Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 230957
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
257 AM MST TUE DEC 23 2014

.SHORT TERM...TODAY THROUGH THURSDAY NIGHT

A FEW AREAS OF LIGHT SNOW REMAIN ON THE RADAR THIS MORNING...WITH
GUSTY WIND STILL PRESENT ACROSS NORTHERN JOHNSON COUNTY. CONDITIONS
WILL STEADILY IMPROVE THROUGH THE MORNING AND AFTERNOON AS HIGH
PRESSURE BUILDS OVER THE INTERMOUNTAIN WEST. GENERALLY DRY
CONDITIONS ARE ANTICIPATED BY THIS EVENING...AND SHOULD LAST THROUGH
WEDNESDAY AFTERNOON FOR MUCH OF THE AREA. THE EXCEPTION MAY BE
NORTHWESTERN WYOMING WHERE MODELS INDICATE THE POTENTIAL FOR SOME
LIGHT SNOWFALL DURING THE AFTERNOON HOURS.

THE NEXT POTENTIALLY SIGNIFICANT WINTER SYSTEM MOVES OVER THE
PACIFIC COAST WEDNESDAY AFTERNOON...AND CONTINUES TO MOVE TOWARDS
THE STATE DURING THE EVENING HOURS. SNOWFALL ASSOCIATED WITH THIS
SYSTEM WILL MOVE INTO NORTHWESTERN WYOMING LATE WEDNESDAY
EVENING...WITH COVERAGE INCREASING THROUGH THE OVERNIGHT HOURS.
SNOWFALL ASSOCIATED WITH THIS SYSTEM WILL MOVE EAST OF THE
CONTINENTAL DIVIDE EARLY THURSDAY MORNING...AND SPREAD TO INCLUDE
THE MAJORITY OF THE FORECAST AREA BY THE AFTERNOON HOURS. THE
ASSOCIATED AREA OF LOW PRESSURE DIVES INTO CENTRAL UTAH...JUST NORTH
OF THE FOUR CORNERS REGION...AND MOVES EAST THROUGH COLORADO. THIS
IS A FAVORABLE SET UP FOR SNOWFALL ACROSS CENTRAL WYOMING...AND
MODELS CONTINUE TO INDICATE THE PRESENCE OF MODERATE SNOWFALL. IT
APPEARS THAT A WHITE CHRISTMAS WILL BE POSSIBLE ACROSS THE COWBOY
STATE UNDER THE INFLUENCE OF THIS SYSTEM. NATIONAL GUIDANCE CENTERS
ARE IN AGREEMENT WITH THE SOLUTIONS PRODUCED BY THE MEDIUM RANGE
MODELS FOR THIS UPCOMING SYSTEM. SOME GUSTY NORTHERLY WIND WILL BE
POSSIBLE...WHICH MAY CREATE HAZARDOUS TRAVEL CONDITIONS. MODELS
DO...HOWEVER...CONTINUE TO SLOW THE ARRIVAL OF THE SYSTEM AS IT WAS
INITIALLY ANTICIPATED TO HAVE A LARGER IMPACT WEDNESDAY EVENING.
SYSTEM PLACEMENT WOULD LEAVE A HIGHER CONFIDENCE...THOUGH THE
NOTABLE TIMING CHANGES DO REDUCE THAT CONFIDENCE SOMEWHAT.

STAY TUNED FOR UPDATES REGARDING ACCUMULATION EXPECTATIONS...MORE
PRECISE TIMING...AND POSSIBLE IMPACTS.

.LONG TERM...FRIDAY THROUGH TUESDAY

ON FRIDAY...THE DAY AFTER CHRISTMAS AND ALL THROUGH THE REGION...
LIGHT SNOW WILL LINGER IN THE MORNING AND THEN LESSEN BY EVENIN`.
A COLD DAY ON FRIDAY WITH HIGHS MAINLY IN THE TEENS TO AROUND 20.
SATURDAY WILL BE DRY AND A LITTLE MILDER DAY. SOME LIGHT SNOW MAY
DEVELOP LATE IN THE DAY IN THE NW WY MOUNTAINS. THE SNOW WILL
INCREASE IN COVERAGE IN THE WEST SATURDAY NIGHT AS THE NEXT WEATHER
SYSTEM APPROACHES. DRY EAST OF THE DIVIDE SATURDAY NIGHT. ON SUNDAY
SNOW CONTINUES OVER THE WEST AND SOUTHWEST. LIGHT SNOW DEVELOPS EAST
OF THE DIVIDE...STARTING OVER THE NORTH SUNDAY MORNING AND SPREADING
SOUTH SUNDAY AFTERNOON AS THE COLD FRONT PUSHES SOUTH AS WELL. LIGHT
SNOW CONTINUES MOST PLACES SUNDAY NIGHT. COLDER HIGHS ON SUNDAY.
MONDAY WILL SEE THE ARCTIC AIR SETTLE OVER THE REGION WITH VERY COLD
HIGH TEMPS. BASED ON THE 700MB TEMPS FROM -17 DEGREES CENTIGRADE TO
-24 DEGREES CENTIGRADE MONDAY AFTERNOON...I LOWERED HIGH TEMPS
CLOSER TO THE ECMWF MOS HIGH TEMPS OR COLDER. MAY NEED TO GO EVEN
COLDER FOR HIGHS MONDAY IF A DECENT SNOW COVER EXISTS AT THE LOWER
ELEVATIONS. PLENTY OF TIME TO ADJUST FORECAST. SOME LIGHT SNOW OR
FLURRIES TO OCCUR MONDAY MORNING BUT DECREASES DURING THE AFTERNOON.
VERY COLD MONDAY NIGHT WITH LOWS BELOW ZERO ALL AREAS AS THE SKY
CLEARS. I HAVE THE FAVORED BASINS AND VALLEYS WITH LOWS 10 TO 20
BELOW ZERO AND THAT MAY NOT HOLD I FEAR. TUESDAY LOOKS DRY WITH
VERY COLD HIGH TEMPS. A PEEK AT NEW YEARS EVE WEATHER SHOWS DRY
CONDITIONS. MILDER TEMPS IN THE MIXED AREAS BUT BASIN INVERSIONS
WILL KEEP THE WARMING LIMITED TO A FEW DEGREES.

&&

.AVIATION.../12Z ISSUANCE/

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

STRONG NW WINDS ACROSS THE INTERSTATE 90 CORRIDOR...VCNTY
KBYG...WILL GRADUALLY DIMINISH EARLY THIS MORNING.  A FEW BANDS OF
SNOW SHOWERS MAY PERSIST MAINLY VCNTY AND EAST OF INTERSTATE 25
UNTIL SHORTLY AFTER 12Z.  OTHERWISE A RIDGE OF HIGH PRESSURE WILL
BUILD ACROSS THE AREA TODAY BRINGING IN A DRIER MORE STABLE
AIRMASS WITH WINDS BECOMING MAINLY LIGHT...10KTS OR LESS...TUESDAY
AFTERNOON.  A LEE SIDE SFC TROUGH WILL INTENSIFY TUESDAY NIGHT WITH
SW WINDS PICKING UP TO 15-25KTS VCNTY 50NE KRKS-KCPR.

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

SCT SHSN OVR THE MTNS WILL MOSTLY DISSIPATE BY SUNRISE AS A DRIER
MORE STABLE AIRMASS PUSHES INTO WESTERN WYOMING.  SOME PATCHY FOG
MAY PARTIALLY OBSCURE THE WESTERN VALLEYS THROUGH THE MORNING
HOURS.  A RIDGE OF HIGH PRESSURE WILL BUILD IN THOUGH THE DAY WITH
UNLIMITED CIGS AND GENERALLY LIGHT WIND PREVAILING THIS AFTERNOON
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 TUESDAY EVENING AND WEDNESDAY MORNING.

&&

.FIRE WEATHER...

HIGH PRESSURE BUILDING OVER THE INTERMOUNTAIN WILL HELP TO END
LINGERING SNOWFALL AND GUSTY WIND ACROSS WESTERN AND CENTRAL WYOMING
THIS MORNING. GENERALLY DRY CONDITIONS ARE ANTICIPATED ACROSS THE
AREA THROUGH WEDNESDAY AFTERNOON. WEDNESDAY 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...
HIGH WIND WARNING UNTIL 6 AM MST EARLY THIS MORNING WYZ010.

&&

$$

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






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