Debris Flow in Washington, January 5, 2015

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
926 PM PST SUN JAN 4 2015

.SYNOPSIS...A STRONG WARM FRONT WILL BRING RAIN TO WESTERN
WASHINGTON TONIGHT THROUGH MONDAY. RAIN WILL BE HEAVY AT
TIMES...ESPECIALLY OVER THE MOUNTAINS. AN UPPER LEVEL RIDGE WILL
MOVE ACROSS THE REGION TUESDAY THROUGH THURSDAY FOR DRY
WEATHER...PATCHY FOG...AND A LITTLE AFTERNOON SUNSHINE. A COLD FRONT
WILL MOVE INTO THE AREA THURSDAY NIGHT OR FRIDAY. WEST FLOW ALOFT
WILL KEEP THE WEATHER UNSETTLED NEXT WEEKEND.

&&

.SHORT TERM...A STRONG WARM FRONT IS BRINGING HEAVY RAIN AND WARMER
TEMPS TO WESTERN WA TONIGHT. TEMPS ARE MILD WITH READINGS IN THE MID
40S TO LOWER 50S THIS EVENING. TEMPS WILL NOT DROP MUCH FURTHER
OVERNIGHT. RAIN IS WIDESPREAD AND HEAVY ALONG THE COAST WITH 3-4
INCHES SO FAR TODAY. IN THE MOUNTAINS...HEAVY SNOW WILL TURN OVER
THE HEAVY RAIN AS WARM AIR CONTINUES TO SPREAD INLAND...SNOW LEVELS
RISING TO 6000-8500 FEET. HURRICANE RIDGE IS ALREADY ABOVE FREEZING
IN THE OLYMPICS. BUT EASTERLY WINDS ARE STILL KEEPING TEMPS BELOW
FREEZING IN THE PASSES. HOWEVER THE CHANGEOVER TO RAIN SHOULD OCCUR
RAPIDLY THIS EVENING AS STRONG WESTERLY FLOW DEVELOPS. THE WINTER
WEATHER ADVISORY EXPIRED AT 9 PM THIS EVENING AS SCHEDULED. THIS
WARM FRONT WILL STALL OVER THE REGION THROUGH MONDAY AFTERNOON WITH
HEAVY RAIN CONTINUING ALONG THE COAST AND IN THE MOUNTAINS. MODELS
SHOW ANOTHER 2-4 INCHES OF RAIN OVER THE OLYMPIC PENINSULA THROUGH
MONDAY AFTERNOON WITH ANOTHER 2-6 INCHES ALONG THE WEST SLOPES OF
THE CASCADES...HIGHEST AMOUNTS FROM SNOHOMISH TO LEWIS COUNTIES.
THIS LEADS TO FLOODING CONCERNS AND A FLOOD WATCH REMAINS IN EFFECT
FOR MUCH OF THE CWA. SEATTLE WILL BE IN THE RAIN SHADOW WITH
WESTERLY DOWNSLOPE WINDS OFF THE OLYMPICS. IN FACT KATX IS ALREADY
SHOWING THIS. SO EXPECT LITTLE PRECIP IN SEATTLE. THIS WARM FRONT
WILL LIFT NORTH INTO BRITISH COLUMBIA MONDAY EVENING WITH HEAVY
RAIN ENDING ACROSS THE MOUNTAINS.

AN UPPER LEVEL RIDGE WILL BUILD OVER THE PAC NW TUESDAY AND
WEDNESDAY FOR DRY WEATHER. WILL LIKELY SEE AREAS OF LOW CLOUDS AND
FOG AS THE LOW LEVEL AIR MASS WILL REMAIN MOIST. TEMPS WILL TREND
CLOSER TO NORMAL. 33

.LONG TERM...PREVIOUS DISCUSSION...THE ECMWF AND GFS HAVE TRENDED
SLOWER WITH THE APPROACHING COLD FRONT LATE THIS WEEK...AND NOW
BRING IT INLAND THURSDAY NIGHT. THIS WILL ALLOW THE MID-WEEK DRY
PERIOD TO EXTEND THROUGH THURSDAY AFTERNOON. INCREASING SW FLOW
ALOFT WILL ALLOW HIGH CLOUDS TO DRIFT OVER THE AREA FOR MOSTLY
CLOUDY SKIES.

THE 18Z GFS SEEMS TO HAVE MIGRATED TO THE 12Z ECMWF SOLUTION. THIS
HAS AN UPPER LEVEL TROUGH FOLLOWING THE COLD FRONT ON FRIDAY. THE
MODELS DIVERGE A LITTLE THIS WEEKEND. WHILE BOTH SHOW A WEAK UPPER
LEVEL RIDGE JUST OFFSHORE...THE GFS HAS A FLATTER MORE PROGRESSIVE
RIDGE WHICH ALLOWS WARM ADVECTION TO BRING RAIN OVER W WA. THE ECMWF
RIDGE HAS HIGHER AMPLITUDE WHICH LEAVES W WA MOSTLY DRY. THE MIDDLE
GROUND IS MOSTLY CLOUDY WITH A CHANCE OF RAIN THIS WEEKEND. KAM

&&

.HYDROLOGY...HEAVY RAIN CONTINUING ALONG THE COAST...OVER
THE OLYMPICS AND IN THE SOUTHWEST INTERIOR THIS EVENING. RAINFALL
AMOUNTS FOR THE LAST THREE HOURS ENDING AT 9 PM INCLUDE...KUIL 1.36
INCHES...HOQUIAM 1.44 INCHES AND SHELTON 1.03 INCHES.

WARM AIR MASS HAS BEEN A LITTLE SLOW TO MOVE INLAND THIS EVENING.
THE TEMPERATURES IN THE PASSES ARE STILL AT FREEZING OR BELOW BUT
THE TEMPERATURE WENT UP 6 DEGREES AT STEVENS PASS LAST HOUR SO THE
WARM AIR IS ON ITS WAY. WITH THE PRECIPITATION FALLING AS SNOW IN
THE CASCADES RIVERS FLOWING OFF THE CASCADES HAVE BEEN SLOW TO
RESPOND THIS EVENING. THIS WILL CHANGE OVERNIGHT WITH THE SNOW
LEVELS RISING AS HIGH AS 8500 FEET BY MORNING. DATA FROM NESDIS THIS
EVENING INDICATES THE AIR MASS OFFSHORE IS EXTREMELY MOIST...3
STANDARD DEVIATIONS ABOVE CLIMATOLOGY...WITH SOME AREAS OVER DOUBLE
THE NORMAL MOISTURE VALUES FOR THIS TIME OF YEAR. THE KUIL RAOB
PWAT...PRECIPITABLE WATER VALUE...WAS RANKED THIRD HIGHEST FOR
JANUARY IN THE LAST 60 YEARS. 00Z GFS STILL SHOWING 4 TO 6 INCHES OF
PRECIPITATION IN THE CASCADES IN THE 24 HOUR PERIOD ENDING AT 00Z
TUESDAY WITH THE HEAVIEST AMOUNTS IN THE CENTRAL CASCADES. A LITTLE
LESS RAIN IN THE OLYMPICS...2 TO NEARLY 4 INCHES ALONG THE WEST
SLOPES. GIVEN THE CURRENT NESDIS DATA THERE IS NO REASON TO BACK OFF
FROM THESE RAINFALL TOTALS. THIS AMOUNT OF RAIN WILL DRIVE MANY OF
THE RIVERS FLOWING OFF THE OLYMPICS AND CASCADES ABOVE FLOOD STAGE
ON MONDAY. THE BEST CHANCES FOR FLOODING FOR THE CASCADE RIVERS WILL
BE THE RIVERS FLOWING OFF THE CENTRAL CASCADES...THE SNOQUALMIE...
TOLT AND PUYALLUP...JUST TO NAME A FEW. FLOOD WARNINGS HAVE ALREADY
BEEN ISSUED FOR THE TOLT AND PUYALLUP. THESE WARNINGS WILL BE
REFRESHED TO PUSH BACK THE TIMING OF THE RIVERS REACHING FLOOD
STAGE. A FLOOD WARNING FOR THE SKOKOMISH WILL BE ISSUED WITH THIS
FORECAST PACKAGE. WITH THE COOL AIR STILL OVER THE CASCADES AND THE
CASCADE RIVERS NOT RISING MUCH YET WILL WAIT UNTIL AT LEAST THE
EARLY MORNING PACKAGE TO ISSUE ADDITIONAL FLOOD WARNINGS WITH THE
EXCEPTION OF THE SKOKOMISH.

IN ADDITION TO THE RIVER FLOODING THE HEAVY RAIN OVER THE WESTERN
WASHINGTON LOWLANDS WILL ALSO INCREASE THE LANDSLIDE THREAT ACROSS
THE AREA. A SPECIAL WEATHER STATEMENT HAS BEEN ISSUED COVERING THIS
THREAT. FELTON

&&

.AVIATION...A WARM FRONT FROM JUST N OF KBLI WESTWARD ACROSS
VANCOUVER ISLAND WILL LIFT NORTHWARD OUT OF THE AREA OVERNIGHT.
STRONG WESTERLY FLOW ALOFT WILL GRADUALLY EASE MONDAY AFTERNOON. THE
STRONG FLOW ALOFT IS GIVING HEAVY RAIN AND MVFR CONDITIONS TO THE
AREA. VISIBILITIES ARE IN THE IFR CATEGORY IN HEAVY RAIN ALONG THE
COAST AND THE WEST SLOPES OF THE CASCADES. THE WESTERLY FLOW ALOFT
IS INTERACTING WITH THE TERRAIN TO INDUCE STRONG SOUTH TO NORTH
SURFACE PRES GRADIENTS WITH AREAS OF WIND TO 30 KT FROM SOUTH OF THE
SAN JUAN ISLANDS SOUTHWARD THROUGH THE PUGET SOUND REGION AND ALONG
THE COAST. THE AIR MASS IS MOIST AND STABLE. CONDITIONS WILL
GRADUALLY IMPROVE MONDAY MORNING AS FLOW ALOFT DECREASES. ALBRECHT

KSEA...CIGS GENERALLY 1-2K FT IN LIGHT TO MODERATE RAIN. VISIBILITY
AT TIMES 3-5SM WITH LIGHT TO MODERATE RAIN. RAINFALL WILL GRADUALLY
TAPER OFF DURING THE DAY MONDAY BUT MVFR CIGS WILL CONTINUE. SOUTH
WINDS 12G25 KT WILL GRADUALLY EASE AFTER 10Z. ALBRECHT

FORECAST WIND FOR KSEA AT 5000 FT...06Z SW 60 KT
                                    12Z W  55 KT
                                    18Z W  35 KT

FORECAST WIND FOR KSEA AT 2000 FT...06Z SW 50 KT
                                    12Z SW 40 KT
                                    18Z SW 30 KT

&&

.MARINE...A WARM FRONT FROM NORTH OF BELLINGHAM WESTWARD ACROSS
VANCOUVER ISLAND WILL LIFT NORTH OF THE AREA OVERNIGHT. HIGH PRES
WILL THEN BUILD INTO THE AREA FROM THE SOUTH MONDAY THROUGH TUESDAY.

FREQUENT GALE FORCE GUSTS CONTINUE OVER THE SOUTHERN TWO-THIRDS OF
THE OUTER COASTAL WATERS WHILE WINDS FARTHER NORTH HAVE EASED. THE
WINDS HAVE PRODUCED A 13 TO 15 FOOT SOUTHWESTERLY SEA WITH A PERIOD
OF 8 TO 10 SECONDS. THE SEAS WILL SUBSIDE LATE TONIGHT THROUGH
MONDAY AS WINDS EASE FROM THE SOUTH. THE SEAS ARE HIGH ENOUGH TO
PRODUCE ROUGH CONDITIONS ON THE GRAYS HARBOR BAR. GRADIENTS ARE
STARTING TO BECOME POSITIVE THROUGH THE STRAIT OF JUAN DE FUCA...SO
THE SMALL CRAFT ADVISORY FOR THE CENTRAL STRAIT OF JUAN DE FUCA WAS
MAINTAINED FOR TONIGHT. FOR THE REST OF THE INLAND WATERS...FLOW
ALOFT IS INTERACTING WITH THE TERRAIN AND IS CAUSING STRONG
SOUTHERLY PRESSURE GRADIENTS. SMALL CRAFT ADVISORY SOUTH WINDS ARE
OCCURING AND WILL BE STRONGEST OVERNIGHT IN THE CENTRAL PUGET SOUND
AREA AT ABOUT 30 KT. WINDS WILL EASE LATER TONIGHT THROUGH MONDAY
MORNING AS FLOW ALOFT RELAXES.

EXPECT GRADIENTS TO BECOME LIGHT MON NIGHT AND TUE AS HIGH PRES
BUILDS OVER THE INLAND WATERS. THE HIGH WILL SHIFT EAST OF THE
CASCADES LATER TUE THROUGH THU GIVING LIGHT OFFSHORE FLOW. ALBRECHT

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...FLOOD WATCH FOR MOST OF WESTERN WASHINGTON.
PZ...GALE WARNING SOUTHERN TWO THIRDS OF THE OUTER COASTAL WATERS
     SMALL CRAFT ADVISORY ALL OTHER WATERS.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR.
&&

WWW.WEATHER.GOV/SEATTLE

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

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SEATTLE WA
141 AM PST MON JAN 05 2015

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0115 AM     FLOOD            1 W ABERDEEN            46.98N 123.86W
01/05/2015                   GRAYS HARBOR       WA   TRAINED SPOTTER

            LOCAL FLOODING OF STREETS AND GARAGES IN HOQUIAM.

1245 AM     FLOOD            HOQUIAM                 46.98N 123.89W
01/05/2015                   GRAYS HARBOR       WA   PUBLIC

            LOCAL FLOODING OF GARAGES AND STREETS IN HOQUIAM.

&&

GBP