Weather Synopsis – January 13, 2025

James Murakami

DayDateHigh/LowForecast
Mon13th67/54Sunny remainder of day. Clear evening and possibly breezy at times.
Tue14th69/56Sunny day. Clear evening.
Wed15th71/55Sunny day. Clear evening.
Thu16th67/53Sunny day. Mostly clear evening.
Fri17th63/50Mostly sunny day except chance of some morning low clouds. Chance of evening low clouds.

Synopsis

[Note: Absence of a issued forecast last Friday was due to technical problems on my end. Problem was resolved earlier today.]

The dry start to the year continues. Yet another off-shore flow event has begun, and occasional, noticeable bouts should persist through Thursday. Even after a predicted waning of the off-shore flow late this week, another upturn in off-shore flow is probable (as early as Sunday).

A weak but inert (cloud-wise), upper level trough was located a couple hundred miles southwest of Point Conception early this afternoon. High pressure aloft was nosing into the Pacific Northwest, and this couplet is responsible for the current increase in the off-shore flow. Unlike last week’s initial wind storm, this one won’t be as ferocious in most areas (nor quite as persistent). The deep layered, wind support this time around will favor more of the west-east oriented canyons/passes than north-south oriented ones (last Tuesday event favored the latter). That is not to say that this developing event won’t be consequential, but the wildfire battered areas should not, in theory, experience as windy weather as early last week. The more easterly oriented winds shouldn’t favor significant wind (25 mph or higher) in the campus area, but I left a chance of occasional, breezy conditions tonight. Again peak gusts should remain far below last week’s highs (UCLA recorded a peak gust to 44 mph last Tuesday evening…as high 100 mph gust was reported in some mountain locales).

After peaking late tonight, Santa Ana winds in most areas should decrease. It should, however, be far from calm in most of those wind prone areas. Another uptick in wind is predicted by most of the numerical models late tomorrow evening and early Wednesday, but that period should be less windy than what’s expected tonight. There should be a general decrease in the off-shore flow on Thursday (NAM model forecast for yet a third uptick in winds currently rejected…solution appears to be an outlier solution).

Marginal on-shore flow is anticipated Friday, and a full fledged, on-shore flow is currently forecast for Saturday (aforementioned upper low pressure predicted to track back inland but south of the border). While I show a chance for marine layer clouds as early as Friday, confidence is low at this time (predicted, low level winds not all that favorable for marine layer clouds). At one time, some model solutions indicated some instability showers developing over parts of the Southland late Thursday or Friday (mainly near southern state border). Current model forecasts have all but abandoned that scenario.

With or without a marine layer, a northerly wind flow aloft will transport cool air into the region on Saturday (on the dry side, if a marine layer doesn’t form). Cooler than normal weather in the Southland may be short-lived though (after slightly warmer than normal weather earlier in the week). The influx of polar air into the interior is expected to return the off-shore flow as early as Sunday (marginal at first). Depending on which model solution verifies, a new, relevant Santa Ana wind event could occur early next week (sometime in Monday-Tuesday window). While weaker with the winds later, off-shore flow potentially could stick around for all of next week. Warmer than normal weather could develop by the middle of next week (lasting into the subsequent weekend).

Longer range model forecast have wavered on a potential return to wet weather in the state. At one time, it looked promising for a couple of storms hitting the state sometime late next week. If today’s model consensus holds true, however, the state may remain dry for the rest of the month (at the least, the southern half of the state). Completely dry Januarys are a very rare.

Next issued forecast/synopsis may be on Friday, 17 January.