FXUS66 KSEW 260537 CCA
AFDSEW
AREA FORECAST DISCUSSION...CORRECTION
NATIONAL WEATHER SERVICE SEATTLE WA
930 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 UPPER LEVEL RIDGE OVER THE PAC NW EARLIER TODAY IS
NOW SHIFTING EAST INTO MONTANA...WHILE A STALLED FRONT LIES OVER
SOUTHERN B.C. AND WESTERN WA. LATEST OBS...ANALYSIS AND SATELLITE
SHOWS THE BULK OF THE MOISTURE AIMED AT THE NORTH COAST...OLYMPICS
AND INTO VANCOUVER ISLAND. KUIL PICKED UP AROUND 1.50 PRECIP SO
FAR TODAY AND ACTUALLY TIED A RECORD HIGH OF 54. FREEZING LEVELS ARE
QUITE HIGH...8400 FT OFF THE 00Z KUIL SOUNDING WITH 38 AND RAIN THIS
HOUR AT HURRICANE RIDGE. OVER TO THE CASCADES...PRECIP MAINLY IN THE
NORTH CASCADES BUT AMOUNTS RELATIVELY LIGHT SO FAR AND UNDER AN
INCH. TEMPS IN THE PASSES ARE ALSO ABOVE FREEZING WITH WA DOT
REPORTS OF RAIN AND DENSE FOG. IN THE INTERIOR LOWLANDS...LIGHT TO
MOD RAIN AT TIMES THROUGH THE NIGHT.
FLOOD CONCERN LOOKS LESS BASED ON THE NEW 00Z MODEL RUNS. WHILE THE
BAROCLINIC BAND REMAINS OVER THE REGION THE FORECAST QPF IS NOT TOO
IMPRESSIVE...AND MOST AREAS SO FAR NOT RECEIVING SIGNIFICANT
AMOUNTS. MAIN FOCUS WILL BE ON THE SKOKOMISH AND BOGACHIEL RIVERS.
SEE HYDROLOGY SECTION BELOW.
THE BAROCLINIC ZONE WILL SHIFT FARTHER E/SE ON THURSDAY WITH RAIN
TAPERING DOWN ACROSS NORTHERN TIER OF CWA ZONES IN THE AFTERNOON.
EXPECT SOME SHOWERS IN THE AREA THU NIGHT AS THE TRAILING UPPER
LEVEL TROUGH BEGINS TO SHIFT INLAND. COOLER AIR WILL ALSO KNOCK SNOW
LEVELS BACK DOWN TO AROUND 3500 FT BY FRI...AND 2000 FT FRI NIGHT.
HOWEVER THERE IS NOT MUCH PRECIP FORECAST AS ANOTHER UPPER LEVEL
RIDGE BUILDS INLAND. A WARM FRONT MAY CLIP THE REGION ON SAT BUT
PRECIP AMOUNTS LOOK MEAGER. 33
.LONG TERM...PREVIOUS DISCUSSION...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...RAIN AMOUNTS HAVE BEEN LIGHT...WITH THE EXCEPTION OF
THE NORTHERN OLYMPIC PENINSULA WHERE STRANGELY THERE IS NO FLOOD
WATCH. KUIL AND THE HOH RANGER STATION ARE PUSHING TWO INCHES OF
RAIN SO FAR...AND BOTH HURRICANE RIDGE AND PORT ANGELES ARE HAVING
GOOD RAINS. THE FREEZING LEVEL SHOT UP ABOVE 8000 FEET. THE
BOGACHIEL RIVER IS RISING RAPIDLY AND WILL CONSIDER ADDING THIS AREA
TO THE FLOOD WATCH.
OF THE OTHER AREAS ONLY THE SOUTHERN OLYMPICS AND NORTH CASCADES ARE
GETTING ANY RAIN AT ALL. THE WILLAPA HILLS AND CENTRAL CASCADES
GAUGES ALL SHOW ZERO RAIN SO FAR. THE FORECAST CALLS FOR ONLY ABOUT
12 MORE HOURS OF SIGNIFICANT PRECIPITATION IN THE OLYMPICS AND NORTH
CASCADES. THEN THE RAIN BAND SHIFTS SOUTHEAST...GIVING AROUND SIX
HOURS OF RAIN TO THE CENTRAL CASCADES. ON THURSDAY NIGHT A MORE
SHOWERY PATTERN DEVELOPS WITH LOWER SNOW LEVELS.
THE BOTTOM LINE IS THIS DOES NOT APPEAR TO BE A FLOOD PRODUCING RAIN
OVER MOST BASINS. THE SKOKOMISH AND THE AFOREMENTIONED BOGACHIEL
COULD EXPERIENCE MINOR FLOODING. IF THERE WAS NO FLOOD WATCH IN
EFFECT FOR NEARLY EVERYWHERE...WOULD NOT ISSUE ONE. WILL CONSIDER
DROPPING THE WATCH FOR SOME AREAS LATER.
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 WILL SEE A TRANSITION INTO A DRY PATTERN WHICH WILL
ALLOW STREAMS TO FINALLY RETURN TO LOWER FLOWS.
NO FLOODING IS EXPECTED ON THE GREEN RIVER. BURKE
&&
.AVIATION...LIGHT RAIN IS DRAPED OVER THE NORTHWEST PORTION OF THE
STATE WITH MVFR CEILINGS. SOUTH OF SEATTLE SO FAR THE EVENING IT HAS
BEEN DRY AND CEILINGS ARE MORE VFR. OVERNIGHT THE NORTHERN AREAS
WILL STAY MVFR WITH LIGHT RAIN AT TIMES AND THE SOUTHERN AREAS WILL
GRADUALLY BECOME MVFR AS RAIN DEVELOPS.
KSEA...CEILINGS WILL GRADUALLY FALL TONIGHT WITH LITTLE IMPROVEMENT
TOMORROW. WINDS WILL BE LIGHT SOUTHERLY OVERNIGHT...BECOMING
NORTHERLY 12-18Z THURSDAY. CHB
&&
.MARINE...WINDS GENERALLY LIGHT OVERNIGHT AND HAVE ALLOWED ALL
WARNINGS AND ADVISORIES TO EXPIRE. EXCEPTION IS A HAZARDOUS SEAS
ADVISORY ALONG THE COAST. THESE CONDITIONS WILL PREVAIL FOR SOME
TIME.
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. STRONG NORTHWESTERLY
PUSH WILL DEVELOP BY FRIDAY MORNING...AND A GALE WATCH IS IN EFFECT
FOR STRONG ONSHORE FLOW IN SEVERAL ZONES. CHB
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...FLOOD WATCH IS IN EFFECT FOR MUCH OF WESTERN WASHINGTON.
PZ...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.
$$
WWW.WEATHER.GOV/SEATTLE
FOR AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION...PLEASE SEE
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML.
