Heavy Snow in Oregon, December 6 to 7, 2004

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE IDAHO
330 AM MON DEC 6 2004

.SHORT TERM...A MAJOR QPF EVENT IS POISED TO MOVE ACROSS THE CWFA
EARLY THIS WEEK (THROUGH WED.).  A SERIES OF DISTURBANCES FROM THE
PACIFIC WITH ABUNDANT MOISTURE FROM OLD TROPICAL SYSTEMS IN THE
WESTPAC ARE FORECAST FOR THE REGION.  FIRST WEAKER WAVE IS MOVING
OVER THE AREA AT PRESENT AND IS PRODUCING LIGHT AMOUNTS OF SNOW IN
THE NORTHERN MOUNTAINS.  NO HIGHLIGHTS REQUIRED FOR THIS FEATURE.
THE NEXT FEATURE TONIGHT IS A WARM ADVECTION SIGNATURE AND PROMISES
TO BRING MODERATE AMOUNTS OF QPF TO THE AREA AFTER MIDNIGHT AND
CONTINUE FOR MUCH OF TUESDAY. CURRENTLY THERE IS A WINTER STORM
WATCH FOR THIS EVENT AND THE WATCH WILL BE EXPANDED TO INCLUDE THE
HIGHLANDS OF SOUTHEAST OREGON AND THE SOUTHWEST CORNER OF IDAHO.
DAYSHIFT STILL HAS AMPLE TIME WITH NEXT MODEL RUNS TO ISSUE
ADVISORIES OR WARNINGS AS NEEDED FOR A START TIME OF TONIGHT.  THE
FOLLOWING SYSTEM ON WEDNESDAY IS THE STRONGEST BUT WILL BE THE MOST
DIFFICULT FORECAST BECAUSE OF RAPIDLY RISING SNOW LEVELS IN THE
STRONG WARM AIR ADVECTION. THIS STORM ALSO HAS THE DEEPEST MOISTURE
AND SHOULD BE A LASTING EVENT OF HEAVY QPF. LOWER ELEVATIONS WILL
MOST CERTAINLY HAVE RAIN WITH THIS ONE AND HEAVY WET SNOW IN THE
MOUNTAINS IS FORECAST BETWEEN 5000 AND 6000 FEET.  WINDS ARE
FORECAST TO INCREASE TONIGHT AS VIGOROUS SURFACE LOW APPROACHES FROM
THE COAST AND GRADIENT TIGHTENS.  THESE STRONG EASTERLY COMPONENT
WINDS WILL ALSO HAVE A WARMING EFFECT ON THE LOWEST ELEVATIONS
MAKING THE CHANGEOVER TO RAIN ALL THAT MORE LIKELY DURING TUESDAY.
TEMPERATURES TO START OUT COLD TODAY THEN DRAMATICALLY RISE TUESDAY
AND WEDNESDAY TO MUCH ABOVE NORMAL VALUES.

.LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY...GOOD MODEL AGREEMENT
LENDS HIGH CONFIDENCE TO A FORECAST OF DECREASING PRECIP CHANCES FOR
OUR SOUTHERN ZONES ALONG WITH MILD TEMPERATURES. WE WILL BE
TRANSITIONING FROM STRONG MOIST ZONAL FLOW INTO A LONGWAVE RIDGE
POSITION BY FRIDAY. AFTER INITIAL MOIST WARM AIR ADVECTION ACROSS
OUR CWA WEDNESDAY NIGHT PRECIP WILL BE SHUNTED NORTH WITH THE
BUILDING UPPER LEVEL RIDGE AND SHOULD BE CONFINED MAINLY TO OUR
NORTHERN MOUNTAINS STARTING FRIDAY. IN THE TREASURE VALLEY STRONG
DOWNSLOPING FROM THE SOUTHEAST AND SOUTH WILL LIMIT QPF.
TEMPERATURES WILL AVERAGE 5-10 DEGREES ABOVE NORMAL. THE ONLY
CHANGES IN THE LONG TERM WERE ADJUSTMENTS FOR ISC CONSISTENCY.

&&
.BOI WATCHES/WARNINGS/ADVISORIES...
ID...WINTER STORM WATCH TUESDAY ZONES 11/13/15/28/29.
OR...WINTER STORM WATCH LATE MONDAY NIGHT THRU NOON TUE ZONE 61 62
      63.

&&

WEATHER.GOV/BOISE

SHORT TERM...GS
LONG TERM...JT

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE BOISE ID
600 AM MST MON DEC 6 2004

IDZ011>016-028>030-ORZ061>064-071300-
BAKER COUNTY-BOISE MOUNTAINS-CAMAS PRAIRIE-HARNEY COUNTY-
LOWER TREASURE VALLEY-MALHEUR COUNTY-OREGON LOWER TREASURE VALLEY-
OWYHEE MOUNTAINS-SOUTHERN TWIN FALLS COUNTY-SOUTHWEST HIGHLANDS-
UPPER TREASURE VALLEY-WEST CENTRAL MOUNTAINS-WESTERN MAGIC VALLEY-
600 AM MST (500 AM PST) MON DEC 6 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHWEST IDAHO AND SOUTHEAST
OREGON.

.DAY ONE...TODAY

POSSIBLE HEAVY SNOW TONIGHT FOR THE MOUNTAINS OF SOUTHEASTERN
OREGON AND SOUTHWESTERN IDAHO AND THE SOUTHWEST HIGHLANDS OF IDAHO.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

POSSIBLE HEAVY SNOW TUESDAY FOR THE MOUNTAINS OF SOUTHEASTERN OREGON
AND SOUTHWESTERN IDAHO AND THE SOUTHWEST HIGHLANDS OF IDAHO.