Funnel Cloud in Washington, April 28, 2009

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
320 PM PDT TUE APR 28 2009

.SYNOPSIS...ISOLATED TO SCATTERED SHOWERS ARE EXPECTED TONIGHT AND
WEDNESDAY ACROSS WESTERN WASHINGTON AS A BROAD UPPER LEVEL LOW
REMAINS OVER THE PACIFIC NORTHWEST. SHOWERS WILL TAPER OFF WEDNESDAY
EVENING AS THE UPPER LOW BEGINS TO SHIFT SOUTHEAST INTO EASTERN
OREGON. DRIER AND WARMER WEATHER IS EXPECTED ON THURSDAY AS THE AREA
REMAINS IN BETWEEN WEATHER SYSTEMS. A WARM FRONT MAY SPREAD RAIN
INTO WESTERN WASHINGTON OVER THE WEEKEND.

&&

.SHORT TERM...THE AIR MASS OVER WESTERN WASHINGTON REMAINS
COOL...MOIST AND UNSTABLE AS A BROAD UPPER LEVEL LOW SPINS OVER THE
REGION. THE CENTER OF THE UPPER LOW IS NOW LOCATED OVER THE COASTAL
WATERS...WITH PRETTY GOOD CYCLONIC FLOW SHOWN ON THE IR SATELLITE.
AS A RESULT...SHOWERS/CUMULUS FIELD OVER THE MOUNTAINS ARE DRIFTING
WEST AND OVER THE LOWLANDS. THE KATX RADAR SHOWS MAINLY SCATTERED
SHOWERS ACROSS THE STRAIT AND CENTRAL INTERIOR...AND SHOULD SEE
SHOWERS TAPERING DOWN OVERNIGHT WITH THE LOSS OF HEATING. DRIER AIR
IS FOUND ACROSS THE NORTH INTERIOR WITH NELY FLOW THROUGH THE FRASER
RIVER VALLEY. BELLINGHAM DEW POINT HAS DROPPED TO THE LOW 20S WITH
NE BREEZE 10 TO 20 MPH...AND KBLI TO CYWL PRES GRADIENT UP TO -9 MB.
THE VISIBLE DOES NOT SHOW MUCH CU ACROSS THE NORTH CASCADES...WITH
JUST ISOLD SHOWERS POSSIBLE EARLY THIS EVENING...THEN DRY CONDITIONS
OVERNIGHT.

THE UPPER LOW WILL SLOWLY DRIFT SOUTH THEN EAST ON WED WITH THE
CENTER MOVING INTO CENTRAL/EASTERN OREGON WED AFTERNOON. MAY STILL
SEE SOME WRAP AROUND SHOWERS ACROSS WESTERN WA...WITH SHOWERS AGAIN
DRIFTING WEST OFF THE CASCADES/OLYMPICS. LOW LEVEL FLOW REMAINS
OFFSHORE SO NOT EXPECTING MUCH ACTION ACROSS THE AREA WITH LOW END
20 POPS ACROSS THE REGION. SHOWERS WILL DIMINISH WED EVE.

WESTERN WASHINGTON REMAINS IN BETWEEN WEATHER SYSTEMS THU INTO FRI
AS A DEFORMATION ZONE SET UP RIGHT OVER THE AREA. CLOUD COVER MAY
BE TRICKY AS CIRRUS INVADES FROM THE SOUTH BUT WILL INDICATE MOSTLY
SUNNY SKIES FOR FRI WITH WARMER TEMPS. MOS GUIDANCE SHOWS TEMPS
SLIGHTLY ABOVE OUR SEASONAL NORMS WITH HIGHS IN THE MID 60S TO
LOWERS 70S FORECAST ACROSS MOST SPOTS. 33

.LONG TERM...MODELS SHOW A WARM FRONT DEVELOPING OFFSHORE ON
FRI...WITH RAIN POSSIBLY SPREADING INLAND FRI NIGHT OR SAT. THE GFS
REMAINS MUCH FASTER WITH THIS FRONT...HOWEVER THERE IS NO
CONSISTENCY WITH THE ECMWF. IN FACT THE EURO ACTUALLY SPLITS THE
SYSTEM AS IT APPROACHES AND KEEPS THE REGION DRY...PERHAPS THE
LIKELY SOLUTION. WILL HOLD OFF ON ANY CHANGES BUT MAY NEED TO CUT OR
REMOVE POPS COMPLETELY IF THE GFS TRENDS TOWARD THE EURO SOLUTION.
TIMING IF OFF THROUGH THE REMAINDER OF THE LONG TERM PERIOD BUT WITH
NEAR ZONAL FLOW WILL KEEP TEMPS AND POPS NEAR CLIMO. 33

&&

.AVIATION...UPPER LEVEL LOW SPINNING OFF THE COAST AND KEEPING CLOUD
BANDS OVER WESTERN WASHINGTON. THERE IS ENOUGH INSTABILITY IN THE
AIR MASS TO KEEP SCATTERED SHOWERS GOING...AT LEAST UNTIL SUNSET.
CONDITIONS ARE MOSTLY VFR WITH CEILINGS 5K FT OR HIGHER. HOWEVER
THERE IS A SCATTERED DECK 2-3K FT WHICH THREATENS TO BECOME AN MVFR
CEILING IN SHOWERS AT ANY TIME.

KSEA...LIGHT SW WIND BECOMING LIGHT NE AFTER 02Z. CHB

&&

.MARINE...OFFSHORE AND NORTHERLY GRADIENTS TODAY...EXCEPT THROUGH
PUGET SOUND WHERE THE GRADIENTS ARE SOUTHERLY AND WINDS ARE LIGHT
SOUTH OR WEST. AT THE MOMENT WINDS ARE NE 15-20 KT IN OUTFLOW AROUND
BELLINGHAM AND E 15-20 KT AT THE WEST ENTRANCE. GRADIENTS ASSOCIATED
WITH THESE WINDS ARE DIMINISHING...UIL-BLI IS ACTUALLY POSITIVE...SO
HAVE OPTED TO STAY BELOW SMALL CRAFT ADVISORY STRENGTH WINDS AT
THESE SPOTS. IN THE SOUND HAVE STARTED WITH LIGHT SW WINDS AND AM
HOPING THE MODELS TURN OUT TO BE RIGHT AND THE WINDS COME AROUND TO
NORTHERLY THIS EVENING.

PATTERN CONTINUES FOR A COUPLE OF DAYS...WITH ADVISORY LEVEL WINDS
POSSIBLE AT THE WEST ENTRANCE AND OVER THE NORTHERN INLAND WATERS
BRIEFLY DURING THIS PERIOD. NEXT REAL FRONT NOT DUE UNTIL SATURDAY
NIGHT OR SO. THIS SEEMS STRONG ENOUGH IN THE MODELS FOR SMALL CRAFT
ADVISORY WINDS MOST WATERS. CHB

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...NONE.

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