High Wind in Montana, December 17, 2001

SOUTH CENTRAL AND SOUTHEAST MONTANA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
206 AM MST MON DEC 17 2001

.SHORT TERM...VALID FOR TDY...TUE...WED...
HIGH WINDS CONTINUING IN UPPER YELLOWSTONE VALLEY. MODELS IN GOOD
AGREEMENT ABOUT SLACKENING SFC PRESSURE GRADIENT TODAY...ALLOWING WINDS
TO DECREASE. SYNOPTIC SCALE COLD AIR ADVECTION ALSO DEVELOPS WHICH WILL
SHUT OFF STRONG SOUTHWEST H7 WINDS...TURNING WINDS TO THE NORTHWEST AT
30 KNOTS OR LESS. WILL LET HIGH WIND WARNING FOR UPPER YELLOWSTONE
VALLEY EXPIRE AT 500 AM.

SFC COLD FRONT WILL MOVE INTO WESTERN ZONES THIS AFTERNOON...AND INTO
EASTERN ZONES TONIGHT. ETA/AVN AGAIN NOT IN GOOD AGREEMENT TONIGHT.
AVN DEVELOPS SFC CYCLOGENESIS IN NORTHERN WYOMING AND SPREADS QPF INTO
SOUTHERN MONTANA BEFORE ENDING IT TUESDAY MORNING. ETA HAS COME AROUND
WITH A LITTLE MORE QPF...BUT STILL MUCH DRIER FOR SOUTHERN MONTANA.
UPPER LEVEL SHORTWAVE NOT VERY IMPRESSIVE...HOWEVER AVN SHOWING A
BULLSEYE OF OMEGA IN NORTH CENTRAL WYOMING AT 06Z. LIKE THE CURRENT
THINKING OF HITTING WYOMING ZONES HARDEST...WITH LOWER POPS TO THE
NORTH AND EAST.

TEMPS WILL BE MUCH COOLER TUESDAY WITH A FEW LINGERING SNOW SHOWERS IN
THE MORNING. SHORTWAVE RIDGE PUSHES INTO ZONES...ENDING ANY PRECIP
EARLY.

SHORTWAVE RIDGE FLATTENS TUESDAY NIGHT WITH INCREASING SFC PRESSURE
GRADIENT AGAIN. PATTERN LOOKS FAMILIAR TO ANOTHER WIND EVENT FOR THE
UPPER YELLOWSTONE VALLEY AGAIN. WILL KEEP MENTION OF WIND IN ZONES AS
IT LOOKS WELL COVERED. TEMPS A BIT WARMER WEDNESDAY AS WARM AIR
ADVECTION KICKS IN ACROSS ZONES. SCARLETT

.LONG TERM...VALID FOR THU...FRI...SAT...SUN...
CONFIDENCE GETTING A BIT HIGHER WITH UPPER TROUGH EARLY PART OF
EXTENDED. MODELS HAVE BEEN VERY INCONSISTENT WITH IT...BUT NOW ALL
MODELS SEEM TO BE IN GOOD AGREEMENT THURSDAY/FRIDAY WITH IT. ECMWF AND
AVN BRING SURFACE LOW INTO WEST CENTRAL MONTANA THURSDAY MORNING...THEN
SLIDE IT TOWARDS BILLINGS BY END OF DAY. MAY SEE SOME SHOWERS LATE
AFTERNOON WESTERN ZONES BY AFTERNOON AND WILL INSERT WORDING FOR THIS.
BEST CHANCES LOOK TO BE IN SOUTHERN ZONES THURS NIGHT WITH THIS SYSTEM
AND WILL ADJUST POPS ACCORDINGLY. TOUGH CALL ON TEMPERATURES AS FRONT
PASSES LATE SO WILL NOT MESS WITH THEM. TROUGH THEN CLOSES OFF OVER
SOUTHERN COLORADO FRIDAY WITH UPPER RIDGE NUDGING INTO MONTANA FOR DRY
CONDITIONS. RASCH

    TDY TUE     WED     THU     FRI     SAT     SUN
-------------------------------------------------------
BIL 046 020/033 020/039 023/035 018/030 024/033 020/030
    0/E 32/J    00/E    03/J    31/B    33/J    22/E
LVM 043 020/031 020/035 017/030 014/027 015/028 017/027
    2/J 32/J    00/E    03/J    31/B    33/J    22/E
HDN 049 018/035 018/040 021/035 015/031 020/034 018/030
    0/E 32/J    00/E    03/J    31/B    33/J    22/E
MLS 050 018/035 015/041 018/038 015/033 016/031 018/029
    0/E 32/J    00/E    01/E    21/B    23/J    22/B
4BQ 048 016/034 014/040 018/035 017/030 015/030 018/030
    0/E 32/J    00/E    01/E    21/B    23/J    22/B
BHK 048 017/034 013/039 018/035 015/030 013/027 016/028
    0/E 32/J    00/E    01/E    21/B    23/J    22/B
SHR 043 015/031 010/038 018/035 014/030 015/034 019/030
    0/E 43/J    00/E    03/E    32/B    23/J    22/B

.BYZ...HIGH WIND WARNING UPPER YELLOWSTONE RIVER VALLEY TIL 500 AM.