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000
FXUS65 KRIW 010502
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1002 PM MST SAT FEB 28 2015

.SHORT TERM...TONIGHT THROUGH SUNDAY (ISSUED AT 253 PM MST)

COLD NORTH NORTHEAST LOW LEVEL FLOW WITH WEAK WEST OVERRUNNING
FLOW...WITH LIMITED MOISTURE IN THE MID LEVELS...WILL CONTINUE TO
PRODUCE CONDITIONS FAVORABLE FOR WIDESPREAD STRATUS...FLURRIES TO
LIGHT SNOW AND LOCAL FOG.  PARTIAL CLEARING WILL OCCUR ACROSS THE
NORTH SUNDAY AFTERNOON.  TEMPERATURES WILL REMAIN ON THE COLD SIDE.
LOCAL SNOWFALL OF AN INCH WITH VERY LOW DENSITY SNOW CAN BE
EXPECTED.

.LONG TERM...SUNDAY NIGHT THROUGH SATURDAY

AN UPPER LOW RACING DOWN THE BACK SIDE OF A TROUGH DIGGING TO OUR
SOUTHWEST WILL FUJIWHARA THE CLOSED UPPER LOW OVER SOUTHERN
CALIFORNIA...WHIPPING IT UP INTO THE FOUR CORNERS AREA. IT WILL
KICK UP SOME MOISTURE ASSOCIATED WITH THAT LOW FURTHER NORTH AND
EAST AS WELL...THIS COULD REACH OUR FAR SOUTHERN BORDER AREA WITH
COLORADO WITH SOME MODELS EVEN SUGGESTING SOME PRECIPITATION AS FAR
NORTH AS THE WIND RIVER RANGE AND CASPER ON MONDAY. SPREAD THE POPS
THAT FAR NORTH AS A RESULT BUT THE HEAVIER PRECIPITATION IS EXPECTED
TO REMAIN SOUTH OF THE FORECAST AREA THROUGH MONDAY AFTERNOON.

THIS DIGGING TROUGH WILL ALSO BE ACCOMPANIED BY A CYCLONICALLY
CURVING JET THAT WILL SERVE TO ENHANCE A SHORT WAVE MOVING IN MONDAY
NIGHT. THIS WAVE IS ASSOCIATED WITH A VERY COLD ARCTIC LOW PRESSURE
SYSTEM MOVING ACROSS CENTRAL CANADA. THIS SOUTHERN PIECE OF THAT
SYSTEM WILL INTERACT WITH THE MOISTURE SUPPLIED BY THE SOUTHERN
STORM...PROVIDING SOME SIGNIFICANT MOISTURE TO WORK WITH FOR THIS
TIME OF YEAR. ADDITIONALLY...THE MODELS ARE SHOWING AN ORGANIZED
BAROCLINIC ZONE WITH THE FRONT AS IT DROPS SOUTH THROUGH THE STATE
MONDAY NIGHT INTO TUESDAY FOLLOWED BY A LONG PERIOD OF UPSLOPE FLOW
FOR AREAS EAST OF THE DIVIDE AS HIGH PRESSURE AT THE SURFACE FILTERS
IN BEHIND THE FRONT. SO THERE WILL BE SEVERAL FEATURES THAT WOULD
SUGGEST SOME AREAS OF SIGNIFICANT SNOW ACCUMULATION WITH THIS
SYSTEM. HOWEVER...IT IS A PRETTY COLD SYSTEM ALOFT SO ONCE THAT
FRONT PASSES BY THE MOISTURE AVAILABLE FOR HEAVY SNOW WILL BE
SQUEEZED OUT AND SHUNTED SOUTH AND EAST. ADDITIONALLY...THERE IS NOT
A LOT OF INSTABILITY ALONG AND BEHIND THE FRONT SO THAT WILL KEEP
MOST OF THE SNOW BANDING AND LOCAL ENHANCEMENTS SOUTH AND WEST OF
THE DIVIDE FOR MONDAY NIGHT INTO TUESDAY.

TUESDAY NIGHT COULD BE A COLD ONE AS WE CLEAR FROM NORTH TO SOUTH.
THERE WILL BE SOME MILDER AIR JUST TO THE EAST IN A HURRY TO MOVE IN
HOWEVER...THIS WILL LIKELY LEAD TO SOME SHARP INVERSIONS AND PATCHY
FOG TUESDAY NIGHT AND WEDNESDAY MORNING BUT GIVEN THE EVER
INCREASING SUN ANGLE AND DEVELOPING LEE SIDE TROUGH ON
WEDNESDAY...THE COLD AIR SHOULD NOT BE TOO STUBBORN WITH AT LEAST
SOME MIXING EXPECTED ON WEDNESDAY IF NOT FULL MIXING BY THURSDAY IN
SOME OF THE SHALLOWER BASINS. AS A RESULT...TEMPERATURES COULD GO
FROM 15 BELOW IN SOME BASINS ON WEDNESDAY MORNING TO HIGHS NEAR 40
ON THURSDAY. THE WARMING TREND CONTINUES INTO FRIDAY AND SATURDAY
WITH NO SIGNIFICANT PRECIPITATION EXPECTED ONCE WE CLEAR OUT ON
TUESDAY.

&&

.AVIATION.../06Z ISSUANCE/

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

COLD NORTH NORTHEAST LOW LEVEL FLOW WITH WEAK WEST OVERRUNNING
FLOW IN THE MID LEVELS WILL CONTINUE TO PRODUCE CONDITIONS
FAVORABLE FOR WIDESPREAD STRATUS...FLURRIES TO LIGHT SNOW AND LOCAL
FOG. MVFR CONDITIONS WILL BE RATHER WIDESPREAD THROUGH 18Z SUNDAY
WITH LOCAL VFR CONDITIONS AT TIMES. THIS WILL CAUSE WIDESPREAD
MOUNTAIN OBSCURATIONS THROUGH 18Z SUNDAY. SOME CLEARING WILL OCCUR
OVER THE REGION AFTER 18Z WITH VFR CONDITIONS PREVAILING BY 21Z.

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

WIDESPREAD STRATUS...FLURRIES TO LIGHT SNOW AND LOCAL FOG OVER THE
SOUTH THROUGH 12Z WITH IFR TO MVFR CONDITIONS. CONDITIONS WILL
IMPROVE AFTER 19Z WITH VFR CONDITIONS PREVAILING BY 22Z.

THE REST OF THE REGION WILL HAVE VFR CEILINGS OVERNIGHT INTO SUNDAY
MORNING. CLOUDS WILL DECREASE AROUND 18Z SUNDAY BUT THEN INCREASE
AGAIN SUNDAY NIGHT WITH VFR CEILINGS BY 03Z MONDAY.

KJAC AIRPORT WILL SEE VFR CONDITIONS PREVAIL THROUGH THE FORECAST
PERIOD.

&&

.FIRE WEATHER...

COLD NORTH NORTHEAST LOW LEVEL FLOW WITH WEAK WEST OVERRUNNING
FLOW...WITH LIMITED MOISTURE IN THE MID LEVELS...WILL CONTINUE TO
PRODUCE CONDITIONS FAVORABLE FOR WIDESPREAD STRATUS...FLURRIES TO
LIGHT SNOW AND LOCAL FOG. THIS WILL ALSO INCREASE STRONG
TEMPERATURE INVERSIONS PRODUCING STRONG THERMAL BELTS...LOW MIXING
HEIGHTS AND GENERALLY POOR SMOKE DISPERSAL.

&&

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

&&

$$

SHORT TERM...C.BAKER
LONG TERM...ALLEN
AVIATION...AR
FIRE WEATHER...C.BAKER