Area Forecast Discussion
Issued by NWS Riverton, WY

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
000
FXUS65 KRIW 160949
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
349 AM MDT WED APR 16 2014

.SHORT TERM...TODAY THROUGH FRIDAY NIGHT

SAT IMAGERY SHOWS VERY PROGRESSIVE UPR PATTERN W/SW TROF AXIS
MOVING RAPIDLY ACROSS THE STATE FROM WNW TO ESE...WITH THE BEST
LIFT NOW OVR THE ERN ZONES OF JOHNSON AND NATRONA COUNTIES. AT THE
SFC...LOW P QUICKLY SPINNING UP TO OUR E OVR THE WRN SD/NE
REGION...DRAGGING SFC FRONT THROUGH MUCH OF THE CWA AT THIS
POINT...WITH THE EXCEPTION OF SRN FREMONT WRN NATRONA AND
SWEETWATER COUNTIES AS THE FRONT/CONVERGENCE ZONE STALLS
OUT...WITH THIS AREA OF CONVERGENCE CONTINUING TO PRODUCE LIGHT
SNOW AND SLEET. UPSTREAM AND JUST OFF SHORE IS AN EPAC HIGH WITH A
JET NOW MOVING DOWN THE E SIDE OF THE RIDGE AND OVR WA/OR. EVEN
FURTHER UPSTREAM LAY ANOTHER STRONGER JET TO THE SOUTH OF THE
ALEUTIAN LOW...DIGGING INTO THE W SIDE OF THAT REGION`S TROF.

TODAY...SW AND ASSOCIATED SFC FRONT CONTINUE OUT OF THE
AREA...LEAVING ONLY A COLD POOL ALOFT UNDER NW FLOW. THE COMBINATION
OF RELATIVELY COOL LOWER LVLS UNDER THE COLD POOL WILL YIELD ONLY
LOW/MODERATE INSTABILITY AT BEST AND WILL LIKELY NEED THE MOUNTAINS
TO ACCOMPLISH THE TASK OF PUTTING ANYTHING ON THE SFC FOR THE MOST
PART. SPITTLE FOR THE MOST PART AT THE LOWER ELEVATIONS IF THAT.
COOL TODAY...BUT THE GOOD NEWS IS THAT MID AND LOWER LVLS WILL NOT
GENERATE MUCH IN THE WAY OF WIND. TONIGHT...WEAK SFC PATTERN WITH
UPR LVLS BEGINNING TO SLOWLY TRANSITION TO RIDGING AND DRYING.
WARMING WILL COMMENCE ON THU...WITH 70S AGAIN WITHIN REACH BY
FRIDAY AS THE RIDGE CENTERS OVERHEAD. HOWEVER...THIS WILL BE
SOMEWHAT SHORT-LIVED AS A WEAK GREAT BASIN LOW GETS THE KICK IT
NEEDS FROM THE ALEUTIAN JET ENERGY/TROF MENTIONED ABOVE...SPINS UP
AND RACES THRU THE FA...DRAGGING SOME EPAC AND SW CONUS MOISTURE
INTO THE REGION ALONG WITH A DEVELOPING MID/SFC FRONT...INCREASING
AND EXPANDING PRECIP CHCS FRI....ESPECIALLY AFTERNOON AND
OVERNIGHT. DOES NOT LOOK ALL THAT SPECIAL ATTM...WITH MOST OF THE
PRECIP COMING DOWN IN LIQUID FORM OUTSIDE OF THE HIGH MOUNTAINS.
WILL HAVE TO WATCH OUR SRN AND PERHAPS FAR SERN ZONES AS THESE
LOOK LIKE THE AREAS THAT WILL MOST LIKELY BE ABLE TO TAKE
ADVANTAGE OF THE BEST MOISTURE COMBO ALONG W/THE BEST FRONTAL
FORCING. WILL ALSO LOOK FOR AT LEAST ISOLATED CHC FOR THUNDER WITH
THIS ACTIVITY.

.LONG TERM...SATURDAY THROUGH WEDNESDAY

NORTH DRIES OUT BEHIND SURFACE COLD FRONT...NORTHERN STREAM TROUGH
ON SATURDAY WHILE FRAGMENTED UPPER LEVEL SYSTEM LINGERS IN THE FOUR
CORNERS REGION.  THIS LATTER SYSTEM WILL CONTINUE TO PUSH MOISTURE
AND SLIGHT INSTABILITY UP TO A STALLED FRONTAL BOUNDARY ACROSS THE
SOUTH WITH CHANCES OF RAIN SHOWERS AND ISOLATED THUNDERSTORMS MAINLY
IN THE VICINITY AND SOUTH OF A ROCK SPRINGS TO CASPER LINE...THE
BEST CHANCES NEAR THE COLORADO BORDER. OTHERWISE...HIGH TEMPERATURES
ON SATURDAY WILL BE ONLY A FEW DEGREES COOLER THAN FRIDAY BEHIND THE
COLD FRONT...AND STILL SEVERAL DEGREES ABOVE AVERAGE.

FOR SUNDAY THROUGH WEDNESDAY...THE MAIN WEATHER
MAKER...EVENTUALLY...WILL BE AN UPPER LOW CURRENTLY NEAR THE WESTERN
END OF THE ALEUTIAN CHAIN.  ECMWF AND GFS ARE IN REASONABLE
AGREEMENT WITH THE TIMING OF THIS SYSTEM PROGRESSING ONTO THE WEST
COAST TUESDAY AND INTO THE GREAT BASIN TUESDAY NIGHT.  ANY AGREEMENT
ENDS THERE WITH THE GFS STALLING OUT A STACKED LOW OVER THE EASTERN
GREAT BASIN WEDNESDAY WHILE THE ECMWF KEEPS AN OPEN TROUGH WITH LEAD
SHORTWAVE SHEARING OUT INTO THE NORTHERN HIGH PLAINS WEDNESDAY.   A
SCENARIO CLOSER TO THE ECMWF SEEMS MORE LIKELY WITH THIS SYSTEM
BOTTOMING OUT NEAR THE WEST COAST BEFORE LIFTING OUT ACROSS THE
ROCKIES.

THE UPPER FLOW WILL GRADUALLY BACK AHEAD OF THIS SYSTEM SUNDAY
THROUGH TUESDAY BRINGING THE WARM BEFORE THE STORM...ESPECIALLY ON
TUESDAY ACROSS CENTRAL AND EASTERN WYOMING.  THE CENTRAL BASINS ARE
LIKELY TO SEE LOWER 70S SUNDAY AND MONDAY.  VERY MILD AND
BREEZY/WINDY CONDITIONS ARE POSSIBLE ON TUESDAY IN THE WARM SECTOR
ACROSS CENTRAL WYOMING AS THE PACIFIC COLD FRONT PUSHES EAST TOWARD
THE WESTERN BORDER.  THE BIGHORN RANGE COULD SEE RAPID SNOWMELT AND
SIGNIFICANT RISES IN CREEKS AND RIVERS IN THIS SETUP.  HIGHER CAPES
MAY ALSO PUSH BACK AS FAR WEST AS THE BIGHORN RANGE WHICH COULD
RESULT IN A FEW STRONG STORMS DEVELOPING OFF THE EAST SLOPES.

COOLER CONDITIONS ON WEDNESDAY WITH UPPER TROUGH OVER THE
ROCKIES...CHANCES OF MOUNTAIN SNOW AND EITHER RAIN OR A WET SNOW IN
THE VALLEYS.


&&

.AVIATION.../12Z ISSUANCE/

A DISTURBANCE OVER EAST CENTRAL WYOMING EARLY THIS MORNING WILL
CONTINUE TO EXIT THE REGION. OUTSIDE OF MOUNTAINOUS AREAS...MVFR
CEILINGS WILL REMAIN POSSIBLE OVER JOHNSON AND NATRONA
COUNTIES...AND COULD IMPACT KCPR AND KBYG THROUGH 15Z. WILL HOLD OFF
UNTIL RIGHT AT TAF ISSUANCE TO DECIDE IF THOSE MVFR CEILINGS WILL BE
NEEDED AT KCPR. 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 THIS MORNING. THE NORTHWEST AND
NORTHERN MOUNTAINS SHOULD BE MAINLY OBSCURED THIS MORNING.

THIS AFTERNOON...ISOLATED TO SCATTERED SHOWERS ARE EXPECTED ACROSS
NORTHERN AND CENTRAL WYOMING...WITH THE BEST SHOT ACROSS THE
ABSAROKA AND BIGHORN MOUNTAINS AND ADJACENT FOOTHILLS. THE BEST SHOT
FOR CONVECTION AT ANY TAF SITE WOULD BE KCOD...BUT KJAC AND EVEN
KCPR COULD SEE SOME ISOLATED 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. EXCEPT FOR BRIEF MVFR/IFR CONDITIONS IN CONVECTION...VFR
CONDITIONS ARE EXPECTED AT TAF SITES THIS AFTERNOON AND TONIGHT.

&&

.FIRE WEATHER...

WITH THE FRONT THROUGH AND A WEAK SURFACE PATTERN SETTING UP...TODAY
WILL BE COOL WITH LESS WIND. ONLY THE MOUNTAINS CAN EXPECT ISOLATED
TO SCATTERED SNOW SHOWERS. A WARMING TREND WILL COMMENCE BY
THURSDAY...WITH MANY OF THE LOWER BASINS GETTING NEAR THE 70
DEGREE MARK BY FRIDAY...AHEAD OF THE NEXT SPRING WEATHER SYSTEM
DUE TO ARRIVE BY FRIDAY AFTERNOON. WINDS WILL PICK UP TO THE
BREEZY CATEGORY ACROSS THE SOUTHERN DISPATCH ZONES FRIDAY
AFTERNOON...AND THERE WILL BE AN INCREASING CHANCE FOR SHOWER AND
ISOLATED THUNDER FRIDAY AFTERNOON AND EVENING...WITH BETTER RAIN
CHANCES OVER THE SOUTHERN ZONES AGAIN AFTER MIDNIGHT.

&&

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

$$

SHORT TERM...BRAUN
LONG TERM...AEM
AVIATION...WM
FIRE WEATHER...BRAUN








USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.