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000
FXUS66 KSEW 121044
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
340 AM PDT WED MAR 12 2014

.SYNOPSIS...AN UPPER LEVEL RIDGE WILL BRING DRY WEATHER TO WESTERN
WASHINGTON THROUGH THURSDAY. A PACIFIC FRONTAL SYSTEM WILL SPREAD
RAIN AND BREEZY CONDITIONS ACROSS THE AREA THURSDAY NIGHT AND
FRIDAY. RELATIVELY WEAK WEATHER SYSTEMS COULD AFFECT THE AREA OVER
THE WEEKEND AND EARLY NEXT WEEK.

&&

.SHORT TERM...SATELLITE IMAGERY SHOWS AN UPPER LEVEL RIDGE OVER
WESTERN WASHINGTON THIS MORNING WITH THE RIDGE AXIS OVER EASTERN
WASHINGTON. TEMPERATURES UNDER CLEAR SKIES WERE IN THE 30S AND LOWER
40S.

ANOTHER DRY DAY IN STORE FOR WESTERN WASHINGTON WITH THE UPPER LEVEL
RIDGE SLOWLY MOVING EASTWARD. WEAKENING FRONT...CURRENTLY OFFSHORE
APPROACHING 130W...WILL CONTINUE TO WEAKEN AS IT MOVES INTO THE
CENTRAL BRITISH COLUMBIA COAST AND VANCOUVER ISLAND LATER THIS
AFTERNOON. OFFSHORE SURFACE GRADIENTS THIS MORNING WILL BECOME FLAT
THIS AFTERNOON. ACARS SOUNDINGS AND SANDPOINT PROFILER INDICATE THE
AIR MASS ALOFT AS WARMED IN THE LAST 24 HOURS WITH 850 MB
TEMPERATURES NOW NEAR PLUS 4C COMPARED TO NEAR 0C LAST NIGHT AT THIS
TIME. WITH THE RIDGE SHIFTING FURTHER EAST TEMPERATURES ALOFT NOT
WARMING ANY MORE TODAY. WITH THE WARMER AIR ALOFT AND AT LEAST A
LITTLE BIT OF OFFSHORE FLOW THIS MORNING EXPECT HIGH TEMPERATURES
TODAY TO BE SLIGHTLY WARMER THAN TUESDAY WITH THE LOCATIONS FROM
SEATTLE SOUTHWARD GETTING INTO THE LOWER 60S WITH 50S FOR THE
REMAINDER OF THE AREA.

SURFACE GRADIENTS REMAIN FLAT OVERNIGHT INTO THURSDAY MORNING AS THE
FRONT DISSIPATES TO THE NORTH OF THE AREA. WINDS IN THE LOWER LEVELS
FROM 850 MB TO THE SURFACE ALSO REMAINING LIGHT. STILL SOME LEFT OF
LOW LEVEL MOISTURE FROM THE RECENT RECORD RAINS AND WITH THE LIGHT
FLOW AT THE LOWER LEVELS EXPECT AREAS OF LOW CLOUDS TO FORM EARLY
THURSDAY MORNING. WILL GO FOR A WEAK PUSH SCENARIO WHICH WILL KEEP
THE NORTHWEST INTERIOR MOSTLY CLEAR WITH MORNING LOW CLOUDS OVER THE
REMAINDER OF THE LOWLANDS. WEAK UPPER LEVEL RIDGE REBUILDING
SLIGHTLY OVER WESTERN WASHINGTON ON THURSDAY. THIS COMBINED WITH
WHAT SHOULD BE A FAIRLY THIN LOW LEVEL MOISTURE LAYER WILL RESULT IN
SOME SUNSHINE FOR THE AFTERNOON HOURS. HAVE WORDED THE FORECAST
PARTLY SUNNY IN MOST PLACES FOR THE INTERIOR ON THURSDAY.
TEMPERATURES WILL BE UP TO 5 DEGREES COOLER WITH MOST PLACES IN THE
50S.

NEXT SYSTEM TO REACH THE AREA CURRENTLY BACK NEAR 160W. THE MODELS
HAVE BEEN CONSISTENT FOR NUMEROUS RUNS IN A ROW KEEPING THIS FRONT
TOGETHER AS IT MOVES INTO WESTERN WASHINGTON LATE THURSDAY NIGHT
INTO FRIDAY. THIS SYSTEM IS NOT NEARLY AS JUICY AS THE PREVIOUS
FRONTS TO MOVE INTO THE AREA THIS MONTH WITH RAINFALL AMOUNTS OF 0.5
TO 0.75 INCHES ALONG THE COAST...0.25 TO 0.75 OVER THE INTERIOR AND
.5 TO 1 INCH IN THE MOUNTAINS. SNOW LEVELS IN THE MOUNTAINS WILL
REMAIN NEAR 5000 FEET.

.LONG TERM...WHILE THE EXTENDED MODELS ARE SHOWING GOOD RUN TO RUN
CONSISTENCY AMONG THEMSELVES THERE IS STILL NO CONSENSUS ON A
SOLUTION FOR THE WEEKEND AND THE FIRST PART OF NEXT WEEK. THE GFS
CONTINUES WITH THE IDEA OF A RIDGE BUILDING BEHIND THE FRONT ON
FRIDAY WITH A DRY WEEKEND FOLLOWED BY A WEAK FRONT ON MONDAY THEN
MORE RIDGING ON TUESDAY. THE ECMWF IS MUCH DIFFERENT WITH THE RIDGE
FURTHER EAST AND ANOTHER POSSIBLE ATMOSPHERIC RIVER EVEN SETTING UP
OVER WESTERN WASHINGTON RESULTING IN A WET WEEKEND. THE ECMWF QPF
FOR SATURDAY NIGHT INTO SUNDAY SHOWS ANOTHER 2 INCHES PLUS IN THE
MOUNTAINS AND ALONG THE COAST WITH ANOTHER 0.75 TO 1.5 INCHES IN THE
LOWLANDS. THE CANADIAN MODEL IS MORE IN LINE WITH THE ECMWF. EVEN
WITH THE BIG DIFFERENCES IN THE SOLUTIONS FOR WESTERN WASHINGTON THE
MODELS ARE NOT THAT FAR APART WITH THE GFS INDICATING THE HEAVY RAIN
OVER NORTHERN VANCOUVER ISLAND AND THE CENTRAL BRITISH COLUMBIA
COAST. STILL NO FAVORITE MODEL IN THE EXTENDED AND WITH THE LACK OF
CONSENSUS WILL STAY WITH THE CHANCE POPS FOR SATURDAY THROUGH
TUESDAY. FELTON

&&

.HYDROLOGY...WITH THE HIGH DEGREE OF UNCERTAINTY IN THE EXTENDED
FORECAST CAN NOT TOTALLY RULE OUT FLOODING IN THE NEXT 7 DAYS. IF
THE ECMWF SOLUTION TURNS OUT TO BE CORRECT THERE WILL BE A CHANCE OF
MINOR RIVER FLOODING AGAIN ON THE MOST FLOOD PRONE RIVERS LATE IN
THE WEEKEND INTO MONDAY. FELTON

&&

.CLIMATE...SO FAR THIS MONTH SEATTLE-TACOMA AIRPORT HAS RECORDED 5
DAYS WITH RAIN 0.50 INCHES OR GREATER. SINCE RECORDS STARTED AT
SEA-TAC IN 1945 THERE HAS NEVER BEEN A MARCH WITH 6 OR MORE DAYS OF
0.50 INCHES OR GREATER RAINFALL. THE OTHER YEARS WITH 5 DAYS ARE
1950...1957...1971...1997...2003 AND 2012. THIS YEARS WET MARCH
CONTINUES THE TREND OF WET MARCH`S THE LAST FEW YEARS. MARCH 2011 IS
THE 7TH WETTEST AT SEA-TAC WITH 6.29 INCHES AND MARCH 2012 IS 3RD
WITH 7.20 INCHES. THE RECORD IS 8.40 INCHES SET IN 1950. CURRENTLY
THIS MONTH IS IN 9TH PLACE WITH 5.98 INCHES. FELTON

&&

.AVIATION...HIGH PRESSURE SURFACE AND ALOFT. LIGHT OFFSHORE FLOW.
DRY STABLE AIR. PATCHY MORNING FOG. A FEW MID AND HIGH CLOUDS LATER
TODAY AND THEN AREAS OF LOW CLOUDS WILL LIKELY REACH THE COAST
OVERNIGHT FROM A DISSIPATING FRONT.

KSEA...CLEAR SKIES...NLY BREEZE. SCATTERED MID AND HIGH CLOUDS LATER
TODAY...LATE TONIGHT AND THU MORNING SOME LOWER CLOUDS MIGHT WORK
INTO THE INTERIOR OF WESTERN WA FROM A DISSIPATING FRONT.

&&

.MARINE...HIGH PRESSURE OVER THE REGION IS SHIFTING INLAND...GIVING
LIGHT ELY FLOW. A WEAK FRONT WILL DISSIPATE AS IT REACHES THE COAST
THU MORNING. A SMALL CRAFT ADVISORY IS UP FOR THE COASTAL WATERS FOR
SEAS THAT WILL BUILD TO AROUND 12 FT THIS MORNING...AND FOR ROUGH
BAR CONDITIONS. A FRONT WILL MOVE TO THE AREA FRIDAY WITH SMALL
CRAFT ADVISORY CONDITIONS LIKELY ON THE COAST AND POSSIBLE ACROSS
THE INLAND WATERS.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS COASTAL WATERS AND FOR
THE GRAYS HARBOR BAR FOR ROUGH CONDITIONS.

&&

$$

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