Expires:No;;289028
FXUS65 KRIW 270947
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
247 AM MST FRI NOV 27 2009
.SHORT TERM...TODAY THROUGH SUNDAY NIGHT
RIDGE AXIS PASSED THROUGH THIS PASSED EVENING AS A SPLITTING TROUGH 
MOVES ONSHORE OVER PAC NW EARLY THIS MORNING WITH HIGH LEE CLOUDS 
BLANKETING NORTH CENTRAL WYOMING.  SURFACE LEE TROUGH OVER CENTRAL 
MONTANA AND WYOMING PRODUCING A FAIRLY TIGHT GRADIENT.  KCPR HAS HAD 
PERIODS OF GUSTY WINDS FOLLOWED BY BREAKS.  ALSO HAVE A CANADIAN 
COLD FRONT MOVING SOUTH INTO NORTHERN MONTANA.  
LEE TROUGH GRADIENT TO STAY TIGHT OVER THE AREA TODAY SO EXPECT 
AREAS BETWEEN NORTHEAST SWEETWATER...SOUTH FREMONT AND NATRONA 
COUNTIES TO BE QUITE WINDY TODAY.  45 TO 50 KT AT H7 LEE OF THE 
GREEN AND FERRIS MOUNTAINS.  THE TELL TALE SIGNS OF EL NINO ARE 
EVIDENT AS YET ANOTHER SPLIT TROUGH TO ESSENTIALLY PASS BY WYOMING 
WITHOUT BRINGING MUCH PRECIPITATION TO THE STATE.  THE SOUTHERN HALF 
OF THE TROUGH TO DIG FAR SOUTH TO OVER THE MEXICAN BORDER BY 
TONIGHT.  THE NORTHERN PIECE IS A MINOR CIRCULATION OVER CENTRAL BC 
THIS MORNING.  THIS PIECE TO BE A CLIPPER SYSTEM AND DIG SOUTHEAST 
THROUGH NORTHEASTERN MONTANA THROUGH MID DAY TOMORROW MOVING INTO 
THE DAKOTAS INTO SATURDAY NIGHT.  A DEFORMATION AXIS BETWEEN THE 
NORTH AND SOUTH PORTIONS OF THE TROUGH WILL SAG SOUTH ACROSS THE 
STATE SATURDAY AND SATURDAY EVENING.  WEAK RRQ JET DYNAMICS DEVELOP 
OVER SOUTH CENTRAL MONTANA TONIGHT...SHIFTING EAST BY LATE 
SATURDAY.  THIS WILL BRING SOME LIGHT SNOW TO NORTHWEST WYOMING 
TONIGHT INTO SATURDAY.  YELLOWSTONE AND THE ABSAROKAS SHOULD SEE THE 
BEST CHANCE FOR SNOW...BUT STILL ONLY EXPECT 1-3 INCHES...WITH 
PERHAPS AN INCH OR SO IN THE TETONS.  COULD SEE SOME OF THE SNOW 
EAST OF THE DIVIDE SATURDAY AS THE COLD FRONT MOVES IN AFTER 
MIDNIGHT TONIGHT WITH AN UPSLOPE FLOW RESULTING AS THE FRONT BANKS 
UP AGAINST THE NORTH AND EAST FACING MOUNTAINS.  THEN THE 
DEFORMATION AXIS DROPS SOUTH ACROSS SATURDAY PROVIDING ADDITIONAL 
LIFT AND MOISTURE.  COULD EVEN HAVE SOME THE RRQ DYNAMICS AS WELL.  
THE NORTH AND EAST FACING SLOPES OF THE BIGHORNS...ABSAROKAS...WINDS 
AND CASPER MOUNTAIN COULD PICK AN INCH OR TWO...WITH LOWER 
ELEVATIONS SEEING A HALF INCH OR LESS.  RIDGE BUILDS IN SATURDAY 
NIGHT WITH A NORTHWEST TO NORTH FLOW OVERHEAD.  THIS COULD GET THE 
NORTHWEST FAVORED AREAS BLOWING.  DRY AIR MOVES FAIRLY SLOW SUNDAY.  
SOME ISENTROPIC LIFT RESULTS FROM THE NORTH FLOW AND WARM AIR 
ADVECTION.  SO COULD SEE SOME LIGHT SNOW OVER THE HIGHER PORTIONS OF 
THE NORTHERN MOUNTAINS.  TEMPERATURES WILL BE ABOVE NORMAL AGAIN 
TODAY MOST AREAS...THOUGH COLDER AIR WILL BE MOVING IN AHEAD OF THE 
TROUGH.  SATURDAY WILL BE COOL WITH TEMPS IN THE 30S TO LOWER 40S.  
.LONG TERM...MONDAY THROUGH FRIDAY
THE WARMEST DAY NEXT WEEK SHOULD BE MONDAY...AHEAD OF A TROUGH 
DIGGING SOUTHEAST OUT OF BRITISH COLUMBIA INTO THE NORTHERN ROCKIES 
MONDAY NIGHT/TUESDAY.  THIS TROUGH IS PROJECTED TO SEND A COLD FRONT 
THROUGH THE AREA TUESDAY/TUESDAY NIGHT.  HAVE GONE WITH A ECMWF/GEM 
BLEND FOR THE TRACK OF THIS TROUGH...DISCOUNTING THE GFS SOLUTION OF 
ONLY BRUSHING THE AREA WITH THIS TROUGH...WHICH IS THE CONSENSUS OF 
SURROUNDING OFFICES AND HPC.  THE ECMWF AND GEM MODELS DIG THE TROUGH 
THROUGH IDAHO/WESTERN WYOMING TUESDAY NIGHT...WITH DEEP NORTH TO
NORTHWEST FLOW OVER THE AREA. THE ECMWF CONTINUES TO ABOUT 10
DEGREES CELSIUS COLDER AT 700MB...THAN THE GFS FROM TUESDAY NIGHT
THROUGH FRIDAY. HAVE GONE ABOUT 5 TO 10 DEGREES COLDER THAN MEX
MOS...ESPECIALLY EAST OF THE DIVIDE WEDNESDAY THROUGH FRIDAY. BEST
PRECIPITATION CHANCES SHOULD OCCUR WITH INITIAL TROUGH
PASSAGE...AND THE UPSLOPE CONDITIONS THAT FOLLOW IT...IN THE
TUESDAY NIGHT/WEDNESDAY TIMEFRAME. PRECIPITATION CHANCES BEYOND
WEDNESDAY ARE HARD TO NAIL DOWN...BUT SHOULD BE MAINLY DRY IF THE
DRY NORTHERLY FLOW OF THE ECMWF PREVAILS.
&&
.AVIATION...
PATCHY FOG AND/OR LOW LIFR CLOUD DECKS ARE EXPECTED VCNTY KJAC 
THROUGH THE MORNING...THOUGH LESS EXTENSIVE THAN THE LAST COUPLE OF 
MORNINGS.  OTHERWISE VFR CONDITIONS WILL PREVAIL ACROSS THE REST OF 
THE REGION THROUGH THIS EVENING WITH SOUTHWEST WIND AT 20-30KTS 
CONTINUING BTWN KRKS-KCPR.  A COLD FRONT WILL PUSH SOUTH INTO 
NORTHERN WYOMING BTWN 03Z-06Z SATURDAY TO NEAR A KRIW-KCPR LINE BY 
12Z SAT.  SCT MVFR/IFR CONDITIONS...FQT MTN OBSCURATIONS ARE EXPECTED 
TO FOLLOW THE FRONT...VCNTY AND NORTH OF A KJAC-KGCC LINE BY 12Z 
SAT.  
&&
.FIRE WEATHER...
VERY WINDY CONDITIONS ARE EXPECTED OVER NORTHEAST SWEETWATER...SOUTH 
FREMONT AND NATRONA COUNTIES AS WELL AS THE EASTERN WINDS AND 
ABSAROKAS.  A COLD FRONT WILL MOVE THROUGH TONIGHT WITH THE WINDS 
BECOMING NORTH.  SOME LIGHT SNOW IS EXPECTED LATE TONIGHT INTO 
SATURDAY OVER THE NORTHWEST...POSSIBLY INTO AREAS EAST OF THE 
DIVIDE.  RIDGE BUILDS IN SUNDAY BRINGING A DRYING AND WARMING TREND.
&&
.RIW WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM...TWB
LONG TERM...WM
AVIATION...AEM
FIRE WEATHER...TWB