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August 2014
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Monday Morning Wx Outlook

Posted: August 18th, 2014

 

Summer returned over the weekend after last week’s lethargic upper level low finally exited the region. (In the event that you’re wondering, that low is currently drifting through Canada, over the top of Lake Superior.)

 

After a warm day today, we’ll experience some good old fashioned onshore flow with some sun, some clouds and pockets of drizzle through Friday. Actually, models even have a weak Puget Sound Convergence Zone forming on Tuesday evening (as if our dwindling dusk wasn’t ominous enough). Later next weekend is showing signs of a return to the warmth that will probably end up defining the summer of 2014.

 

Excerpts from this morning’s NWS Area Forecast Discussion:

THE WEAK UPPER LEVEL TROUGH OVER THE REGION THIS MORNING WILL DRIFT AWAY THIS AFTERNOON AS STRONGER NW FLOW ALOFT OVER THE NE PACIFIC PUSHES EAST OVER W WA. MODELS ARE REMAINING ON TRACK WITH THE INITIAL UPPER LEVEL SHORTWAVE TROUGH AND THE ASSOCIATED HIGH LEVEL MOISTURE THAT SHOULD MOVE ACROSS W WA LATE TONIGHT AND TUESDAY. THIS SYSTEM WAS OVER THE CENTRAL B.C. COAST THIS MORNING AND EXTENDS OFFSHORE TO THE SW.

THE MODELS CONTINUE TO SHOW CONSISTENCY AND AGREEMENT THROUGH THE EXTENDED FORECAST PERIOD THURSDAY THROUGH SUNDAY. SHORTWAVE ENERGY WILL CARVE OUT A SOMEWHAT DEEPER UPPER TROUGH OVER THE REGION THURSDAY AND FRIDAY…AND THEN THE UPPER TROUGH WILL PROGRESS SLOWLY EASTWARD SATURDAY AND SUNDAY AHEAD OF AN OFFSHORE UPPER RIDGE. THE LOWLANDS WILL PROBABLY CONTINUE TO HAVE DRY WEATHER…AND EVEN IN THE MOUNTAINS — ASIDE FROM POSSIBLY THE NORTH CASCADES — PRECIPITATION AMOUNTS WILL NOT BE ENOUGH TO PROVIDE WETTING RAINS.

 

Climate Notes:

  • 30-year normal high and low temperatures for this week are 76° and 56°; we should stay within bounds until the weekend.
  • Seatac record daily rainfall for this week range from 0.70 to 1.63 inches; not a chance at touching those amounts.
  • This week marks the 10th anniversary of one of the most intense rainfall events on SPU record. An early season frontal system kicked off thunderstorms and heavy rainfall on August 24th, 2004. Capitol Hill, Madison Valley and the University District were hardest hit. One SPU rain gauge (25) collected 0.70 inches in 30 minutes, 1.16 inches in an hour, and 2.26 inches in 6 hours, all good for 100-year (or 99th percentile) recurrences.
  • Though progressing slowly, El Niño remains on track (65% chance) according to the latest from the Climate Prediction Center.

 
References:
SPU Climate Change program