Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 160545
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1145 PM MDT TUE APR 15 2014

.SHORT TERM...TONIGHT AND WEDNESDAY

STRONG COLD FRONT TO RACE SOUTHEAST ACROSS THE AREA INTO THE EARLY
EVENING HOURS. VERY DRY AND WINDY AHEAD OF IT THEN A PERIOD OF
SHOWERS WITH FROPA AND POTENTIALLY EVEN STRONGER WINDS. IF WE HAD
MORE LOW LEVEL MOISTURE...WE`D HAVE SOME DECENT THUNDERSTORMS BUT
WITH DEW POINTS UNDER 15 IN MOST AREAS...AND UNDER ZERO IN SOME
CASES...INSTABILITY WILL BE VERY LIMITED AND LOCALIZED.
HOWEVER...THESE DRY SOUNDINGS AND WARM LOW LEVELS OPEN THE DOOR FOR
A LOT OF WIND AHEAD OF AND WITH FROPA. ISSUED ANOTHER SPS FOR
FREMONT COUNTY FOR THE VERY STRONG WINDS THROUGH EARLY EVENING AND
BEEFED UP THE WIND CORRIDOR ONE EVEN MORE. COULD SEE A BRIEF PERIOD
OF HIGH WINDS IN THE WIND CORRIDOR BUT THE ONLY AREA LIKELY TO BE IN
A POPULATION AREA WOULD BE THE SOUTH SIDE OF CASPER ALONG OUTER
DRIVE AND AREA WHERE WINDS COULD GUST BRIEFLY AROUND 60 MPH.
OTHERWISE...A LOT OF 40 TO 50 MPH WINDS WITH LOCALLY HIGHER GUSTS
FOR A PERIOD WITH AND JUST AHEAD OF THE COLD FRONT. A PERIOD OF
MOUNTAIN SNOW SHOWERS OUT WEST WITH RAIN SHOWERS BRIEFLY MIXING WITH
AND TURNING TO SNOW SHOWERS IN MOST OF THE WESTERN VALLEYS. NOT A
LOT OF PCPN BUT PCPN NONETHELESS. SHOULD ALSO SEE A PERIOD OF
SHOWERS ALONG AND BEHIND THE COLD FRONT IN THE NORTH AND
NORTHEASTERN ZONES...ESPECIALLY THIS EVENING. COOL...CYCLONIC NW
FLOW ON WEDNESDAY BUT WITH LIMITED ENERGY ALOFT. DAYTIME HEATING AND
MARGINAL MOISTURE WILL LIKELY RESULT IN BUILDING MOUNTAIN SNOW
SHOWERS WITH A FEW TRYING TO MAKE IT OFF THE FOOTHILLS AND MOVE SE
ONTO THE LOWER ELEVATIONS OF CENTRAL WYOMING. MOST WILL DIE OFF TO
JUST FLURRIES OR SPRINKLES OR NOTHING. MUCH LESS WIND ON WEDNESDAY
BUT ALSO CONSIDERABLY COOLER.

.LONG TERM...WEDNESDAY NIGHT THROUGH TUESDAY

THE LEFTOVER BOUNDARY FROM THE WEDNESDAY SYSTEM WILL ALLOW A CHANCE
OF SHOWERS TO REMAIN OVERNIGHT ACROSS NORTHERN WYOMING...WITH A
SLIGHT CHANCE IN THE LOWER ELEVATIONS.  SHORTWAVE RIDGING WILL BE
OVER THE STATE ON THURSDAY ALLOWING TEMPERATURES TO WARM BACK UP TO
NEAR 60 EAST OF THE DIVIDE.  A FAST MOVING SHORTWAVE TROUGH WILL
MOVE ACROSS THE NORTHERN ROCKIES IN SOUTHERN CANADA AND MONTANA ON
FRIDAY...INCREASING THE SOUTHERLY FLOW ACROSS THE STATE AND AGAIN
INCREASING THE MID LEVEL TEMPERATURES SO THAT LOW 70S WILL ARRIVE
EAST OF THE DIVIDE.  SHOWERS WILL IMPACT NORTHWEST WYOMING FRIDAY
AFTERNOON AND EVENING AS THE TAIL OF THE SYSTEM DRAPES ACROSS THE
NORTHERN HALF OF THE STATE FRIDAY NIGHT.

SATURDAY AND SUNDAY SHOULD SEE WEAK RIDGING OVER THE AREA WITH SOME
SHOWER ACTIVITY ACROSS SOUTHERN WYOMING.  WHILE TEMPS COOL SOMEWHAT
ON SATURDAY...THEY WILL REBOUND ON SUNDAY.  BOTH THE 12Z GFS AND 12Z
ECMWF ARE IN PRETTY GOOD AGREEMENT FOR THE THURSDAY TO SUNDAY TIME
FRAME.

HOWEVER...THE MODELS ARE STILL QUITE DIFFERENT WITH THE WEATHER
PATTERN FOR NEXT WEEK.  THE GFS IS STILL GOING FOR A MORE AMPLIFIED
PATTERN WITH A STRONG TROUGH DEVELOPING OVER SOUTHERN CALIFORNIA BY
TUESDAY MORNING.  WITH THIS PATTERN...WYOMING WILL SEE INCREASED
SOUTHERLY FLOW WITH MINOR RIPPLES OF ENERGY PROVIDING SOME SHOWERS
MONDAY AND TUESDAY.  HAVE TRENDED TOWARD THIS SOLUTION WITH THE
FORECAST BASED ON THE PROGRESSIVE PATTERN AND RECENT EXPERIENCE.
THE ECMWF MAINTAINS MORE OF A WEAKENED RIDGE OVER THE AREA WITH THE
CORE OF THE ENERGY REMAINING MUCH FURTHER NORTH.  AGAIN THE ECMWF
TAKES THE ENERGY AND MOISTURE MUCH MORE INTO NORTHWEST WYOMING
THROUGH TUESDAY NIGHT...BUT WITH THIS TRACK KEEPS THE MAIN FOCUS
NORTH INTO MONTANA BY MID WEEK.  WILL CERTAINLY NEED TO SEE WHAT
FUTURE MODEL GUIDANCE PROVIDES FOR EARLY NEXT WEEK.

&&

.AVIATION.../06Z ISSUANCE/

A STORM SYSTEM AND THE ASSOCIATED COLD FRONT ARE BEGINNING TO EXIT
THE FORECAST AREA. THE BULK OF THE MVFR/IFR CONDITIONS IN LOW CLOUDS
AND RAIN/SNOW SHOWERS FOR THE NEXT FEW HOURS WILL BE ACROSS JOHNSON
AND NATRONA COUNTY. IMPROVING CONDITIONS ARE EXPECTED BETWEEN 09Z
AND 15Z IN THOSE AREAS. OTHERWISE...VFR CONDITIONS ARE EXPECTED IN
THE LOWER ELEVATIONS WITH MAINLY SCT-BKN MID AND HIGH LEVEL
CLOUDINESS...WITH A SLIGHT POSSIBILITY FOR PATCHY FOG LATER TONIGHT
INTO WEDNESDAY MORNING. CONDITIONS OVER THE CENTRAL AND SOUTHWEST
MOUNTAINS WILL IMPROVE TONIGHT...BUT THE NORTHWEST AND NORTHERN
MOUNTAINS SHOULD CONTINUE TO BE OBSCURED MUCH OF THE TIME THROUGH AT
LEAST 18Z WEDNESDAY IF NOT BEYOND.

WEDNESDAY AFTERNOON...ISOLATED TO LOCALLY SCATTERED MAINLY MOUNTAIN
SNOW SHOWERS ARE EXPECTED AGAIN ACROSS NORTH/NORTHWEST WYOMING...IN
A WEAKLY UNSTABLE NORTHWEST FLOW. SOME OF THIS ACTIVITY COULD SPILL
INTO THE LOWER ELEVATIONS...BUT SHOULD BE ISOLATED IN NATURE. WILL
HAVE VCSH IN KJAC...KCOD AND KCPR TAFS...WITH PROBABLY KCOD HAVING
THE BEST SHOT AT GETTING SOME WEAK CONVECTION. MOST OF THE
CONVECTION WILL END BY 04Z THURSDAY...BUT SOME VERY ISOLATED
ACTIVITY IN THE NORTHWEST FLOW COULD POTENTIALLY CONTINUE OVER THE
NORTHERN MOUNTAINS.

&&

.FIRE WEATHER...

DRY AND WINDY TO VERY WINDY EAST OF THE DIVIDE BUT GRADUALLY
IMPROVING RELATIVE HUMIDITIES BEHIND THE COLD FRONT LATER THIS
EVENING. UNTIL THEN...FIRE DANGER WILL BE ELEVATED WITH RH`S IN THE
TEENS OR LESS IN MANY AREAS. SOME SHOWERS WILL ACCOMPANY THE FRONT...
ESPECIALLY IN THE MOUNTAINS AND THE NORTH HALF OF THE DISTRICT.
LESSER CHANCES FURTHER SOUTH BUT STILL ISOLATED SHOWERS POSSIBLE.
MANY AREAS WILL SEE 30 TO 40 MPH WINDS WITH SOME AREAS OVER 50 MPH
INTO THE EVENING. WEDNESDAY WILL BE COOL WITH LESS WIND AND
SCATTERED MAINLY MOUNTAIN SNOW SHOWERS.

&&


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

&&

$$

SHORT TERM...SKRBAC
LONG TERM...MCDONALD
AVIATION...WM
FIRE WEATHER...SKRBAC












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