Flooding in Washington, December 16 to 19, 2001

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
230 AM PST SUN DEC 16 2001

.SYNOPSIS...A VERY STRONG AND MOIST WEATHER SYSTEM WILL CONTINUE TO
BRING HEAVY RAIN AND STRONG WINDS TO WESTERN WASHINGTON TODAY. A COLD
FRONT IS EXPECTED TO SWING ONSHORE LATE TONIGHT...BRINGING AN END TO
THIS WET AND WINDY WEATHER. A COOLER AIR MASS IN THE WAKE OF THIS
SYSTEM WILL BRING SHOWERS WITH SNOW IN THE MOUNTAINS MONDAY. MORE
PACIFIC WEATHER SYSTEMS WILL MAINTAIN COOL AND WET WEATHER THE REST
OF THIS COMING WEEK.

.DISCUSSION...THE FIRST PART OF THIS ONE-TWO PUNCH HAS PROBABLY
PEAKED IN THE LAST COUPLE HOURS AS THE WARM FRONT SWEPT INLAND...BUT
NOT WITHOUT IMPRESSIVE RAINFALL AMOUNTS OVER THE SOUTH OLYMPICS. FOR
EXAMPLE 2.11 INCHES IN 5 HOURS AT WYNOOCHEE DAM.

VERY STRONG SWLY FLOW IS EXPECTED TO CONTINUE THIS MORNING WITH
STRONG OROGRAPHICS GIVING LITTLE BREAK IN PRECIP BEFORE THE NEXT
FRONTAL WAVE IMPACTS US AROUND MIDDAY TODAY. FLOODING STILL LOOKS
LIKELY ALTHOUGH PERHAPS DELAYED SOME IN THE CASCADES GIVEN THE SLOWER
THAN EXPECTED WARM UP AND SWITCH OVER TO RAIN.

WARM AIR HAS PENETRATED ALL BUT THE CASCADE PASSES THIS MORNING. SMP
AND LOWER PASSES ARE NOW GETTING FREEZING RAIN. WILL LOWER WINTER
STORM TO WINTER WEATHER ADVISORY FOR PASSES THIS MORNING.

A MUCH COOLER AIR MASS SWEEPS IN MONDAY FOR A BIT OF A BREAK.
ALTHOUGH A DEVELOPING POLAR LOW WEST OF 150W IS SOMEWHAT INDICATED IN
THE AVIATION AND IS CARRIED ONSHORE LATER MONDAY.

EXTENDED...A STRONGER SYSTEM REACHES US TUESDAY AND THE AIR MASS
STAYS COOL. PATTERN IS NOT QUITE RIGHT FOR LOWLAND SNOW BUT A BIT OF
A MIX EARLY TUESDAY IS POSSIBLE HIGHER HILLS AND KITSAP PENINSULA.

A COOL FRONTAL SYSTEM IS STILL INDICATED TO MOVE ONSHORE WEDNESDAY
AND NEWER MODEL RUNS ARE CARRYING IT FARTHER NORTH FOR MORE OF A WET
AND WINDY PATTERN. ECMWF STILL HAS A RATHER WEAK SYSTEM FARTHER NORTH
BUT CANADIAN AND NCEP MODELS SWING STRONG LOW ACROSS NW WASHINGTON.
ANOTHER BREAK THU BEFORE A WARMUP AND WETTER FRI AND SAT. COLMAN

UIL ++9  SEA ++7  OLM ++7
.SEW...GALE WARNING...ALL WATERS EXCEPT ADMIRALTY INLET
       SMALL CRAFT ADVISORY...ADMIRALTY INLET
       WINTER WEATHER ADVISORY CASCADE PASSES THIS MORNING
       HIGH WIND WATCH NORTH AND CENTRAL COAST

.KATX...VCP21/CSR21...OPERATIONAL.