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000
FXUS65 KRIW 090645
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
222 PM MST SUN DEC 8 2013

.SHORT TERM...TONIGHT THROUGH MONDAY

WITH CYCLONIC NORTHWEST FLOW ALOFT OVER WESTERN AN CENTRAL WYOMING
A COUPLE OF SHORT WAVE TROUGHS WILL SWEEP ACROSS THE AREA TONIGHT
AND MONDAY. THIS WILL KEEP AREAS OF LIGHT SNOW IN THE NORTH AND
WEST MOUNTAINS. EAST AND SOUTH OF THE MOUNTAINS...VARIABLE CLOUD COVER
CAN BE EXPECTED WITH INCREASING WEST TO SOUTHWEST WINDS ALONG THE
EAST SLOPES OF THE MOUNTAINS AND ACROSS THE SOUTHWEST AND WIND CORRIDOR
FROM ROCK SPRINGS TO CASPER. THE INCREASED WINDS WILL CAUSE
WARMING AND COMPLICATE TEMPERATURE FORECASTS TONIGHT AND MONDAY.
VERY STRONG TEMPERATURE GRADIENTS ARE LIKELY BETWEEN THE WINDY
AREAS AND THE AREAS IN THE VALLEYS AND BASINS THAT DO NOT MIX OUT
WITH THE COLD AIR REMAINING TRAPPED. SNOWFALL AMOUNTS WILL BE VERY
LIGHT WITH VERY LOW DENSITY SNOW EXPECTED.

.LONG TERM...MONDAY NIGHT THROUGH SUNDAY

THE PARADE OF ALBERTA CLIPPERS WILL CONTINUE MONDAY NIGHT WITH THE
SECOND IN THE SERIES CONTINUING TO WORK ACROSS THE AREA. THIS
SYSTEM...LIKE THE PREVIOUS ONE...IS MOISTURE STARVED SO ONLY LIGHT
SNOW IS EXPECTED...MAINLY ACROSS THE MOUNTAINS. THE LAST IN THE
SERIES WILL MOVE INTO THE AREA ON TUESDAY AND TUESDAY EVENING. THIS
ONE HAS A BIT MORE MOISTURE TO WORK WITH...BUT EMPHASIS IS ON THE
WORD BIT. THERE COULD BE A UP TO A FEW INCHES ACROSS THE HIGHER
ELEVATIONS OF THE WESTERN MOUNTAINS WITH THE HIGH SNOW RATIO TO WITH
THE COLD AIR IN PLACE. WE CAN`T COMPLETELY RULE OUT ONE OF THE
HIGHEST PEAK GETTING 6 INCHES BUT SINCE IMPACTS WILL BE MINIMAL
HIGHLIGHTS ARE NOT ANTICIPATED AT THIS TIME. THERE COULD BE SOME
VERY LIGHT SNOW ACROSS THE LOWER ELEVATIONS EAST OF THE DIVIDE BUT
NOTHING SIGNIFICANT. THERE WILL ALSO BE SOME GUSTY WINDS WITH THE
TIGHTENING PRESSURE GRADIENT ACROSS THE USUAL AREAS LIKE NEAR CLARK
AND THE SOUTHWESTERN WIND CORRIDOR FROM ROCK SPRINGS TO CASPER. AT
THIS TIME...ONCE AGAIN...HIGHLIGHTS DO NOT LOOK NECESSARY. THERE
WILL BE SOME MODERATION IN TEMPERATURES FOR TUESDAY ACROSS AREAS
THAT MIX...BUT STILL BELOW NORMAL.

RIDGING AND SURFACE HIGH PRESSURE WILL THEN BUILD ACROSS THE AREA
FOR WEDNESDAY AND BRING MAINLY DRY CONDITIONS. THE QUESTION WILL BE
FOR HIGH TEMPERATURES.  WE DID RAISE HIGH TEMPERATURES A BIT ACROSS
AREAS WHERE WIND WILL MIX THINGS OUT A BIT LIKE CASPER AND ROCK
SPRINGS. IN THE BASINS...WE LEFT TEMPERATURES BELOW GUIDANCE
THINKING THE INVERSIONS WILL HOLD ON FOR ANOTHER DAY. THE CURRENT
THINKING IS THAT THE INVERSION SLOWLY WEAKENING AND WITH THE ARCTIC
AIR MODIFYING IN THE BASINS ON THURSDAY A SLOW WARM UP WILL
COMMENCE. HOWEVER...WITH THE LACK OF MIXING OR COLD ADVECTION TO
SCOUR OUT THE COLD AIR WE STILL LEFT TEMPERATURES BELOW GUIDANCE
HOWEVER AS IT IS CONVENTIONAL WISDOM THAT TEMPERATURES ALMOST ALWAYS
TAKE LONGER TO BREAK THAN THE MODELS INDICATE. A GUSTY BREEZE WILL
CONTINUE ACROSS THE WIND CORRIDOR AS WELL. AS FOR THE NEXT CHANCE OF
PRECIPITATION...NOW IT LOOKS TO BE FRIDAY AFTERNOON AT THE EARLIEST
AS THE NEXT SYSTEM APPROACHES FROM THE WEST. BOTH THE EUROPEAN AND
GFS MODELS SHOW THE SYSTEM SPLITTING AS IT APPROACHES SO WE KEPT
POPS AT CHANCE OR LESS.

&&

.AVIATION.../06Z ISSUANCE/

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

VFR AND VERY COLD CONDITIONS WILL PREVAIL OVERNIGHT WITH LOCAL IFR
FOG AND -SN PARTIALLY OBSCURING THE TERRAIN.  CIGS WILL GRADUALLY
LOWER FROM N-S DURING THE DAY MONDAY WITH AREAS OF MVFR/IFR WILL
SPREAD INTO THE NORTHWEST MTNS TO VCNTY KJAC THROUGH THE AFTERNOON.
IFR/MVFR -SN IS EXPECTED TO PREVAIL FROM YELLOWSTONE NATIONAL PARK
THROUGH VCNTY KJAC-KAFO BY MONDAY EVENING AND CONTINUE OVERNIGHT.
THESE CONDITIONS ARE EXPECTED TO BE MORE LOCALIZED FURTHER SOUTH
FROM VCNTY KBPI-KRKS.  WEST WIND WILL INCREASE ALONG THE INTERSTATE
80 CORRIDOR MONDAY MORNING WITH 20-30KT WINDS COMMON BY 18Z MONDAY
ALONG WITH AREAS OF MVFR BLSN.

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

AN UPPER LEVEL DISTURBANCE WILL PUSH OUT OF THE AREA LEAVING LOCAL
MVFR/IFR -SN AND FG IN ITS WAKE...PARTIALLY OBSCURING TERRAIN
OVERNIGHT.  WINDS WILL INCREASE ALONG THE EAST SLOPES OF THE DIVIDE
MONDAY MORNING WITH AREAS OF LLWS DEVELOPING VCNTY KLND-KCOD AND
CONTINUING THROUGH MONDAY NIGHT.  WINDS WILL MIX DOWN TO THE SURFACE
VCNTY KRKS-KCPR WITH 20-30KT WINDS COMMON IN THE AFTERNOON ALONG
WITH AREAS OF MVFR BLSN.  AN UPPER LEVEL DISTURBANCE WILL SPREAD
LOCAL AREAS OF MVFR/IFR -SN PRIMARILY VCNTY AND NORTH OF INTERSTATE
90 LATE MONDAY AFTERNOON AND MONDAY EVENING.


&&

.FIRE WEATHER...

COLD WINTER WEATHER WILL CONTINUE WITH AREAS OF INCREASED SURFACE WINDS
ALONG AND NEAR THE EAST SLOPES OF THE MOUNTAINS...ACROSS THE
SOUTHWEST AND WIND CORRIDOR FROM ROCK SPRINGS TO CASPER. THE WINDY
AREAS WILL SEE WARMING.  WITH LIMITED MOISTURE IN NORTHWEST FLOW
ALOFT...AREAS OF LIGHT SNOW WILL OCCUR IN THE NORTHERN AND WESTERN
MOUNTAINS WITH LIGHT SNOW ACCUMULATIONS OF LOW DENSITY SNOW.  MIXING
HEIGHTS WILL REMAIN LOW WITH GENERALLY POOR SMOKE DISPERSAL. SOME OF
THE WINDIER AREAS MAY SEE FAIR SMOKE DISPERSAL MONDAY AFTERNOON DESPITE
THE LOW MIXING HEIGHTS.

&&

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

$$

SHORT TERM...C.BAKER
LONG TERM...HATTINGS
AVIATION...AEM
FIRE WEATHER...C.BAKER