Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 220516
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1116 PM MDT MON APR 21 2014

.SHORT TERM...TONIGHT AND TUESDAY (ISSUED AT 201 PM MDT)

RIDGE AXIS MOVING INTO THE WEST WITH ONLY SOME HIGH CLOUDS FILTERING
THROUGH WITH IT. OTHERWISE...ANOTHER MILD DAY WITH MOST AREAS NOT
SEEING ANY SIGNIFICANT WINDS. WEATHER PATTERN STARTS TO CHANGE LATER
THIS EVENING AS THE FIRST SHORTWAVE MOVES OUT OF OUR APPROACHING
UPPER LOW. THIS SHORTWAVE MOVES ACROSS THE NORTHWEST LATER TONIGHT
WITH AN INCREASING CHANCE OF RAIN AND SNOW SHOWERS. NOTHING TOO
SIGNIFICANT BUT A DECENT CHANCE OF SHOWERS FROM ABOUT THE TETONS
NWD. THE TROUGH MOVES INTO THE GREAT BASIN DURING THE DAY TUESDAY
WITH INCREASING SLY FLOW ACROSS OUR AREA. TIMING IS A LITTLE SLOWER
THAN YESTERDAY SO EVEN THOUGH IT WILL STILL BE WINDY IN MOST AREAS
TOMORROW...IT SEEMS THE RISK OF HIGH WINDS HAS DIMINISHED DURING THE
AFTERNOON HOURS TUESDAY. SHOWERS AND HIGHER MOUNTAIN SNOW STILL
LOOKS GOOD OUT WEST WITH ISOLATED AT BEST FOR MOST OF THE AREA EAST
OF THE DIVIDE. A FEW THUNDERSTORMS ARE POSSIBLE IN THE FAR WEST
BASED ON ADJUSTED SOUNDINGS. NOT THAT EXCITING EAST OF THE DIVIDE
BUT COULD BE SOME LOCALIZED SMALL CAPE SO WON`T CHANGE IDEA OF
ISOLATED THUNDERSTORMS FOR THE ENTIRE CWFA TUESDAY AFTERNOON.
OTHERWISE...WARM WITH 70S TO 80 IN THE WARMEST LOCALES EAST OF THE
DIVIDE WITH 50S AND 60S WEST. CONTINUED SNOWMELT IN THE MOUNTAINS
WITH HIGHS IN THE 50S UP TO 9000 FEET EAST OF THE DIVIDE WITH MAINLY
40S WEST. SNOW LEVEL IN THE FAR WEST WILL LIKELY BE AROUND 10K FEET
DURING THE DAY.

.LONG TERM...TUESDAY NIGHT THROUGH MONDAY

THE FOREMENTIONED COLD FRONT WILL SWEEP ACROSS THE AREA TUE NIGHT
AND INTO WEDNESDAY. THE PERIOD OF STEADIEST PRECIPITATION OUT WEST
STILL LOOKS TO BE TUESDAY EVENING WITH THE FRONT. WITH COLD AIR
PUSHING IN BEHIND THE FRONT WE EXPECT SNOW LEVELS TO DROP TO THE
VALLEY FLOORS DURING THE NIGHT. WITH THE BEST ENERGY GONE BY
WEDNESDAY WE EXPECT THE PRECIPITATION TO BECOME MORE SHOWERY AT
THAT POINT. MEANWHILE...EAST OF THE DIVIDE WE EXPECT THE
PRECIPITATION TO BE A LOT MORE SCATTERED TUESDAY NIGHT DUE TO THE
STRONG WESTERLY DOWNSLOPING FLOW FOR MANY AREAS. WITH THE BEST
ENERGY ACROSS NORTHERN AREAS WE KEPT THE POPS HIGHER IN THIS
VICINITY. AS FOR WEDNESDAY EAST OF THE DIVIDE...IT WILL BE MUCH
COOLER...AROUND 20 DEGREES COOLER FOR MANY LOCATIONS. IT WILL ALSO
BE A TOUPEE ALERT DAY WITH A TIGHT PRESSURE GRADIENT REMAINING
OVER THE AREA WITH HIGH PRESSURE TO THE WEST AND DEVELOPING LOW
PRESSURE TO THE EAST. AS FOR POSSIBLE HIGH WIND HIGHLIGHTS...700
MILLIBAR WINDS DO NOT LOOK TO BE QUITE STRONG ENOUGH AT THIS
POINT. GFS MOS DOES SHOW 40 KNOTS AT THE ROCK SPRINGS AIRPORT BUT
THIS TENDS TO OVERDO THE WIND. HOWEVER...A BLUSTERY DAY FOR MANY
AREAS. AS FOR PRECIPITATION...BOTH MODELS SHOW LITTLE ACROSS THE
AREA. WITH SOME INSTABILITY THERE COULD BE A FEW SHOWERS HOWEVER
MOST AREAS OTHER THAN THE MOUNTAINS SHOULD BE PRECIPITATION FREE A
VAST MAJORITY OF THE TIME WITH DOWNSLOPING OFF OF THE MOUNTAINS.

THINGS SHOULD QUIET DOWN A BIT AS WE HEAD INTO WEDNESDAY NIGHT AND
THURSDAY AS SOME SHORT WAVE RIDGING MOVES ACROSS THE AREA. AS A
RESULT WE REDUCED POPS A BIT ACROSS THE AREA. WITH THE PRESSURE
GRADIENT RELAXING A BIT WINDS SHOULD BACK OFF A BIT ALTHOUGH IT WILL
STILL BE BREEZY TO WINDY IN MANY LOCATIONS.

THE WEATHER THEN LOOKS TO TAKE ANOTHER UNSETTLED TURN AS A TROUGH
CARVES OUT ACROSS THE WESTERN UNITED STATES. AREAS EAST OF THE
DIVIDE SHOULD SQUEEZE OUT ONE MORE DRY DAY ON FRIDAY THOUGH. SHOWERS
WILL SPREAD BACK INTO WESTERN WYOMING HOWEVER. THERE ARE DIFFERENCES
THAT SHOW UP STARTING SATURDAY. THE GFS DEVELOPS A CLOSED UPPER LOW
ACROSS THE SOUTHERN GREAT BASIN AND SLOWLY DRIFTS IT EAST ACROSS
COLORADO THROUGH MONDAY. THE EUROPEAN HAS MORE OF A TROUGH.
HOWEVER...BOTH MODELS HAVE IT UNSETTLED WITH CHANCES OF SHOWERS EACH
DAY FROM SATURDAY THROUGH MONDAY. CLOSED UPPER LEVEL LOWS ARE VERY
HARD TO PREDICT MOVEMENT ON THOUGH WITH THE MODELS CHANGING THEIR
OPINIONS MORE THAN A POLITICIAN. AS A RESULT...PINPOINTING A WETTER
DAY IS NEARLY IMPOSSIBLE AT THIS POINT. SO THE SOLUTION WAS TO KEEP
A CHANCE OF SHOWERS THROUGH THE PERIOD. AS FOR THUNDERSTORMS...THE
BEST CHANCE WOULD BE SATURDAY AS A COLD FRONT MOVES THROUGH THE
STATE. TEMPERATURES LOOK TO BE NEAR TO BELOW NORMAL FROM SATURDAY
THROUGH MONDAY WITH CLOUD COVER AND GENERAL TROUGHINESS OVER THE
AREA.

&&

.AVIATION.../06Z ISSUANCE/

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

VFR CONDITIONS WILL OCCUR TODAY AND TONIGHT. EXPECT A GUSTY WIND AT
MOST TERMINAL SITES TODAY INTO THIS EVENING. ISOLATED SHOWERS AND
THUNDERSTORMS WILL OCCUR AFTER 19Z UNTIL 03Z. A STRONG COLD FRONT
WILL PUSH EAST OF THE DIVIDE BETWEEN 05Z AND 10Z WEDNESDAY. ISOLATED
SHOWERS WILL OCCUR WITH THE FRONTAL PASSAGE ALONG WITH A WIND SHIFT
TO THE WEST. SEE INDIVIDUAL TERMINAL SITES FOR MORE DETAILS.

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

VFR CONDITIONS WILL PREVAIL THROUGH 00Z ACROSS THE REGION. EXPECT A
GUSTY WIND AT MOST TERMINAL SITES. SCATTERED SHOWERS WILL DEVELOP
OVER THE AREA AFTER 18Z WITH ISOLATED THUNDERSTORMS. WIND GUSTS TO
50 MPH MAY OCCUR WITH STORMS. LOCAL MVFR CONDITIONS MAY OCCUR OVER
AND NEAR THE MOUNTAINS DURING THE AFTERNOON AND EARLY EVENING. A
STRONG COLD FRONT WILL MOVE THROUGH THE WEST BETWEEN 00Z AND 05Z
WEDNESDAY. THIS WILL USHER IN COLDER AIR WITH RAIN SHOWERS TURNING
TO SNOW SHOWERS. THE WESTERN MOUNTAINS WILL SEE SNOW SHOWERS TONIGHT
WITH WIDESPREAD MVFR TO IFR CONDITIONS. AS THE FRONT MOVES ACROSS
THE WEST THE WIND WILL SHIFT TO THE WEST OR SOUTHWEST AND WILL BE
GUSTY. SEE INDIVIDUAL TERMINAL SITES FOR MORE DETAILS.

&&

.FIRE WEATHER...

...HAZARDOUS BURNING CONDITIONS ON TUESDAY AND WEDNESDAY...

DRY WITH BREEZY AREAS...MAINLY IN THE MOUNTAINS AND FOOTHILLS
THROUGH TONIGHT. A WEAK WEATHER DISTURBANCE AHEAD OF A MAJOR WEATHER
SYSTEM WILL MOVE INTO THE NORTHWEST TONIGHT WITH A CHANCE OF SHOWERS
WITH HIGH SNOW LEVELS. SOUTHERLY WINDS WILL BE ON THE INCREASE
TONIGHT AND ESPECIALLY TUESDAY INTO WEDNESDAY. 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...HATTINGS
AVIATION...AR
FIRE WEATHER...SKRBAC









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