Sprinklers or Not?

The first of at least two waves will move through on Monday morning.  This will bring clouds and drizzle or light showers during the morning hours. Only partial clearing is expected later Monday.  Highs in the upper 60’s.

Scott and I have been watching this developing system for a few days, and I think now, with some confidence, we can say that it is likely to rain Tuesday night through Thursday AM. There is a big, broad low pressure developing in the northeast Pacific (associated with a strengthening Aleutian Low). The low will continue to dig a trough out of the jet, as well as slowly push eastward. As it does, it actually entrains an impressive fetch of tropical moisture.

The broad area of vorticity will start to consolidate and push eastward by Tuesday. As it does so, a surface low is projected to develop just off the Northern Washington coast. The low will generate a vigorous surface front that will drape southward all the way to Southern California.

Favorable jet conditions will deliver a whopping amount of rain and snow to the Sierras, and possibly the Santa Barbara area. Our locations looks to be just barely south of the major precipitation, but as of now, the frontal passage should be slow, and bring with it a solid potential for some significant accumulation (for us, anyway). It’s much too early to be able to predict exactly how much, and when.

For now, here’s what we know:

Rain begins along the central coast Monday night into Tuesday morning. The slow moving front may reach Orange County by rush hour on Tuesday. As it does so, the front will weaken, and may not ever *really* reach San Diego. Rain should taper off by Wednesday evening.

Again, this is preliminary, and will likely be amended. Stay tuned for updates!

-Mike

CONTINUED COOL AND MOIST THROUGH WEDNESDAY….

Synopsis: A weak upper-level trough will move over us on Sunday, deepening the marine layer.  As a result, low clouds will return early Saturday evening and deepen overnight Saturday.  Some drizzle could actually happen on Sunday morning.  Hey, we’ll take any moisture we can get. A brief bit of ridging will occur on Monday which will bring slightly warmer temps.  Tuesday, a deeper and more extensive trough will occupy our region.

Saturday eve: Low clouds returning early.  Drizzle is possible against the foothills late.  Lows near 60°F.

Sunday: Mostly cloudy during the morning with a chance of drizzle (mainly against the foothills).  The low clouds will persist throughout the morning hours at least with morning temps in the low 60’s.  Partial clearing during the afternoon is a possibility.  Highs (depending on when the clouds clear) between 68° and 72°F.  Clouds may not clear at all along the coast.

Synopsis: Amplified meridional flow is the dominant pattern across the northern hemisphere.  We are now on the backside of the trough which brought us the cool temperatures of the past couple of days.  Our lowest overnight temperature for the season beginning July 1st is 50°F (Tuesday morning).  Temperatures will rebound slightly for all levels as a ridge currently to our west slides east.  With the exception of night and morning low clouds, upper-level clouds will be a rare occurrence through the weekend.  also, moisture within the atmospheric column will decrease slightly over the next couple of days as we reside under a dry, northwest flow.  A strengthening subsidence inversion will allow for an increase in the depth and persistence of the night and morning low clouds.  Overnight lows will be bumped up a bit into the upper 50’s and possibly low 60’s.  Daytime highs will be mild (upper 60’s to 70’s).

Long-term: A decent system (for this time of year) is projected to hit northern and central California Monday (Oct 12th) through Wednesday.  We could catch the tail-end of a trailing cold front on Wednesday afternoon.  Stay tuned…

Thursday night: Mostly cloudy (low clouds), breezy with a low between 57 and 60°F.

Friday: Morning low clouds clearing to mostly clear skies with a high near 76°F.

Wednesday night: Lows near 53°F with some clouds possible late.

Thursday: Mostly clear with highs in the upper 70’s.

UPDATE:  A solid cloud cover brought on by moisture and dynamics of the upper low moving down our coast from the east will keep temperatures above 50°F Tuesday night.  With expected clearing after midnight, overnight lows are expected to be near 53°F for inland Irvine.  If the clouds persist through the night, lows should stay above 55°F.  Highs near 75°F on Wednesday.

Tranquil conditions will persist for Tuesday evening with a dry and clear atmosphere aloft.  This will allow for the possibility of the coolest overnight lows of the season so far.  Monday and Tuesday morning were the coolest so far since the start of the  season (started in July).  Tuesday night/Wednesday morning could see temperatures in the upper 40’s.  Mike is calling for low temperatures near 49.8F.

Synopsis: A vigorous trough will continue to slide down California through Sunday.  This will bring cooler temperatures, a stronger onshore flow and winds.  A front associated with this system will drag through our region late Saturday night.  There is very little moisture associated with this system so, partly cloudy skies with only a chance of drizzle is possible Sunday morning against the foothills.

Saturday eve: Temperatures will decrease to the low 60’s with breezy, moist conditions and increasing low clouds.

Sunday: Partly cloudy skies with drizzle possible near the mountains and foothills.  Gusty winds are possible during the afternoon (especially for the mountains and passes) with highs only in the upper 60’s/low 70’s.  Sunday or Monday night could be the coldest night so far this fall.  The coldest was 53°F last week.  Low Sunday night of 51°F.

Monday morning: Temperatures in the low-50’s with patly cloudy skies early.

Monday: Nice, mostly clear and breezy.  Temperatures still rather cool, into the low 70’s inland.  Cold overnight temperatures once again, low 50’s.

A big pool of tropical moisture has been lurking off the coast of Baja for the last few days (Correction: The area of tropical moisture formed into Tropical Storm Olaf). Unexpectedly a band of this moisture has drifted northward and is bringing some ACTUAL shower activity to San Diego county this afternoon (see radar image below). An approaching trough from the north will prevent this tropical moisture from moving much further north…thus the headline: “Near Miss!” Ah shucks. We came close, anyway, to an early October shower!

-Mike

PS: There *is* an actual, slight chance of showers this weekend – most likely Sunday. More on this later. (Sunday temps look to be below 70, by the way!)

Synopsis: High temperature at Northpark was 95°F on Thursday, the result of a brief offshore flow.  Troughing along the west coast will dominate the weather for at least the next 4 days.  So, much cooler temperatures are on the way:  The boundary layer will re-moisten on Friday with temperatures in the low-to-mid 80’s;  low 70’s on Saturday.

The possibility for some showers exists Saturday night/early Sunday.  However, there is alot of uncertainty involved.  Stay tuned….