FXUS66 KSEW 252351
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
340 PM PST WED NOV 25 2009
.SYNOPSIS...A FRONTAL BAND WILL MOVE OVER WESTERN WASHINGTON TONIGHT
AND BECOME STATIONARY INTO THURSDAY. A WEAK LOW WILL MOVE UP ALONG
THE FRONT LATE THURSDAY...PASSING NORTHEAST OF THE AREA LATE
THURSDAY NIGHT. AFTER A BRIEF BREAK LATE FRIDAY A WEAK WARM FRONT
WILL AFFECT THE REGION FRIDAY NIGHT INTO SATURDAY THEN LIFT OUT OF
THE AREA SUNDAY. THEN A FINAL COLD FRONT WILL SWEEP SOUTHEAST
THROUGH WASHINGTON LATER MONDAY WITH DRY AND PARTLY SUNNY WEATHER
FOLLOWING FOR THE MIDDLE OF NEXT WEEK.
&&
.SHORT TERM...THE FRONT IS HEADING STEADILY INLAND AND THE IS AS
WELL. IT HAS BEEN RAINING MOST OF THE DAY OVER THE NW HALF OF THE
OLYMPIC PENINSULA WHERE 0.25 TO AROUND AN INCH. THIS WILL CONTINUE
TO SPREAD INLAND TONIGHT WITH FAIRLY STEADY RAIN OCCURRING JUST
ABOUT EVERYWHERE OVERNIGHT. IT WILL BE ANOTHER MILD NIGHT WITH LOW
IN THE 40S WITH THE WARM AIR MASS IN PLACE.
THE FRONT WILL STALL OVER THE AREA LATE TONIGHT AND A WEAK SURFACE
LOW IS EXPECTED TO DEVELOP OVER THE PACIFIC AND TRACK NE ALONG THE
FRONT. THE WEAKER AND FURTHER SOUTH SOLUTION IS BEGINNING TO LOOK
LIKE IT IS PANNING OUT AND THAT HAS BEEN THE ONE WE HAVE LEANED
TOWARD THIS WEEK. THIS MEANS NO REAL CONCERNS FOR STRONG WINDS AND
A RAINFALL DISTRIBUTION THAT IS A LITTLE MORE EVEN RATHER THAN
HEAVILY FOCUSED ON THE OLYMPICS. THE LOW IS EXPECTED TO REACH THE
COAST NEAR ASTORIA AROUND SUN SET THANKSGIVING DAY THEN CONTINUE
MOVING NE INTO NORTHEAST WASHINGTON OVERNIGHT. SO BASICALLY A
MOSTLY RAINY DAY WITH TEMPERATURES 45 TO 50 DEGREES. THE FREEZING
LEVELS WILL BE HIGH THROUGH THURSDAY...SO EXPECT RAIN BELOW ABOUT
5500 FEET NORTH CASCADES AND 6500 FEET CENTRAL AND SOUTHERN
CASCADES.
WITH THE LOW MOVING EAST OF THE AREA THURSDAY NIGHT...THE COLDER AIR
MASS WILL BEGIN TO FILTER IN WITH A SW BREEZE KICKING UP. SNOW
LEVELS WILL FALL TO AROUND 3500 FEET FRIDAY MORNING THEN CLOSER TO
2000 FEET BY FRIDAY EVENING. HOWEVER THE PRECIPITATION WILL BE
WINDING DOWN THROUGH THE DAY FRIDAY SO NOT EXPECTING MUCH
SNOWFALL...GENERALLY A FEW INCHES TO FLUFF THINGS UP A BIT. OUTSIDE
OF THE CASCADES...THE RAIN WILL COME TO AN END FRIDAY MORNING
LEAVING A DRY AFTERNOON WITH THE GOOD POSSIBILITY OS SOME SUNSHINE
IF THE SYSTEM MOVES ALONG AS QUICKLY AS EXPECTED.
THE DRY PERIOD WILL BE SHORT LIVED HOWEVER AS A WARM FRONT WILL
APPROACH THE PACIFIC NW AND SPREAD CLOUDS OVERHEAD FRIDAY EVENING
AND THEN THIS WILL BE FOLLOWED BY RAIN. AT THIS POINT IN TIME THE
RAIN IS PRIMARILY GOING TO BE OVER THE REGION SATURDAY WITH SNOW
LEVELS AROUND 2500 TO 3500 FEET. THIS WILL BE A WARM OVERRUNNING
EVENT AND WE WILL BE ALONG THE SOUTHERN EDGE OF THE SIGNIFICANT
OVERRUNNING...SO AT THIS POINT IT IS HAD TO TELL HOW MUCH
PRECIPITATION WE WILL END UP WITH. THIS IS NOT A CONCERN FOR
FLOODING WE WILL JUST NEED TO PAY ATTENTION TO HOW MUCH SNOW WE WILL
END UP WITH IN THE MOUNTAINS AS THIS WILL AFFECT TRAVEL ACROSS THE
CASCADES SATURDAY. CERNIGLIA
.LONG TERM...DEPENDING ON HOW PRONOUNCED THE RIDGE BECOMES ON THE
WEST COAST SUNDAY WILL DETERMINE HOW MUCH IF ANY PRECIPITATION WE
WILL GET SUNDAY. WITH THE WAY THINGS HAVE BEEN OF LATE WOULD BET ON
A LEAST MOSTLY CLOUDY AND SOME LIGHT RAIN SUNDAY. HOWEVER...IT WILL
NOT TAKE MUCH MORE BUILDING OF THE RIDGE TO SHOVE THE MOISTURE NORTH
OF THE AREA FOR A DRY AND PARTLY SUNNY DAY SO STAY TUNED.
WHAT HAS BEEN FAIRLY CONSISTENT IN THE LONG RANGE MODELS IS A
PATTERN CHANGE TAKING PLACE BEGINNING LATER MONDAY. A COLD FRONT IS
EXPECTED TO SWEEP SOUTHEAST ACROSS THE AREA LATE MONDAY (GIVE OR
TAKE) WITH DRY NW FLOW TAKING OVER IN ITS WAKE. THIS SYSTEM WILL
HELP TO DIG A DEEP TROUGH OVER THE CENTRAL PART OF THE COUNTRY
LEAVING A RIDGE UP OVER THE EASTERN PACIFIC AND PACIFIC NORTHWEST
FOR A PERIOD OF PARTLY CLOUDY SKIES. THIS IS EXPECTED TO BE FOR AT
LEAST TUESDAY AND WEDNESDAY AND QUITE POSSIBLY SIGNIFICANTLY
LONGER. WITH THE CLEARING SKIES WILL COME COOLER TEMPERATURES WITH
LOWS AROUND FREEZING AND HIGHS GENERALLY IN THE 40S. CERNIGLIA
&&
.HYDROLOGY...THE FRONTAL BAND IS MOVING OVER THE AREA NOW WITH RAIN
HAVING PUSHED AS FAR EAST AS THE PUGET SOUND AND THE NORTH
CASCADES. WE HAVE ALREADY PICKED UP OVER AN INCH ON THE NORTH COAST
TODAY WITH THIS BAND. THIS WILL MOVE INLAND TONIGHT AND LAY ACROSS
THE AREA THROUGH THE NIGHT AND INTO THURSDAY. THE MOST SIGNIFICANT
RAINS WILL OCCUR TONIGHT WITH SOMEWHAT LIGHTER RAIN LATER THURSDAY.
THE SURFACE LOW IS NOT EXPECTED TO HAVE SIGNIFICANT DEVELOPMENT AS
IT MOVES INLAND LATE THURSDAY WHICH WILL HELP TO DISTRIBUTE THE RAIN
A BIT MORE EVENLY ACROSS THE REGION AS IT WILL BE TAKING A MORE
SOUTHERN TRACK. THE RAIN WILL TAPER OFF LATE THURSDAY NIGHT BEFORE
ENDING FRIDAY MORNING.
THE AMOUNT OF RAIN EXPECTED WITH THIS SYSTEM WOULD NOT NORMALLY POSE
PROBLEMS WITH AREA RIVERS...HOWEVER MANY OF THEM ARE STILL RUNNING
ABOVE NORMALS AS THEY ARE IN THE PROCESS OF DRAINING OFF THE RAINS
FROM THE EARLIER SYSTEMS. THUS THE EXPECTED RAINFALL WILL
POTENTIALLY PUSH SEVERAL RIVERS IN WESTERN WASHINGTON NEAR TO OR
POSSIBLY A BIT ABOVE FLOOD STAGE THURSDAY EVENING INTO FRIDAY.
OVERALL THIS IS A BIT OF A BORDERLINE SITUATION AND WILL NEED TO BE
WATCHED. CURRENTLY THE RIVERS THAT ARE EXPECTED TO HAVE SIGNIFICANT
RISES AND BE AT RISK OF MINOR FLOODING ARE THE SKOKOMISH...SATSOP
AND POSSIBLY THE BOGACHIEL RIVERS ON THE OLYMPIC PENINSULA AND THE
NOOKSACK...SKAGIT...STILLAGUAMISH NEAR ARLINGTON...SNOQUALMIE NEAR
CARNATION...PUYALLUP AT ORTING AND THE LOWER REACHES OF THE CHEHALIS
RIVER. NOT INCLUDING THE SKOKOMISH...EACH OF THESE ARE CURRENTLY
FORECAST TO CREST A BIT BELOW FLOOD STAGE...IN SOME CASES JUST A FEW
INCHES. BASED ON THAT I WILL BE ISSUING A FLOOD WATCH FOR THESE
RIVERS FOR THE POTENTIAL OF FLOODING LATE THURSDAY INTO THURSDAY
NIGHT.
ONCE WE GET BEYOND THIS SITUATION...THE SYSTEMS OVER THE WEEKEND ARE
TOO WEAK AND COLD TO CAUSE ANY ADDITIONAL RIVER FLOODING PROBLEMS
AND NEXT WEEK WE WILL BE TRANSITIONING INTO A DRY PATTERN WHICH WILL
ALLOW WATER LEVELS TO FINALLY RETURN TO LOWER FLOWS.
NO FLOODING IS EXPECTED ON THE GREEN RIVER DURING THE ENTIRE
PERIOD. CERNIGLIA
&&
.AVIATION...UPPER LEVEL RIDGE AXIS HAS SHIFTED OVER INTO MONTANA
THIS AFTERNOON AS THE BROAD UPPER LEVEL TROUGH OVER THE GULF OF
ALASKA SLOWLY SLIDES TOWARD THE REGION. A FRONTAL BOUNDARY IS
STALLED OFFSHORE...WITH LIGHT RAIN PENETRATING SLIGHTLY FURTHER
INLAND THAN THIS MORNING. VFR CIGS REMAIN FOR THE INTERIOR...
ESPECIALLY SOUTH. AS THE FRONT MOVES IN...CIGS WILL CONTINUE TO
LOWER INTO THIS EVENING SETTLING INTO 3-5 KFT. THE FRONTAL BOUNDARY
WILL WEAKEN AND REMAIN STATIONARY OVER THE AREA OVERNIGHT. CEILINGS
WILL APPROACH IFR AROUND 09Z THURSDAY MORNING AND SEE LITTLE
RECOVERY ON THANKSGIVING. A NEW LOW PRES WILL DEVELOP ALONG THE
STALLED FRONTAL BOUNDARY THURSDAY AND PASS SOUTH OF THE PUGET SOUND
AROUND 00Z FRIDAY. SURFACE WINDS SHOULD GENERALLY REMAIN LIGHT
SOUTHERLY THROUGH THIS EVENING BECOMING OFFSHORE LATE TONIGHT.
NORTHERLY GRADIENTS WILL PICK UP LATE THURSDAY AFTERNOON IN RESPONSE
TO THE LOW TRACKING TO OUR SOUTH. CONFIDENCE HAS INCREASED FOR A
SOUTHERLY TRACK WITH THE SURFACE LOW TOMORROW.
KSEA...CIGS CONTINUE TO GRADUALLY FALL TONIGHT WITH LITTLE
IMPROVEMENT TOMORROW. WINDS WILL BE LIGHT SOUTHERLY
OVERNIGHT...BECOMING NORTHERLY 12-18Z TOMORROW.
&&
.MARINE...SOUTHEASTERLY WINDS WILL EASE THIS EVENING WITH A
FRONTAL BOUNDARY STALLED OVER WESTERN WASHINGTON. WINDS WILL
GENERALLY BE LIGHT OVERNIGHT WILL WEAK PRESSURE GRADIENTS. SEAS WILL
INCREASE OVERNIGHT THROUGH THURSDAY...AND A SCA FOR HAZARDOUS SEAS
HAS BEEN RAISED FOR THE WEST ENTRANCE AND COAST.
A NEW LOW WILL FORM ALONG THE FRONTAL BOUNDARY PASSING THROUGH
WASHINGTON THURSDAY EVENING. CURRENT MODELS HAVE THE LOW TRACKING
SOUTH OF THE WILLAPA HILLS ON A NORTHEAST PATH AND NOT DEEPENING ALL
THAT MUCH. GOOD NORTHWESTERLY PUSH SHOULD DEVELOP BY FRIDAY
MORNING...GENERALLY EASING THROUGH THE DAY ON FRIDAY. DAMICO
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...FLOOD WATCH IS IN EFFECT FOR MUCH OF WESTERN WASHINGTON.
PZ...SMALL CRAFT ADVISORY...COAST...ENTRANCES TO THE STRAIT...
ADMIRALTY INLET...AND NORTH INLAND WATERS THROUGH THIS EVENING.
SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR.
SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS WEST ENTRANCE AND
COAST THROUGH THURSDAY AFTERNOON.
GALE WATCH COAST AND STRAIT OF JUAN DE FUCA LATE THURSDAY NIGHT
THROUGH FRIDAY AFTERNOON
$$
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