823
FXUS65 KRIW 161749
AFDRIW
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE RIVERTON WY
1150 AM MDT WED OCT 16 2013
.SHORT TERM...TODAY THROUGH FRIDAY NIGHT
CLEAR SKIES AND LIGHT WINDS THIS MORNING MAY LEAD TO SOME PATCHY
MORNING FOG EARLY ALONG WITH SOME RATHER IMPRESSIVE SURFACE
INVERSIONS FOR THIS TIME OF YEAR. TEMPERATURES WILL BE ABOUT 5
DEGREES WARMER TODAY WITH SOME BRISK WESTERLIES DEVELOPING ACROSS
THE SOUTH LATER THIS AFTERNOON AS THE NEXT SYSTEM APPROACHES. THIS
NEXT SYSTEM WILL BE MOVING RIGHT ALONG AT A PRETTY GOOD
CLIP...DELIVERING A BLAST OF SNOW TO THE NORTHERN HALF OF WYOMING
LATE TONIGHT INTO THURSDAY MORNING...AND SOUTH BY THURSDAY
AFTERNOON...MAINLY ALONG AND EAST OF THE DIVIDE. GIVEN THE EXPECTED
TRACK OF THE SYSTEM THERE COULD BE SOME QUICK SNOW ACCUMULATION
ALONG THE WEST SIDE OF THE BIGHORNS...THIS WILL CERTAINLY BE WATCHED
AS THE SYSTEM APPROACHES. THE PRECIPITATION CLEARS FROM WEST TO EAST
THURSDAY EVENING AS THE BACK SIDE OF THE UPPER TROUGH MOVES IN...BUT
A FAIRLY TIGHT GRADIENT WILL LIKELY PREVENT ANY FOG FORMATION
OVERNIGHT.
FRIDAY WILL BE MOSTLY CLEAR WITH MODERATING TEMPS...WARMING QUITE
NICELY IN THE WEST AND SOUTH WITH THE HELP OF SOME MODERATE
WESTERLIES. COOL NORTHWESTERLY FLOW WILL PREVAIL OVER EASTERN
WYOMING WITH A FEW RESIDUAL CLOUDS.
.LONG TERM...SATURDAY THROUGH WEDNESDAY
A NORTHWEST FLOW WILL REMAIN ACROSS THE ROCKIES THROUGH THE PERIOD
WITH A COUPLE OF CLIPPERS IN THIS FLOW.
16/00Z ECMWF HAS SIGNIFICANTLY SLOWED THE PROGRESSION OF UPPER RIDGE
...CURRENTLY ALONG 130W...INTO THE INTERMOUNTAIN WEST NEXT WEEK.
THIS BRINGS THE ECMWF INTO BETTER AGREEMENT WITH THE GFS. SLOWER
PROGRESSION IS THE PREFERRED SOLUTION IN THIS HIGH AMPLITUDE FLOW
WITH CLIPPERS REINFORCING UPPER TROUGH EAST OF THE ROCKIES.
SATURDAY WILL BE DRY WITH TEMPERATURES REBOUNDING INTO THE 50S
ACROSS MOST VALLEYS AND BASINS...THE MILDEST DAY IN OVER A WEEK.
THE NEXT OF A SERIES OF CLIPPERS WILL DIVE SOUTHEAST INTO THE
NORTHERN HIGH PLAINS ON SUNDAY WITH THE ECMWF ON THE FAST AND
FURTHER EAST SIDE OF GUIDANCE...CANADIAN ON THE SLOW SIDE AND THE
GFS THE COMPROMISE SOLUTION. GFS ALSO BRINGS MORE PRECIPITATION AND
COLD AIR FURTHER WEST INTO WYOMING SUNDAY/SUNDAY EVENING. FORECAST
IS WEIGHTED TOWARD GFS WITH BEST CHANCES OF RAIN/SNOW IN THE
VICINITY OF THE BIGHORN MOUNTAINS.
GFS IS ALSO FURTHER WEST WITH NEXT CLIPPER ON MONDAY NIGHT...THOUGH
KEEPING THE FRONTAL PRECIPITATION WITH THIS SYSTEM FURTHER EAST IN
THE NORTHERN PLAINS. BOTH GFS AND ECMWF SHOW MOIST NW FLOW
LINGERING BEHIND THIS SYSTEM THROUGH WEDNESDAY WITH ECMWF QUICKER TO
MOVE WARM FRONT ACROSS NORTHERN HIGH PLAINS ON WEDNESDAY WHILE GFS
KEEPS THIS MOIST NW FLOW AND UPGLIDE PRECIPITATION OVER THE BIGHORN
RANGE THROUGH WEDNESDAY. FORECAST KEEPS CHANCES OF SNOW OVER AND IN
THE VICINITY OF THE BIGHORN RANGE LATE MONDAY THROUGH WEDNESDAY MORE
IN LINE WITH THE GFS WHILE KEEPING TEMPERATURES BELOW NORMAL EAST OF
THE DIVIDE...THOUGH MILDER THAN WHAT WE HAVE SEEN OVER THE LAST
SEVERAL DAYS AND WHAT WE WILL CONTINUE TO SEE IN THE SHORT-TERM.
&&
.AVIATION.../18Z ISSUANCE/
LOCAL MVFR AND IFR CEILINGS THROUGH 19Z EARLY THIS AFTERNOON AROUND
010-020 KFT AGL WILL AFFECT PORTIONS OF THE SOUTHERN PORTION OF THE
UPPER GREEN RIVER BASIN AS WELL AS SOUTH PASS WEST OF THE
CONTINENTAL DIVIDE. OTHERWISE MOSTLY CLEAR SKIES AND MAINLY LIGHT
WINDS WILL OCCUR.
A QUICK MOVING STORM SYSTEM DIVING SOUTHEAST WILL BEGIN TO AFFECT
THE AREA LATE TODAY...BUT WILL ESPECIALLY IMPACT THE AREA TONIGHT.
INCREASING MID/HIGH LEVEL CLOUDS WILL OCCUR THIS AFTERNOON. SNOW
SHOWERS ARE EXPECTED TO BREAK OUT ACROSS THE NORTH BETWEEN 00Z AND
06Z THURSDAY...WITH THE BIGGEST IMPACT OVER THE BIGHORN MOUNTAINS.
SOME SNOW SHOWER ACTIVITY COULD IMPACT THE LOWER ELEVATIONS. THE
ASSOCIATED COLD FRONT WITH THIS SYSTEM IS EXPECTED TO PUSH SOUTHWARD
INTO NORTHERN WYOMING BY AROUND 02Z...REACHING THE DIVIDE BETWEEN
09Z AND 12Z. IN WAKE OF THIS FRONT...MVFR CEILINGS ARE EXPECTED TO
DEVELOP IN SOME AREAS...WITH THE GREATEST LIKELIHOOD ACROSS THE CODY
FOOTHILLS...NORTHERN BIG HORN BASIN...AS WELL AS JOHNSON AND NATRONA
COUNTIES AND THE LANDER FOOTHILLS AS WELL AS THE ADJACENT EAST SLOPE
OF THE WIND RIVER MOUNTAINS. AREAS WEST OF THE DIVIDE SHOULD REMAIN
MOSTLY DRY BUT WITH A FEW SNOW SHOWERS FROM THIS SYSTEM.
&&
.FIRE WEATHER...
STRONG VALLEY/BASIN INVERSIONS WILL BREAK LATE THIS MORNING.
EXPECT PATCHY MORNING FOG IN THE WESTERN AND CENTRAL BASINS AND
VALLEYS. EXPECT A MILDER DAY LONG WITH NO PRECIPITATION. HIGH AND
MID CLOUDS WILL INCREASE FROM THE NORTHWEST THIS AFTERNOON
AHEAD OF AN APPROACHING PACIFIC TROUGH. A QUICK SHOT OF RAIN AND
SNOW WILL SWEEP ACROSS WYOMING TONIGHT THROUGH THURSDAY
EVENING AS THIS TROUGH PASSES ON THROUGH. FRIDAY WILL BE WARMER
AND CLEARING WITH SOME BREEZES ACROSS THE SOUTH.
&&
.RIW WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...ALLEN
LONG TERM...AEM
AVIATION...LIPSON
FIRE WEATHER...ALLEN