Heavy Snow in Oregon, March 18 to 19, 2002

NORTHWEST OREGON AND SOUTHWEST WASHINGTON FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
230 AM PST MON MAR 18 2002

.SYNOPSIS...BREAKS IN CLOUD COVER AND A COLD MOIST AIR MASS WILL
ALLOW SOME PATCHY FOG TO FORM THIS MORNING IN THE VALLEYS. A WARM
FRONT ASSOCIATED WITH A FAIRLY STRONG WEATHER SYSTEM IN THE GULF OF
ALASKA WILL SPREAD CLOUDS AND PRECIPITATION OVER THE PACIFIC
NORTHWEST LATE THIS AFTERNOON...AND MOVE ONSHORE TONIGHT. SNOW LEVELS
WILL RISE TO AROUND PASS LEVELS LATE TODAY AND TONIGHT. MOIST
WESTERLY FLOW ALOFT WILL PRODUCE MOUNTAIN SNOW MONDAY AFTERNOON
THROUGH TUESDAY WITH SOME HEAVY SNOW DEVELOPING IN THE SOUTH
WASHINGTON AND NORTH AND CENTRAL OREGON CASCADES.

.DISCUSSION...
.SHORT TERM...MODELS BRINGING WARM FRONT PRECIPITATION INTO THE
FORECAST AREA SOMETIME THIS AFTERNOON WITH AVN MODEL A LITTLE FASTER
THAN THE NGM AND ETA. EXPECT A LOW END GALE THIS AFTERNOON AND NIGHT
NORTH HALF OF COASTAL WATERS BASED ON MODEL SURFACE GRADIENTS. SNOW
LEVEL AT ONSET MAY BE AS LOW 1500 TO 2000 FEET...THEN RISE TO AROUND
3500 FEET BY EARLY TONIGHT. MOISTURE PLUME WITH THIS SYSTEM HAS 0.8
PRECIPITABLE WATER...AND COMBINED WITH 45 KT WEST TO SOUTHWEST 850 MB
WIND FLOW SHOULD SUPPORT FAIRLY HEAVY MODEL FORECAST PRECIPITATION
TONIGHT INTO TUESDAY. WINTER STORM WATCH STILL LOOKS GOOD FOR THE
CASCADES...COULD SEE ANOTHER 2 FEET IN THE CASCADES BY LATE TUESDAY
DUE TO THE STRONG MOIST ORTHOGONAL OROGRAPHIC FLOW THAT WILL DEVELOP
THERE.

.LONG TERM...WILL SHOW SOME IMPROVEMENT WITH WARM FRONT LIFTING NORTH
WEDNESDAY THEN PAC COLD FRONT SPREADS PRECIPITATION BACK INLAND THU
AND FRI. WILLSON

AST ++994 PDX 8+974 SLE 89963 EUG 49931

.PQR...WINTER STORM WATCH...LATE THIS AFTERNOON THROUGH TUESDAY FOR
        THE WASHINGTON CASCADES...AND TONIGHT THROUGH TUESDAY FOR
        THE NORTH AND CENTRAL OREGON CASCADES.
     .GALE WARNING...CAPE SHOALWATER TO CASCADE HEAD THIS AFTERNOON
         AND EARLY NIGHT.
      .SMALL CRAFT ADVISORY...THIS AFTERNOON THROUGH EARLY TONIGHT

ORZ003-004-010-012-WAZ020-040-182300-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE PORTLAND OR
352 AM PST MON MAR 18 2002

...BRIEF PERIOD OF SNOW TODAY IN THE SOUTH WASHINGTON AND NORTH AND
CENTRAL CASCADES FOOTHILLS...THE NORTH AND CENTRAL OREGON COAST
RANGE...AND THE WILLAPA HILLS...

ANOTHER STORM SYSTEM WILL SPREAD PRECIPITATION INTO SOUTHWEST
WASHINGTON AND NORTHWEST OREGON LATE THIS MORNING AND THIS
AFTERNOON. SOME LIGHT RAIN WAS ALREADY FALLING AT ASTORIA THIS
MORNING. SNOW LEVELS WILL INITIALLY BE NEAR 1500 FEET...THEN RISE TO
NEAR 3000 FEET LATE MONDAY AND MONDAY EVENING.

ONE TO TWO INCH SNOW ACCUMULATIONS ARE POSSIBLE THIS AFTERNOON IN
THE WILLAPA HILLS...THE NORTH AND CENTRAL OREGON COAST RANGE...AND
THE SOUTH WASHINGTON AND NORTH AND CENTRAL OREGON CASCADE FOOTHILLS
ABOVE ABOUT 1500 FEET PRIOR TO THE EXPECTED RISE IN THE SNOW LEVEL
LATER IN THE DAY.