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September 2014
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Weekend Wx Outlook

Posted: September 18th, 2014
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Passing weak systems (via NWS Enhanced AFD)

Clouds and scattered showers will linger into tomorrow (Fri) after another weak system passes through the region tonight. Skies will begin to clear tomorrow afternoon, and dry, warm conditions will prevail through the weekend. Forecast models currently show a series of systems affecting the region, perhaps late Monday, and again by late Tuesday/early Wednesday.

 

While there’s plenty of uncertainty, the National Weather Service currently predicts 0.54 inches citywide and 0.79 inches across both SPU watersheds during the 24-hours ending at 5 PM Wednesday.

 

Excerpts from this afternoon’s NWS Area Forecast Discussion (emphasis added):

 

ZONAL FLOW ALOFT WILL PREVAIL ACROSS THE AREA TONIGHT. A WEAK
SHORT WAVE TROF EMBEDDED IN THIS FLOW WILL RESULT IN SOME SHOWERS
ACROSS MAINLY THE NORTHERN PART OF THE CWA. THE SHOWERS WILL
PERSIST INTO FRI MORNING.

AN UPPER RIDGE WILL BEGIN BUILDING OVER THE REGION ON FRI. THE
RIDGE WILL AMPLIFY THIS WEEKEND. THIS COMBINED WITH LOW LEVEL
OFFSHORE FLOW WILL RESULT IN WELL ABOVE NORMAL DAYTIME TEMPS.
SOME PLACES COULD END UP TYING OR BREAKING DAILY RECORDS.

THE UPPER RIDGE AXIS WILL MOVE OVER THE INTERMOUNTAIN WEST ON MON
AND THIS WILL ALLOW A WEAKENING OCCLUDED FRONT TO APPROACH THE
COAST. THIS FRONT WILL LIKELY DISSIPATE AS IT MOVES ONSHORE. THE
MAIN IMPACT WILL BE COOLER AND CLOUDIER WEATHER MON AND TUE.

BEYOND TUE…A STRONGER SYSTEM WILL IMPACT THE PACIFIC NORTHWEST
DURING THE LATTER PART OF THE EXTENDED PERIOD…RESULTING IN BELOW
NORMAL DAYTIME TEMPS AND BREEZY CONDITIONS. THIS SYSTEM IS
EXPECTED TO REMAIN OFF THE COAST THRU THU.

 

References:
NWS Area Forecast Discussion
NWS Forecast Table Interface