Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 202033
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
233 PM MDT SUN APR 20 2014

.SHORT TERM...TONIGHT THROUGH WEDNESDAY

COLD FRONT MOVING QUICKLY SOUTH THROUGH THE BIG HORN BASIN AND INTO
FAR NRN NATRONA COUNTY ATTM. FRONT WILL LIKELY MAKE IT INTO THE RED
DESERT TONIGHT BEFORE WASHING OUT. STILL A SMALL CHANCE OF SHOWERS
WITH FROPA IN OUR SERN ZONES BUT MODIFIED SOUNDINGS ARE SHOWING VERY
LIMITED CAPE OF 100-200 J/KG AT MOST. LITTLE BETTER IN FAR SRN
SWEETWATER WHERE MOISTURE LINGERS FROM YESTERDAY`S WEAK SYSTEM AND
DYING FRONTAL BOUNDARY SO A FEW SHOWERS WILL CONTINUE THERE WITH AN
ISOLATED LIGHTNING STRIKE POSSIBLE UNTIL AROUND SUNSET. OTHERWISE...
DRY INTO MONDAY AS SHORTWAVE RIDGE MOVE OVERHEAD. MONDAY WILL BE
ANOTHER MILD TO WARM DAY WITH MOST AREAS NOT SEEING ALL THAT MUCH
WIND. LEFT IN THE SMALL POPS OVER THE HIGHER TERRAIN OF SRN
SWEETWATER AS THERE COULD STILL BE A COUPLE SHOWERS TRYING TO MOVE
EAST OR NORTHEAST OFF THE UINTAS INTO THAT AREA. DON`T SEE MUCH HOPE
OF ANYTHING IN THE FAR WEST SO REMOVED OUR SMALL POPS UNTIL MONDAY
EVENING. MONDAY EVENING OR OVERNIGHT IS WHEN OUR FIRST WEAK PIECE OF
ENERGY MOVE NE ACROSS THE AREA IN ADVANCE OF OUR SIGNIFICANT TUESDAY/
WEDNESDAY TROUGH. LIMITED THE MONDAY EVENING POPS TO JUST THE FAR NW
AND THEN ACROSS MOST OF THE FAR WEST...ESPECIALLY NW IN THE 06-12Z
TUESDAY TIMEFRAME. ODDS OF PCPN INCREASE ACROSS THE WEST ON TUESDAY
AS THE FRONT NEARS AND THE TROUGH DYNAMICS BEGIN TO COME INTO PLAY.
AHEAD OF THE FRONT...AN INCREASING SLY FLOW WILL DEVELOP AS EARLY AS
MONDAY NIGHT LEADING TO MILDER OVERNIGHT LOWS WITH A FEW ELEVATED
AREAS LIKELY SEEING SOME RATHER WARM OVERNIGHT LOWS. OTHERWISE...THE
MAIN EFFECT AHEAD OF THE COLD FRONT WILL BE INCREASING SLY WINDS
WITH SOME AREAS APPROACHING OR NEARING HIGH WIND TUESDAY AFTERNOON
AND EVENING AHEAD OF AND EVENTUALLY WITH FRONTAL PASSAGE. LET IN THE
ISOLATED SHOWERS AND THUNDERSTORMS DURING THE AFTERNOON TUESDAY BUT
THE MAIN WEATHER FEATURE WILL BE THE VERY WARM TEMPERATURES...STRONG
SLY WINDS AND LOW RH`S INCREASING THE FIRE DANGER. COLD FRONT SWEEPS
ACROSS TUESDAY NIGHT BUT WITH THE MORE AND MORE NLY TRACK...PCPN
WILL MAINLY BE CONFINED TO THE MOUNTAINS...AND FOOTHILLS WITH A
QUICK SHOT ALONG THE FRONT. WEDNESDAY WILL BE CONSIDERABLY COOLER TO
COLDER IN SOME INSTANCES WITH MOUNTAIN SNOW SHOWERS...DECREASING TO
SCATTERED RAIN OR SNOW SHOWERS IN AND NEAR THE FOOTHILLS AND MORE
ISOLATED OUT IN THE BASINS AND SOUTH. WIND WILL CONTINUE QUITE
STRONG ON WEDNESDAY IN MANY AREAS...ESPECIALLY MOUNTAINS AND EAST OF
THE DIVIDE. SNOW LEVELS WILL BE QUITE HIGH ON TUESDAY AND MAINLY ABOVE
10K FEET LOWERING TO THE VALLEY FLOOR TUESDAY NIGHT AND REMAINING
THERE ON WEDNESDAY. SOME SIGNIFICANT SNOW IS STILL POSSIBLE TUESDAY
NIGHT THROUGH WEDNESDAY IN THE WRN MOUNTAINS AND BIGHORNS.

.LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY

THE GFS AND THE ECMWF NOW BOTH AGREE ON TRACKING THE CLOSED LOW
FARTHER NORTH...EAST ACROSS NORTHERN MT WED NT WITH MORE OF A
WESTERLY COMPONENT BEHIND THE ASCT TROUGHPA. THUS...WILL HAVE TO
ELIMINATE THE MUCH ANTICIPATED CONVECTIVE SNOW BANDING EAST OF THE
DIVIDE AND REPLACE THEM WITH DRY WINDY WEATHER AND RESTRICT THE
SNOWFALL THERE WED NT. ANY RAIN/SNOW SHOWERS EAST OF THE DIVIDE WILL
BE RESTRICTED TO THE FAR NORTH. THE COLDEST AIR WILL REMAIN TO THE
NORTH OF THE CWA WITH H7 TEMPS NOT FORECAST TO BE QUITE AS COLD AS
EARLIER ADVERTISED WITH H7 TEMPS RANGING FROM -6C TO -8C SO MUCH OF
THE SNOW SHOWERS IN THE NORTHERN BIG HORN BASIN AND NORTHERN JOHNSON
COUNTY WILL BE MIXED WITH RAIN. HOWEVER...WITH THE CONTINUED STRONG
WEST NORTHWESTERLY UPSLOPE COMPONENT...THE FAR WEST WILL CONTINUE TO
HAVE NUMEROUS SNOW SHOWERS...BECOMING STEADIER AND LIGHTER AFTER
MIDNIGHT WED NT AS ISENTROPIC LIFT GETS UNDERWAY WITH THE RETURN
FLOW BEHIND THE TROUGHPA. SOME RAIN AND SNOW SHOWERS WILL CONTINUE
IN THE NORTHERN MTNS THURSDAY AS THE MOIST WEST NORTHWEST UPSLOPE
FLOW CONTINUES BEHIND THE EXITING TROUGH. THEN...EXCEPT FOR A FEW
ISOLATED RAIN AND SNOW SHOWERS IN THE NORTHERN MTNS...DRY WEATHER
CAN BE EXPECTED THURSDAY NIGHT AS A TRANSIENT RIDGE APPROACHES THE
AREA. THAN A CLOSED LOW WHICH WILL THEN BE OFF THE PAC NW COAST BY
12Z FRIDAY WILL SWING THE ASCT DIGGING TROUGH ACROSS THE GREAT BASIN
THROUGH SATURDAY. THE GFS SPLITS THE ENERGY OF THE TROUGH AND CLOSES
OFF THE BASE OF THE TROUGH OVER CO WITH THE BULK OF THE ENERGY OF
THE TROUGH REMAINING TO OUR SOUTH. THE ECMWF KEEPS THE FLOW MORE
ZONAL. WITH THIS UNCERTAINTY HAVE NOT COMMITTED TO FOCUSING THE ASCT
PRECIP TO ANY ONE PERIOD AND JUST KEPT A BROADBRUSHED IDEA OF WHEN
THE PRECIP WOULD OCCUR OVER THE FAR WEST FRIDAY THROUGH SUNDAY. IF
IT TURNS OUT THAT IT LOOKS LIKE THE EURO EVENTUALLY WILL COME TO
FRUITION...POPS WILL NEED TO BE DECREASED TOWARD SUNDAY AS THE FLOW
BACKS TO A LESS UPSLOPE COMPONENT AND THE ENERGY SLIPS TO OUR SOUTH.
TEMPS WILL BE NORMAL TO SLIGHTLY ABOVE NORMAL THROUGH THE
PERIOD.

&&

.AVIATION.../00Z ISSUANCE/

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

VFR CONDITIONS WILL OCCUR THROUGH TONIGHT. ISOLATED SHOWERS ARE
POSSIBLE ACROSS SOUTHERN NATRONA COUNTY THROUGH 02Z AS A COLD FRONT
NOW EXTENDING ALONG THE OWL CREEK MTNS TO NORTHERN NATRONA COUNTY
CONTINUES TO PUSH SOUTH AND BUILDS THE FIELD OF CUMULUS CLOUDS THAT
ARE ALREADY IN PLACE IN SOUTHERN NATRONA COUNTY. THE SHOWERS ARE NOT
FORECAST TO HIT THE KCPR AIRPORT. THE COLD FRONT WILL CONTINUE TO
PUSH THROUGH CENTRAL WY THROUGH 00Z. A WIND SHIFT TO THE NORTH WILL
BE THE MAIN IMPACT.

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

VFR CONDITIONS WILL OCCUR TODAY AND TONIGHT. ISOLATED SHOWERS AND
THUNDERSTORMS ARE POSSIBLE ACROSS SOUTHERN WY UNTIL 02Z. THIS
ACTIVITY SHOULD REMAIN SOUTH OF THE KRKS AIRPORT DURING THIS
TIMEFRAME.


&&

.FIRE WEATHER...

IT WILL BE DRY THROUGH MONDAY AFTERNOON EXCEPT FOR ISOLATED
SHOWERS AND THUNDERSTORMS IN SOUTHERN AND EASTERN SWEETWATER
COUNTY NORTHEAST TO NEAR CASPER MOUNTAIN THE REMAINDER OF THIS
AFTERNOON THROUGH ABOUT 02Z MONDAY. MONDAY WILL BE DRY AND WARM
WITH BREEZY AREAS...MAINLY IN THE MOUNTAINS AND FOOTHILLS. A WEAK
WEATHER DISTURBANCE AHEAD OF A MAJOR WEATHER SYSTEM WILL MOVE INTO
THE NORTHWEST MONDAY NIGHT WITH A CHANCE OF SHOWERS WITH HIGH SNOW
LEVELS. SOUTHERLY WINDS WILL BE ON THE INCREASE MONDAY NIGHT AND
ESPECIALLY TUESDAY. THE COMBINATION OF STRONG TO VERY STRONG
SOUTHERLY WINDS ON TUESDAY COMBINED WITH WARM TEMPERATURES AND LOW
RH`S WILL INCREASE THE FIRE DANGER. OUT WEST...RAIN SHOWERS WITH
BE LIKELY ON TUESDAY WITH THE SNOW LEVEL NEAR 10K FEET. A STRONG
COLD FRONT WILL SWEEP EAST ACROSS THE AREA TUESDAY NIGHT WITH A
BAND OF SHOWERS AND ISOLATED THUNDERSTORMS. IT WILL CONTINUE VERY
WINDY THROUGH WEDNESDAY. WEDNESDAY WILL ALSO BE CONSIDERABLY
COOLER THAN TUESDAY BUT STILL RATHER DRY EAST OF THE DIVIDE WITH
MIN RH`S IN THE TEENS AND 20S.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

SHORT TERM...SKRBAC
LONG TERM...LIPSON
AVIATION...LIPSON
FIRE WEATHER...SKRBAC







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