Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 240428
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1028 PM MDT MON MAR 23 2015

.SHORT TERM...TONIGHT THROUGH TUESDAY (ISSUED AT 218 PM MDT)

COMPLEX LITTLE WEATHER SYSTEMS TO DEAL WITH THROUGH TUESDAY
AFTERNOON. FIRST DISTURBANCE FORMED ON THE SRN STREAM AND IN THE
FAVORABLE LEFT EXIT REGION OF A JET STREAK PRODUCING A SWATCH OF
COLD RAIN AND SNOW SHOWERS FROM THE SWRN CORNER NEWD INTO NATRONA
COUNTY. ALTHOUGH...IT WAS RUNNING OUT OF MOISTURE AND FORCING THE
FURTHER EAST IT WENT. THE MAIN NEGATIVELY TILTED SHORTWAVE IS MOVING
INTO THE WEST ATTM WITH ENOUGH COLD AIR TO DROP THE SNOW LEVELS DOWN
TO THE VALLEY FLOOR WITH ACCUMULATION OCCURRING. BEEFED UP POPS AND
LOWERED HIGHS EARLIER TODAY TO ACCOUNT FOR THIS. JUST ENOUGH
INSTABILITY THAT THERE COULD BE A FEW THUNDERSTORMS RUMBLING THROUGH
DURING THE COURSE OF THE AFTERNOON. OVERALL THEN...A BREAK BEHIND
THIS SYSTEM BEFORE THE NEXT ONE ARRIVES BY LATE MORNING IN THE WEST.
THERE WILL CONTINUE TO BE SOME LIGHT SNOW SHOWER AT TIMES OVERNIGHT
BUT MAINLY IN THE MOUNTAINS OUT WEST. THIS NEXT SYSTEM IS OFF THE
OREGON COAST AND WILL SLIDE IN QUICKLY ON A JET STREAK SEEN JUST TO
ITS SOUTH AND SOUTHEAST. SNOW WILL RESUME ACROSS THE ENTIRE FAR WEST
BY OR EVEN BEFORE NOON AND CONTINUE THROUGH THE AFTERNOON QUICKLY
SPREADING IN THE REST OF THE WEST. POTENTIAL ADVISORY MAY VERY WELL
BE NEEDED FOR THIS SYSTEM THAT CARRIES OVER INTO TUESDAY EVENING...
ESPECIALLY WHEN COMBINED WITH STRONG WEST WIND. SPEAKING OF THE
WIND...THERE WILL BE QUITE A BIT BEHIND THIS SYSTEM TODAY BUT EVEN
MORE TOMORROW...ESPECIALLY IN THE MOUNTAINS...RKS TO NEAR CPR AND
COMING DOWN FROM DUBOIS INTO THE WIND RIVER BASIN WITH TIME. WILL
ISSUE A STRONGLY WORDED SPS FOR WINDS OF 50 MPH PLUS AND HAVE THE
NEXT SHIFT WATCH IT CLOSELY. WILL ALSO UPDATE OUR CURRENT SPS OUT
WEST TO INDICATE MORE SNOW WITH THIS NEXT SYSTEM.

.LONG TERM...TUESDAY NIGHT THROUGH MONDAY

ANOTHER SHORT WAVE DIGS ALONG OUR WESTERN BORDER TUESDAY
NIGHT...DRAWING DOWN A COLD FRONT AND SETTING UP A MID LEVEL
CONVERGENCE ZONE ACROSS CENTRAL WYOMING. ADDITIONALLY...THERE WILL
BE SOME INCREASING LAPSE RATES AS THE COLD POOL SETTLES IN
ALOFT...LEADING TO SOME SNOW BANDING ACTIVITY WELL INTO WEDNESDAY
MORNING. NORTHWEST FLOW SETS UP AGAIN AS THE TROUGH EXITS WEDNESDAY
AFTERNOON WITH SHOWERS ONGOING INTO THE EVENING. THERE WILL ALSO BE
THE NOSE OF THE JET MOVING INTO THE AREA ON WEDNESDAY...PROVIDING
ADDITIONAL SUPPORT WELL INTO THE EVENING. THIS WILL BE A COLDER
SYSTEM THAT THE CURRENT SYSTEM MOVING THROUGH...AND THERE WILL BE A
DECENT AMOUNT OF MOISTURE FOR THIS TIME OF YEAR...ABOVE THE 75TH
PERCENTILE. THERE COULD BE SOME DECENT SNOW BANDS AS A RESULT...WITH
SOME OF THE HEAVIER BANDS DROPPING AN INCH OF SNOW PER HOUR WHEREVER
THEY DECIDE TO FORM.

THERE WILL BE A BRIEF BREAK IN THE ACTION WEDNESDAY EVENING AHEAD
OF THE NEXT SHORT WAVE ZIPPING BY IN THE NORTHWEST FLOW. THIS NEXT
SYSTEM LOOKS LIKE IT WILL PRIMARILY AFFECT THE NORTHERN BIGHORN
BASIN AND BUFFALO AREA ON THURSDAY WITH STEADY SNOW AND VERY GUSTY
WINDS...IT DOES NOT LOOK LIKE MUCH ON THE MODELS BUT SIMILAR
SYSTEMS HAVE ENDED UP CLOSING INTERSTATE 90 FOR SEVERAL HOURS IN
THE PAST...ESPECIALLY IF ONE OF THE DIVERGENT REGIONS OF THE JET
MOVE OVERHEAD...IT WILL BE WATCHED CLOSELY.

TEMPERATURES FINALLY START TO REBOUND ON FRIDAY AS HEIGHTS GO BACK
ON THE RISE...WITH TEMPERATURES BACK INTO THE 60S WITH A FEW MORE
DEGREES ADDED ON FOR SATURDAY. ANOTHER POTENTIAL SYSTEM MOVES
THROUGH ON SATURDAY NIGHT AND SUNDAY. WITH ITS ARRIVAL INTO MILD
SURFACE TEMPERATURES AND COLD POOLING ALOFT...THERE COULD BE SOME
DECENT SHOWER ACTIVITY AS INSTABILITY GROWS ON SATURDAY AFTERNOON
AND THEN AGAIN ON SUNDAY AFTERNOON. ANOTHER WAVE IS POSSIBLE
SUNDAY NIGHT INTO MONDAY WITH MOSTLY RAIN SHOWERS EXPECTED ACROSS
THE HIGHER ELEVATIONS AND THE SOUTH.

&&

.AVIATION.../06Z ISSUANCE/

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

ISOLATED RAIN SHOWERS OVERNIGHT. SNOW SHOWERS IN THE BIGHORN
MOUNTAINS WILL END BY 12Z. A NEW STORM SYSTEM WILL BRING ANOTHER
ROUND OF RAIN SHOWERS TUESDAY AFTERNOON WITH LOWERING SNOW LEVELS
AND VERY STRONG WEST WIND. EXPECT MOUNTAINS TO BE FREQUENTLY
OBSCURED TUESDAY AFTERNOON AND EVENING WITH MVFR TO OCNL IFR
CONDITIONS. A COLD FRONT PUSHES INTO NORTHERN WY AROUND 00Z WED AND
CONDITIONS WILL LOWER TO MVFR BEHIND THE FRONT WITH AREAS OF LIGHT
SNOW DEVELOPING OVER THE NORTH. THIS WILL IMPACT AREAS FROM CODY TO
BUFFALO BETWEEN 01Z AND 06Z WED.

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

ISOLATED SNOW SHOWERS WILL OCCUR IN THE WESTERN MOUNTAINS OVERNIGHT
AND VCNTY OF KJAC AIRPORT. EXPECT SOME MVFR CONDITIONS AT TIMES IN
THE MOUNTAINS.

ANOTHER POTENT STORM SYSTEM WILL ARRIVE LATE TUESDAY MORNING AND
CONTINUE THROUGH THE DAY WITH MORE SNOW SHOWERS AND ISOLATED
THUNDERSTORMS. EXPECTING LOWERING CONDITIONS AT THE KJAC TERMINAL BY
16Z AND IFR CONDITIONS AND GUSTY WIND AFTER 18Z THROUGH 01Z WED.
STRONG WEST WIND FOR THE MOUNTAINS TUESDAY INTO TUE EVENING.
EXPECT MVFR TO IFR CONDITIONS DURING SNOW SHOWERS WITH FQT MTN
OBSCURATION. AT KRKS AIRPORT...VFR CONDITIONS WILL PREVAIL WITH
STRONG WIND AND GUSTS DURING THE DAY...WITH ONLY ISOLATED SHOWERS
LATE IN THE AFTERNOON INTO THE EARLY EVENING.

&&

.FIRE WEATHER...

ISOLATED THUNDERSTORMS ARE POSSIBLE THROUGH 01Z THIS EVENING...MAINLY
IN THE WEST AND SOUTH. STRONG AND GUSTY WEST WINDS WILL CONTINUE
AS OUR CURRENT WEATHER DISTURBANCE MOVES NORTHEAST ACROSS THE
AREA. A NEW WEATHER SYSTEM WILL MOVE QUICKLY INTO THE FAR WEST BY
LATE TUESDAY MORNING AND INTO AREAS EAST OF THE DIVIDE TUESDAY
AFTERNOON. NUMEROUS RAIN AND SNOW SHOWERS CAN BE EXPECTED...MOST
SNOW WEST OF THE DIVIDE AND IN THE SOUTH WITH EVEN STRONGER WEST
WINDS. THE EAST SLOPE OF THE MOUNTAINS...THE WIND CORRIDOR FROM NEAR
RKS TO CPR AND AROUND DUBOIS WILL SEE WEST WIND INCREASE TO 25 TO 35
MPH WITH GUSTS OF 45 TO 55 MPH. MIN RH`S WILL DROP BRIEFLY INTO 20S
EAST OF THE DIVIDE BEFORE THE COLD FRONT MOVES THROUGH LATER IN THE
AFTERNOON AND EVENING.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

SHORT TERM...PS
LONG TERM...ALLEN
AVIATION...PS/AR
FIRE WEATHER...PS





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