Area Forecast Discussion
Issued by NWS Riverton, WY

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
325
FXUS65 KRIW 252148
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
348 PM MDT MON APR 25 2016

.SHORT TERM...TONIGHT THROUGH THURSDAY

ANOTHER COLD AND WET STORM SYSTEM IS TAKING AIM ON WYO COUNTRY THIS
AFTERNOON...ESPECIALLY FOR AREAS EAST OF THE DIVIDE TONIGHT THROUGH
AT LEAST TUESDAY. A LITTLE LONGER IN THE ERN ZONES. PCPN WILL BECOME
WIDESPREAD ACROSS MUCH OF CENTRAL WYOMING BY THE EVENING HOURS AND
ACROSS MOST OF THE WEST...ESPECIALLY IN AND NEAR THE MTNS. AS THE
LOW DRAWS CLOSER...CYCLONICALLY CURVED NOSE OF THE JET PROVIDES
STRONG FORCING BY THIS EVENING IN THE CENTRAL ZONES ALONG WITH
INCREASING QG FORCING AND UPGLIDE NORTH OF THE FRONT. PCPN COULD BE
QUITE HEAVY DURING THE EVENING HOURS WITH FALLING TEMPS. IT LOOKS
LIKE THE RAIN HAS A DECENT CHANCE TO TURN OVER IN LANDER FOOTHILLS
SHORTLY AFTER MIDNIGHT AS UPSLOPE DEEPENS...PCPN INCREASES AND COLD
AIR DAMMING SIGNATURE SHOWS UP. WINTER STORM WATCH FOR THERE WILL BE
UPGRADED WITH THE AFTN PACKAGE TO A WARNING STARTING AT MIDNIGHT.
THE WIND RIVER MTNS SHOULD SEE WIDESPREAD SNOW BY EARLY THIS EVENING
SO WILL UPGRADE THEM TO A WARNING STARTING AT 6 PM. IT LOOKS LIKE IT
WILL TAKE A WHILE LONGER FOR THE GREEN MTNS/RATTLESNAKE RANGE AND
CPR MTN TO CHANGE OVER SO DELAYING THE HIGHLIGHT UNTIL MIDNIGHT BUT
WILL STILL UPGRADE TO A WARNING...JUST 6 HOURS LATER. FOR THE
BIGHORNS...WE ARE THINKING A WINTER WEATHER ADVISORY WILL SUFFICE
WITH WIDESPREAD 6 TO 12 INCHES EAST OF THE DIVIDE AND LESS WEST.
COULD BE SOME LOCAL AREAS OVER A FOOT BUT WITH LOW FAR ENOUGH
SOUTH...THINKING IS MOST AREAS WILL NOT SEE OVER A FOOT. OTHER LOWER
ELEVATION ZONES MAY NEED ADVISORIES FOR TUESDAY LIKE THE WIND RIVER
BASIN AND OWL CREEKS AND FOR CASPER AND POSSIBLY JOHNSON COUNTY FROM
TUE/TUE MID-MORNING THROUGH TUE NGT (AND POSSIBLY LONGER). STILL A
CHANCE OF MORE SIGNIFICANT SNOW IN CPR BUT LEANING ADVISORY RIGHT
NOW WITH INITIAL ELY FLOW. STILL NEEDS TO BE WATCHED VERY CLOSELY.
NEXT SHIFT CAN LOOK AT THIS ONE MORE TIME AND DECIDE IF A SHORT
NOTICE WATCH SHOULD BE ISSUED THIS EVENING AND THEN UPGRADED BY
TUE MORNING OR IF AN ADVISORY WILL SUFFICE. TOUGH CALL. ALSO MAY
NEED ERN SWEETWATER COUNTY IN AN ADVISORY FOR TUE. COMBINATION OF
JET SUPPORT...QG FORCING...UPGLIDE TO START US OFF ALONG WITH A
GOOD UPSLOPE COMPONENT ARE LIKELY TO MAKE THIS YET ANOTHER
SIGNIFICANT STORM. STORM SLOWS DOWN OVER NEBRASKA ON WED AND THAT
WILL HAVE TO BE WATCHED ONCE THE PCPN/SNOW GETS GOING IN OUR ERN
ZONES. HOW LONG WILL IT CONTINUE AND AT WHAT INTENSITY. LONGER
DURATION ADVISORY FOR JOHNSON AND NATRONA OR ??. WE`LL BE WATCHING
IT CLOSELY. NOT MUCH BREAK IN BETWEEN THIS SYSTEM AND ANOTHER
CLOSED LOW OVER THE DESERT SW THURSDAY. A WESTWARD MOVING
SHORTWAVE WED NGT AND THU MAY SPREAD SOME LIGHT PCPN WESTWARD INTO
CENTRAL AND WRN WYOMING WED NGT AND THURSDAY MORNING BEFORE
AFTERNOON CONVECTION DEVELOPS WITH OUR COOL...UNSTABLE AIRMASS IN
THE WEST ESPECIALLY THURSDAY AFTN. QUITE THE BUSY AND CHALLENGING
FORECAST ONCE AGAIN!

.LONG TERM...THURSDAY NIGHT THROUGH MONDAY

NOT MUCH CHANGE FROM THE PREVIOUS LONG TERM FORECAST..SEE PREVIOUS
DISCUSSION BELOW. JUST MINOR UPDATES WITH CONSENSUS OF LATEST
GUIDANCE.

INCLEMENT WEATHER WITH BELOW AVERAGE TEMPERATURES CONTINUES THROUGH
THE EXTENDED...BUT NOT AS IMPACTFUL AS WHAT WILL OCCUR DURING THE
SHORT TERM. BY THURSDAY MORNING...GLOBAL MODELS SHOW YET ANOTHER
UPPER LEVEL LOW OVER THE SOUTHERN GREAT BASIN REGION. THIS FEATURE
IS EXPECTED TO PUSH INTO THE DESERT SOUTHWEST/ARIZONA ON THURSDAY.
AT THE SAME TIME...SOME SHEARED ENERGY FROM THE UPPER LOW THAT
IMPACTS THE AREA TUESDAY/EARLY WEDNESDAY...IS PROGGED TO RETROGRADE
WEST ACROSS MONTANA. FORCING LOOKS TO BE WEAK THURSDAY...BUT ENOUGH
MOISTURE AROUND FOR CONTINUATION OF SLIGHT VALLEY/CHANCE MTN POPS
FOR NOW. PRECIPITATION TYPE WILL BE MOUNTAIN SNOW AND MIX OF
RAIN/SNOW IN THE VALLEYS. ON FRIDAY...MODELS SHOW THE UPPER LOW
EJECTING NORTHEAST INTO EASTERN COLORADO...BUT THIS UPPER LOW IS
PROGGED TO BE WEAKER AND A BIT FARTHER SOUTH THAN THE UPPER LOWS
THAT IMPACTED THE AREA YESTERDAY...AND THE ONE ON TUESDAY.  THE BEST
SHOT AT PRECIPITATION WILL PROBABLY BE ACROSS THE FAR EAST/SOUTHEAST
WHERE THE INFLUENCE OF THE UPPER LOW WOULD BE THE GREATEST...AS WELL
AS A MOIST LOW LEVEL EASTERLY UPSLOPE FLOW. THE 00Z ECMWF KEEPS THE
UPPER LOW FARTHER SOUTH WITH A DRIER SOLUTION FRIDAY. MODELS THEN
SHOW ANOTHER UPPER LOW DIVING FROM THE PACIFIC NORTHWEST...SOUTHEAST
INTO NEVADA SATURDAY. AT THE SAME TIME...THE 00Z GFS TRIES TO
RETROGRADE SOME ENERGY FROM THE UPPER LOW ON FRIDAY BACK INTO THE
FORECAST AREA...WHILE THE ECMWF PUSHES ALL THE ENERGY ASSOCIATED
WITH THE UPPER LOW INTO THE MISSOURI VALLEY. THE AFOREMENTIONED
UPPER LOW IN NEVADA SATURDAY THEN PUSHES INTO ARIZONA SUNDAY AND
REMAINS ACROSS ARIZONA/FOUR CORNERS REGION THROUGH MONDAY. WILL KEEP
LOW END PRECIPITATION CHANCES SATURDAY THROUGH MONDAY WITH THIS
ACTIVE PATTERN.

&&

.AVIATION.../00Z ISSUANCE/

COMPLEX STORM SYSTEM CONTINUES THIS EVENING WITH THE UPPER LEVEL LOW
TO THE SOUTHWEST IN UTAH. WYOMING IS CURRENTLY SEEING SOUTHERLY MID
LEVEL FLOW OVERRIDING NORTHERLY SURFACE FLOW ACROSS NORTHERN AND
CENTRAL PARTS OF THE STATE.  INSTABILITY HAS BROUGHT WEAK
THUNDERSTORMS...WHICH HAVE PRODUCED BB TO PEA SIZE HAIL ALONG WITH
BRIEF HEAVY RAIN.  MVFR TO IFR CONDITIONS AROUND AND UNDER THESE
STORMS WILL CONTINUE INTO THE EVENING.  EXPECTING AREAS OF MODERATE
RAIN TO DEVELOP ACROSS CENTRAL WYOMING DURING THE EVENING AND
OVERNIGHT HOURS...WITH A FEW LOCATIONS TURNING OVER TO SNOW AFTER
MIDNIGHT...AND OTHERS TURNING TO SNOW AROUND 12Z. TUESDAY LOOKS TO
BE A LONG DURATION PRECIPITATION EVENT...WITH HEAVY WET SNOW ACROSS
CENTRAL WYOMING IN MOSTLY NORTHERLY SURFACE FLOW. HIGHER TERRAIN
WILL BE OBSCURED FOR THE NEXT 36 TO 48 HOURS...WITH THE SNOW LEVEL
OF 8-9K FT DROPPING TO 5-6K FT BY TUESDAY EVENING. LLWS A
POSSIBILITY ALSO ACROSS CENTRAL WYOMING.  CONDITIONS LOOK TO IMPROVE
TUESDAY AFTER 18Z AROUND KJAC...YET NOT SPREAD EASTWARD TO REST OF
TAF SITES UNTIL 12Z WED.

&&

.FIRE WEATHER...

ANOTHER WET AND COLD STORM SYSTEM WILL BRING SIGNIFICANT
PRECIPITATION...BOTH RAIN AND SNOW...TO THE AREA THROUGH TUESDAY AND
IN THE EASTERN SECTIONS THROUGH WEDNESDAY. A CHANCE OF SHOWERS AND A
FEW THUNDERSTORMS WILL ALSO BE AROUND ON THURSDAY. THE FAR NORTHWEST
CORNER WILL SEE THE LIGHTEST PRECIPITATION WHILE THE CENTRAL ZONES
SEE THE HEAVIEST ALONG WITH SIGNIFICANT SNOWFALL.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 6 AM MDT WEDNESDAY
FOR WYZ022.

WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO MIDNIGHT MDT
TUESDAY NIGHT FOR WYZ019.

WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 6 PM MDT TUESDAY
FOR WYZ018.

WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO MIDNIGHT MDT
TUESDAY NIGHT FOR WYZ008-009.

WINTER STORM WARNING FROM 6 PM THIS EVENING TO MIDNIGHT MDT
TUESDAY NIGHT FOR WYZ015.

&&

$$

SHORT TERM...SKRBAC
LONG TERM...MCDONALD/MURRELL
AVIATION...MCDONALD
FIRE WEATHER...SKRBAC



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.