FXUS65 KBYZ 060351
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT 
851 PM MST SAT DEC 5 2009

.SHORT TERM...VALID FOR SUN AND MON...

LIGHT SNOW CONTINUES ACROSS MUCH OF WESTERN AND SOUTHERN PARTS OF
THE FORECAST AREA. AMOUNTS TO THIS POINT HAVE BEEN PRETTY MEAGER
FOR THE MOST PART. RED LODGE SPOTTER REPORTED 4 INCHES SO FAR AND
JUDITH GAP 3 INCHES...BUT OTHERWISE LOWER ELEVATIONS HAVE ONLY
RECEIVED AN INCH OR LESS. WATER VAPOR IMAGERY SHOWS A PUSH OF
DRIER AIR FROM THE NE...AND IN FACT THIS IS ALREADY HAPPENING AT
BAKER AND MILES CITY WHERE THE LIGHT SNOW HAS QUIT AS OF 03Z. A
SHALLOWING OUT OF MOISTURE ALONG WITH SHRINKING DENDRITIC LAYER AS
TEMPS CONTINUE TO COOL WILL RESULT IN AN EVEN LIGHTER SNOW ACROSS
OUR WEST AS THE NIGHT WEARS ON...THOUGH IT SHOULD CONTINUE IN
UPSLOPE AREAS. WITH THIS AND SNOW AMOUNTS IN MIND WILL CANCEL A
LARGE PORTION OF OUR HIGHLIGHTS. WILL KEEP JUDITH GAP WARNING AS
SPOTTER CALL INDICATED LOW VSBYS STILL EXIST...THOUGH NO DOUBT
THINGS ARE BEGINNING TO IMPROVE AS WINDS ARE NOW LESS THAN 20 MPH
WITH LIGHTER SNOW. WILL KEEP THE BEARTOOTH AND RED LODGE FOOTHILLS
ADVISORY GOING AS A VEERING OF THE FLOW TO NELY WILL INCREASE THE
UPSLOPE IN THIS AREA. WILL ALSO KEEP THE ADVISORY GOING AT
LIVINGSTON AS WINDS WILL SHIFT EAST SOON AND THIS SHOULD ENHANCE
THE LIGHT SNOW AS WELL AS POSSIBLY CAUSE SOME TRAVEL ISSUES THERE
AND OVER BOZEMAN PASS. HAVE CANCELLED ALL REMAINING AREAS...WITH
AN INCH OR LESS OF ADDITIONAL SNOW EXPECTED TONIGHT...PROBABLY
LESS...AND WITH MUCH LESS WIND TO CAUSE BLOWING/DRIFTING SNOW.

HAVE TWEAKED TEMPS/WINDS A BIT AS WELL. LOWS WILL FALL TOWARD ZERO
TONIGHT...A BIT BELOW ZERO IN OUR NE WHERE COLDER POOL OF AIR IS
BEING ADVECTED FROM THE NE AND THERE COULD BE SOME PARTIAL
CLEARING. BRRR.

UPDATE COMING SHORTLY.

JKL

.LONG TERM...VALID FOR TUE...WED...THU...FRI...SAT...

CHALLENGES REMAIN WITH THE EXTENT OF THE COLD AIR THROUGH THE END
OF THE WEEK INTO EARLY NEXT WEEKEND. NOT MANY CHANGES MADE TO
GOING FORECAST AS TRENDS REMAINED ON TRACK. MAIN ENERGY LIFTS OUT
OF BASE OF WESTERN TROUGH FROM THE 4-CORNERS AREA AND INTO THE
PLAINS LATE TUESDAY. ANY LINGERING LIGHT SNOW ACROSS THE REGION
SHOULD TAPER OFF BY THEN AS UPSLOPE PATTERN ENDS AND MOISTURE
RETREATS. HIGH PRESSURE AND CLEARING SKIES OVER TOP OF SNOW COVER
COULD RESULT THE COLDEST MORNING OF THIS COLD OUTBREAK FOR TUESDAY.
MAINTAINED TEMPERATURES WELL BELOW ZERO FOR THIS TIME FRAME.
NORTHWEST FLOW CONTINUES THROUGH AT LEAST FRIDAY AND SO RETREAT OF
COLD AIR WILL BE SLOW AS EXPECTED THROUGH THE REST OF THE WEEK.
TRANSITION TO MORE ZONAL FLOW AND A WARMER PACIFIC AIRMASS NOW IN
QUESTION FOR THE END OF THE WEEK INTO NEXT WEEKEND. MEDIUM RANGE
GUIDANCE DIVERGING AT THIS POINT. THE ECMWF STILL TRIES TO BRING
IN A MORE ZONAL PATTERN BY SATURDAY. THE GFS ON THE OTHER HAND HAS
BEEN TRENDED AWAY FROM THE ZONAL PATTERN AND ADVERTISING AN EVEN
STRONGER PUSH OF COLD AIR SOUTH INTO THE REGION INTO NEXT WEEKEND.
IF WE ARE ABLE TO ERODE SOME OF THIS COLD AIR LATE THIS
WEEK...MIGHT BE SHORT LIVED. FRIEDERS

&&

.AVIATION...

PERIODS OF LIGHT SNOW WILL CONTINUE THROUGH SUNDAY ACROSS MUCH OF
THE FORECAST AREA. EXPECT PERIODS OF MVFR CONDITIONS ACROSS THE
LOWER ELEVATIONS THROUGH SUNDAY. THE HEAVIEST SNOW WILL BE
CONFINED TO THE BEARTOOTH FOOTHILLS WEST INTO KLVM THIS EVENING
INTO THE EARLY MORNING HOURS. EXPECT PERIODS OF IFR CONDITIONS
WITH LOCALIZED LIFR CONDITIONS THROUGH EARLY SUNDAY MORNING.
SCHUKNECHT

&&

.PRELIMINARY POINT TEMP/POPS...

    SUN     MON     TUE     WED     THU     FRI     SAT     
-----------------------------------------------------------
BIL 004/006 910/901 912/000 908/012 005/022 015/027 020/029
    +6/S    43/S    34/S    11/B    11/B    11/B    11/B
LVM 001/004 917/901 918/002 909/017 007/026 016/030 021/032
    +6/S    44/S    23/S    22/S    12/S    22/S    22/S
HDN 003/008 910/005 905/007 908/017 003/023 009/029 013/031
    76/S    32/S    34/S    11/B    11/B    11/B    11/B
MLS 901/009 909/006 911/004 910/010 901/018 006/019 009/023
    23/S    22/S    24/S    11/B    11/B    11/B    11/B
4BQ 002/009 906/009 905/010 909/011 001/024 006/026 009/030
    64/S    22/S    34/S    11/B    11/B    11/B    11/B
BHK 903/007 908/007 906/005 910/012 000/019 005/019 010/024
    22/S    22/S    23/S    11/B    11/B    11/B    11/B
SHR 003/008 910/007 908/008 911/013 901/026 006/031 012/032
    56/S    34/S    34/S    12/S    12/S    22/S    22/S

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...WINTER WEATHER ADVISORY IN EFFECT UNTIL 5 AM MST SUNDAY FOR
      ZONES 56-65-66.
     WINTER STORM WARNING IN EFFECT UNTIL 5 AM MST SUNDAY FOR ZONE
      63.
WY...NONE.

&&

$$
WEATHER.GOV/BILLINGS