Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 252241 AAA
AFDSEW

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SEATTLE WA
341 PM PDT SAT APR 25 2015

UPDATED THE INCLUDE THE AVIATION AND MARINE SEGMENTS.

.SYNOPSIS...HIGH PRESSURE ALOFT WILL MOVE OVER THE REGION TONIGHT
IN THE WAKE OF THE SYSTEM THAT BROUGHT THE RECENT INCLEMENT
WEATHER. ANTICIPATE A WARM FRONT TO BRING A THREAT OF RAIN TO THE
AREA SUNDAY THROUGH MONDAY MORNING...OTHERWISE HIGH PRESSURE
ALOFT WILL PREVAIL. A COLD OR OCCLUDED FRONT WILL MOVE ACROSS THE
REGION ON TUESDAY.

&&

.SHORT TERM...
THERE WERE SCATTERED SHOWERS ACROSS THE CWA AT THIS TIME. A FEW OF
THE SHOWERS WERE HEAVY AND CONTAINED SMALL HAIL. THE ACTIVITY
SHOULD BECOME CONFINED TO MAINLY THE SOUTHEAST PART OF THE CWA
THIS EVENING. SO FAR...THERE HAS NOT BEEN ANY LIGHTNING STRIKES
BUT THERE IS STILL A POSSIBILITY OF A TSTM OVER MAINLY THE
CASCADES BETWEEN NOW AND DUSK.

MEANWHILE...THE UPPER LOW PRESENTLY OVER THE CWA WILL MOVE INTO
EASTERN WASHINGTON BY LATE TODAY. EXPECT AN UPPER RIDGE TO FOLLOW
IN ITS WAKE. THIS WILL LEAD TO A PERIOD OF DRY WEATHER...
ESPECIALLY OVER THE INTERIOR. A WARM FRONT CURRENTLY WELL OFFSHORE
WILL APPROACH THE AREA DURING THE DAY...RESULTING IN A THREAT OF
PRECIP ACROSS THE WESTERN PART OF THE CWA. THE FRONT IS
ANTICIPATED TO DISSIPATE BEFORE REACHING THE COAST...HOWEVER WARM
AIR ADVECTION WILL RESULT IN A THREAT OF LIGHT RAIN SUNDAY NIGHT.
THE BEST CHANCE WILL BE OVER THE NORTHWEST HALF OF THE CWA.

AMPLIFICATION OF THE RIDGE ON MON WILL CAUSE THE PRECIP THREAT TO
BECOME SHUNTED NORTHWEST OF THE AREA DURING THE DAY. THEREFORE...
EXPECT FILTERED SUNSHINE OVER MUCH OF THE CWA IN THE AFTERNOON.
TEMPS WILL ALSO WARM TO WELL ABOVE NORMAL.

LOOK FOR AN UPPER TROF AND ASSOCIATED COLD OR OCCLUDED FRONT TO
APPROACH THE PACIFIC NORTHWEST MON NIGHT. THE FRONT WILL LIKELY
SWEEP ACROSS THE REGION TUE MORNING. TEMPS SHOULD FALL BACK TO
NEAR NORMAL ON TUE.

.LONG TERM...
CONFIDENCE IN THIS PERIOD REMAINED LOW. THE MODELS WERE IN
BETTER AGREEMENT AS FAR AS WED AND THU WERE CONCERNED...AND
INDICATED AN UPPER TROF WILL MOVE ACROSS THE REGION. THE PRIMARY
DIFFERENCES WERE IN THE DETAILS. BEYOND THU...THE MEDIUM RANGE
SOLUTIONS DIVERGED IN THE TIMING AND STRENGTH OF AN UPPER TROF
DEVELOPING OVER THE PACIFIC NORTHWEST LATE IN THE PERIOD. THE
FORECAST WAS...MORE OR LESS...BROADBRUSHED.

&&

.AVIATION...THE AIR MASS IS CURRENTLY RATHER MOIST AND UNSTABLE BUT
WILL STABILIZE AS THE EVENING PROGRESSES. THE FLOW ALOFT IS BECOMING
NORTHERLY.

SHOWER ACTIVITY WILL DECREASE THIS EVENING AND MOVE SOUTHEAST OUT OF
THE AREA WITH THE UPPER LEVEL LOW. AREAS SOUTH OF SEATTLE ARE MOST
LIKELY TO HAVE ISOLATED SHOWERS FOR THE REMAINDER OF THE EVENING.
VFR CONDS ARE EXPECTED OVERNIGHT WITH THE EXCEPTION OF POSSIBLE FOG
FORMING AT OLM AND HQM. CIGS WILL LIKELY LOWER TO MVFR AND RAIN IS
LIKELY WITH A FRONTAL SYSTEM APPROACHING SUNDAY EVENING.

KSEA...NWLY SFC WINDS WILL CONTINUE THROUGH AROUND 6Z...THERE IS A
BIT OF UNCERTAINTY REGARDING WHEN WINDS WILL SWITCH TO SOUTH
OVERNIGHT...BUT SHOULD BE BETWEEN 3Z AND 9Z. SHOWERS NEAR THE
TERMINAL WILL DISSIPATE OVER THE NEXT FEW HOURS. JSMITH

&&

.MARINE...TONIGHT SCA LEVEL WINDS ARE LIKELY IN THE CENTRAL AND EAST
STRAIT...SO I WENT WITH AN ADVISORY. A WEAK FRONT WILL MOVE THROUGH
THE AREA LATE SUNDAY...AND SOUTHERLIES WILL PICK UP OVER THE WATERS
SUNDAY IN ADVANCE OF THE FRONT. MID TO HIGH END SMALL CRAFT ADVISORY
LEVEL WINDS ARE EXPECTED OVER THE COAST AND MARGINAL SMALL CRAFT
ADVISORY LEVEL WINDS ARE POSSIBLE OVER INLAND WATERS EXPOSED TO A
SOUTHERLY FETCH...HOWEVER HAVE HELD OFF ON ISSUING SCAS FOR ANY
INLAND WATERS.

ANOTHER FRONT WILL SPEED THROUGH THE AREA TUESDAY MORNING...WITH
WINDS OVER THE COASTAL WATERS SHARPLY SWITCHING FROM SOUTHERLY TO
NWLY WITH THE PASSAGE OF THE FRONT. A STRONG WESTERLY PUSH IS LIKELY
IN THE STRAIT WITH THIS FRONT. HIGH PRESSURE WILL BUILD IN BEHIND
THE FRONT ON WEDNESDAY. JSMITH

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORIES ARE IN EFFECT FOR THE CENTRAL/EASTERN
     STRAIT OF JUAN DE FUCA AND THE COASTAL WATERS.

&&

$$

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