Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 142055
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
155 PM MST SUN DEC 14 2014

.SHORT TERM...TONIGHT THROUGH MONDAY

WHILE THE WINTER STORM WAS SLIGHTLY SLOWER DEVELOPING OVER NIGHT
AND EARLY THIS MORNING...SNOWFALL HAS BECOME WIDESPREAD ALONG AND
EAST OF THE CONTINENTAL DIVIDE. A SOUTHEAST MID LEVEL FLOW FROM
NORTHEAST COLORADO MOVING FROM THE SOUTHEAST CORNER OF WYOMING TO
THE NORTHWEST CORNER...IS PROVIDING ABUNDANT MOISTURE WITH UPPER
LEVEL DIVERGENCE OVER A COLD FRONT HUNG UP ALONG THE CONTINENTAL
DIVIDE. NOW THAT THE STORM HAS DEVELOPED AND CONTINUES TO INTENSIFY
A SLOWER MOVEMENT TO THE EAST IS EXPECTED. THIS WILL BRING MORE
SNOWFALL INTO MONDAY MORNING. WINTER WEATHER WARNINGS HAVE BEEN
ISSUED FOR NATRONA COUNTY AND SOUTHERN FREMONT COUNTY...AS WELL
AS HOT SPRINGS AND WASHAKIE COUNTIES. THE SURFACE FLOW WITH
OVERRUNNING MID LEVEL MOISTURE OVER THE BRIDGER RANGE IS NOW
EXPECTED TO PRODUCE HEAVIER SNOWFALL FROM TEN SLEEP THROUGH BIG
TRAILS TO AREAS AROUND THERMOPOLIS. TEMPERATURES WILL REMAIN COLD
THROUGH MONDAY AND MOST AREAS HAVE BEEN COOLED SLIGHTLY.

.LONG TERM...MONDAY NIGHT THROUGH SUNDAY

SNOWFALL ASSOCIATED WITH THE CURRENT WINTER STORM WILL CONTINUE TO
MOVE OUT OF THE FORECAST AREA MONDAY NIGHT...WITH A RIDGE OF HIGH
PRESSURE LOOKING TO REPLACE THE SYSTEM. GENERALLY DRY CONDITIONS
EXPECTED BY TUESDAY MORNING...THOUGH SOME MODELS CONTINUE TO SHOW
SOME WEAK SNOWFALL ACROSS SOUTHWESTERN WYOMING THROUGH TUESDAY
AFTERNOON.

THE RIDGE WILL CONTINUE THROUGH TUESDAY EVENING...WITH THE NEXT
APPROACHING AREA OF LOW PRESSURE MOVING INTO THE INTERMOUNTAIN WEST.
SNOWFALL WILL BEGIN ACROSS THE WESTERN MOUNTAINS AND VALLEYS BY LATE
TUESDAY NIGHT. MOST SNOW SHOULD REMAIN CONFINED TO AREAS WEST OF THE
CONTINENTAL DIVIDE...THOUGH THE GFS AND GEM MODELS DO DEMONSTRATE
SOME SNOWFALL MOVING EAST OF THE DIVIDE BY WEDNESDAY AFTERNOON. THE
AREA OF LOW PRESSURE IS EXPECTED TO DROP INTO THE DESERT
SOUTHWEST...THOUGH THE IMPACTS FROM THIS TRACK TO VARY DEPENDING ON
THE MODEL. THE ECMWF SHOWS AN AREA OF HIGH PRESSURE WORKING TO BUILD
IN THE AREA THURSDAY AFTERNOON...WHILE THE GFS SHOWS MORE OF A
TROUGH SCENARIO. THE GEM TAKES THE MIDDLE ROAD BETWEEN THE TWO
SOLUTIONS WITH A NEAR ZONAL FLOW AND LIGHT SNOWFALL.

REGARDLESS...ALL MODELS DEMONSTRATE A DEFINITE RETURN OF HIGH
PRESSURE BY FRIDAY NIGHT AND SATURDAY MORNING...THOUGH THIS RIDGE
WILL BEEN QUICK. ANOTHER APPROACHING WAVE OF LOW PRESSURE WILL MOVE
INTO THE INTERMOUNTAIN WEST BY LATE SATURDAY MORNING...SPREADING
SOME LIGHT SNOWFALL ACROSS WESTERN WYOMING BY SATURDAY AFTERNOON.
AGAIN...THE SPEED AND OVERALL PATH OF THIS SYSTEM VARIES BY
MODEL...WITH THE GFS MOVING THE SYSTEM THROUGH MORE QUICKLY WITH

&&

.AVIATION.../00Z ISSUANCE/

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

WIDESPREAD MVFR TO IFR CEILINGS WITH VISIBILITIES REDUCED IN SNOW
AND FOG WILL IMPACT THE AREA INCLUDING THE AIRPORTS THROUGH 15Z
MONDAY BEFORE IMPROVEMENT GRADUALLY OCCURS THROUGH 00Z TUESDAY FROM
NORTHWEST TO SOUTHEAST. MOUNTAINS WILL BE OBSCURED ACROSS THE
REGION.

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

WIDESPREAD MVFR TO IFR CEILINGS WITH VISIBILITIES REDUCED IN SNOW
AND FOG WILL IMPACT THE AREA INCLUDING THE AIRPORTS THROUGH 06Z
MONDAY BEFORE IMPROVEMENT OCCURS FROM NORTHWEST TO SOUTHEAST.
MOUNTAINS WILL BE OBSCURED ACROSS THE REGION WITH SLOW CLEARING
AFTER 12Z MONDAY.

&&

.FIRE WEATHER...

COLD SNOWY WEATHER WILL CONTINUE OVER MUCH OF WESTERN AND CENTRAL
WYOMING THROUGH TONIGHT WITH GRADUALLY IMPROVING CONDITIONS
THROUGH THE DAY MONDAY.  VARIOUS WINTER STORM WARNINGS AND WINTER
WEATHER ADVISORIES ARE IN EFFECT INTO MONDAY MORNING FOR AREAS
ALONG AND EAST OF THE CONTINENTAL DIVIDE. PLEASE REFER TO THESE
WARNINGS AND ADVISORIES FOR MORE DETAILS ON EXPECTED SNOWFALL.
WITH COLD AIR IN PLACE...INVERSIONS WILL BE IN PLACE WITH LOW
MIXING HEIGHTS AND POOR SMOKE DISPERSAL.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 5 AM MST MONDAY WYZ003-004-017-030.

WINTER STORM WARNING UNTIL 5 AM MST MONDAY
WYZ005>007-015-018>020-022.

WINTER WEATHER ADVISORY UNTIL 8 AM MST MONDAY WYZ008>011.

&&

$$

SHORT TERM...C.BAKER
LONG TERM...BRANHAM
AVIATION...C.BAKER
FIRE WEATHER...C.BAKER





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