206 
FXUS65 KBYZ 240318
AFDBYZ

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT 
918 PM MDT SAT OCT 23 2004

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

WILL ISSUE AN UPDATED ZONE FORECAST PACKAGE THIS EVENING...BUT NO
UPDATE WILL BE NEEDED FOR THE STATE FORECAST. ONLY MAKING MINOR
ADJUSTMENTS TO THE CURRENT FORECAST PACKAGE...WARMING LOW
TEMPERATURES SLIGHTLY IN SOME EASTERN LOCATIONS AND EXPANDING THE
LIKELY CHANCES FOR PRECIPITATION FARTHER INTO THE SOUTHEAST ZONES.

PRECIPITATION AT LIVINGSTON CHANGED OVER TO SNOW AT 750 PM
MDT. ALONG THE FOOTHILLS OF THE BEARTOOTH/ABSAROKA MOUNTAINS AT
530 PM MDT THIS EVENING...PRECIPITATION WAS ACCUMULATING ABOVE
ABOUT 5500 FEET. THEREFORE...DID ADD TO THE FORECAST SNOW
ACCUMULATIONS JUST BELOW 6000 FEET. PRECIPITATION AT LIVINGSTON
CHANGED OVER TO SNOW AT 750 PM MDT...AND WITH ANOTHER JET STREAK
DROPPING INTO THE UPPER TROUGH AND SNOW SHOWER ACTIVITY STILL ON
TRACK TO STREAM ACROSS THE AREA WILL LEAVE THE WINTER WEATHER
ADVISORY FOR SNOW AND HEAVY SNOW WARNINGS FOR PARK COUNTY IN
PLACE. THE MAIN UPPER PLUME OF MOISTURE EVIDENT IN SATELLITE
IMAGERY HAS BEGUN TO MOVE EAST OF PARK COUNTY WITH WEB-CAM IMAGERY
INDICATING DECREASED PRECIPITATION EARLIER THIS EVENING.
HOWEVER...THE PREFERRED GFS MODEL SOLUTION INDICATES LOWER LEVEL 
(700 TO 500MB) MOISTURE AND INSTABILITY LINGERING BENEATH THE
DECREASING MOISTURE AT HIGHER LEVELS OF THE ATMOSPHERE THROUGH THE
NIGHT. THIS IS SUPPORTED BY UPSTREAM SATELLITE IMAGERY.

HIGH PRESSURE STILL ON TRACK TO MOVE INTO THE FORECAST AREA SUNDAY
AS UPPER LEVEL NORTHWEST FLOW SETS UP OVER THE AREA. AS THE
SURFACE HIGH MOVES IN...PRECIPITATION WILL GRADUALLY MOVE EAST OUT
OF THE AREA DURING THE MORNING. A WEAKER SHORTWAVE DISTURBANCE IN
THE NORTHWEST FLOW WILL KEEP A SLIGHT CHANCE OF SNOW SHOWERS IN
THE HIGHER TERRAIN SUNDAY AFTERNOON. CARPENTER

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

WEATHER PATTERN CONTINUES TO LOOK UNSETTLED THROUGH MOST OF NEXT
WEEK AS ANOTHER LARGE TROUGH MOVES OUT OF THE GULF OF ALASKA
SOUTHWARD ALONG THE WEST COAST. GFSLR WAS STARTING TO COME IN LINE
WITH THE ECMWF BUT LAST NIGHTS GFSLR RUN SHOWS IT ONCE AGAIN
DIVERGING AWAY FROM THE ECMWF. THE GFS PROGRESSES THE TROUGH AND
VORT AREA ACROSS THE NORTHERN ROCKIES WHEREAS THE ECMWF SLOWS IT
DOWN AND DIGS IT FURTHER SOUTH INTO CALIFORNIA. PREFER THE ECMWF
AS THIS HAS BEEN THE PATTERN AS OF LATE.

UPPER LOW IS EXPECTED TO BE OVER NORTHERN CALIFORNIA LATE TUESDAY
AND OVER SOUTHERN CALIFORNIA LATE IN THE DAY WEDNESDAY. AS A
RESULT...A LARGE TROUGH IS EXPECTED TO BE CARVED OUT ACROSS THE
WESTERN STATES. THE POSITION OF THE 500MB LOW WILL PROVIDE A MOIST
SOUTHWEST FLOW ALOFT OVER THE AREA...ESPECIALLY OUR SOUTHWEST
MOUNTAINS. WILL KEEP A SLIGHT CHANCE FOR RAIN AND SNOW SHOWERS
ACROSS THE ENTIRE AREA THROUGH FRIDAY NIGHT. BEST CHANCES MAY COME
WEDNESDAY INTO THURSDAY MORNING AS THE ECMWF MOVES A SURFACE LOW
ACROSS SOUTHERN WYOMING WITH THE GFS PLACING THE LOW MUCH FURTHER
NORTH ACROSS SOUTH CENTRAL MONTANA. AT THE MOMENT...WILL NOT PUT MUCH
FAITH IN THE GFS SURFACE LOW. IN ANY CASE...WILL INCREASE
POPS INTO THE CHANCE CATEGORY FOR THIS TIME FRAME AND THIS WILL
COORDINATE WELL WITH SURROUNDING OFFICES. TUESDAY LOOKS TO BE THE
WARMEST DAY WITH TEMPERATURES IN THE 50S BEFORE READINGS COOL OFF INTO
THE 40S FOR THE REMAINDER OF THE WEEK.   HOOLEY


&&

.PRELIMINARY POINT TEMP/POPS...

    SUN     MON     TUE     WED     THU     FRI     SAT     
-----------------------------------------------------------
BIL 033/049 028/051 030/052 030/045 028/046 029/049 031/054
    +2/W    00/B    33/W    33/W    33/W    33/W    30/E
LVM 027/047 025/051 025/050 029/045 026/042 024/047 027/049
    +0/E    00/B    33/W    33/W    33/W    33/W    30/E
HDN 033/050 027/053 032/055 034/052 030/048 028/049 030/055
    +2/W    00/B    03/W    33/W    33/W    33/W    30/B
MLS 035/050 027/052 030/055 032/053 030/047 028/046 028/050
    92/W    00/B    00/B    03/W    33/W    33/W    30/B
4BQ 034/050 025/053 031/058 032/054 031/049 029/048 028/053
    63/W    00/B    00/B    03/W    33/W    33/W    30/B
BHK 033/048 024/049 031/053 034/053 028/044 025/047 026/049
    93/W    00/B    00/B    03/W    33/W    33/W    30/B
SHR 035/051 023/052 023/053 029/052 027/048 025/049 024/052
    73/W    00/B    33/W    33/W    33/W    33/W    30/E

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...HEAVY SNOW WARNING ABOVE 6000 FEET IN EFFECT UNTIL 6 AM MDT 
     SUNDAY FOR ZONE 40.
     WINTER WEATHER ADVISORY FOR SNOW BELOW 6000 FEET IN EFFECT
     UNTIL 6 AM MDT SUNDAY FOR ZONE 40.
WY...NONE.

&&

$$