS SYSTEM FRIDAY NIGHT AND BEYOND WITH LARGE
DIFFERENCES BETWEEN THE OP EURO AND THE GFS WITH OUR POTENTIAL
ARCTIC COLD FRONTS SLIDING DOWN FROM THE NORTH LATE IN THE WEEKEND
AND AGAIN EARLY NEXT WEEK. DID NOT MAKE SIGNIFICANT CHANGES TO THE
EXTENDED WITH ALL THE WEATHER IN THE SHORT TERM. WITH EXPECTED FRESH
SNOW COVER AND BITTER COLD AIR COMING DOWN ALOFT...IT WILL BE
POTENTIALLY VERY COLD IF NOT BITTER COLD.

&&

.AVIATION.../00Z ISSUANCE/

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

HIGH PRESSURE WILL HOLD FOR MUCH OF THE FORECAST PERIOD WITH
WINDS MAINLY LIGHT...10KTS OR LESS FOR THE REMAINDER OF THIS
AFTERNOON AFTER THE NORTH WINDS AT KBYG SUBSIDE HERE IN THE NEXT
COUPLE OF HOURS. A LEE SIDE SFC TROUGH WILL INTENSIFY TONIGHT WITH SW
WINDS PICKING UP TO 15-25KTS VCNTY 50NE KRKS-KCPR.

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

HIGH PRESSURE WILL HOLD WITH UNLIMITED CIGS AND GENERALLY LIGHT
WIND PREVAILING INTO THIS EVENING. INCREASING MOISTURE IN A
WESTERLY FLOW WILL LIKELY BRING SOME MID-LEVEL CIGS AT FL110-130
INTO THE FAR WEST...VCNTY KJAC- KAFO LATE THIS EVENING AND
WEDNESDAY MORNING. A PACIFIC TROUGH WILL APPROACH THE GREAT
BASIN ON CHRISTMAS EVE. AS A RESULT...LIGHT SNOWFALL WILL GRADUALLY SPREAD
ACROSS THE AREA AFTER 18Z CHRISTMAS EVE AND WILL INITIATE THE
POTENTIAL FOR MVFR CONDITIONS IN SOME AREAS.

&&

.FIRE WEATHER...

AFTER DRY CONDITIONS AND DECREASING WIND DURING THE REMAINDER OF
THIS AFTERNOON...THIS EVENING WILL SEE THE BEGINNING OF THE NEXT WINTRY
SYSTEM...AS SNOWFALL MOVES INTO NORTHWESTERN WYOMING. SNOWFALL
WILL INCREASE THROUGH THE OVERNIGHT HOURS...MOVING EAST OF THE
CONTINENTAL DIVIDE BY THURSDAY MORNING. ALONG WITH SNOWFALL...SOME
GUSTY WIND MAY BE PRESENT ACROSS THE AREA THURSDAY. UPDATES TO
THIS UPCOMING SYSTEM WILL PROVIDE ADDITIONAL DETAIL AND CONFIDENCE
ON THE ARRIVAL OF THE SYSTEM.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FROM LATE WEDNESDAY NIGHT THROUGH THURSDAY
EVENING WYZ015-017>020-022-028>030.

WINTER STORM WATCH FROM LATE WEDNESDAY NIGHT THROUGH THURSDAY
EVENING WYZ027.

WINTER STORM WATCH FROM LATE WEDNESDAY NIGHT THROUGH THURSDAY
EVENING WYZ005-007.

&&

$$

SHORT TERM...LIPSON
LONG TERM...SKRBAC
AVIATION...LIPSON
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.