Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 151759
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1159 AM MDT WED APR 15 2015

.SHORT TERM...WEDNESDAY THROUGH FRIDAY NIGHT

UPDATED SNOWFALL AMOUNTS THROUGH TONIGHT.  LOOKS GOOD FOR CONTINUED
DEVELOPMENT OF A MID LEVEL TROWAL TROUGH OF WARM AIR ALOFT
EXTENDING EAST WEST ACROSS NATRONA AND FREMONT COUNTIES. HEAVY SNOW
SHOULD INCREASE ACROSS THIS AREA WITH SOMEWHAT LIGHTER SNOWFALL
NORTH AND SOUTH OF THE TROWAL.  ISSUED WINTER STORM WARNING FOR NATRONA
AND FREMONT COUNTIES AS WELL AS HOT SPRINGS COUNTY.  ISSUED WINTER
WEATHER ADVISORY FOR SWEETWATER AND SUBLETTE COUNTIES.  WARNINGS
AND ADVISORIES IN EFFECT THROUGH 12Z THURSDAY MORNING.  OTHER
ADVISORIES CONTINUE TO LOOK VALID AND WILL CONTINUE THEM AT THIS TIME.
TEMPERATURES REMAIN ON THE BORDER ESPECIALLY IN THE NORTH IN THE LOWER
ELEVATIONS AND MAY GET RAIN SNOW MIX AT TIMES.  PLEASE REFER TO THE
WINTER STORM WARNINGS AND ADVISORIES FOR DETAILS IN YOUR AREA.

THE DIFFERENCES CONTINUE INTO THURSDAY AS WELL. THE NAM PUSHES A
RIDGE OF HIGH PRESSURE INTO THE COWBOY STATE WITH THE UPPER LEVEL
LOW DOWN OVER THE FOUR CORNERS REGION. THIS HAS BEEN FAIRLY
CONSISTENT THE PAST DAY OF SO. THE GFS MEANWHILE KEEPS
PRECIPITATION ACROSS MUCH OF THE AREA INTO THURSDAY MORNING AS
WELL. THE EUROPEAN IS IN THE MIDDLE WITH LIGHT
PRECIPITATION...SOME OF WHICH COULD BE RAIN INSTEAD OF SNOW. WE
DID BRING SOME SLIGHT POPS BACK FURTHER NORTH AND WEST BUT DECIDED
NOT TO GO FOR MAJOR CHANGES WITH THE MODELS DIFFERENCES.

THERE IS EVEN SOME UNCERTAINTY INTO FRIDAY. AGAIN...MUCH HAS TO DO
WITH WHAT HAPPENS WITH THAT CUT OFF UPPER LEVEL LOW...THE UPPER
LEVEL DEVIL THAT COULD REEK HAVOC INTO THE FORECAST. AGAIN...THE
MODELS ARE ALL OVER THE PLACE...WITH THE NAM THE DRIEST AND THE
OTHER MODELS A LITTLE WETTER. AGAIN...NOTICING A TREND HERE...WE
MADE FEW CHANGES TO CONTINUITY UNTIL...HOPEFULLY...THINGS COME
INTO SOMEWHAT BETTER AGREEMENT.

.LONG TERM...SATURDAY THROUGH WEDNESDAY NIGHT

THE CUT OFF LOW WILL KEEP SLIGHT CHANCES OF RAIN AND SNOW GOING OVER
SOUTHEAST PORTIONS OF THE FORECAST AREA SATURDAY...AS THIS FEATURE
SLOWLY MAKES ITS WAY INTO THE CENTRAL PLAINS. AS IT DOES SO...A NEW
CANADIAN COLD FRONT WILL QUICKLY MOVE INTO NORTHERN PORTIONS
SATURDAY NIGHT INTO SUNDAY MORNING. THIS WILL KEEP A SLIGHT CHANCE
TO CHANCE RAIN AND SNOW SHOWERS ACROSS MUCH OF THE FORECAST
AREA...MAINLY EAST OF THE DIVIDE.

THE REST OF THE FORECAST PERIOD WILL BE UNDER THE INFLUENCE OF A
NORTHWEST FLOW PATTERN...AS AN UPPER LEVEL LOW BEGINS TO STALL NORTH
OF THE GREAT LAKES OVER NORTHERN ONTARIO. THE GFS AND ECMWF DIFFER
ON ROTATING SHORTWAVES FROM THIS FEATURE IMPACTING THE COWBOY STATE
TUESDAY AND WEDNESDAY. KEPT A SLIGHT CHANCE FOR RAIN/SNOW SHOWERS AT
THIS TIME IN A FEW LOCATIONS...MAINLY ALONG SOUTHERN PORTIONS OF THE
CONTINENTAL DIVIDE. OVERALL...TEMPERATURES ARE EXPECTED TO BE NEAR
NORMAL...WITH NO PERIODS OF GUSTY WINDS.

.AVIATION.../18Z ISSUANCE/

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

SNOW...POSSIBLY MIXED WITH RAIN AT TIMES...WILL FILL IN ACROSS
TERMINAL SITES EAST OF THE DIVIDE THIS AFTERNOON. IFR CONDITIONS
WILL LIKELY PREVAIL ACROSS THE KLND SITE...WITH PERIODS OF SNOW
AND IFR CONDITIONS EXPECTED ACROSS THE REMAINDER OF THE SITES THIS
AFTERNOON. SNOW MAY DELAY ACROSS EASTERN PORTIONS...MAINLY AROUND
KCPR...UNTIL LATE THIS AFTERNOON OR EARLY THIS EVENING. WIDESPREAD
SNOW THEN CONTINUES THROUGH THE EVENING INTO THE EARLY OVERNIGHT
HOURS. CONDITIONS WILL IMPROVE FROM NORTH TO SOUTH THURSDAY
MORNING.

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

EXPECT SCATTERED AREAS OF SNOW TO OCCUR TODAY...DECREASING IN
COVERAGE AFTER 00Z. EXPECT AREAS OF MVFR/IFR CONDITIONS THROUGH THE
DAY INTO THE EVENING. MOUNTAINS WILL BE FREQUENTLY OBSCURED INTO
THIS EVENING. ISOLATED VFR CONDITIONS WILL BEGIN TO OCCUR AT SOME
OF THE TERMINAL SITES THIS AFTERNOON AND EVENING...WITH WIDESPREAD
VFR CONDITIONS RETURNING THURSDAY MORNING. PLEASE SEE INDIVIDUAL
TERMINAL SITES FOR MORE DETAILS.

.FIRE WEATHER...

SNOW WILL SPREAD FROM NORTHWEST ACROSS THE AREA TODAY. STRONG
NORTH WINDS WILL BE AROUND AS WELL. SOME LOWER ELEVATION
AREAS IN THE BIGHORN BASIN...JOHNSON COUNTY...NATRONA COUNTY AND
THE WIND RIVER BASIN MAY SEE SNOW CHANGE TO RAIN OR MIX WITH RAIN
DURING THE DAY TODAY. THE SNOW WILL START ENDING IN THE
NORTHWEST WEDNESDAY EVENING CONTINUING ON IN THE EAST UNTIL
THURSDAY. TEMPERATURES WILL BE MUCH COLDER WITH SIGNIFICANT
INCREASE IN RELATIVE HUMIDITY.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 6 AM MDT THURSDAY
WYZ008-009-016-028-030.

WINTER STORM WARNING UNTIL 6 AM MDT THURSDAY
WYZ005-007-014-015-017>020-022.

WINTER WEATHER ADVISORY UNTIL 6 PM MDT THIS EVENING WYZ012.

WINTER WEATHER ADVISORY UNTIL 6 AM MDT THURSDAY WYZ010-011.

WINTER WEATHER ADVISORY UNTIL MIDNIGHT MDT TONIGHT
WYZ002-003-006-025-026.

&&

$$

SHORT TERM...C.BAKER
LONG TERM...LAVOIE
AVIATION...ANGLIN
FIRE WEATHER...HATTINGS








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