Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 250529
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1128 PM MDT WED JUN 24 2015

.SHORT TERM...TONIGHT THROUGH THURSDAY

WV IMAGERY SHOWS FLAT RIDGING RUNNING OVR LARGE UPR HIGH IN PLACE
ACROSS THE SRN CONUS ACROSS THE WEST. TAIL END OF ONE EMBEDDED SW
NOW TRYING TO EXIT NERN WY...WITH A COUPLE OF ATTENDANT STRONG
STORMS. FURTHER UPSTREAM...ANOTHER EMBEDDED WAVE IS JUST NOW
ENTERING WRN MT WHICH WILL AFFECT THE FA LATER TODAY...WHILE A
SOMEWHAT STRONGER WAVE STILL OFFSHORE WASHINGTON...THAT WILL
INFLUENCE THE CWA ON THURSDAY. SFC HAS WEAKLY DEVELOPING LOW P OVR
SCNTRL WY...THE INVERTED EXTENSION OF LOW P OVR ERN CO....WITH AN
ASSOCIATED STATIONARY FRONT DRAPED ACROSS THE THE SRN FA FROM W TO
E.

TODAY/TONIGHT...SIMILAR SET-UP TO THAT OF TUESDAY LATER THIS
AFTERNOON/EVENING WITH A LITTLE BETTER SFC TO MID LVL FORCING OF THE
FRONT OVR THE ERN ZONES...AND ALONG ANY LEFT OVR BOUNDARY FROM LAST
NIGHT`S/THIS MORNING`S STORM COMPLEX. ASIDE FROM A FEW POSSIBLE NRN
BORDER CRAWLERS...AND SRN CWA HIGH BASED STORMS ALONG/NEAR THE
STATIONARY FRONT...IT SHOULD BE A LITTLE EASIER FOR CI TO COMMENCE AS
THE WEAKER CAP IS WORN DOWN BY EMBEDDED SW CURRENTLY OVR WRN MT...
MENTIONED ABOVE...AND ISOLATED TO WIDELY SCATTERED STRONG/SEVERE
STORMS FORM ACROSS PORTIONS OF JOHNSON AND NRN NATRONA COUNTIES.
ATTM...THE OUTFLOW BOUNDARY LEFT FROM THE EARLIER MORNING`S STORMS
HAS KEPT THE NERN HALF OF JOHNSON COUNTY UNDER STABLE CLOUD COVER
WITH THE CURRENT BOUNDARY POSITIONED FROM JUST SOUTH OF KAYCEE...EWD
TO THE FA BORDER. THIS BOUNDARY IS ACTING LIKE A SLOW RETREATING
WARM FRONT. THIS WILL BE ONE AREA TO MONITOR LATER THIS AFTERNOON
AND EVENING. WHILE SMALL HAIL STRONG GUSTY WINDS MAY BE FOUND WITH
THE ISOLATED SRN CWA STORMS...AND SMALL HAIL AND GENERAL GUSTY WINDS
WITH ANY STORM THAT FORMS ON THE REST OF THE PERIMETER...THE ERN CWA
IS MORE LIKELY TO SEE ISOLATED STRONG/SEVERE STORMS. THE ERN CWA
WILL HAVE ML CAPE OF 1500 TO 2500 J/KG...MU CAPE PERHAPS BETWEEN
3000 AND 3500 J/KG...AND EFFECTIVE SHEAR FROM 40 TO 55 KTS. STORMS
IN THIS REGION WILL ALL ROTATE/ORGANIZE/MAINTAIN. PRIMARY THREAT
WILL BE ISOLATED HEAVY RAIN...LARGE HAIL TO 2 INCHES...STRONG/SEVERE
WIND BURSTS...AND A SMALL TORNADO THREAT ESPECIALLY WITH A STORM ON
OR NORTH OF THE BOUNDARY...PROBABLY OVR NRN/ERN JOHNSON COUNTY THEN
EWD INTO UNR/CYS TERRITORY. ANOTHER MCS MAY EVOLVE FROM THIS
ACTIVITY AND MOVE INTO THE NE AREA AGAIN...BUT MUCH BETTER CHANCES
FOR A LARGER MCS WILL COME LATER THURSDAY MORNING.

THURSDAY...THE STRONGER SW TROF...CURRENTLY OVR THE PAC NW...ALONG
WITH AN ASSOCIATED FRONT...WILL BE AN AREA OF FOCUS THRU THE REST OF
THE FORECAST PERIOD. FRONTOGENESIS AND A BROAD AREA OF SHOWERS AND
EMBEDDED THUNDER WILL BEGIN TO FORM ACROSS NERN WY BEFORE SUNRISE.
SEASONALLY HIGH PWS WILL BRING A HEAVY RAIN THREAT WITH THIS
ACTIVITY WITH THE HEAVIER CORES MOVING SERLY AT 25 TO 30 MPH. SMALL
HAIL AND GUSTY OUT FLOW WILL ALSO ACCOMPANY THIS AREA OF STORMS
THROUGH MOST OF THE MORNING BEFORE MOVING OFF INTO THE CNTRL PLAINS
BY MID-DAY. NEAR SEVERE STORMS MAY BE MOST LIKELY OVR THE SRN
PORTION OF THIS ACTIVITY...ESPECIALLY ACROSS ERN NATRONA COUNTY
LATER IN AFTERNOON AS NEW DESTABILIZATION OCCURS. OTHERWISE...A FEW
ISOLATED STORMS WILL BE POSSIBLE OVR THE CNTRL AND NRN MOUNTAINS.

.LONG TERM...THURSDAY NIGHT THROUGH WEDNESDAY

NORTH NORTHWEST FLOW ALOFT WILL REMAIN OVER WESTERN AND CENTRAL
WYOMING THROUGH THE PERIOD AS A LARGE SCALE HIGH PRESSURE RIDGE
ALOFT BUILDS OVER THE GREAT BASIN.  MOST OF THE AREA...WEST OF THE
BIGHORN MOUNTAINS...WILL BE HOT...MID TO UPPER 90S IN THE BIGHORN
BASIN LOWER TO MID 90S IN THE WIND RIVER AND GREEN RIVER BASINS.
SUBTROPICAL AND PACIFIC MOISTURE GETS ENTRAINED IN THE ANTICYCLONIC
FLOW AROUND THE HIGH WHICH WILL INTERACT WITH COLDER CANADIAN AIR
ASSOCIATED WITH COLD FRONTS FROM ALBERTA AND SASKATCHEWAN EXTENDING
SOUTH ALONG THE BIGHORN MOUNTAINS IN JOHNSON COUNTY EXTENDING SOUTH
ACROSS EASTERN NATRONA COUNTY.  WITH DAYTIME HEATING AND OROGRAPHIC
LIFT AND AND FRONTAL BOUNDARY AS LIFTING MECHANISMS...EXPECTED
DAILY SHOWERS WITH ISOLATED THUNDERSTORMS OVER AND NEAR THE WESTERN
AND NORTHERN MOUNTAINS.  CONVECTION SHOULD BE MOST WIDESPREAD IN
THE AFTERNOONS AND EVENINGS WITH THE MAIN ACTIVITY OVER THE ABSAROKA
AND BIGHORN MOUNTAINS AND THE A LESSER DEGREE OVER THE WIND RIVER
MOUNTAINS WITH THE LEAST ACTIVITY OVER THE TETON...GROS VENTRE...
WYOMING AND SLAT RIVER MOUNTAINS OF THE WEST AND SOUTHWEST.  SOME
CONVECTION WILL OCCUR OVER THE BIGHORN AND WIND RIVER BASINS AND
THE EASTERN PLAINS OF JOHNSON AND NATRONA COUNTIES.


&&

.AVIATION.../06Z ISSUANCE/

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

MVFR CEILINGS ARE EXPECTED TO IMPACT PORTIONS OF JOHNSON AND NATRONA
COUNTIES THROUGH ABOUT 16-18Z THURSDAY. OTHERWISE...VFR CONDITIONS
ARE EXPECTED AT AREA TERMINALS...EXCEPT FOR BRIEF MVFR/IFR
CONDITIONS IN CONVECTION.

A DISTINCT SHORTWAVE IN THE WESTERLY FLOW MOVING INTO SOUTHERN
MONTANA/NORTHERN WYOMING EARLY THURSDAY MORNING IS EXPECTED TO PUSH
INTO THE NORTHERN PLAINS BY EARLY THURSDAY AFTERNOON. THIS
DISTURBANCE SHOULD RESULT IN ISOLATED TO LOCALIZED SCATTERED SHOWERS
WITH A FEW THUNDERSTORMS THURSDAY MORNING. THE BEST CHANCE OF
CONVECTION WILL BE OVER JOHNSON AND NATRONA COUNTIES. THE MAIN
ACTIVITY IS EXPECTED TO PUSH EAST OF THE FORECAST AREA BETWEEN 18Z
AND 21Z...BUT THERE WILL BE ENOUGH MOISTURE AND INSTABILITY FOR
ISOLATED CONVECTION THROUGH ABOUT 02Z...ESPECIALLY OVER THE FAR EAST
INCLUDING JOHNSON AND NATRONA COUNTIES.

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

A MAINLY DRY IS EXPECTED WITH A BREEZY WEST TO NORTHWEST WINDS IN
THE AFTERNOON AND EVENING. WINDS MORE SOUTH TO SOUTHWEST IN JACKSON
HOLE. THERE WILL BE AN OUTSIDE CHANCE FOR AN ISOLATED SHRA/TSRA
ALONG THE HIGHER TERRAIN ALONG THE DIVIDE...AND NEAR THE WYOMING AND
UTAH/COLORADO BORDERS FOR ACTIVITY COMING OFF THE UINTA MTS. ANY
ROUTES GOING INTO EASTERN WYOMING WILL HAVE A SHOT OF SOME
CONVECTION THROUGH EARLY THURSDAY EVENING.

&&

.FIRE WEATHER...

FIRE DANGER WILL REMAIN BELOW CRITICAL FOR ANOTHER DAY OR SO AS THE
AREA REMAINS IN GREEN-UP. HOWEVER...FIRE DANGER WILL BE ENHANCED
BOTH TODAY AND TOMORROW ACROSS THE SOUTHERN HALF OF THE FORECAST
AREA AS HOT DAY TIME TEMPERATURES CONTINUE WITH MINIMUM RH VALUES IN
THE LOWER TO MID TEENS...COMBINING WITH WINDS OCCASIONALLY GUSTING
TO AROUND 25 MPH THROUGH EARLY EVENING. NO PRECIPITATION EXPECTED
ACROSS MOST OF THE FORECAST AREA EXCEPT FOR SMALL CHANCES OVR THE
FAR NORTHERN...NORTHEASTERN...AND EASTERN ZONES WHERE ISOLATED TO
WIDELY SCATTERED STORMS WILL BE POSSIBLE THIS AFTERNOON AND EVENING.
MUCH BETTER CHANCES FOR A WETTING RAIN WILL OCCUR THURSDAY
MORNING ACROSS JOHNSON AND NATRONA COUNTIES.

&&

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

&&

$$

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



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