Funnel Cloud in Washington, April 24, 2010

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
345 PM PDT SAT APR 24 2010

.SYNOPSIS...IMPROVING WEATHER WILL OCCUR OVERNIGHT AS HIGH PRESSURE
ALOFT MOVES OVER THE REGION. LOOK FOR DRY WEATHER WITH NEAR NORMAL
TEMPERATURES ON SUNDAY UNDER HIGH PRESSURE ALOFT. ANOTHER STRONG
PACIFIC STORM WILL APPROACH THE REGION ON MONDAY...WITH RAIN
DEVELOPING ON THE COAST BY THE AFTERNOON. WET AND UNSETTLED WEATHER
WILL PREVAIL OVER THE AREA MONDAY NIGHT AND TUESDAY UNDER LOW
PRESSURE ALOFT.

&&

.SHORT TERM...
SCATTERED SHOWERS PERSISTED OVER THE CWA THIS AFTERNOON AS EXPECTED.
THIS ACTIVITY WILL WIND DOWN DURING THIS EVENING AS THE UPPER TROF
RESPONSIBLE MOVES OFF TO THE E AND SUBSIDENCE TAKES PLACE.

AN AMPLIFIED...UPPER RIDGE WILL MOVE OVER THE PAC NW OVERNIGHT AND
DOMINATE THE WEATHER PATTERN OVER THE AREA ON SUNDAY. THUS
ANTICIPATE DRY WEATHER ON SUNDAY WITH NEAR NORMAL TEMPS. THE OVERALL
LONG WAVE PATTERN WAS PROGRESSIVE...THEREFORE EXPECT THE UPPER RIDGE
TO MOVE EWD SUNDAY NIGHT AND MON. THIS WILL ALLOW A LARGE AND FAIRLY
COOL UPPER TROF OVER THE NE PAC TO APPROACH THE REGION. THE MODELS
CONTINUED TO DIFFER ON THE TIMING OF THIS UPCOMING SYSTEM...WITH THE
GFS BEING THE FASTEST AND THE NAM THE SLOWEST. THE 12Z ECMWF
APPEARED TO BE A COMPROMISE BETWEEN THESE TWO MODELS. PRIOR TO
SEEING THE LATEST RUN OF THE ECMWF...THE FORECAST WAS ADJUSTED TO
COMPROMISE BETWEEN THE FASTER AND SLOWER SOLUTIONS. CONSEQUENTLY...
THE FORECAST MORE OR LESS FOLLOWS THE ECMWF SOLUTION.

RAIN IS EXPECTED TO DEVELOP OVER THE COAST ON MON AND THEN SLOWLY
SPREAD EWD MON AFTERNOON. IT SHOULD BE RAINING EVERYWHERE BY LATE
MON NIGHT. THE EXCEPTION WILL LIKELY BE PARTS OF THE ERN STRAIT OF
JUAN DE FUCA AND N INTERIOR WHERE STRONG...LEE-SIDE SHADOWING OFF
THE OLYMPICS WILL KEEP THIS AREA DRY FOR A TIME.

SHOWERY WEATHER WILL PREVAIL OVER THE THE CWA ON TUE BEHIND THE
OCCLUDED FRONT. THERE IS A POSSIBILITY OF ISOLATED TSTMS OVER THE
CWA TUE AFTERNOON BUT HAVE OPTED TO LEAVE OUT THEM OF THE FORECAST
FOR NOW DUE TO UNCERTAINTY.

.LONG TERM...
THE PAC NW WILL REMAIN ON THE POLEWARD SIDE OF THE UPPER JET DURING
MUCH OF THIS PERIOD...THUS ANTICIPATE UNSETTLED WEATHER CONDITIONS
TO PERSIST. DAYTIME TEMPS WILL RUN A LITTLE BELOW NORMAL FOR THIS
TIME OF THE YEAR. AN UPPER RIDGE MAY BUILD OVER THE PAC NW DURING
THE LATTER PART OF THIS PERIOD FOR A TREND TOWARD DRIER AND WARMER
WEATHER BUT CONFIDENCE IS NOT VERY HIGH THIS WILL OCCUR.

&&

.HYDROLOGY...
THE MON SYSTEM HAS THE POTENTIAL TO PRODUCE SIGNIFICANT RAINFALL
OVER THE S AND SW FACING SLOPES OF THE OLYMPIC RANGE LATE MON
THROUGH MON NIGHT. RISING FREEZING LEVELS ALONG WITH STRONG LOW TO
MID LEVEL SLY FLOW WILL PROBABLY SERVE TO ENHANCE RAINFALL RATES
OVER THIS AREA. AT PRESENT...RAINFALL AMOUNTS COULD LOCALLY TOTAL
1.5 TO 3 INCHES BY TUE MORNING OR BEFORE THE SNOW LEVEL PLUMMETS TO
NEAR 3500 FEET. AT ANY RATE...WILL NEED TO KEEP A CLOSE EYE ON THE
SKOKOMISH RIVER. IF MODEL TRENDS CONTINUE...A FLOOD WATCH WILL
PROBABLY BE NEEDED AT SOME POINT.

&&

.AVIATION...SCATTERED SHOWERS AND BREEZY THRU EVENING. COOL AIR MASS
IN UPPER TROF OVR B.C. BUT FAIRLY COLD ALOFT AND SOMEWHAT UNSTABLE
OVR WRN WA AS WELL THRU THIS EVENING. THE MTNS WILL CONTINUE TO BE
MOSTLY OBSCURED THRU THIS EVENING IN SNOW SHOWERS AND CLOUDS...WITH
CONTINUED SUNBREAKS FOR THE LOWLANDS...A COUPLE OF GOOD HOLES IN THE
LEE OF THE OLYMPICS AS WELL. LATER TONIGHT THERE WILL LIKELY BE SOME
AREAS OF BKN020 SC THAT SET UP BUT THEN DISSIPATE ARND MID MORNING
SUN IN DRYING AIR MASS AND DVLPG OFFSHORE FLOW. 19

KSEA...BREEZY SW WIND WILL SETTLE DOWN THIS EVENING...KSEA IS IN THE
MIDDLE OF A PRETTY GOOD HOLE IN THE LEE OF THE OLYMPICS SO NOT TIL
LATE TONIGHT IS THAT LIKELY TO FILL IN WITH LOWER SC AND WILL
CONTINUE TO JUST KEEP THAT IN A TEMPO GROUP AROUND DAYBREAK.

&&

.MARINE...DROPPED SOME OF THE SMALL CRAFT ADVISORIES...BUT STILL
RATHER BREEZY COASTAL WATERS...WEST ENTRANCE OF THE STRAIT...AND
PUGET SOUND THIS EVENING. LIGHT OFFSHORE FLOW SUN. STRONG FRONT MON
AND MON NITE. 19

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...A SMALL CRAFT ADVISORY IS IN EFFECT FOR THE COASTAL WATERS...
     WEST ENTRANCE TO THE STRAIT OF JUAN DE FUCA...AND THE PUGET
     SOUND TIL 9 PM TONIGHT.

     SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR ROUGH GRAYS HARBOR
     BAR CONDITIONS TIL 5 AM SUNDAY.

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