Area Forecast Discussion
Issued by NWS Riverton, WY

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
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 031720
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1120 AM MDT TUE MAY 3 2016

.SHORT TERM...TUESDAY THROUGH THURSDAY NIGHT

A RIDGE OF HIGH PRESSURE WILL BE IN CONTROL OVER THE AREA...AND THAT
MEANS SUNSHINE AND JUST A FEW PASSING CLOUDS...LIGHT TO MODERATE
WINDS AND PLEASANT TEMPERATURES. THE MODELS ARE SHOWING A FEW
SHOWERS OVER THE HIGHER ELEVATIONS OF THE MOUNTAIN RANGES...BUT WITH
THE DRY LOWER LEVELS WE KEPT THE FORECAST DRY. WE CAN NOT RULE
SOMETHING OUT...BUT 99 PERCENT OF THE AREA WILL BE DRY.

THINGS WILL BEGIN TO CHANGE ON THURSDAY AS A POTENT TROUGH MOVES IN
FROM THE WEST AND AGAIN BEGINS TO TURN THE WEATHER PATTERN BACK TO
ACTIVE. WITH MID LEVEL MOISTURE ADVECTING IN FROM THE WEST AND WARM
TEMPERATURES HELPING TO DESTABILIZE THE ATMOSPHERE THERE WILL BE A
BETTER CHANCE OF AFTERNOON THUNDERSTORMS WEST OF THE DIVIDE.
HOWEVER...EVEN HERE MOST OF THE TIME WILL BE RAIN FREE.
MEANWHILE...EAST OF THE DIVIDE THERE WILL BE ONE MORE DRY DAY. THIS
WILL ALSO BE THE WARMEST DAY OF THE WEEK...MAYBE THE WARMEST DAY SO
FAR THIS YEAR. SOME OF THE WARMER LOCATIONS LIKE GREYBULL AND
WORLAND COULD REACH THE MIDDLE 80S.

.LONG TERM...FRIDAY THROUGH TUESDAY

SYNOPSIS...AN UPPER LEVEL LOW PRESSURE SYSTEM WILL SLOWLY DRIFT INTO
THE SW U.S. FRIDAY...AND ACROSS THE GREAT BASIN/CENTRAL ROCKIES OVER
THE WEEKEND...BEFORE EXITING INTO THE PLAINS EARLY NEXT WEEK.
SHOWERS AND THUNDERSTORMS WILL SPREAD ACROSS THE AREA FRIDAY WITH A
FEW STRONG/SEVERE THUNDERSTORMS POSSIBLE ACROSS CENTRAL WYOMING.
RAIN AND HIGHER MOUNTAIN SNOW WILL INCREASE ACROSS THE AREA FRIDAY
NIGHT AND SATURDAY WITH THE HEAVIER PRECIPITATION EXPECTED TO SHIFT
OUT INTO THE PLAINS ON SUNDAY.  ISOLATED TO SCATTERED SHOWERS AND
SEASONABLY COOL WEATHER WILL LINGER BEHIND THE SYSTEM EARLY NEXT
WEEK.

DISCUSSION...PATTERN AT THE OUTSET ON FRIDAY MORNING CONSISTS OF AN
OMEGA BLOCK WITH UPPER RIDGE OVER THE HIGH PLAINS FLANKED BY UPPER
LOWS ALONG THE COASTS.  ON THE WESTERN FLANK OF THIS BLOCK...UPPER
LOW ALONG THE SOUTHERN CALIFORNIA COAST WILL DRIFT INTO THE GREAT
BASIN BY SATURDAY WITH UPPER RIDGE BUILDING NORTH OF LOW FORMING A
REX BLOCK OVER THE INTERMOUNTAIN WEST.  MEDIUM-RANGE MODELS IN
OVERALL AGREEMENT ON THIS SETUP THROUGH THE WEEKEND WITH AN OVERALL
SLOWER TREND WITH PROGRESSION OF THE SW LOW. GFS AND ECMWF ALSO
IN BETTER AGREEMENT WITH THE NORTHERN STREAM...PUSHING THE
`KICKER` INTO WESTERN CANADA LATE SATURDAY THAT WILL BOOT CUTOFF
SW LOW ACROSS THE CENTRAL ROCKIES SUNDAY AND INTO THE CENTRAL HIGH
PLAINS ON MONDAY.

ON FRIDAY...MAIN CONCERN REMAINS POTENTIAL FOR A FEW STRONG/SEVERE
THUNDERSTORMS ALONG FRONTAL BOUNDARY EXPECTED TO PUSH SOUTH TO NEAR
A LANDER-CASPER LINE BY FRIDAY AFTERNOON.  LOW LEVEL SE FLOW IS
EXPECTED TO WRAP HIGHER CAPES ALONG THE FRONT WITH SOUTHERLY
DIFLUENT FLOW ALOFT.  NATRONA...FREMONT AND SOUTHERN JOHNSON
COUNTIES LOOK TO BE AREAS WITH THE MOST FAVORABLE ENVIRONMENT FOR
STRONGER STORMS AT THIS TIME.

FRIDAY NIGHT AND SATURDAY...UPSLOPE E-NE FLOW IS EXPECTED TO
INTENSIFY EAST OF THE DIVIDE WITH MORE WIDESPREAD PRECIPITATION
BREAKING OUT.  STILL LOOKING AT 1-2 INCHES OF WATER OVER 24-36 HOUR
PERIOD FROM FRIDAY NIGHT THROUGH SATURDAY NIGHT ACROSS UPSLOPE
FAVORED AREAS FROM NEAR CODY TO LANDER WITH HIGHER CONFIDENCE ON ON
THE SOUTH END.  SIGNIFICANT RAIN REMAINS POSSIBLE ON SNOWPACK BELOW
9KFT...ELEVATING THE FLOOD THREAT THROUGH THE WEEKEND.

SUNDAY THROUGH TUESDAY...UPSLOPE AND WARM CONVEYOR BELT
PRECIPITATION IS EXPECTED TO BREAKDOWN OVER THE AREA SUNDAY LEAVING
AREAS OF LIGHTER VALLEY RAIN AND HIGHER MOUNTAIN SNOW. TRAILING
KICKER SYSTEM DIVING ACROSS THE NORTHERN ROCKIES ON MONDAY WILL KEEP
COOL AND SHOWERY WEATHER OVER THE AREA THROUGH TUESDAY.

&&

.AVIATION.../18Z ISSUANCE/

WEST OF THE CONTINENTAL DIVIDE...KJAC/KRKS/KPNA/KBPI AIRPORTS

CONDITIONS WILL REMAIN VFR AT ALL TERMINALS THROUGH 18Z/WEDNESDAY
WITH UPPER RIDGE IN PLACE ACROSS THE GREAT BASIN AND INTERMOUNTAIN
WEST. WIND SPEEDS WILL BE LESS THAN 12KTS AT ALL SITES.

EAST OF THE CONTINENTAL DIVIDE...KCPR/KCOD/KRIW/KWRL/KLND AIRPORTS

CONDITIONS WILL REMAIN VFR AT ALL TERMINALS THROUGH 18Z/WEDNESDAY
WITH UPPER RIDGE IN PLACE ACROSS THE GREAT BASIN AND INTERMOUNTAIN
WEST. WIND SPEEDS WILL BE LESS THAN 12KTS AT ALL SITES WITH ONE
EXCEPTION. THAT WILL BE KCPR WHERE SOUTHWEST WIND AROUND 12KTS WILL
INCREASE BETWEEN 13Z-15Z/WEDNESDAY.

&&

.FIRE WEATHER...

MAINLY DRY WEATHER WILL CONTINUE THROUGH THURSDAY MORNING ALONG WITH
GRADUALLY WARMING TEMPERATURES. RELATIVE HUMIDITY WILL FALL INTO THE
TEENS AT TIMES ACROSS THE LOWER ELEVATIONS THROUGH THURSDAY.
HOWEVER...WINDS ARE EXPECTED TO REMAIN LIGHT TO MODERATE. A SPOT OR
TWO OVER THE MOUNTAINS MAY SEE A LATE DAY SHOWER THROUGH WEDNESDAY.
AN APPROACHING TROUGH WILL BRING A CHANCE OF THUNDERSTORMS WEST OF
THE DIVIDE THURSDAY AFTERNOON AND NIGHT. WITH LIGHT WINDS...EXPECT
FAIR TO POOR SMOKE DISPERSAL TODAY. MIXING WILL INCREASE WEDNESDAY
AND ESPECIALLY THURSDAY AHEAD OF THE APPROACHING TROUGH.

&&

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

&&

$$

SHORT TERM...HATTINGS
LONG TERM...AEM
AVIATION...CNJ
FIRE WEATHER...HATTINGS


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