Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 250455
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
955 PM MST TUE FEB 24 2015

.UPDATE...

JUST ISSUED A WINTER WEATHER ADVISORY FOR THE BIGHORN MTS AND
NORTHERN JOHNSON COUNTY. THIS WILL BE FOR A COMBINATION OF SNOW
AND WIND...ESPECIALLY ACROSS NORTHERN JOHNSON COUNTY WHERE
NORTHWEST WINDS BETWEEN 20 AND 35 MPH...WITH GUSTS OF 45 MPH ARE
EXPECTED TO DEVELOP. THIS WIND WHEN COMBINED WITH EVEN A LITTLE
SNOW WILL CREATE SOME DIFFICULT TRAVEL AT TIMES ALONG INTERSTATE 25 AND
90. THE FAVORED UPSLOPE AREAS...SUCH AS CASPER AND LANDER STILL
HAVE A SHOT OF LOW END ADVISORY AMOUNTS...BUT WIND AND IMPACTS ARE
NOT EXPECTED TO BE AS MUCH AT THIS TIME. ANOTHER PROBLEM AREA
COULD BE EASTERN SWEETWATER COUNTY BETWEEN 21Z AND 07Z WEDNESDAY
NIGHT.


.PREV DISCUSSION... /ISSUED 234 PM MST TUE FEB 24 2015/

SHORT TERM...TONIGHT THROUGH WEDNESDAY

THINGS ARE SIGNIFICANTLY MORE ACTIVE IN THE SHORT TERM FORECAST
TODAY THAN YESTERDAY. THERE ARE NO ISSUES THIS AFTERNOON SO WE WILL
NOT TALK ABOUT IT. THE FUN STARTS TONIGHT.

A COLD FRONT WILL DROP SOUTHWARD ACROSS THE AREA TONIGHT. AT THIS
TIME WE EXPECT LITTLE BEFORE 06Z WITH ONLY LIGHT ACTIVITY ACROSS THE
BIG HORN BASIN. THINGS WILL BEGIN TO RAMP UP LATER TONIGHT AS THE
LEFT FRONT QUADRANT OF A JET STREAK MOVES ACROSS CENTRAL WYOMING.
THERE ARE SOME DIFFERENCES IN THE MODELS WITH THE DETAILS HOWEVER.
THE NAM IS SIGNIFICANTLY DRIER WITH THE GFS A LITTLE DRIER. THE
AREAS THAT CONCERN US THE MOST ARE NORTHERN JOHNSON COUNTY AS WELL
AS THE NORTHERN BIG HORN BASIN. WITH THE JET ENERGY MOVING ACROSS WE
HAVE BEEN BURNED ON THIS BEFORE. AT THIS TIME...AMOUNTS DO NOT LOOK
QUITE HIGH ENOUGH TO WARRANT ADVISORIES. HOWEVER...THIS HAS TO BE
WATCHED CLOSELY. WE DID INCREASE SNOWFALL AMOUNTS A BIT ACROSS THESE
AREAS TONIGHT. AS A RESULT...WE WILL ISSUE A SPECIAL WEATHER
STATEMENT FOR THE AREAS THAT WILL BE EFFECTED TONIGHT...MAINLY FROM
A CODY TO WORLAND TO CASPER AND NORTHWARD LINE.

BY TOMORROW THE FOCUS WILL SHIFT FURTHER SOUTH AND WEST AS COLD AIR
CONTINUES TO PRESS IN. JUST ABOUT EVERYONE WILL GET A CHANCE FOR
SNOW BY TOMORROW AFTERNOON. BOTH THE NAM AND GFS ARE CUEING IN ON A
COUPLE OF AREAS. LATE TOMORROW...WITH FLOW TURNING MORE NORTHERLY
AND ADDITIONAL JET DYNAMICS GETTING INVOLVED...THE AREA FROM THE
EAST SLOPES OF THE ABSAROKAS TO THE LANDER FOOTHILLS. THERE COULD A
PERIOD OF HEAVIER SNOW JUST IN TIME FOR THE EVENING RUSH HOUR.
ANOTHER CONCERN IS FOR EASTERN SWEETWATER COUNTY...INCLUDING
INTERSTATE 80 FOR ABOUT THE SAME TIME. STILL SOME TIME TO WATCH IT
SO WE WILL NOT ISSUE HIGHLIGHTS YET. ANOTHER CONCERN WILL BE WIND AS
THE MODELS SHOW 700 MILLIBAR WINDS INCREASING TO 30 TO 40 KNOTS
TOMORROW AFTERNOON. WITH THE BLOWING SNOW IT COULD GET FAIRLY NASTY
FOR SOME AREAS LATE TOMORROW.

LONG TERM...WEDNESDAY NIGHT THROUGH TUESDAY

THE MID WEEK STORM SYSTEM WILL CONTINUE TO SLIDE SOUTH WEDNESDAY
NIGHT...ESPECIALLY BRINGING THE SHARP FRONT THROUGH SWEETWATER
COUNTY INTO SOUTHWEST WYOMING.  BEHIND THE FRONT THE NORTH WIND WILL
BRING COLD UNSTABLE AIR TO PROVIDE FOR SCATTERED SNOW SHOWERS AND
POSSIBLE WEAK BANDING THROUGH THE NIGHT INTO THURSDAY MORNING.
AREAS EAST OF THE CONTINENTAL DIVIDE WILL CERTAINLY FEEL THE BRUNT
OF THE IMPACT WHILE FAR WESTERN WYOMING WILL ONLY SEE LIGHT SNOW
SHOWERS AND COLDER TEMPS.  MODELS ARE ALSO INDICATING A FAIR AMOUNT
OF SNOW FOR THE EASTERN FOOTHILLS OF THE ABSAROKAS AND WIND RIVERS
FROM WEDNESDAY AFTERNOON INTO THE EVENING HOURS.  TRAVEL CONDITIONS
LOOK TO BE HAZARDOUS WEDNESDAY AFTERNOON INTO THURSDAY MORNING.  A
WEAK SHORTWAVE WILL LIKELY PRODUCE SOME HEAVIER SNOW SHOWERS OVER
THE WESTERN MOUNTAINS THOUGH THURSDAY AFTERNOON AND EVENING IN THE
MID LEVEL NORTHWEST FLOW.

WITH CLEARING SKIES EAST OF THE DIVIDE FRIDAY MORNING...LOW
TEMPERATURES ARE LIKELY TO BE NEAR OR BELOW ZERO.  BY FRIDAY
AFTERNOON...A SHORTWAVE TROUGH IN THE PACIFIC NORTHWEST WILL BEGIN
TO BRING MOISTURE INTO WESTERN WYOMING.  MUCH OF THE ENERGY WITH
THIS WAVE WILL MOVE SOUTHWEST OF WYOMING...WHILE A WEAK NORTHERN
PORTION WILL KEEP SOME SNOW IN WESTERN AND NORTHWEST WYOMING THROUGH
SATURDAY EVENING.  WITH THE LOW SETTING UP OVER NEVADA..SOUTHERN
WYOMING WILL SEE EASTERLY FLOW THROUGH THE WEEKEND WITH SOME SNOW
SHOWERS POSSIBLE.

SUNDAY AND MONDAY APPEAR TO BE FAIRLY CLEAR AT THIS TIME WITH
SEASONABLE TEMPERATURES.  BOTH THE GFS AND ECMWF ARE INDICATING A
STRONG TROUGH DROPPING OUT OF ALBERTA INTO THE WESTERN US MONDAY
NIGHT INTO TUESDAY...BRINGING ANOTHER GOOD CHANCE OF SNOW AND COLD
AIR TO ALL OF WYOMING.  OVERALL...THE LONG TERM WILL BE MOSTLY
UNSETTLED WITH COOLER THAN NORMAL TEMPERATURES.

AVIATION.../00Z ISSUANCE/

MAINLY VFR CONDITIONS WILL CONTINUE THROUGH 06Z TONIGHT. AFTER
06Z...CEILINGS AND VISIBILITIES WILL LOWER AS A COLD FRONT DROPS IN
FROM THE NORTH AND BRINGS A CHANCE OF SNOW. THE BEST CHANCE OF MVFR
CONDITIONS BY 12Z WEDNESDAY WILL BE APPROXIMATELY A LINE NORTH OF A
KCOD-KWRL-KCPR. SNOW AND LOWER CEILINGS WILL THEN SPREAD
SOUTHWESTWARD DURING THE DAY ON WEDNESDAY ACROSS OTHER TAF
SITES...ESPECIALLY EFFECTING KRIW...KLND AND EVEN KRKS BY 00Z
THURSDAY.

FIRE WEATHER...

A COLD FRONT AND A COUPLE OF ASSOCIATED UPPER LEVEL DISTURBANCES
WILL CROSS THE AREA TONIGHT AND TOMORROW AND BRING INCREASED CLOUD
COVER ALONG WITH A GOOD CHANCE OF SNOW LATER TONIGHT AND INTO
WEDNESDAY...ESPECIALLY EAST OF THE DIVIDE. GUSTY NORTH WINDS WILL
ACCOMPANY THE SNOW...ESPECIALLY ON WEDNESDAY AFTERNOON. BELOW NORMAL
TEMPERATURES WILL CONTINUE INTO THE END OF THE WEEK ALONG WITH POOR
SMOKE DISPERSAL AND LOW MIXING HEIGHTS.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM 2 AM WEDNESDAY TO MIDNIGHT MST
WEDNESDAY NIGHT WYZ008>010.

&&

$$

UPDATE...WM
SHORT TERM...HATTINGS
LONG TERM...MCDONALD
AVIATION...HATTINGS
FIRE WEATHER...HATTINGS




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