AREA FORECAST DISCUSSION
NWS SEATTLE WA
AFDSEW 930 AM PST WED FEB 19 2003
.SYNOPSIS...A WEAK PACIFIC FRONTAL SYSTEM WILL SPREAD RAIN ONSHORE
THIS MORNING. THE RAIN WILL TURN TO SCATTERED SHOWERS THIS AFTERNOON
AS THE FRONT MOVES INLAND. ANOTHER FRONTAL SYSTEM IS EXPECTED
THURSDAY FOR MORE RAINFALL. A COOLER NORTHWEST FLOW ALOFT WILL FOLLOW
FOR A MORE SHOWERY PATTERN THROUGH FRIDAY. HIGH PRESSURE ALOFT IS
EXPECTED TO BUILD OFFSHORE SATURDAY FOR DRIER WEATHER THIS WEEKEND.
.DISCUSSION...HARD TO FIND THE FRONT THIS MORNING. SURFACE PRESSURES
ARE ON THE RISE BUT THERE HAS BEEN NO WIND SHIFT. ACARS SOUNDINGS
HAVE WINDS 10 KNOTS OR LESS BELOW 8000 FEET. CLOUD TOP WARMING OVER
WESTERN WASHINGTON WITH THE FRONT SPLITTING AS IT MOVES INLAND.
LEADING EDGE OF COOL AIR POCKET BEHIND THE FRONT ABOUT 50 NM OFFSHORE
BUT MOVING SOUTHEAST SO EXPECT THE BULK OF THIS TO MOVE INLAND SOUTH
OF WASHINGTON. SURFACE PRESSURES RISING FASTER ALONG THE COAST WITH
POSSIBLE CONVERGENCE ZONE TONIGHT BUT WITHOUT A STRONG PUSH THROUGH
THE STRAIT ZONE SHOULD STAY NORTH OF METRO AREA. WARM FRONT ON TRACK
TO MOVE INTO THE AREA LATE THURSDAY. LATEST SSMI IMAGERY HAS PW
VALUES OF 1 TO 1.5 AND A SMALL CORE OF HOURLY PRECIP RATES OF 1/3 OF
AN INCH. FIRST LOOK AT 12Z MODELS SHOWS STRONGER OROGRAPHICS THAN
PREVIOUS MODEL RUNS. SNOW LEVEL A LITTLE TRICKY BUT AT THIS TIME
LOOKS LIKE IT WILL PEAK OUT AROUND 4000 FEET RIGHT AHEAD OF THE
FRONT. WILL HOLD OFF ON UPDATE UNTIL LOOKED AT ALL MODELS BUT
CRANKING UP SNOW AMOUNTS IN THE CASCADES LOOKS LIKE A GOOD BET FOR
THURSDAY THROUGH FRIDAY WITH A WINTER STORM WATCH A STRONG
POSSIBILITY FOR AT LEAST THE NORTH CASCADES FOR THURSDAY NIGHT INTO
FRIDAY. REST OF THE FORECAST IN GOOD SHAPE. felton
UIL 95+ SEA 848 OLM 958
.KSEW...SMALL CRAFT ADVISORY COAST AND STRAIT.
.KATX...VCP21/CSR21...OPERATIONAL.
$$