Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 240520
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1120 PM MDT SAT AUG 23 2014

.SHORT TERM...TONIGHT THROUGH SUNDAY (ISSUED AT 226 PM MDT)

WV IMAGERY CONTINUES WITH WINTER-LIKE TROF OVR THE NRN ROCKIES
INCLUDING WRN/NRN WY. THE POSITION OF THE TROF IS FURTHER SOUTH
AGAIN THAN WHERE IT WAS THOUGHT TO BE AT THIS TIME. LEADING EDGE
WITH DIFFLUENT UPR FLOW AND EMBEDDED VORT MAX NOW RIDING INTO
NCNTRL/NERN WY THIS AFTERNOON. THIS WILL ALLOW FOR BETTER PRECIP TO
SPREAD FURTHER SOUTH ACROSS THE FA THROUGH A LONGER
PERIOD...INCLUDING EVEN THE WIND RIVER AND NRN GREEN RIVER BASINS.
OTHERWISE...CYCLO/FRONTO GENESIS ONGOING OVR THE FA AS THE APPROACH
UPR TROF...AND FRONT/BOUNDARY(S) CUTTING DIAGONALLY FROM THE SW TO
NCNTRL WY AND DEVELOPING LOW OVR ECNTRL WY. GENERALLY...MOISTURE
FROM THE DESERT SW MONSOON WILL GET CAUGHT UP SOUTH AND EAST OF THE
SFC LOW...WHILE EPAC MOISTURE MOVES ACROSS THE NRN FA AND INTO MT
WITH THE UPR TROF. GOOD INSTABILITY WITH SHOWERS AND EMBEDDED
THUNDER MOVING NNE ALONG THE FAR ERN BORDER OF THE FA. THIS AND
POINTS MAINLY EAST OF THIS CURRENT LINE OF CONVECTION WILL BE WHERE
TO LOOK FOR A COUPLE OF STRONGER THUNDERSTORMS THIS AFTERNOON. DEEP
SHEAR BETWEEN 25 AND 35 KTS IN THIS AREA WILL COMBINE WITH  CAPE
GENERALLY AOB 800 J/KG. HOWEVER...A FEW AREAS THAT WILL GET MORE
SUNSHINE SWD COULD SEE CAPE AS HIGH AS 1000 J/KG. ADDITIONALLY...THE
SW PORTION OF THE FA...ALTHOUGH UNDER A LITTLE WEAKER FORCING...WILL
SEE MORE CLEARING AND SUNSHINE AND MORE INSTABILITY...BUT LESS CAPE
TO WORK WITH...EARLY THIS AFTERNOON...SO WILL LOOK FOR FIRST THUNDER
IN THIS AREA. STORMS INVOF JOHNSON COUNTY MAY BE ABLE TO PRODUCE
SMALL HAIL JUST BELOW SVR LVLS AND WIND GUSTS TO 45 MPH. AS THE SFC
LOW SPINS UP THIS AFTERNOON AND EVENING...WINDS ACROSS THE SRN FA
WILL RESPONDING BY INCREASING OUT OF THE WEST UP TO 25 MPH WITH
GUSTS TO 35 MPH POSSIBLE.

TONIGHT...BOTH UPR AND LOWER PORTIONS OF THE SYSTEM EJECT TO THE
NE...WITH THE SFC LOW ENDING UP OVR THE NRN PLAINS AND THE UPR TROF
TILT WWD AND ON TOP OF SERN MT BY SUNDAY MORNING. WRAP-AROUND SHRA
AND ISO TSRA WILL ALSO END FROM CNTRL WY TO SERN MT DURING THIS
PERIOD. EXPECT MORE SNOWFALL OR ANOTHER CHANGEOVER TO LIGHT SNOWFALL
DURING THE LATE AFTERNOON AND OVERNIGHT PERIODS FOR ELEVATIONS ABOVE
9500 FT TO BEGIN WITH TONIGHT...FALLING TO 9000 FT THROUGH THE
NIGHT...BUT ALSO WITH PRECIP ENDING IN MANY PLACES. HIGHER AMOUNTS
WILL BE FAVORED IN THE UPPER BIG HORN MOUNTAINS WITH 12 HR SNOWFALL
TOTALS DURING THE EVENING/OVERNIGHT PERIOD AT 1 TO 2 INCHES FOR MOST
MANY SPOTS...WITH ISOLATED 2 TO 4 INCHES POSSIBLE OVER THE HIGHER
MOUNTAINS SUCH AS AROUND CLOUD PEAK. PATCHY FOG MOST PROBABLE IN
NEAR MOUNTAINS AND ADJACENT VALLEYS...SO HAVE ADDED FOG TO FCST
AFTER 04Z NEAR JACKSON AND INTO THE GREEN RIVER BASIN...NEAR LANDER
AFTER 09Z.

SUNDAY...WITH THE SFC LOW AND UPR TROF NOW LOCATED NE OF THE
FA...MOST OF THE CWA WILL BE RAIN FREE WITH A COUPLE OF EXCEPTIONS.
1 THE FAR NRN FA THAT WILL STILL BE UNDER SOME INFLUENCE OF THE
EXITING TROF AND EPAC MOISTURE...AND 2 NEAR AND SOUTH OF THE SRN
BORDER W/ CO UNDER THE EFFECTS OF AN UPPER SW MOVING INTO THE AREA
FROM THE GREAT BASIN. HIGH TEMPS QUITE A BIT COOLER AND ATMOSPHERE
MUCH MORE STABLE BEHIND ALL THIS CURRENT MESS.

.LONG TERM...SUNDAY NIGHT THROUGH SATURDAY

SUNDAY NIGHT A COMPLEX LONG WAVE TROUGH WITH NORTHERN SHORT WAVES
MOVING SOUTH FROM MONTANA AND SOUTHERN SHORT WAVES MOVING NORTHEAST
FROM NORTHERN UTAH WILL KEEP SOME SHOWERS AND EVENING THUNDERSTORMS
GOING ACROSS THE FORECAST AREA.  SLIGHT WARMING MAY OCCUR IN THE
SOUTHWEST WITH THE NORTH REMAINING ON THE COLD SIDE WITH POSSIBLE
FREEZING TEMPERATURES IN YELLOWSTONE NATIONAL PARK AND THE HIGHER
MOUNTAINS OF THE NORTH.

MONDAY AND MONDAY NIGHT WILL SEE THE SOUTHERN STREAM OF SHORTWAVE
ENERGY WIN OUT WITH SCATTERED SHOWERS AND ISOLATED AFTERNOON AND
EVENING THUNDERSTORMS.  WITH WARM AIR ADVECTION COMING UP FROM THE
GREAT BASIN...SLIGHT WARMING IS EXPECTED.

TUESDAY AND TUESDAY NIGHT A PORTION OF THE LONG WAVE TROUGH WILL
DEEPEN OVER WESTERN IDAHO WITH INCREASING ENERGY AND MOISTURE IN THE
SOUTHERN STREAM ADVECTING NORTHWEST FROM THE GREAT BASIN OVER
SOUTHERN AND WESTERN WYOMING.  ANOTHER ROUND OF SCATTERED SHOWERS
AND ISOLATED AFTERNOON AND EVENING THUNDERSTORMS IS EXPECTED WITH
CONTINUED GRADUAL WARMING.  THE WESTERN IDAHO LOW WILL TRACK EAST
THROUGH CENTRAL WYOMING LATE TUESDAY NIGHT WITH DRYING LATE.

WEDNESDAY AND WEDNESDAY NIGHT A DRY HIGH PRESSURE RIDGE IS EXPECTED
TO BUILD OVER THE WESTERN U.S. WITH NORTHERLY FLOW ALOFT OVER
WESTERN AND CENTRAL WYOMING.  EXPECT CLEARING WITH WARMING
CONTINUING.

THURSDAY AND THURSDAY NIGHT  THE WESTERN U.S. RIDGE WILL SHIFT
SLOWLY EAST WITH CONTINUED DRY CONDITIONS WITH NORTHWEST FLOW
ALOFT.  WARMING IS EXPECTED TO CONTINUE.

FRIDAY AND FRIDAY NIGHT  THE HIGH PRESSURE RIDGE WILL BEGIN MOVING
EAST THROUGH THE AREA WITH SOUTHWEST FLOW ALOFT DEVELOPING FRIDAY
NIGHT AS THE RIDGE AXIS MOVES INTO THE NORTHERN AND CENTRAL HIGH
PLAINS. DRY CONDITIONS WITH CONTINUED WARMING IS EXPECTED AT LEAST
UNTIL LATE FRIDAY NIGHT WHEN CLOUDS AND ISOLATED SHOWERS WILL MOVE
INTO THE NORTHWEST.

SATURDAY AS A PACIFIC TROUGH MOVES INTO THE PACIFIC NORTHWEST... THE
SOUTHWEST FLOW ALOFT WILL INTENSIFY WITH INCREASING PACIFIC MOISTURE
IN THE FLOW.  SHOWERS WILL INCREASE ACROSS THE WESTERN MOUNTAINS WITH
GENERALLY ISOLATED THUNDERSTORMS EXPECTED BY AFTERNOON.  SATURDAY
SHOULD SEE THE WARMEST TEMPERATURES THROUGH THE MID AND EXTENDED
FORECAST PERIODS.  OVERALL MODELS ARE IN FAIR AGREEMENT THROUGH THE
PERIOD.


&&

.AVIATION.../06Z ISSUANCE/

AREAS OF RAIN AND HIGH MOUNTAIN SNOW ACROSS THE NORTH OVERNIGHT
THROUGH 15Z. AFTER 15Z SCATTERED RAIN AND HIGH MOUNTAIN SHOWERS WILL
CONTINUE THROUGH 21Z OVER FAR NORTHERN WY. EXPECT MVFR CONDITIONS IN
PLACES UP NORTH WITH MOUNTAINS OBSCURED. CONDITIONS WILL IMPROVE
OVER THE NORTH AFTER 00Z MONDAY WITH SHOWERS BECOMING ISOLATED AND
VFR CONDITIONS PREVAILING.

ELSEWHERE...VFR CONDITIONS OVERNIGHT WITH ISOLATED SHOWERS UNTIL 12Z
ACROSS CENTRAL WY. THE FAR SOUTH WILL BE DRY. AFTER 12Z...VFR
CONDITIONS WILL OCCUR THROUGH 06Z MONDAY. ISOLATED SHOWERS WILL
OCCUR OVER THE FAR SOUTH ALONG THE UTAH/COLORADO BORDER FROM 18Z
UNTIL 06Z MONDAY. A FEW SHOWERS FOR THE CENTRAL MOUNTAINS AS WELL
SUNDAY AFTERNOON INTO EARLY EVENING.

&&

.FIRE WEATHER...

FIRE WEATHER CONCERNS WILL CONTINUE LOW TODAY...REMAINING LOW ACROSS
MOST OF THE FORECAST AREA THROUGH SUNDAY...AS A VIGOROUS UPPER LEVEL
DISTURBANCE COMBINES WITH DEEP MOISTURE TO GOOD RAINFALL CHANCES
STATEWIDE THIS AFTERNOON THROUGH SUNDAY MORNING. WIND HOWEVER WILL
BE OF SOME CONCERN ACROSS THE SOUTHERN DISPATCH ZONES AS THE GUST
OUT OF THE WEST TO SOUTHWEST AT 25 TO 35 MPH AT TIMES TODAY...UP TO
25 MPH ON SUNDAY. ABOVE 9000 FEET...OVER THE NEXT FEW
DAYS/NIGHTS/...THIS YEAR`S FIRST SNOWFALL WILL ALSO CONTINUE FOR
ANOTHER NIGHT...WITH 1 TO 2 INCHES POSSIBLE...AND A FEW ISOLATED
AREAS INT HE BIG HORN MOUNTAINS RECEIVING BETWEEN 2 AND 4 INCHES.
ADDITIONALLY...A FEW STRONGER STORMS WILL HAVE HEAVY RAIN ALONG WITH
ISOLATED SMALL HAIL. SUNDAY WILL BE WELL BELOW AVERAGE FOR HIGH
TEMPERATURES WITH RH VALUES STILL REMAINING HIGH ALTHOUGH RAIN
CHANCES WILL DROP SIGNIFICANTLY FOR MOST LOCATIONS AS THE WEATHER
SYSTEM THAT HAS BEEN CAUSING SHOWERS AND THUNDER THE PAST FEW DAYS
FINALLY EXITS THE AREA. TWO EXCEPTIONS WILL BE ALONG THE FAR NORTHER
BORDER AREA WITH MONTANA STILL UNDER THE INFLUENCE OF THE EXITING
DISTURBANCE...AND THE OTHER SOUTH NEAR/ALONG THE SOUTHERN BORDER
AREA WITH COLORADO AND A WEAK DISTURBANCE FLIES THROUGH OVERHEAD OUT
OF THE GREAT BASIN.


&&

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

$$

SHORT TERM...BRAUN
LONG TERM...C.BAKER
AVIATION...AR
FIRE WEATHER...BRAUN








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