Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 300909
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
309 AM MDT SAT APR 30 2016

.SHORT TERM...SATURDAY THROUGH MONDAY NIGHT

FINALLY SOME HOPE FOR SOME DRIER AND MORE SPRINGLIKE WEATHER IS ON
THE WAY. HOWEVER...WE HAVE TO GET THROUGH ONE TO ONE AND A HALF MORE
DAYS OF SOUP BEFORE WE GET THERE.

AN UPPER LEVEL LOW NOW SPINNING OVER EASTERN COLORADO WILL CONTINUE
TO WRAP MOISTURE BACK INTO CENTRAL WYOMING. AS A RESULT...EXPECT
MORE OF THE SAME WITH PERIODS OF RAIN AND SNOW THROUGH MUCH OF THE
DAY. WITH THE SOUTHEAST FLOW...THE HEAVIEST PRECIPITATION WILL FALL
ALONG THE EAST TO NORTHEAST FACING SLOPES OF THE MOUNTAINS AND
PLACES LIKE THE UPPER WIND RIVER BASIN. AS FOR THE ADVISORIES...WE
WILL LEAVE THEM UP. ALTHOUGH AMOUNTS WOULD REACH ADVISORY
CRITERIA...IMPACTS MAY BE MINIMAL FOR THE FOLLOWING REASONS. THE AIR
WITH THIS SYSTEM IS NOT TERRIBLY COLD WITH MOST OF THE LOWER
ELEVATIONS EXPECTED TO REMAIN NEAR TO ABOVE FREEZING. THIS COMBINED
WITH THE STRONG LATE APRIL SUN WILL MAKE IT DIFFICULT FOR SNOW TO
ACCUMULATE AT TIMES UNLESS THE RATE IS HEAVY...ESPECIALLY ON ROADS
AND OTHER PAVED SURFACES. THIS COULD BE A SITUATION WHERE THERE
COULD BE 3 TO 5 INCHES ON THE GRASS AND CAR TOPS WHILE THE ROADS ARE
ONLY WET TO SLUSHY IN SPOTS. IN ADDITION...WITH TEMPERATURES ABOVE
FREEZING FOR MUCH OF THE TIME IN THE LOWER ELEVATIONS...THE SNOW
WILL LIKELY MIX WITH RAIN AND SNOW AT TIMES. THE BIGGEST TIMES OF
CONCERN WOULD BE UNTIL AROUND 9 AM THIS MORNING AND AFTER 8 PM
TONIGHT AFTER THE SUN GOES DOWN. THE MODELS HAVE COME IN BETTER
AGREEMENT IN ENDING THE STEADY PRECIPITATION BY LATER SATURDAY NIGHT.

SUNDAY AT THIS POINT LOOKS TO BE A MAINLY DRY DAY WITH ONLY A SMALL
CHANCE OF SOME LEFTOVER SHOWERS...MAINLY DURING THE MORNING HOURS IN
CENTRAL AND SOUTHERN AREAS. AS DRIER AIR MOVES IN FROM THE
NORTH...EXPECT THE CHANCE FOR A RETURN APPEARANCE OF THAT YELLOW ORB
IN THE SKY...WHAT IS THAT THING CALLED?  OH...THE SUN. MANY AREAS
HAVE NOT SEEN IT IN SO LONG I FORGOT WHAT IT WAS CALLED. SINCE IT
HAS TAKEN LONGER TO CLEAR THAT THE MODELS HAVE INDICATED...WE KEPT
THINGS CLOUDIER WITH THE REASONING THAT IF IT GETS SUNNIER AND
WARMER...MOST PEOPLE WILL BE HAPPY. TEMPERATURES WILL BE WARMER THAN
THE PREVIOUS FEW DAYS HOWEVER.

MONDAY AT THIS POINT LOOKS TO BE ONE OF THE NICER DAYS THAT WE HAVE
HAD IN A WHILE. AT THIS POINT...THE ONLY PLACE WITH THE CHANCE OF A
FEW SHOWERS OR THUNDERSTORMS WOULD BE OVER THE FAR SOUTH WITH SOME
MOISTURE GETTING THROWN NORTHWARD FROM AN UPPER LEVEL LOW OVER THE
FOUR CORNERS REGION. BUT EVEN HERE...THEY LOOK FEW AND FAR BETWEEN.
TEMPERATURES WILL CONTINUE TO MODERATE AS WELL WITH MORE SUNSHINE.

.LONG TERM...TUESDAY THROUGH SATURDAY

SYNOPSIS...AN UPPER RIDGE OF HIGH PRESSURE WILL BRING WARMER AND
MAINLY DRY CONDITIONS ACROSS THE AREA TUESDAY AND WEDNESDAY.  AN
UPPER LEVEL LOW PRESSURE SYSTEM WILL SLOWLY MOVE ACROSS THE
SOUTHWEST U.S. INTO THE FOUR CORNERS REGION FRIDAY AND SATURDAY.
SHOWERS AND THUNDERSTORMS ARE EXPECTED TO SPREAD INTO THE WEST
THURSDAY AND INTO CENTRAL WYOMING FRIDAY.  CLOUDY AND COOLER WEATHER
WITH CHANCES OF SHOWERS ARE EXPECTED ACROSS THE AREA ON SATURDAY.

DISCUSSION...BLOCKY PATTERN WITH HIGH AMPLITUDE RIDGE CENTERED OVER
THE ROCKIES...PACIFIC TROUGH ALONG THE WEST COAST BEGIN THIS PERIOD
ON TUESDAY AND WEDNESDAY.  SOME MOISTURE AND SLIGHT INSTABILITY OVER
THE WESTERN MOUNTAINS MAY RESULT IN ISOLATED SHOWERS...OTHERWISE
PLENTIFUL SUNSHINE WITH HIGH TEMPERATURES ACROSS THE VALLEYS AND
BASINS IN THE 60S AND 70S WILL BE THE RULE.

UPPER RIDGE WILL SHIFT EAST INTO THE PLAINS ON THURSDAY WITH
INCREASING SOUTHERLY FLOW ACROSS THE REGION.  WIDELY SCATTERED
SHOWERS AND THUNDERSTORMS ARE EXPECTED ALONG AND WEST OF A KEMMERER-
DUBOIS-POWELL LINE THURSDAY AFTERNOON/EVENING.  WARM SOUTH WIND WILL
BRING MUCH ABOVE NORMAL TEMPERATURES EAST OF THE DIVIDE WITH A FEW
NEAR 80F READINGS POSSIBLE ACROSS THE LOWER BASINS.

ECMWF IS INITIALLY SLOWER THAN GFS BRINGING SW LOW INTO THE FOUR
CORNERS REGION FRIDAY AND SATURDAY...BUT ECMWF THEN ACCELERATES
UPPER LOW INTO THE CENTRAL HIGH PLAINS BY 00Z SUNDAY WHILE GFS SHOWS
MORE OF A REX BLOCK SETTING UP OVER THE ROCKIES WITH UPPER LOW
REMAINING IN THE FOUR CORNERS AREA.  THE SLOWER SOLUTION...GFS IN
THIS CASE...USUALLY WINS OUT WITH A SW LOW AND STRONG DOWNSTREAM
RIDGING.


&&

.AVIATION.../12Z ISSUANCE/

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

ISOLATED RAIN OR SNOW SHOWERS OVER THE WEST UNTIL 15Z WITH SOME
MVFR CIGS. OTHERWISE VFR CONDITIONS OVER WESTERN WY THROUGH THE
MORNING. SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WILL DEVELOP
OVER THE WEST THIS AFTERNOON INTO THE EVENING. AREAS OF MVFR
CONDITIONS WILL OCCUR ALONG WITH PARTIAL MOUNTAIN OBSCURATION.
SHOWERS WILL DECREASE TO ISOLATED ACTIVITY BY 06Z SUNDAY. HOWEVER
AREAS OF MVFR CIGS WILL LINGER THROUGH 12Z SUNDAY.

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

PERIODS OF RAIN AND SNOW THROUGH EARLY THIS EVENING. FAR NORTHERN
WY WILL SEE LESS RAIN COVERAGE TODAY. EXPECT MVFR TO IFR CONDITIONS
OVER MOST OF THE REGION. MOUNTAINS WILL BE FREQUENTLY OBSCURED.
THE RAIN AND SNOW WILL DECREASE AFTER 00Z. AREAS OF MVFR/IFR CIGS
WILL REMAIN OVER MUCH OF THE REGION THROUGH 12Z SUNDAY.
&&

.FIRE WEATHER...

FIRE DANGER SHOULD REMAIN LOW INTO THE WEEKEND AS EASTERLY FLOW
KEEPS TEMPERATURES ON THE COOL SIDE AND RELATIVE HUMIDITY ON THE
HIGH SIDE. MANY AREAS ACROSS CENTRAL AND EASTERN WYOMING WILL HAVE A
GOOD CHANCE OF A WETTING RAIN TODAY WITH PERIODS OF MIXED RAIN AND
SNOW. HIGH PRESSURE BUILDING IN FROM THE NORTH WILL BEGIN A DRYING
TREND SUNDAY AND INTO THE FIRST PART OF NEXT WEEK.
&&

.RIW WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM 6 AM THIS MORNING TO MIDNIGHT MDT
TONIGHT FOR WYZ002-011-015>020-022.

&&

$$

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



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