National Weather Service

Visible satellite image at 12:30 p.m. shows a disorganized low off the south-central Oregon coast draping a weak front off California's Redwood Coast. This front has brought overcast to the far northern Sacramento Valley.

National Weather Service

Visible satellite close-up of cloud cover over far Northern California and Southern Oregon. Overcast is gradually dissolving over the Sacramento Valley as the lower atmosphere dries and westerly flow sinks with the terrain. But lift provided by the mountains will probably keep up-country skies socked in.

Unisys

Ridge-trough pattern forecast for 500 mb (roughly 19,000 feet, or half-way through the atmosphere) at 5 p.m. today. The mound of orange contours indicates higher heights and warmer air (since warmer air pushes higher into space) moving over the north state today. The trough (the U-shaped green wedge indicating lower 500 mb heights and cooler air) that brought us Friday's rain and Saturday's showers has moved over the Rockies. Warmer -- though not too warm -- and drier weather is on the way.

Unisys

Ridge-trough pattern at 500 mb (19,000 feet, or half-way through the atmosphere) forecast for 5 a.m. Wednesday. Warm air sits over Northern California with cooler air over the Pacific Northwest, creating a tight thermal gradient indicated by the tightly-packed contours. This pattern indicates strong westerly winds aloft. The black isobars or lines of equal surface pressure are also tightly packed across Northern California, indicating strong surface winds. Isobars oriented west-to-east across the north state indicate a north-south pressure gradient. Winds will start blowing out of the north Tuesday afternoon and may keep blowing into Saturday.

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UPDATE:

Moisture ahead of a weak occluded front sitting off the Redwood Coast has brought clouds which have threatened rain on a day that was supposed to bring abundant sunshine.

As the front weakens this afternoon, the widespread overcast will give way to sun breaks and even partly cloudy skies over the far northern Sacramento Valley. But the clouds may not clear the mountains.

The persistent cloud cover has helped hold temperatures in the low 60s as we approach the warmest part of the day. The latest forecast soundings indicate less clearing later today than those consulted earlier.

Given the persistent overcast, top temps in and around Redding will struggle to hit 70 degrees.

END UPDATE

Warmer and drier air will push in from the Pacific today as the deep disturbance that brought us our most significant precipitation since February barrels into the Rockies.

But temperatures won’t exactly be shooting up just yet. A weak warm front off the Redwood Coast is spreading mid-level clouds across the north state.

The valley floor should top out in the mid-70s, or possibly a little higher, depending on the clouds. We'll wind up well below the 84-degree normal for the date. It’ll be just warm enough for shorts and a t-shirt.

Redding Municipal Airport reported a mild 55 degrees just before 5 a.m. with overcast skies. The dew point temp was 53 degrees, indicating the air this morning is rather moist and close to saturation.

This moist air will keep us from getting quite as warm as we might if the air were dry, since some of the sun’s energy will go to evaporation. And of course, the clouds will block the sun.

Forecast soundings suggest the atmosphere will stay fairly moist up to about 10,000 feet well into afternoon. So we should see lots of clouds much of the day, though less cloudiness as the day goes on.

Even though warmer air is moving in aloft, there are no strong boundaries between warm and cool air at the surface and pressure gradients are close to zero. So winds will stay light.

Windy week ahead

Monday should bring us another excellent Indian summer day, with afternoon temps touching the low 80s and continued light winds.

But Tuesday brings a change that will quickly erase Friday’s soaking rain.

The pressure gradient between Medford and Redding is forecast to jump to 6.8 mb (millibars) by late Tuesday morning and hit 9.2 mb by that evening as a surface high builds over the Pacific Northwest. This is a classic recipe for dry, gusty north winds over the far northern Sacramento Valley.

These winds won’t blow too hot – top temps will likely stay in the seasonably mild mid-80s and may even cool back into the upper-70s later in the week.

But we may be stuck moisture-eating north to northeast winds until Saturday afternoon, when pressure gradients across the north state are supposed to finally ease.

Bottom line: we’re not out of fire danger yet.

More rain after mid-month?

Long-range forecasts indicate fair and seasonably warm weather through Wednesday, Oct. 15, and then a pattern change leading to somewhat cooler-than-normal conditions with slight precip chances Oct. 16-20.

Forecasters will be watching this possible pattern change around mid-month. It doesn’t look like much now, but could become significant as models over the next week or so get a better handle on how the global atmosphere will evolve.

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