SLO County weather forecast for the week of Sept. 16

pgeweather@pge.comSeptember 15, 2013 

Here is this week’s weather forecast from PG&E meteorologist John Lindsey:

A few areas of coastal morning low clouds and fog will develop this morning, but will quickly clear later in the morning in advance of an approaching trough of low pressure that will give another day with mild temperatures and plentiful sunshine. Today’s maximum temperatures will be in the 60s along northwesterly facing beaches (Morro Bay, Los Osos, Montaña De Oro and the Nipomo Mesa) and the westerly facing beaches (Pismo Beach, Grover Beach and Cambria). Southwesterly facing beaches (Cayucos, Avila Beach and Shell Beach) will reach the low 70s. Coastal valleys will hit the mid-70s, with low 90s across the North County.

An upper-level trough will pass through California tonight. A 1,025-millibar Eastern Pacific high will move in behind this area of low pressure and will produce moderate gale to fresh gale-force (32- to 46-mph) northwesterly winds along the coastline by Tuesday afternoon, decreasing Tuesday night. These winds will mix out the temperature inversion layer and will give clear and sunny skies throughout San Luis Obispo County.

Gentle to moderate (8- to 18-mph) northerly winds during the morning hours will keep the marine layer to a bare minimum along the beaches Wednesday and Thursday. Strong to gale force (25- to 38-mph) afternoon northwesterly winds will continue to produce plenty of sunshine and mild temperatures through Friday.

An early season cold front will move through Northern California this weekend with increasing chances for rain for areas north of the Bay Area. Along the Central Coast, moderate gale to fresh gale-force (32- to 46-mph) northwesterly winds, cooler temperatures and variably cloudy skies are expected this weekend. Warmer weather is then set to return to the region the following week as we begin to settle into autumn. The long-range models are not indicating any rain for San Luis Obispo County.

Today’s surf report

The surface charts and models are indicating a steep pressure gradient developing along the California coastline today through Friday. This condition will produce a 4- to 6-foot northwesterly (310-degree deep-water) sea and swell (with a 5- to 11-second period) along our coastline later today, increasing to 5 to 7 feet (with a 7- to 11-second period) Tuesday into Wednesday. This northwesterly (310-degree deep-water) sea and swell will decrease to 4 to 6 feet (with a 7- to 11-second period) Thursday, further lowering to 3 to 5 feet by Friday.

Tropical Storm Man-yi will become extratropical as it moves across the northern Pacific Ocean and intensify to 960 millibars. A 6- to 8-foot northwesterly (300-degree deep-water) swell (with a 14- to 16-second period) from this system will arrive along our coastline Saturday. Combined with this northwesterly swell will be 4- to 6-foot locally generated short period seas this weekend.

Seawater temperatures

Seawater temperatures will range between 57 and 61 degrees through Thursday, decreasing to 55 to 58 degrees on Friday and will remain at this level through Saturday.

John Lindsey’s Weekly Forecast is special to The Tribune. Email him at pgeweather@pge.com.

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