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 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS65 KRIW 241722
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1121 AM MDT FRI APR 24 2015

.SHORT TERM...TODAY THROUGH SUNDAY NIGHT

OVERALL AN ACTIVE SHORT TERM PERIOD IS IN STORE FOR THE FORECAST
AREA AS SEVERAL DISTURBANCES MOVE INTO THE REGION. THE NEXT SYSTEM
BEGINS TO MOVE INTO THE WEST THIS AFTERNOON JUST AS THE PREVIOUS
ONE EXITS. INSTABILITY LOOKS TO BE ABOUT ON PAR WITH THURSDAY BUT
WITH COOLING MID LEVELS IN THE NORTHWEST...THAT SHOULD BOOST
AFTERNOON SHOWER AND STORM ACTIVITY IN A PLACE THAT WAS LEFT
UNTOUCHED DURING YESTERDAY`S CONVECTION. OTHERWISE...THERE ARE NO
PARAMETERS THAT STAND OUT FOR ANY KIND OF SEVERE THUNDERSTORM
ACTIVITY WITH SUB SEVERE HAIL AND WIND GUSTS OVER 40 MPH EXPECTED
WITH THE STRONGER STORMS. THE WAVE TAKES A WHILE TO EXIT THE AREA
WHICH COULD KEEP A FEW STORMS GOING LATE TONIGHT...ESPECIALLY
ACROSS THE NORTH.

THE NEXT WAVE IS QUICK TO MOVE IN EARLY ON SATURDAY WITH
TEMPERATURES EXPECTED TO BE COOL ENOUGH FOR SOME ACCUMULATING SNOW
IN THE WESTERN MOUNTAINS...WITH GENERALLY 1 TO 3 INCHES EXPECTED
AT PASS LEVEL. OTHERWISE...SATURDAY AND SUNDAY WILL BE COOL AND
RAINY AS A LARGE UPPER LEVEL SYSTEM WORKS ITS WAY THROUGH THE
AREA. SATURDAY WILL STILL BE PRETTY UNSTABLE AND SHOWERY BUT A
SURFACE COLD FRONT WILL DROP SOUTH ON SUNDAY...UNDERCUTTING MOST
OF THE INSTABILITY AND LEADING TO MORE OF A STRATIFORM TYPE RAIN
WITH A STEADY WET SNOW IN THE MOUNTAINS. TEMPERATURES WILL BE
TRICKY TO FORECAST ON SUNDAY AS WILL THE SNOW LEVELS...WHICH COULD
REACH BASIN LEVEL BY SUNDAY AFTERNOON IN SOME AREAS...ESPECIALLY
ACROSS THE NORTH. WENT WITH MAINLY A RAIN/SNOW MIX IN THE BASINS
WITH SNOW ABOVE 7KFT FOR NOW BUT THIS WILL LIKELY BE ADJUSTED IF
THE MODELS COME INTO BETTER AGREEMENT ON THE SOUTHERN EXTENT OF
THE COLD AIR COMING ALONG WITH THE NORTHERN STREAM OF THIS
SYSTEM...IN ADDITION TO WHEN THE BULK OF THE PRECIPITATION IS
EXPECTED TO OCCUR.

.LONG TERM...MONDAY THROUGH FRIDAY

SYNOPSIS...AREAS OF RAIN AND MOUNTAIN SNOW WILL TAPER OFF ACROSS
EAST CENTRAL WYOMING MONDAY.  AN UPPER RIDGE WILL BRING DRIER AND
WARMER WEATHER TUESDAY AND WEDNESDAY.  SOME SHOWERS AND
THUNDERSTORMS COULD RETURN TO THE WESTERN MOUNTAINS THURSDAY AND
FRIDAY WHILE THE REST OF THE AREA WILL REMAIN DRY AND UNSEASONABLY
WARM.

DISCUSSION...SPLIT FLOW BEGINS THIS PERIOD WITH UPPER LOW MOVING OUT
OF THE SOUTHERN ROCKIES ACROSS NORTH TEXAS ON MONDAY AND NORTHERN
STREAM SHORTWAVE MOVING INTO THE NORTHERN HIGH PLAINS.  SURFACE
NORTHERLY UPSLOPE FLOW WILL RESULT IN SOME LINGERING UPSLOPE LIGHT
RAIN AND SNOW MAINLY IN THE CASPER AREA THROUGH MONDAY MORNING.
UPPER RIDGE WILL THEN PUSH INTO THE AREA MONDAY AFTERNOON AND
EVENING...CLEARING SKIES OUT NW-SE.  UPPER RIDGE AXIS WILL TRANSLATE
THE DIVIDE TUESDAY NIGHT AS A SERIES OF PACIFIC SHORTWAVES BEGIN TO
PUSH INTO BACKSIDE OF THE RIDGE ACROSS THE NW U.S.  PREVIOUS ECMWF
RUNS WERE QUICK TO FLATTEN THE RIDGE BY WEDNESDAY. 24/00Z RUN HOLDS
ON TO MORE RIDGING ACROSS THE HIGH PLAINS THROUGH THURSDAY...MORE IN
LINE WITH GFS.   FOR THE LATTER PORTION OF THE WEEK...GEFS MEAN WAS
A GOOD COMPROMISE WITH UPPER TROUGH ALONG THE WEST COAST AND RIDGE
AXIS ROUGHLY ALONG 100W.  THIS WILL PUT MOST OF THE AREA UNDER WARM
SW FLOW WITH SHORTWAVE ENERGY MOVING NE ACROSS THE INTERMOUNTAIN
WEST CLIPPING WESTERN WY.  HIGH TEMPERATURES ACROSS MOST OF THE AREA
WILL BE AROUND 15-20F ABOVE NORMAL WEDNESDAY AND THURSDAY...OR
MAINLY IN THE 70S TO LOWER 80S ACROSS THE BASINS AND VALLEYS.


&&

.AVIATION.../18Z ISSUANCE/

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

VFR CONDITIONS WILL PERSIST THROUGH THE FORECAST PERIOD.
HOWEVER...BETWEEN 21Z AND 00Z THIS AFTERNOON...AND INTO THE
EVENING...TERMINALS LOCATED ADJACENT TO MOUNTAINS WILL SEE VCNTY
SHRA/TSRA ALONG WITH GUSTY VARIABLE WINDS TO G25KTS AT TIMES.
WEATHER WILL BECOMING INCREASINGLY MOIST AND UNSTABLE THROUGH THE
WEEKEND...WITH MVFR TO OCCASIONAL IFR CONDITIONS PREVAILING AFTER
MIDNIGHT SATURDAY.

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

VFR BECOMING MVFR TO NEAR MVFR THIS AFTERNOON IN LOW CIGS AS SHOWERS
AND ISOLATED THUNDERSTORMS BECOME INCREASINGLY LIKELY...LASTING
THROUGH EARLY EVENING. LIGHT SNOW SHOWERS WILL ALSO BE POSSIBLE
LATER THIS EVENING ESPECIALLY NEAR KJAC AND KPNA AFTER 04Z. AFTER
09Z...VCNTY FOG NEAR KPNA...BUT IMPROVING CONDITIONS LASTING THROUGH
THE END OF THE FORECAST PERIOD AT THE OTHER TERMINALS.

&&

.FIRE WEATHER...

COOL AND WET OVER THE NEXT SEVERAL DAYS AS SEVERAL STORM SYSTEMS
MOVE THROUGH THE AREA. THE BEST CHANCE FOR A WETTING RAIN OR SNOW
WILL BE ON SUNDAY FOR MOST AREAS. SHOWERS AND WET THUNDERSTORMS
WILL BE THE PRIMARY DELIVERY METHOD FOR WETTING RAINS TODAY AND
TOMORROW WITH MORE OF A STRATIFORM RAIN OR SNOW ON SUNDAY. A
WARMING AND DRYING TREND BEGINS ON MONDAY AND COULD LAST THE WEEK.

&&

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

$$

SHORT TERM...ALLEN
LONG TERM...AEM
AVIATION...JB
FIRE WEATHER...ALLEN











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