Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 242123 CCA
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
316 PM MDT SUN APR 24 2016

.SHORT TERM...TONIGHT THROUGH MONDAY

COLD NORTHWEST FLOW WITH RESIDUAL MOISTURE...ESPECIALLY EAST OF
THE CONTINENTAL DIVIDE...WILL BE OVER THE AREA TONIGHT...AS THE
UPPER LEVEL LOW DRIFTS EAST ACROSS SOUTHERN SOUTH DAKOTA AND
NORTHERN NEBRASKA. WIDESPREAD MOUNTAIN SNOW SHOWERS WILL LINGER
OVER THE BIGHORN MOUNTAINS AND CASPER MOUNTAIN WITH MORE SCATTERED
SHOWERS OVER THE WESTERN MOUNTAINS.  AS BRIEF HIGH PRESSURE MOVES
IN WITH PARTIAL CLEARING LATE TONIGHT...LOW STRATUS AND AREAS OF
FOG IS EXPECTED TO DEVELOP IN THE VALLEYS AND BASINS ESPECIALLY
ALONG THE RIVERS AND LAKES. BY MID DAY...AS ANOTHER LOW PRESSURE
CENTER DEEPENS IN THE GREAT BASIN...THE FLOW ALOFT WILL SWITCH TO
THE SOUTHWEST WITH INCREASING MID LEVEL MOISTURE AND INSTABILITY
MOVING IN OVER THE WEST. SHOWERS WILL INCREASE TROUGH THE
AFTERNOON ACROSS THE WESTERN MOUNTAINS AND ALONG AND EAST OF THE
CONTINENTAL DIVIDE. EAST OF THE MOUNTAINS SHOWERS WILL BE MORE
WIDELY SCATTERED. EMBEDDED THUNDERSTORMS WITH SMALL HAIL AND
STRONG WIND GUSTS WILL ALSO INCREASE WITH SOME MAKING IT OVER THE
WIND RIVER AND BIGHORN BASINS. TEMPERATURES WILL BE GENERALLY
WARMER

.LONG TERM...MONDAY NIGHT THROUGH SUNDAY

THE NEXT UPSTREAM CIRCULATION OVER THE GULF OF ALASKA HAS EJECTED A
DOWNSTREAM TROUGH NOW OUT AT 130W WHICH WILL CLOSE OFF OVER THE
GREAT BASIN AND SHOULD BE OVER UTAH BY 00Z TUE. BY 00Z TUESDAY WE
WILL HAVE COME FULL CIRCLE FROM LAST SATURDAY AS THIS NEXT
CIRCULATION ONCE AGAIN DRAWS UP A SOUTHERLY DIFLUENT FLOW AHEAD OF
IT AS IT BISECTS A FIELD OF INSTABILITY FOR A CONTINUATION OF THE
THREAT OF NUMEROUS SHOWERS AND THUNDERSTORMS MONDAY EVENING.
THEN THE LOW WILL TRACK EAST ACROSS THE COLORADO/UTAH BORDER MONDAY
NIGHT WITH THE MID LEVEL CIRCULATION TRACKING EAST ACROSS SOUTHERN
WY. LEFT FRONT QUAD DYNAMICS AND Q VECTOR FORCING WILL KEEP PRECIP
GOING ALL NIGHT STATEWIDE MONDAY NIGHT WITH THE PRECIP STRATIFORMING
OUT AFTER MIDNIGHT. A WEAK SFC LOW WILL BE OVHD AS WELL. THE PRECIP
WILL BE ALL SNOW IN THE MOUNTAINS AFTER MIDNIGHT MONDAY NIGHT. THEN
ON TUE SNOW LEVELS WILL DROP TO AROUND 5500 FEET AS COLDER AIR WRAPS
AROUND THE BACKSIDE OF THE LOW. BY TUESDAY THE CONTINUED DIFLUENT
FLOW WILL BACK TO THE EAST ACROSS THE CWA WITH EVER DEEPENING
UPSLOPE FLOW EAST OF THE DVD. ALSO...WE WILL SEE WRAP AROUND
ISENTROPIC LIFT IN THE EASTERN ZONES. BY 00Z WEDNESDAY THE H5 LOW
WILL BE OVER SOUTHEAST WY WITH CONTINUED DEEP UPSLOPE AS WELL AS
CONTINUED WRAP AROUND ISENTROPIC LIFT IN THE EAST. SNOW LEVELS WILL
DRIP TO THE VALLEY AND BASIN BOTTOMS TUE NT. FOR NOW HAVE SNOW AMOUNTS
JUST OVER WARNING AMNTS ON THE BIG HORN AND EAST SLOPE OF THE WND
RVR MTNS AS WELL AS OVER CPR MTN FOR THE PERIOD MONDAY NIGHT THROUGH
TUE NT. RATHER THAN ISSUE A WINTER STORM WATCH FOR THESE ZONES NOW
...WILL JUST ISSUE AN SPS FOR THE EAST SLOPE OF THE WIND RVRS FOR
NOW. WE ALREADY HAVE ONGOING HILITES FOR THE BIG HORN MTNS AND
CASPER MTN...SO LATER SHIFTS CAN EITHER ISSUE HILITES OR AN SPS FOR
THE BIG HORNS AND CASPER MTN FOR THE NEXT SNOW EVENT. SNOW ADVISORY
AMNTS ARE IN PLACE FOR THE SALT/WYOMING RANGE AS WELL AS FOR THE
ABSAROKA MTNS FOR MON NT THROUGH TUE NT. FOR THE REST OF THE MTNS
INCLUDING THE GREEN MTNS...2 TO 5 INCHES WILL BE COMMON MON NT
THROUGH TUE NT. LATER SHIFTS CAN DECIDE WHETHER OF NOT OTHER HILITES
ARE JUSTIFIED FOR THESE OR OTHER AREAS. 1 TO 2 INCHES OF SNOW WILL
BE COMMON ACROSS THE WIND RIVER BASIN AS WELL AS THE WESTERN VALLEYS
AND BASINS...1 TO 3 INCHES IN THE POWDER RIVER BASIN AND CASPER
ALONG WITH LESS THAN AN INCH IN THE BIG HORN BASIN. BY 12Z WEDNESDAY
THE MID LEVEL CIRCULATION WILL BE IN THE CENTRAL PLAINS UNDER A
WEAKLY UNSTABLE NW FLOW WHICH IS A GOOD FLOW FOR CONVECTIVE
RAIN/SNOW BANDS SO INCREASED POPS SOMEWHAT OVER EASTERN FREMONT AND
NATRONA COUNTIES WITH A CONTINUED GOOD CHANCE OF RAIN AND SNOW
SHOWERS OVER THE HIGH COUNTRY. PRECIP WILL SLOWLY DECREASE DURING
WED AFTERNOON UNDER A COL REGION. ON WED NT WE WILL HAVE AN ALMOST
TRANSPARENT BREAK IN THE ACTION BEFORE THE TENTACLES OF THE TROUGH
EXTENDING NORTHEAST FROM THE NEXT EJECTED LOW OVER VEGAS REACHES WY
ON 12Z THU. RAIN AND SNOW SHOWERS WILL CONTINUE OVER THE NORTH HALF
WED NT BEFORE RAIN AND MTN SNOW SHOWERS INCREASE AGAIN THU WITH
SOUTHERLY DIFLUENT FLOW AHEAD OF THIS NEXT LOW ONCE AGAIN ENHANCING
LIFT. THIS LOW WILL ARRIVE AS A BAGGY TROUGH AXIS BY FRIDAY. THEN
ANOTHER WEAK LOW WILL DUMBBELL AROUND THE EXITING TROUGH PROLONGING
THE THREAT OF SHOWERS THROUGH NEXT WEEKEND. WITH THIS PARTICULAR WX
FEATURE BEING LESS ORGANIZED ALONG WITH INCREASING INSTABILITY
DURING THE AFTERNOON HOURS WILL JUST WORD THE REST OF THE FCST FOR
NEXT FRIDAY THROUGH SUNDAY AS SHOWERY BUT MAINLY OCCURRING IN THE
AFTERNOONS.
TEMPERATURES WILL WARM DURING THE WEEK BUT WILL REMAIN SEASONABLY
COOL.

&&

.AVIATION.../00Z ISSUANCE/

WEST OF THE CONTINENTAL DIVIDE...KJAC/KRKS/KPNA/KBPI AIRPORTS

COLD NORTHWEST FLOW WITH LIMITED MOISTURE WILL BE OVER THE WEST
TONIGHT.  SOME MOUNTAIN SNOW SHOWERS WILL LINGER OVER THE HIGHER
TERRAIN. AS BRIEF HIGH PRESSURE MOVES IN WITH PARTIAL CLEARING...
LOW STRATUS AND AREAS OF FOG IS EXPECTED TO DEVELOP IN THE VALLEYS
ESPECIALLY ALONG THE RIVERS AND LAKES WITH AREAS OF IFR CEILINGS
AND VISIBILITY REDUCED IN FOG.  THE AIRPORTS MOST LIKELY TO
EXPERIENCE MVFR TO IFR CONDITIONS FROM 09Z - 15Z WILL BE KJAC...
KAFO...KEMM...KBPI AND KPNA. BY MID DAY...AS ANOTHER LOW PRESSURE
CENTER DEEPENS IN THE GREAT BASIN...THE FLOW ALOFT WILL SWITCH TO
THE SOUTHWEST WITH INCREASING MID LEVEL MOISTURE AND INSTABILITY
MOVING IN OVER THE WEST. SHOWERS WILL INCREASE TROUGH 18Z - 00Z
TIMEFRAME WITH MOUNTAIN OBSCURATIONS BECOMING FREQUENT. EMBEDDED
THUNDERSTORMS WITH SMALL HAIL AND STRONG WIND GUSTS WILL ALSO
INCREASE WITH A THREAT OF MVFR CONDITIONS AT ALL AIRPORTS.

EAST OF THE CONTINENTAL DIVIDE...KCPR/KCOD/KRIW/KWRL/KLND AIRPORTS

COLD NORTHWEST FLOW WITH RESIDUAL MOISTURE WILL BE OVER THE AREA
EAST OF THE CONTINENTAL DIVIDE TONIGHT...AS THE UPPER LEVEL LOW
DRIFTS EAST ACROSS SOUTHERN SOUTH DAKOTA AND NORTHERN NEBRASKA.
WIDESPREAD MOUNTAIN SNOW SHOWERS WILL LINGER OVER THE BIGHORN
MOUNTAINS AND CASPER MOUNTAIN OBSCURING THE HIGHER TERRAIN. AS
BRIEF HIGH PRESSURE MOVES IN WITH PARTIAL CLEARING LATE TONIGHT...
LOW STRATUS AND AREAS OF FOG IS EXPECTED TO DEVELOP IN THE VALLEYS
AND BASINS ESPECIALLY ALONG THE RIVERS AND LAKES WITH AREAS OF
IFR CEILINGS AND VISIBILITY REDUCED IN FOG. THE AIRPORTS MOST
LIKELY TO EXPERIENCE MVFR TO IFR CONDITIONS FROM 09Z - 15Z WILL BE
KLND...KRIW...KWRL AND KGEY. BY MID DAY...AS ANOTHER LOW PRESSURE
CENTER DEEPENS IN THE GREAT BASIN...THE FLOW ALOFT WILL SWITCH TO
THE SOUTHWEST WITH INCREASING MID LEVEL MOISTURE AND INSTABILITY
MOVING IN OVER THE WEST. SHOWERS WILL INCREASE TROUGH 18Z - 00Z
TIMEFRAME ALONG AND EAST OF THE CONTINENTAL DIVIDE WITH SOME
MOUNTAIN OBSCURATIONS BECOMING MORE FREQUENT. EAST OF THE
MOUNTAINS SHOWERS WILL BE MORE WIDELY SCATTERED. EMBEDDED
THUNDERSTORMS WITH SMALL HAIL AND STRONG WIND GUSTS WILL ALSO
INCREASE WITH A THREAT OF MVFR CONDITIONS ACROSS THE WIND RIVER
AND BIGHORN BASINS FROM 12Z - 00Z.

&&

.FIRE WEATHER...

COLD NORTHWEST FLOW WITH RESIDUAL MOISTURE...ESPECIALLY EAST OF
THE CONTINENTAL DIVIDE...WILL BE OVER THE AREA TONIGHT...AS THE
UPPER LEVEL LOW DRIFTS EAST ACROSS SOUTHERN SOUTH DAKOTA AND
NORTHERN NEBRASKA. WIDESPREAD MOUNTAIN SNOW SHOWERS WILL LINGER
OVER THE BIGHORN MOUNTAINS AND CASPER MOUNTAIN WITH MORE SCATTERED
SHOWERS OVER THE WESTERN MOUNTAINS.  AS BRIEF HIGH PRESSURE MOVES
IN WITH PARTIAL CLEARING LATE TONIGHT...LOW STRATUS AND AREAS OF
FOG IS EXPECTED TO DEVELOP IN THE VALLEYS AND BASINS ESPECIALLY
ALONG THE RIVERS AND LAKES. BY MID DAY...AS ANOTHER LOW PRESSURE
CENTER DEEPENS IN THE GREAT BASIN...THE FLOW ALOFT WILL SWITCH TO
THE SOUTHWEST WITH INCREASING MID LEVEL MOISTURE AND INSTABILITY
MOVING IN OVER THE WEST. SHOWERS WILL INCREASE TROUGH THE
AFTERNOON ACROSS THE WESTERN MOUNTAINS AND ALONG AND EAST OF THE
CONTINENTAL DIVIDE. EAST OF THE MOUNTAINS SHOWERS WILL BE MORE
WIDELY SCATTERED. EMBEDDED THUNDERSTORMS WITH SMALL HAIL AND
STRONG WIND GUSTS WILL ALSO INCREASE WITH SOME MAKING IT OVER THE
WIND RIVER AND BIGHORN BASINS. TEMPERATURES WILL BE GENERALLY
WARMER WITH ELEVATED RELATIVE HUMIDITY. MIXING HEIGHTS WILL BE
RATHER LOW WITH FAIR TO LOW END GOOD SMOKE DISPERSAL IN THE
AFTERNOON.


&&

.RIW WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL MIDNIGHT MDT TONIGHT FOR WYZ008-
009-022.

&&

$$

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



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