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000
FXUS65 KRIW 031205
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
505 AM MST TUE DEC 3 2013

.UPDATE...

ALLOWED THE WINTER STORM WARNING OUT WEST TO EXPIRE AT 5 AM. NO OTHER
CHANGES.

&&

.PREV DISCUSSION... /ISSUED 239 AM MST TUE DEC 3 2013/

SHORT TERM...TODAY THROUGH THURSDAY NIGHT

SAT IMAGERY CURRENTLY SHOWING DEVELOPING LW TROF ACROSS ALL OF THE
CONUS...WITH AN EMBEDDED DEEP UPR LVL TROF DEVELOPING AND DIGGING OVR
THE NWRN CONUS...SLOWLY BEGINNING TO STRETCH EWD. BELOW THE CLOUDS
AT THE SFC...ASSOCIATED SFC LOW CONTINUES TO DEVELOP AND DRIFT
SWD...DRAGGING A FRONT ALONG WITH IT...OOZING INTO THE NRN HALF OF
THE CWA ATTM WITH A GOOD NRLY WIND SHIFT...BUT THE VERY COLD ARCTIC
AIR STILL HELD BACK TO THE NORTH INTO MT.

UPR JET SPEEDS NEAR H3 HAS TURNED THE CORNER UNDER THE TROF AND IS
RACING ALONG AT 110 TO 130 KTS TO OUR SOUTH/SOUTHWEST. THE RESULT
WILL BE OUR FIRST INTRUSION OF TRULY ARCTIC AIR FROM WESTERN CANADA
THAT WILL OVER RIDE OUR ENTIRE CWA. WIDESPREAD SNOWFALL IS EXPECTED
OVER THE FA WITH THE STRONG HEIGHT FALLS IN ADDITION TO SOME PAC
MOISTURE THIS MORNING ALONG THE FRONT AS IT SAGS SWD ACROSS THE
STATE...AND AGAIN POST-FRONTAL ACROSS MAINLY OUR S TO SERN ZONES AS
THE ROBUST UPPER TROUGH AMPLIFIES OVER OUR REGION UNDER DECENT UPR
JET DYNAMICS. ATTM HOWEVER...THE BEST OVERALL DYNAMICS AND MOISTURE
SEEM TO FAVOR OUR EXTREME SRN FA...MAINLY S OF THE I80 CORRIDOR.
WITH THIS COMPLICATED SYSTEM...AND WHILE SOME OF THE SNOW TOTALS
COULD BE A BIT HIGH...ESPECIALLY IN THE BASINS...THE COMBINATION OF
COLD...SNOW AND WIND WITH THE FRONTAL SYSTEM AND VERY COLD AND LIGHT
SNOW CHCS POST FRONTAL...GIVE CREDENCE TO CURRANT WX
ADVISORIES/WARNINGS...SO HAVE NOT CHANGED ANY OF THE CURRENT
POP/QPF/SNOW PARAMETERS THRU WED. BEYOND THAT...JUST SOME RELATIVELY
MINOR ADJUSTMENTS. THIS MORNING WILL CERTAINLY BE THE WARMEST POINT
OF THE ENTIRE SHORT TERM THRU THU NIGHT...WITH HIGH TEMPS IN THE
SINGLE DIGITS TO BE A FEW BELOW ZERO...AND NIGHTTIME TEMPS FALLING TO
10 TO 20+ BELOW ZERO BY THU MORNING. THERE COULD BE SOME
AREAS...ESPECIALLY ACROSS THE FAR S WHERE CLOUDS MAY HOLD LOW TEMPS
UP JUST A BIT...INTO THE SINGLE DIGITS BELOW ZERO. ALSO...SNOW FALL
OVR THE FA WILL ALSO HELP DICTATE THE EXTENT OF THE COLD TOO. WILL
ADJUST AS SNOW COVER BECOMES MORE APPARENT LATER
TODAY/TONIGHT.

LONG TERM...FRIDAY THROUGH TUESDAY

THE ARCTIC AIR MASS IN THE SHORT TERM WILL REMAIN ENTRENCHED ACROSS
THE REGION WITH MOST AREAS LIKELY REMAINING BELOW THE FREEZING MARK
THROUGHOUT THE EXTENDED. THERE WILL BE SOME MODERATION IN
TEMPS...BUT ANOTHER ARCTIC COLD FRONT AROUND SUNDAY COULD PUT US
BACK IN THE DEEP FREEZE. THE 00Z ECMWF IS MORE AMPLIFIED AND IS MUCH
COLDER BEHIND THIS COLD FRONT...THAN THE FLATTER GFS EARLY NEXT
WEEK.

A MOIST WESTERLY FLOW IS EXPECTED TO DEVELOP FRIDAY...AS A TROUGH
DIGS SOUTHWARD INTO PACIFIC NORTHWEST. THIS TROUGH IS THEN EXPECTED
TO PUSH INTO THE INTERMOUNTAIN WEST/GREAT BASIN AREA
SATURDAY...BEFORE THE TROUGH AXIS SHIFTS EAST INTO THE PLAINS IN THE
SUNDAY/SUNDAY NIGHT TIME FRAME. THE BULK OF THE ENERGY WITH THIS
SYSTEM IS EXPECTED TO BE SOUTH OF THE FORECAST AREA ACROSS THE
SOUTHERN ROCKIES. THIS SYSTEM SHOULD RESULT IN SOME LIGHT SNOW
MAINLY ACROSS THE WEST/SOUTHWEST FRIDAY AND SATURDAY...WITH SOME
LIGHT SNOW/FLURRIES SPILLING OVER THE DIVIDE SATURDAY/SATURDAY NIGHT.

ANOTHER SHORTWAVE TROUGH PUSHING OUT OF CANADA COULD IMPACT THE AREA
NEXT MONDAY AND TUESDAY BRINGING ANOTHER SHOT OF SNOWFALL...MAINLY
ACROSS THE WEST. THE 00Z GFS ACTUALLY SPLITS THIS TROUGH...WITH THE
MAIN ENERGY ENDING UP OFF THE PACIFIC NORTHWEST COAST MONDAY...WITH
A MOIST WESTERLY FLOW ACROSS THE REGION.

AVIATION.../12Z ISSUANCE/

EAST OF THE CONTINENTAL DIVIDE...

MVFR TO IFR CONDITIONS WILL OCCUR MOST OF THE DAY AND TONIGHT. AREAS
OF LIGHT SNOW WILL ALSO OCCUR THROUGH TONIGHT. A GUSTY NORTH WIND
WILL BE COMMON TODAY WITH WIND SPEEDS DECREASING AFTER 03Z THIS
EVENING.

WEST OF THE CONTINENTAL DIVIDE...

VFR CONDITIONS WILL OCCUR OVER MOST OF THE REGION TODAY AND TONIGHT.
SCATTERED AREAS OF LIGHT SNOW WILL OCCUR WITH A LITTLE MORE COVERAGE
IN THE MOUNTAINS. MVFR CONDITIONS WILL OCCUR AT TIMES THROUGH
TONIGHT. IN SOUTHWEST WY...CONDITIONS MAY DECREASE TO MVFR/IFR AS A
NEW BATCH OF SNOW DEVELOPS AROUND 00Z WED. THIS WOULD INCLUDE THE KRKS
AIRPORT.

FIRE WEATHER...

OVERALL...NORTH WINDS GUSTING 30 TO 40 MPH CAN BE EXPECTED AT TIMES
ACROSS AREAS MAINLY EAST OF THE DIVIDE TODAY AND TONIGHT.
HOWEVER...OVERALL FIRE WEATHER CONCERNS WILL REMAIN ON THE LOW SIDE
THROUGH THE REST OF THIS WORK WEEK AND WEEKEND AS BITTER COLD
TEMPERATURES AND WIDESPREAD LIGHT TO MODERATE SNOWFALL OCCURS ACROSS
ALL DISPATCH ZONES OVER THE NEXT SEVERAL DAYS.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING UNTIL 5 PM MST WEDNESDAY WYZ019-020-022-030.

WINTER WEATHER ADVISORY UNTIL 5 PM MST WEDNESDAY
WYZ008>011-015-017-018-027>029.

WINTER WEATHER ADVISORY UNTIL 5 PM MST THIS AFTERNOON WYZ003>007.

&&

$$

UPDATE...WM
SHORT TERM...BRAUN
LONG TERM...WM
AVIATION...AR
FIRE WEATHER...BRAUN