Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 180547
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1146 PM MDT THU APR 17 2014

.SHORT TERM...TONIGHT THROUGH FRIDAY

QUIET WEATHER FOR WEST CENTRAL WYOMING THROUGH TONIGHT WITH WEAK
RIDGING ALOFT. ONLY EXPECT SOME MID TO HIGH LEVEL CLOUDINESS INTO
EARLY FRIDAY MORNING. WILL THEN WATCH NEXT SHORTWAVE TROUGH TO
APPROACH THE NORTHERN ROCKIES BY FRIDAY AFTERNOON. MOST OF THIS
ENERGY LOOKS TO STAY OVER MONTANA...BUT SYSTEM WILL DRAG A COLD
FRONT ACROSS WYOMING LATER FRIDAY. ADDITIONALLY...SCATTERED
SHOWERS AND ISOLATED THUNDERSTORMS TO DEVELOP MAINLY OVER THE
NORTHWEST MOUNTAINS...FROM THE TETON RANGE TO THE ABSAROKA RANGE.
LIKELY TO BE CONVECTIVE SNOW SHOWERS OVER THE HIGHEST MOUNTAIN
RANGES AND PARTS OF YELLOWSTONE NATIONAL PARK. TEMPERATURES WILL
BE WARM AND ABOVE NORMAL...JUST AHEAD OF THE COLD FRONT...EAST OF
THE CONTINENTAL DIVIDE ON FRIDAY.

.LONG TERM...FRIDAY NIGHT THROUGH THURSDAY NIGHT

THE SHORTWAVE AND ASSOCIATED COLD FRONT WILL BE EXITING THE COWBOY
STATE RATHER QUICKLY FRIDAY EVENING...WITH CLEARING CONDITIONS BY
SATURDAY MORNING. THE WEEKEND WILL BE CALM AND SEASONAL WITH DRY
CONDITIONS EXPECTED AND LITTLE TO WIND. BY MONDAY...AN AMPLIFIED
RIDGE BUILDS OVER THE NORTHERN AND CENTRAL ROCKIES INTO CENTRAL
ALBERTA. AT THE SAME TIME...THE NORTH PACIFIC LOW THAT HAS BEEN NEAR
THE ALUETIAN CHAIN BEGINS TO DIG AND MOVE SOUTHEASTWARD TOWARD THE
PACIFIC NORTHWEST. THIS SYSTEM QUICKLY MAKES ITS WAY ONSHORE BY
TUESDAY MORNING...TRANSITIONING THE RIDGE EASTWARD AND TURNING THE
UPPER LEVEL FLOW TO THE SOUTHWEST. A WEAK SHORTWAVE AHEAD OF THE
SYSTEM WILL BRING WEAK RAIN AND SNOW SHOWERS ACROSS THE WESTERN
MOUNTAINS EARLY TUESDAY MORNING.

ON TUESDAY...SCATTERED SHOWERS WITH ISOLATED THUNDERSTORMS WILL
OCCUR ACROSS THE AREA AS THE COLD FRONT NEARS WESTERN PORTIONS OF
THE FORECAST AREA. AREAS EAST OF THE DIVIDE WILL BE IN THE WARM
SECTOR THROUGH LATE AFTERNOON...THUS GUSTY SOUTHWEST WINDS WILL
OCCUR FROM SWEETWATER TO SOUTHERN JOHNSON COUNTY. THIS WILL ALSO
KEEP SNOW LEVELS AT OR ABOVE 10KFT AHEAD OF THE COLD FRONT. THIS
WILL ALSO ACCELERATE SNOWMELT IN THE CENTRAL MOUNTAINS...WHICH MAY
CAUSE SIGNIFICANT RISES IN CREEKS AND STREAMS. ALTHOUGH THUNDERSTORM
ACTIVITY WILL BE MOSTLY ISOLATED...STRONG GUSTY WINDS WILL BE THE
MAIN HAZARD AS THE COLD FRONT MOVES THROUGH BY TUESDAY EVENING.

THE MAIN AREA OF LOW PRESSURE WILL MOVE INTO EAST-CENTRAL MONTANA BY
WEDNESDAY...TURNING THE UPPER LEVEL FLOW IN A MORE CYCLONIC
WEST-NORTHWEST FLOW. THIS...IN ADDITION TO H7 TEMPS OF -6 TO -9 WILL
BRING MORE WIDESPREAD SNOW ACROSS THE WEST. SNOW WILL ALSO REACH THE
VALLEY FLOOR TUESDAY NIGHT INTO WEDNESDAY MORNING. A DRY SLOT IS
EXPECTED BEHIND THE COLD FRONT DURING THIS TIME...IMPACTING AREAS
EAST OF THE DIVIDE. THIS WILL RESULT IN DOWNSLOPING...DRY
CONDITIONS. THIS WILL BE SHORT-LIVED...AS THE AFOREMENTIONED
CYCLONIC FLOW SPREADS ACROSS THE STATE. THIS WILL ALLOW FOR SHOWERS
AND ISOLATED THUNDERSTORMS TO ONCE AGAIN FORM DURING THE DAY
WEDNESDAY. SNOW WILL BE CONFINED TO THE HIGHER ELEVATIONS...WITH ANY
RAIN SHOWERS IN THE LOWER ELEVATIONS CHANGING OVER TO SNOW WEDNESDAY
NIGHT. SNOW ACCUMULATIONS WILL BE HEAVIEST IN THE MOUNTAINS DUE TO
FAVORED UPSLOPE CONDITIONS.

&&

.AVIATION.../06Z ISSUANCE/

A STORM SYSTEM PASSING NORTH OF THE COWBOY STATE WILL RESULT IN
SCATTERED TO LOCALLY NUMEROUS MOUNTAIN SNOW/VALLEY RAIN
SHOWERS...MAINLY ALONG AND NORTHWEST OF A KAFO...KPNA...KDUB...KCOD
LINE FRIDAY. THE BEST CHANCE OF CONVECTION IN THIS AREA WILL BE FROM
ABOUT 13Z TO 19Z...WITH THE PRECIPITATION SHIFTING EAST AND
SOUTH WITH TIME...BUT BECOMING LESS WIDESPREAD DURING THE AFTERNOON.
KJAC WILL LIKELY SEE MVFR CONDITIONS IN RAIN SHOWERS FRIDAY
MORNING...POSSIBLY LINGERING INTO THE AFTERNOON. EAST OF THE
DIVIDE...AS WELL AS SWEETWATER COUNTY...THE MAIN CONCERN WILL BE THE
VERY WINDY WESTERLY WINDS IN THE KRKS-KCPR WIND CORRIDOR AS WELL AS
LEE SIDE OF MOUNTAINS AND ADJACENT FOOTHILLS. SOME LOW LEVEL WIND
SHEAR IS EXPECTED AT KCOD AND KLND FRIDAY MORNING...BEFORE STRONGER
WINDS MIX TO THE SURFACE BY MIDDAY. DOWNSLOPING AND A VERY DRY
ATMOSPHERE EAST OF THE DIVIDE WILL INHIBIT MOST IF NOT ALL
CONVECTION...WITH THE BEST SHOT AT CONVECTION ACROSS NORTHERN
WYOMING. CANNOT RULE OUT SOME THUNDER...BUT TIMING OF CONVECTION OUT
WEST...AND DRY CONDITIONS EAST SHOULD KEEP LIGHTNING ISOLATED AT
BEST. A PACIFIC COLD FRONT WILL PUSH ACROSS THE AREA LATER
FRIDAY AFTERNOON AND EVENING...WITH A SLIGHT WIND SHIFT IN MOST
CASES...WITH BREEZY WINDS CONTINUING...BUT MORE IMPORTANTLY
IMPROVING CONDITIONS WITH CONVECTION WANING QUICKLY BETWEEN 00Z AND
03Z SATURDAY. ALSO WINDS WILL BEGIN TO WEAKEN BY LATE EVENING.
NORTHWEST/WESTERN MOUNTAINS WILL BE OBSCURED MUCH OF THE TIME
THROUGH EARLY FRIDAY AFTERNOON...WITH IMPROVING CONDITIONS BY LATE
AFTERNOON/EARLY EVENING.

&&

.FIRE WEATHER...

LOW PRESSURE WILL MOVE OVER MONTANA FRIDAY AFTERNOON AND EVENING.
THIS WILL BRING A FRONTAL BOUNDARY ACROSS NORTHERN AND CENTRAL
WYOMING. SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WILL DEVELOP
OVER NORTHWEST WYOMING...INCLUDING THE TETONS AND YELLOWSTONE
NATIONAL PARK. GUSTY WINDS WILL BE COMMON MOST AREAS FRIDAY
AFTERNOON AND EVENING. WIND DIRECTION WILL GENERALLY BE FROM THE
WEST...RESULTING IN VERY GOOD SMOKE DISPERSAL. OTHERWISE...THERE
WILL BE A QUIET WEATHER PATTERN SHAPING UP THIS WEEKEND ACROSS WEST
CENTRAL WYOMING WITH VERY LITTLE OR NO PRECIPITATION AND LESS WIND.

&&

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

&&

$$

SHORT TERM...KPL
LONG TERM...LAVOIE
AVIATION...WM
FIRE WEATHER...KPL







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