Heavy Snow in Oregon, January 31, 2004

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OREGON
230 PM PST SAT JAN 31 2004

.SHORT TERM...A SHORTWAVE TROUGH OVER VANCOUVER ISLAND WILL MOVE
EAST OF THE CASCADES LATE THIS EVENING.  NUMEROUS SHOWERS HAVE BEEN
OBSERVED ACROSS WESTERN WASHINGTON AND NW OREGON WITH THIS SYSTEM.
SCATTERED TO NUMEROUS SNOW SHOWERS WILL BE OBSERVED OVER THE
FORECAST AREA TONIGHT...AND ACCUMULATIONS AROUND 2-4 INCHES ARE
POSSIBLE ALONG THE WEST FACING SLOPES OF THE BLUE MOUNTAINS.  THE
SYSTEM WILL EXIT THE REGION SUNDAY MORNING AROUND 10 AM-NOON WITH A
BREAK IN PRECIPITATION SUNDAY AFTERNOON.  THE NEXT SYSTEM TO INVADE
THE REGION WILL ARRIVE SUNDAY NIGHT AND EARLY MONDAY MORNING. THE
12Z GFS IS DEEPER WITH THE LOW AND MOVES THE LOW FARTHER SOUTH THAN
THE ETA.  PREFER THE GFS WHICH SEEMS A LITTLE MORE CONSISTENT WITH
ITS PREVIOUS RUN AND ALSO IS SIMILAR TO ECMWF AND UKMET. WARM AIR
ADVECTION WILL INCREASE OVER CENTRAL OREGON SUNDAY EVENING WITH
MOISTURE SPREADING OVER THE REMAINDER OF THE AREA SUNDAY NIGHT.
SNOW LEVELS WILL SLOWLY RISE OVER MOST OF OREGON AND WILL INCREASE
TO AROUND 3500-4000 FEET BY MONDAY MORNING. HOWEVER...COLD AIR WILL
BE DEEPER OVER EASTERN WASHINGTON AND ALONG THE WA/OR BORDER.
THUS...LIGHT SNOW WILL FALL OVER MOST OF THE REGION WITH LIGHT
ACCUMULATIONS EXPECTED.  THE LOW WILL TRACK S-SE MONDAY WITH
PRECIPITATION TAPERING OFF FROM THE NORTH.

&&

.HYDROLOGY...THE UMATILLA AND WALLA WALLA RIVERS REMAIN HIGH BUT
HAVE FALLEN BELOW BANKFULL.  WATER LEVELS WILL CONTINUE TO RECEDE
TONIGHT.

&&

.LONG TERM...TUESDAY THROUGH SATURDAY...
THREE SYSTEMS TWO AFFECT THE FORECAST AREA IN THE EXTEND PERIOD. THE
FIRST WILL MOVE ACROSS OREGON AND WASHINGTON TUESDAY NIGHT AND
WEDNESDAY IN NORTHWEST FLOW ALOFT...BRINING A CHANCE OF VALLEY RAIN
AND MOUNTAIN SNOW. COULD BE SOME ACCUMULATIONS IN THE BLUE MOUNTAINS
SO THIS SYSTEM BEARS WATCHING. NEXT SYSTEM WILL AFFECT THE REGION ON
THURSDAY INTO FRIDAY WITH A CONSIDERABLE AMOUNT OF PACIFIC MOISTURE.
WITH SEASONABLE TEMPERATURES IN PLACE...SNOW WILL GENERALLY BE
CONFINED TO ELEVATIONS ABOVE THE 2500-3500 FOOT LEVEL. THE THIRD
SYSTEM WAS FORECAST BY THE 00 UTC MRF TO IMPACT THE AREA ON
SATURDAY...BUT THE 12 UTC RUN OF THE GFS MOVES THE SYSTEM MUCH
FARTHER NORTH INTO BRITISH COLUMBIA...WITH MINIMAL IMPACT INTO
SOUTHEAST WASHINGTON AND NORTHEAST OREGON. FOR NOW HAVE LEFT LOW
CHANCE POPS FOR SATURDAY FOR LATER EVALUATION AND FINE TUNING. 78

&&

.PRELIMINARY POINT TEMPS/POPS...
PENDLETON (AIRPORT) 32 40 31 39 / 40 30 30 40
WALLA WALLA         33 41 31 38 / 40 30 20 40
TRI-CITIES          30 45 31 40 / 40 30 20 40
YAKIMA              25 42 29 36 / 40 20 30 40
&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
&&

85

HAZARDOUS WEATHER OUTLOOK...CORRECTED...
NATIONAL WEATHER SERVICE PENDLETON OR
500 AM PST SAT JAN 31 2004

ORZ041>050-WAZ024>030-011300-

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL AND NORTHEAST OREGON
AS WELL AS SOUTH CENTRAL AND SOUTHEAST WASHINGTON.

.DAY ONE...TODAY AND TONIGHT...

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

THE REGION WILL BE UNDER NORTHWEST FLOW ALOFT. LOWER ELEVATIONS EAST
OF THE CASCADES WILL BE DRY. HOWEVER...THERE WILL BE A CHANCE OF
SNOW SHOWER SHOWERS ALONG THE EAST SLOPES OF THE SOUTHERN
WASHINGTON CASCADES AND THE WEST FACING SLOPES OF THE NORTHERN BLUE
MOUNTAINS. A WEAK DISTURBANCE WILL MOVE EAST OF THE CASCADES TONIGHT
FOR A CHANCE OF RAIN OR SNOW IN THE LOWER COLUMBIA BASIN...AND ID
CENTRAL AND NORTH CENTRAL OREGON WITH SNOW LIKELY IN THE MOUNTAINS.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY...

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

THE AFOREMENTIONED DISTURBANCE WILL MOVE THROUGH THE REGION ON
SUNDAY FOR MOUNTAIN SNOW SHOWERS. THE LOWER COLUMBIA BASIN AND AREAS
IMMEDIATELY EAST OF THE CASCADES WILL BE DRY O SUNDAY. HIGH
PRESSURE WILL BUILD OVER THE REGION FOR DRY CONDITIONS SUNDAY
NIGHT...EXCEPT FOR MOISTURE SPREADING INTO CENTRAL AND NORTH CENTRAL
OREGON ASSOCIATED WITH A WARM FRONT FOR A CHANCE OF SNOW. AN UPPER
LEVEL LOW PRESSURE SYSTEM WILL MOVE INTO SOUTHWEST OREGON ON MONDAY
PUSHING PRECIPITATION ASSOCIATED WITH A WARM FRONT ACROSS NORTHEAST
OREGON AND SOUTHEAST WASHINGTON. TUESDAY THROUGH FRIDAY WEAK
DISTURBANCES WILL MOVE ACROSS THE PACIFIC NORTHWEST. THE BEST CHANCE
FOR PRECIPITATION WILL BE ON THURSDAY AND FRIDAY ASSOCIATED WITH AN
UPPER LEVEL SHORT WAVE MOVING SOUTHEAST FROM THE GULF OF ALASKA
THROUGH THE PACIFIC NORTHWEST. SNOW LEVELS WILL BE LOW ENOUGH FOR
SNOW POSSIBLE IN THE LOWER COLUMBIA BASIN.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED AT THIS TIME.

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.