Flood Watch 2, NWS Seattle, WA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
300 AM PST TUE FEB 11 2014

.SYNOPSIS...A VIGOROUS FRONTAL SYSTEM WILL BRING COPIOUS RAIN...
MOUNTAIN SNOW...AND WINDY CONDITIONS TO WESTERN WASHINGTON LATER
TODAY AND TONIGHT. ANOTHER WEAKER SYSTEM WILL FOLLOW ON WEDNESDAY...
FOLLOWED BY A RELATIVE BREAK IN THE WEATHER THURSDAY. THEN ANOTHER
STRONG FRONTAL SYSTEM WILL ARRIVE THURSDAY NIGHT AND FRIDAY...AND
THE STORMY PATTERN WILL CONTINUE THIS WEEKEND.

&&

.SHORT TERM...THE WARM FRONT THAT BROUGHT RAIN AND MILD TEMPERATURES
TO WESTERN WASHINGTON MONDAY IS MOVING THROUGH THE ROCKY
MOUNTAINS...WHILE ANOTHER MORE VIGOROUS FRONTAL SYSTEM IS
APPROACHING THE AREA FROM THE NORTHEAST PACIFIC OCEAN. SCATTERED
SHOWERS CONTINUE OVER THE FORECAST AREA EARLY THIS MORNING IN MOIST
WESTERLY FLOW ALOFT. TEMPERATURES AT 2 AM WERE IN THE UPPER 30S AND
40S.

A RELATIVE BREAK IN PRECIPITATION WILL CONTINUE FOR MUCH OF THE
FORECAST AREA THROUGH TODAY...BUT RAIN WILL SPREAD TO THE COAST AND
OLYMPIC PENINSULA THIS AFTERNOON. RAIN WILL INCREASE ACROSS WESTERN
WASHINGTON TONIGHT...THEN DECREASE OVER MOST OF THE LOWLANDS
WEDNESDAY AND WEDNESDAY NIGHT AS A WEAKER SHORTWAVE FOLLOWS THE
FRONT. RAINFALL TOTALS THROUGH WEDNESDAY AFTERNOON WILL PROBABLY BE
0.5 TO 1.5 INCHES AT THE COAST AND IN THE SOUTHWEST INTERIOR....WITH
GENERALLY 0.25 TO 1 INCH IN THE PUGET SOUND REGION AND NORTHWEST
INTERIOR. THE AREA ALONG HOOD CANAL WILL GET THE HEAVIEST RAINFALL
OF THE LOWLANDS...PROBABLY 1 TO 3 INCHES. THE HEAVIEST RAIN WILL
OCCUR TONIGHT.

PRECIPITATION WILL BE HEAVIER IN THE MOUNTAINS. THE OLYMPICS WILL
GET UP TO 4 INCHES OF WATER EQUIVALENT DURING THE 48 HOUR PERIOD
ENDING LATE WEDNESDAY NIGHT...AND 1 TO 3 INCHES WILL FALL IN THE
CASCADES. THE SNOW LEVEL WILL RISE TO 4500 TO 6000 FT AHEAD OF THE
COLD FRONT TONIGHT. THE WINTER STORM WATCH WILL BE UPGRADED TO A
WARNING FOR THE NORTH CASCADES...BUT I WILL GO WITH AN ADVISORY FOR
THE CENTRAL CASCADES AND HURRICANE RIDGE ON THE NORTH SIDE OF THE
OLYMPICS. THE HIGHWAY PASSES WILL PROBABLY GET AROUND 4 TO 12 INCHES
OF SNOW.

THIS SYSTEM WILL BE A WIND PRODUCER ALSO...WITH A 991 MB SURFACE LOW
MOVING NORTHEAST FROM THE WASHINGTON OFFSHORE WATERS ACROSS THE
SOUTH END OF VANCOUVER ISLAND LATE TONIGHT. THE LOW WILL PROBABLY
STARTING TO FILL AS IT MAKES LANDFALL...BUT IT IS TAKING A FAIRLY
CLASSIC SOUTHEAST SUCKER TRACK. FINER SCALE MODELS... ESPECIALLY THE
UW 4KM WRF-GFS JUSTIFIES A LOW-END HIGH WIND WATCH FOR THE TWO COAST
ZONES AND THE FOUR NORTH INTERIOR ZONES...AND WE WILL GO WITH THAT.

IF CURRENT MODEL TIMING IS CORRECT...THEN THERE WILL BE ANOTHER
RELATIVE BREAK IN THE WEATHER ON THURSDAY.   MCDONNAL

.LONG TERM...ANOTHER FAIRLY VIGOROUS FRONTAL SYSTEM WILL MOVE
THROUGH WESTERN WASHINGTON LATER THURSDAY NIGHT AND FRIDAY BRINGING
MORE RAIN...MOUNTAIN SNOW...AND WIND. ANOTHER SIMILAR SYSTEM WILL
ARRIVE AROUND SATURDAY...AND YET ANOTHER SUNDAY NIGHT OR MONDAY.
MCDONNAL

&&

.HYDROLOGY...THE FRONTAL SYSTEM MOVING THROUGH WESTERN WASHINGTON
LATE TODAY AND TONIGHT AND THE SHORTWAVE FOLLOWING WEDNESDAY AND
WEDNESDAY NIGHT WILL RESULT IN UP TO 4 INCHES OF RAIN OVER THE
SKOKOMISH RIVER BASIN. THIS COULD PRODUCE A MINOR FLOOD ON THE
SKOKOMISH...AND I WILL ISSUE A FLOOD WATCH WITH THE EARLY MORNING
FORECAST PACKAGE.

EVEN IF THE RAIN IN THE NEXT COUPLE DAYS DOES NOT DRIVE THE
SKOKOMISH TO FLOOD STAGE...THERE IS A FARLY GOOD CHANCE THAT IT WILL
FLOOD LATER IN THE WEEK AS THE SUCCESSION OF FRONTS BRING MORE RAIN.

RIVER FLOODING IS NOT EXPECTED ELSEWHERE OVER THE NEXT 7 DAYS.
HOWEVER THE WET AND MILDER WEATHER PATTERN THIS WEEK WILL PRODUCE
SHARP RISES ON RIVERS THROUGHOUT WESTERN WASHINGTON.   MCDONNAL

&&

.AVIATION...STRONG WESTERLY FLOW ALOFT WILL CONTINUE. SCATTERED
SHOWERS WILL CONTINUE TODAY THOUGH THERE IS SOME RAIN SHADOWING IN
THE SEATTLE METRO AREA. AIR MASS IS SLIGHTLY UNSTABLE. A STRONG
FRONTAL SYSTEM WILL APPROACH THE COAST THIS EVENING AND MOVE INLAND
OVERNIGHT. MODERATE TO STRONG SOUTHERLY SURFACE WINDS WILL BEGIN
THIS EVENING AND CONTINUE TONIGHT.

CEILINGS ARE MOSTLY VFR BUT ARE MVFR 2-3K FT IN SHOWERS. THERE WILL
BE A BRIEF IMPROVING TREND THIS MORNING BUT CEILINGS WILL GENERALLY
FALL TO MVFR TONIGHT AS THE FRONT APPROACHES.

KSEA...DISCUSSION ABOVE APPLIES. MVFR CEILINGS WILL LIKELY BECOME
VFR LATER THIS MORNING. SOUTH TO SOUTHWEST WIND 8-12 KT TODAY WILL
BECOME SOUTHEAST 15G25KT TONIGHT. CHB

&&

.MARINE...WINDS SHOULD GENERALLY REMAIN BELOW 20 KT THIS MORNING AS
A WEAK SURFACE RIDGE MOVES ACROSS THE AREA.

A STRONG SYSTEM WILL ARRIVE TONIGHT. MODELS ARE IN GOOD AGREEMENT IN
BRINGING A FILLING SURFACE LOW ASHORE SOMEWHERE BETWEEN CAPE
FLATTERY AND TOFINO EARLY WEDNESDAY MORNING. SOUTHERLY WINDS WILL
INCREASE BEGINNING THIS AFTERNOON AND GALES ARE LIKELY OVER ALL
WATERS TONIGHT. A SMALL CRAFT ADVISORY TO RAMP UP THE WINDS THIS
AFTERNOON IS IN EFFECT. A GALE WARNING IS IN EFFECT TONIGHT.

POST-FRONTAL ONSHORE FLOW WILL CONTINUE WEDNESDAY AND THURSDAY.
WESTERLY GALES IN THE STRAIT ARE LIKELY. BOTH GFS AND ECMWF HAVE
ANOTHER FRONT ARRIVING THURSDAY NIGHT...AND THEN ANOTHER SATURDAY
NIGHT. THESE FRONTS COULD ALSO PRODUCE GALES. CHB

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...HIGH WIND WATCH COAST TONIGHT.
     WINTER STORM WARNING NORTHERN CASCADES TONIGHT AND WEDNESDAY
       MORNING.
     WINTER WEATHER ADVISORY OLYMPICS THIS AFTERNOON AND TONIGHT.
     WINTER WEATHER ADVISORY CENTRAL CASCADES TONIGHT AND WEDNESDAY
       MORNING.
     FLOOD WATCH SKOKOMISH RIVER LATE TONIGHT THROUGH LATE WEDNESDAY
       NIGHT.

PZ...SMALL CRAFT ADVISORY ALL WATERS TODAY.
     GALE WARNING ALL WATERS TONIGHT.

&&

YOU CAN SEE AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML