Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 240557
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1157 PM MDT SAT MAY 23 2015

.UPDATE...WESTERN BIGHORN RANGE AND WASHAKIE COUNTY ADDED TO FLASH
FLOOD WATCH THROUGH SUNDAY AFTERNOON.

&&

.AVIATION.../06Z ISSUANCE/

WIDESPREAD MVFR CONDITIONS AND MTN OBSCURATIONS...LCL IFR CONDITIONS
WITH NMRS -SHRA WILL CONTINUE ALONG AND EAST OF THE DIVIDE THROUGH
16Z SUNDAY.   THESE CONDITIONS WILL NOT BE AS WIDESPREAD WEST OF THE
DIVIDE WHICH MAY SEE MORE FOG DEVELOPMENT THROUGH THE MORNING
HOURS.

THE UPPER LOW OVER WESTERN COLORADO WILL SLOWLY LIFT NE INTO EASTERN
WYOMING ON SUNDAY...AND THERE WILL LIKELY BE SOME LIFTING OF CIGS
LATE SUNDAY MORNING INTO EARLY SUNDAY AFTERNOON FOLLOWED BY RAPID
DEVELOPMENT OF SHOWERS AND THUNDERSTORMS THROUGH THE AFTERNOON AND
EARLY EVENING.  WIDESPREAD MVFR -RA/AREAS OF IFR RA BR...MTN
OBSCURATIONS ON THE BACKSIDE OF THE UPPER LOW WILL FOLLOW AFTER 03Z
SUNDAY ACROSS MOST OF THE AREA.

&&

.PREV DISCUSSION... /ISSUED 305 PM MDT SAT MAY 23 2015/

SHORT TERM...TONIGHT THROUGH SUNDAY

..FLASH FLOOD WATCH IN EFFECT FROM 3 PM MDT THIS AFTERNOON THROUGH
6 PM MDT SUNDAY AFTERNOON...

SATURATED TO NEAR SATURATED SOILS FROM RECENT RAINFALL WILL
COMBINE WITH AREAS OF POTENTIAL HEAVY RAIN ACROSS JOHNSON...
NATRONA AND FREMONT COUNTIES THIS EVENING THROUGH 6 PM MDT ON
SUNDAY. THE THREAT OF FLASH FLOODING WILL BE ALONG SMALL STREAMS
AND IRRIGATION CANALS IN AND NEAR THE FOOTHILLS OF THE BIGHORN AND
WIND RIVER MOUNTAINS... AS WELL AS CASPER MOUNTAIN AND THE GREEN
AND RATTLESNAKE MOUNTAINS. A STRONG SPRING STORM WILL PRODUCE
CONDITIONS FAVORABLE FOR PROLONGED HEAVY RAIN WITH RAINFALL RATES
OF A HALF INCH TO AN INCH AN HOUR WITH TOTAL RAINFALL OF 2 TO 4
INCHES POSSIBLE.  SNOWFALL WILL BE LIMITED TO ELEVATIONS ABOVE
8500 FEET TONIGHT INCREASING TO 9000 FEET ON SUNDAY.  COOLER
TEMPERATURES WILL RESULT WITH WIDESPREAD CLOUD COVER AND EVAPORATIVE
COOLING FROM PRECIPITATION.

LONG TERM...SUNDAY NIGHT THROUGH SATURDAY

THE DEPARTING AREA OF LOW PRESSURE WILL CONTINUE TO LIFT ALONG THE
EASTERN BORDER OF THE FORECAST AREA...BRINGING PERSISTENT SHOWER
ACTIVITY ACROSS NATRONA AND JOHNSON COUNTIES. WHILE THE HEAVIEST
RAINS ARE ANTICIPATED TO FALL DURING THE AFTERNOON HOURS...SOME
SHOWERS WILL REMAIN OVER THE AREA THROUGH THE EVENING HOURS AS THE
SYSTEM BREAKS DOWN.

SHOWERS WILL WEAKEN THROUGH THE OVERNIGHT HOURS...BUT WILL RETURN ON
MONDAY FOLLOWING THE TYPICAL PATTERN OF AFTERNOON SHOWERS AND
THUNDERSTORMS. MODELS AGAIN ARE PEGGING NATRONA AND JOHNSON COUNTIES
WITH SHOWER ACTIVITY. SHOWER AND THUNDERSTORM ACTIVITY WILL WANE IN
THE AFTERNOON AS A VERY BRIEF TRANSITORY RIDGE WORKS ITS WAY THROUGH
WESTERN AND CENTRAL WYOMING.

A RETURN OF SOUTHWEST FLOW TUESDAY EVENING WILL ALLOW ADDITIONAL
SHOWER AND THUNDERSTORMS TO RETURN...THOUGH COVERAGE WILL REMAIN
LIMITED OVERNIGHT. A STRONGER SOUTHWEST FLOW WILL PERMIT
MORE WIDESPREAD SHOWER AND THUNDERSTORM ACTIVITY ACROSS THE STATE
FOR BOTH WEDNESDAY AND THURSDAY. MODELS DO VARY A BIT FRIDAY
AFTERNOON...THOUGH BOTH AGREE THAT ANOTHER ROUND OF SHOWER ACTIVITY
IS FAVORABLE. HOWEVER...THE LOCATION OF THE POTENTIALLY STRONGER
AREAS OF SHOWER ACTIVITY REMAINS IN QUESTION. OVERALL...TEMPERATURES
WILL WARM THROUGH THE EARLY PORTIONS OF THE FORECAST PERIOD...AND
THEN REMAIN SEASONABLE IN THE MID 60S THROUGH MUCH OF THE FORECAST
PERIOD.

AVIATION.../00Z ISSUANCE/

AREAS OF MVFR TO IFR CEILINGS AND VISIBILITY REDUCED IN RAIN AND
FOG WILL INCREASE ACROSS THE AREA THIS AFTERNOON AND EVENING WITH
MOUNTAIN OBSCURATIONS BECOMING MORE WIDESPREAD.  THE HEAVIEST
AND MOST WIDESPREAD SHOWERS...WITH ISOLATED EMBEDDED THUNDERSTORMS
WITH SMALL HAIL...WILL BE ALONG AND EAST OF THE CONTINENTAL DIVIDE.
ALL OF THE AIRPORTS WILL HAVE A THREAT OF MVFR TO IFR CONDITIONS...
ESPECIALLY FROM 06Z TO 15Z SUNDAY.

FIRE WEATHER...

..FLASH FLOOD WATCH IN EFFECT FROM 3 PM MDT THIS AFTERNOON THROUGH
6 PM MDT SUNDAY AFTERNOON...

SATURATED TO NEAR SATURATED SOILS FROM RECENT RAINFALL WILL
COMBINE WITH AREAS OF POTENTIAL HEAVY RAIN ACROSS JOHNSON...
NATRONA AND FREMONT COUNTIES THIS EVENING THROUGH 6 PM MDT ON
SUNDAY. THE THREAT OF FLASH FLOODING WILL BE ALONG SMALL STREAMS
AND IRRIGATION CANALS IN AND NEAR THE FOOTHILLS OF THE BIGHORN AND
WIND RIVER MOUNTAINS... AS WELL AS CASPER MOUNTAIN AND THE GREEN
AND RATTLESNAKE MOUNTAINS. A STRONG SPRING STORM WILL PRODUCE
CONDITIONS FAVORABLE FOR PROLONGED HEAVY RAIN WITH RAINFALL RATES
OF A HALF INCH TO AN INCH AN HOUR WITH TOTAL RAINFALL OF 2 TO 4
INCHES POSSIBLE.  SNOWFALL WILL BE LIMITED TO ELEVATIONS ABOVE
8500 FEET TONIGHT INCREASING TO 9000 FEET ON SUNDAY.  COOLER
TEMPERATURES WILL RESULT WITH WIDESPREAD CLOUD COVER AND EVAPORATIVE
COOLING FROM PRECIPITATION. RELATIVE HUMIDITY WILL BE HIGH WITH LOW
MIXING HEIGHTS AND GENERALLY POOR SMOKE DISPERSAL.  AREAS OF THE
WEST AND NORTHWEST HAVE THE BEST CHANCE FOR GOOD SMOKE DISPERSAL
SUNDAY AFTERNOON.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH THROUGH SUNDAY AFTERNOON
WYZ006-008>011-015-018>020-022.

&&

$$

SHORT TERM...C.BAKER
LONG TERM...BRANHAM
AVIATION...C.BAKER
FIRE WEATHER...C.BAKER




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