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000
FXUS65 KRIW 091415
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
815 AM MDT SUN MAR 9 2014

.UPDATE...

EXTENDED HIGH WIND WARNING FOR PARK COUNTY UNTIL 9 PM MDT THIS
EVENING...AND THE HIGH WIND WARNING FOR NATRONA COUNTY AND
SOUTHERN FREMONT COUNTY UNTIL 3 PM MDT TODAY. THE THREAT OF
MOUNTAIN WAVE FORMATION WILL CONTINUE ALONG THE EAST SLOPES
OF THE ABSAROKA MOUNTAINS.  THE STRONG SURFACE PRESSURE GRADIENT
FROM CENTRAL WYOMING NORTHEAST WYOMING SHOULD REMAIN STRONG
ENOUGH FOR HIGH WINDS THROUGH THE WIND CORRIDOR THROUGH THIS
AFTERNOON.

&&

.SHORT TERM...TODAY THROUGH TUESDAY NIGHT

WINDS ARE BEGINNING TO PICK UP IN THE CODY FOOTHILLS AND THE
SURROUNDING MOUNTAINS. EARLIER CLARK EAST GUSTED FROM THE WEST AT
55 MPH WHERE THE TEMP HAS WARMED TO 57 DEGREES. GAP FLOW SEEMS TO
BE THE CULPRIT WITH A 14C TEMP SPREAD PROGGED FROM YNP TO CLARK.
CLARK EAST WOULD BE MORE LIKELY TO BLOW THAN CLARK WEST WITH GAP
FLOW. MTN WAVE POTENTIAL DOES NOT LOOK IMPRESSIVE. WILL LET THE
HIGH WIND WARNING RUN THROUGH THIS EVENING FOR THE CODY FOOTHILLS. AS
FOR THE HIGH WIND WARNING FOR THE GREEN MTNS AND NATRONA COUNTY IN
EFFECT THROUGH THIS AFTERNOON...A TIGHT SFC PRESSURE GRADIENT OF
15MB FROM GCC TO RKS AS WELL AS 50 KNOT H7 WINDS MIXING DOWN
SHOULD ENCOURAGE STRONG WINDS TO BLOW THROUGH THAT WIND CORRIDOR
WITH OUTER DRIVE ALREADY SEEING GUSTS OF 66 MPH JUST SOUTH OF
CASPER.

OTHERWISE TODAY IS SHAPING UP TO BE A FAIRLY WARM AND DRY DAY FOR
MUCH OF THE CWA FOR EARLY MARCH WITH H7 TEMPS OF 3C EXPECTED OVER
NATRONA CO...0.5C FOR CENTRAL WY AND -3C IN WESTERN WY WHICH WILL
TRANSLATE TO HIGHS IN THE 60S EXPECTED IN CPR/BYG...50S CENTRAL
BASINS AND IN THE 40S AT THE LOWER ELEVATIONS WEST.

THE RIDGE CURRENTLY OVER US NOW WILL MOVE EAST AND FLATTEN TODAY
WITH THE WESTERLY PACIFIC FLOW INCREASING WITH SOME ISENTROPIC LIFT
DEVELOPING IN FAR WESTERN WYOMING OUT AHEAD OF THE NEXT APPROACHING
UPSTREAM TROUGH OFF THE PACIFIC COAST. THIS WILL RESULT IN AN
INCREASING CHANCE OF RAIN AND SNOW IN NW WY LATER THIS AFTERNOON.
SNOW LEVELS TODAY SHOULD BE AROUND 7K. LIGHT RAIN AND SNOW SHOULD
CONTINUE IN THE FAR WEST TONIGHT AND INTO MONDAY MORNING WITH THE
WESTERLY UPSLOPE FLOW CONTINUING. AS THE PACIFIC TROUGH APPROACHES
THE PRECIPITATION IN WESTERN WY WILL INCREASE IN COVERAGE AND
INTENSITY MONDAY AFTERNOON. BY EARLY MONDAY EVENING THE SNOW WILL
LOWER TO THE VALLEY FLOOR AROUND SUNSET BY 00Z TUE. SNOW WILL
CONTINUE IN THE WEST THROUGH MONDAY NIGHT. ADVISORY AMOUNTS APPEAR
LIKELY IN THE WEST FROM TONIGHT THROUGH MONDAY NIGHT. HOWEVER...THE
SNOWFALL IN THE VALLEYS WILL LIKELY MELT AS FAST AS IT PILES UP AT
THE LOWER ELEVATIONS. AN ASSOCIATED H7 CIRCULATION WILL TRACK SSE
ACROSS CENTRAL WY ON MONDAY NT...ACROSS SHOSHONI IF YOU TAKE THE
TRACK LITERALLY...WITH A SURFACE LOW TRACKING SOUTH ACROSS JOHNSON
AND NATRONA COUNTIES. AN ASSOCIATED COLD FRONT WILL MOVE SOUTH
MONDAY NIGHT. THE FRONT WILL HELP SPREAD SNOWFALL TO AREAS EAST OF
THE DIVIDE MONDAY NIGHT. MODERATELY STRONG Q VECTOR FORCING AND THE
H7 CIRCULATION WILL ENHANCE THE SNOWFALL...ESP EAST OF THE DIVIDE.
AFTER THE H7 CIRCULATION SHIFTS TO THE SOUTH...THE UPSLOPE FLOW WILL
DEEPEN AND STRENGTHEN FOR ACCUMULATING SNOWFALL EAST OF THE
DIVIDE...ESPECIALLY IN THE UPSLOPE FAVORED AREAS FROM LND TO CPR.
THE AFOREMENTIONED DYNAMICS WILL HELP SEED THE LOWER DECK OF UPSLOPE
INDUCED SNOW CLOUDS. THE PRECIP WILL BE ALL SNOW ACROSS THE WHOLE
CWA MONDAY NIGHT AND INTO TUESDAY WITH H7 TEMPS FALLING TO THE MINUS
LOW TEENS. HAVE INDICATED ADVISORY SNOW AMOUNTS FOR THE MOUNTAINS
AND ELEVATED BASIN AREAS ALONG AND SOUTH OF THE OWL CREEK MTNS AND
ALONG AND EAST OF THE BIG HORN MTNS WITH MOST OF THE SNOW OCCURRING
LATE MONDAY NIGHT AND TUESDAY MORNING. THE TRACK OF THE ASSOCIATED
VORT MAX IS FAVORABLE FOR SNOWFALL IN LANDER. SNOW WILL DIMINISH
TUESDAY AFTERNOON. CLEARING WILL TAKE PLACE TUESDAY NIGHT WITH FOG
DEVELOPING LATE WITH FAVORABLE SOUNDINGS SUPPORTING FOG ALONG WITH
CLEAR SKIES AND FRESH SNOW COVER. SHOULD SEE LOWS IN THE SINGLE
DIGITS IN THE FAR WEST BY 12Z WED.

ICE JAM FLOODING REMAINS AN ISSUE IN THE BIG HORN BASIN AND
JOHNSON COUNTY. URBAN AND SMALL STREAM FLOODING ASSOCIATED WITH
MELTING SNOW REMAINS A THREAT IN THE WEST TODAY.

.LONG TERM...WEDNESDAY THROUGH SUNDAY

A CHILLY START TO MEDIUM RANGE PERIOD BEHIND OUR EARLY WEEK SNOW.
MORNING FOG IS QUITE POSSIBLE IN THE FRESHLY SNOW COVERED AREAS
WHERE WINDS ARE LIGHT AND A GENERALLY CLEAR SKY WILL EXIST.
TEMPERATURES WILL BE SLOW TO REBOUND WEDNESDAY IN THE SNOW COVERED
AREAS BUT IT`S STILL MARCH SO TEMPERATURES WILL STILL WARM INTO THE
30S AND 40S. RIDGE FLATTENS ALLOWING A NW FLOW TO DEVELOP FOR THE
SECOND HALF OF THE WEEK WITH A COUPLE WEAK DISTURBANCES PRODUCING
PROBABLY NOTHING MORE THAN SOME PASSING CLOUDS UNTIL SATURDAY WHEN A
STRONGER SEWD MOVING DISTURBANCE IS FORECAST TO MOVE THROUGH. SO
WARMER THURSDAY AND FRIDAY AND THEN A LITTLE COLDER AND POTENTIALLY
UNSETTLED ACROSS THE NORTH AND EAST WITH RAIN AND SNOW SHOWERS OR
RAIN SHOWERS TURNING TO SNOW SHOWERS ON SATURDAY. MODELS HAVE BEEN
CHANGING A LOT IN THIS DEVELOPING NW FLOW SO CONFIDENCE IS STILL
LOW ON TIMING AND DETAILS FOR NEXT WEEKEND YET. AS OF NOW...THAT
IS THE ONLY DAY WITH ANY REAL CHANCE OF PRECIPITATION IN THE
EXTENDED PERIOD.

.AVIATION.../12Z ISSUANCE/

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

VFR CONDITIONS WILL OCCUR TODAY AND TONIGHT. GUSTY WIND CONDITIONS
AROUND THE KCOD AND KCPR TERMINAL SITE THROUGH MOST OF THE PERIOD.
STRONG MID LEVEL WIND SPEEDS WILL OCCUR WHICH WILL CAUSE SOME WIND
SHEAR AT TIMES OVER THE NEAR THE MOUNTAINS.

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

PATCHY FOG MAY OCCUR IN THE VALLEYS UNTIL 16Z WITH LOCAL MVFR TO IFR
CONDITIONS. OTHERWISE VFR CONDITIONS WILL OCCUR AT MOST TERMINAL
SITES THROUGH THE PERIOD. AT THE KJAC TERMINAL SITE CLOUDS WILL BE
LOWERING BY 00Z AS RAIN AND SNOW DEVELOPS IN THE NW MOUNTAINS AFTER
22Z. SNOW WILL OCCUR IN THE NW MOUNTAINS AFTER 01Z THROUGH 12Z
MONDAY. CONDITIONS AT KJAC TERMINAL SITE WILL LOWER TO MVFR BY 06Z
MONDAY AS SNOW DEVELOPS...WITH POSSIBLE IFR CONDITIONS BY 12Z MONDAY.

.FIRE WEATHER...

INVERSIONS AND POOR SMOKE DISPERSAL ARE EXPECTED THIS MORNING IN
THE BASINS AND VALLEYS. STRONG WEST SOUTHWEST WINDS WILL BLOW
TODAY FROM SOUTH PASS TO CASPER AS WELL AS ALONG THE CODY
FOOTHILLS AND EAST SLOPE OF THE CONTINENTAL DIVIDE. HIGHS WILL
RANGE FROM THE 60S EAST...50S CENTRAL AND 40S LOW ELEVATIONS OF
THE WEST. AREAS OF LIGHT SNOW WILL DEVELOP LATER THIS AFTERNOON IN
WESTERN WYOMING TODAY WITH THE SNOWFALL BECOMING STEADIER AND
HEAVIER TONIGHT AND INTO MONDAY ALONG WITH A MIX OF RAIN AND SNOW
OR ALL RAIN AT TIMES IN THE WESTERN VALLEYS. ALL SNOW WILL
CONTINUE MONDAY NIGHT AND SPREAD TO AREAS EAST OF THE DIVIDE
MONDAY NIGHT AND TUESDAY. SIGNIFICANT ACCUMULATION IS EXPECTED
EAST AND WEST OF THE DIVIDE. CLEARING WILL TAKE PLACE WITH FOG
DEVELOPING TUESDAY NIGHT. INVERSIONS AND POOR SMOKE DISPERSAL ARE
EXPECTED LATE TUESDAY NIGHT AND WEDNESDAY MORNING IN THE BASINS
AND VALLEYS.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
HIGH WIND WARNING UNTIL 9 PM MDT THIS EVENING WYZ002-003.

HIGH WIND WARNING UNTIL 3 PM MDT THIS AFTERNOON WYZ019-020.

&&

$$

UPDATE...C.BAKER
SHORT TERM...LIPSON
LONG TERM...SKRBAC
AVIATION...AR
FIRE WEATHER...LIPSON