More Wet Weather Possible Today and Tomorrow.

The unseasonably energetic upper level low that replaced our unseasonably strong high has resulted in dramatic weather in Southern California, including heavy rain, hail, thunderstorms, lightning, and even a pair of tornadoes near March Air Force base. This UCAR regional radar image from yesterday at 5:00 p.m. shows the intense cell that likely spawned the tornadoes.

In Los Angeles County, very heavy rain was recorded in the San Gabriel Valley. According to a NWS Public Information Statement, as of 7:00 p.m. yesterday, 2.29" was recorded at Santa Fe Dam, 1.51" at Whitter Narrows, and 1.42" at the San Gabriel River at Valley. Yesterday, Downtown Los Angeles (USC) recorded 0.05 inch of rain, bringing the water year total to 13.47 inches.

Intellicast radar shows showers continuing in Southern California this morning. The upper level low is forecast to remain over Southern California into Sunday, and BUFKIT analysis of 12z NAM data for several Southern California stations (VNY, LAX, ONT) suggest on and off rain showers may occur through Sunday morning. As long as the cut-off upper low remains over the area there is also the possibility of an isolated heavy shower or thunderstorm developing. We'll see!

Update Sunday, May 26, 2008. Here is an archived copy of a NWS Public Information Statement with rainfall totals for this event through 6:00 p.m. Saturday.

More information concerning Southern California weather can be found using our WEATHER LINKS page.

Chance of a Shower Next Weekend?

An unseasonably strong and extended Pacific jetstream has resulted in a very high amplitude high pressure ridge over the West Coast with record and near record temperatures seen from Seattle to San Diego.

Yesterday, Woodland Hills set a new high temperature record for the date of 101°F. Record high temperatures were also recorded at Ojai, Sandberg, Santa Ana, El Cajon, Red Bluff, Redding, Sacramento, Stockton, Modesto, San Jose, Eureka and several other stations in California. Triple digit highs were recorded across much of the interior of the state.

It's hot again today, and will be hot again tomorrow, but the GFS, ECMWF and other guidance is suggesting that as the extended Pacific jet collapses, the west coast ridge will retrograde off the coast and be replaced by a trough by Memorial Day Weekend. This would result in cooler weather in California, and even the possibility of showers in some areas, such as the Sierra and our local mountains. We'll see!

More information concerning Southern California weather can be found using our WEATHER LINKS page.

In it's April 30 ENSO Wrap-Up, the Australian Bureau of Meteorology characterizes Pacific climate patterns as being generally neutral, "with the majority of indicators returning to near-normal levels." The April 28 ENSO Update from the CPC suggests that La Niña will continue through May-July 2008, but many of the factors discussed indicate general weakening of the cold ENSO episode.

We've had only a smattering of rain at Downtown Los Angeles since 0.46 inch was recorded back on February 24. A miniscule 0.01 inch was recorded on March 15, and 0.04 inch on April 2. These NOAA/NWS AHPS Precipitation Analyses map the 60 day Departure from Normal Precipitation and 60 day Percent of Normal Precipitation for the southwestern U.S., as of April 30, 2008.

As of May 1, the water year rainfall total for Downtown Los Angeles (USC) stands at 13.42 inches. This is 90% of the 1921-2006 average of 14.87 inches. According to the 1921-2006 dataset, the average amount of precipitation in May and June has been 0.3 inch and 0.1 inch, respectively. Today's NWS 6-10 Day and 8-14 Day Precipitation Outlooks for Southern California continues to indicate Normal precipitation. We'll see!

More information concerning Southern California weather can be found using our WEATHER LINKS page.

A blustery Spring storm is expected to produce measurable rain over much of Southern California tomorrow. As has often been the case this year, the 12z NAM and 12z GFS are at odds, with the NAM generating less than 0.25 inch at Los Angeles, and the GFS more than 0.5 inch.

Today's NWS Precipitation Outlooks for Southern California indicate normal precipitation in the 6-10 day period and below normal for the 8-14 day period. We'll see!

More information concerning Southern California weather can be found using our WEATHER LINKS page.

A weak cold front held together a little better than expected, producing a few showers in the Los Angeles area early Sunday morning. Here is an archived PDF of a NWS Public Information Statement with some preliminary rainfall totals as of 5:00 p.m. No measurable rain was recorded at Downtown Los Angeles (USC- KCQT).

Only 0.01 inch of rain was recorded at Downtown Los Angeles (USC- KCQT) the entire month of March, pulling the water year rainfall total more than a 0.5 inch below normal for the first time this rain season. It looks like there's a pretty good chance of some rain Wednesday. We'll see!

More information concerning Southern California weather can be found using our WEATHER LINKS page.

Weather conditions were tough for the Amgen Tour of California cyclists cranking over Mill Creek Summit yesterday. The Mill Creek RAWS recorded an average temperature of 35°F, with winds of 25 mph, gusting to 40 mph, at about the time the peloton cleared the summit. The Clear Creek RAWS, where riders turned right onto Angeles Crest Highway, recorded about 0.20 inch of rain during the afternoon, with the temperature hovering at around 40°F.

As bad as it was for the tour cyclists, the system was generally not as wet as expected -- particularly in the Los Angeles County mountains, where precipitation amounts ranged from about 0.25 inch to about 1.0 inch. Similar rainfall amounts were recorded in the Los Angeles basin and valleys.

Downtown Los Angeles (USC- KCQT) recorded 0.07 inches of rain Saturday, and 0.46 inches Sunday, bringing the water year total (since July 1) to 13.37 inches, which is about 3.1 inches above normal for the water year to date.

Since mid-week last week some Sierra snow sensors have recorded as much as 8 or 9 inches snow water equivalent of precipitation -- the rough equivalent of 6 or 7 feet of snow. Today's Statewide Summary of Snow Water Equivalents, provided by the California Cooperative Snow Surveys, reports the Sierra snowpack at 119% of normal for the date and 101% of the average April 1 seasonal total.

It looks like most of the west coast weather action will be shifting to the Pacific Northwest for the next week or so. Today's NWS 6-10 Day and 8-14 Day Precipitation Outlooks for Southern California continues to indicate Below Normal precipitation. We'll see!

More information concerning Southern California weather can be found using our WEATHER LINKS page.

Rapidly intensifying Pacific low pressure system approaching the west coast looks very impressive on satellite images this afternoon, with strong upper and low level jet dynamics, a good moisture feed, and a classic baroclinic leaf.

The system is forecast to be filling as it moves onshore, but a very strong jet max moving through the base of the trough should keep the dynamics interesting. In any case, significant rain is expected throughout much of California over the weekend, with heavy snow in the Sierra.

Southern California is forecast to be on the southern margin of the action, however in keeping with the wet trend this rain season, the 18z GFS is forecasting about 1.5 inches of rain at Los Angeles from midday Saturday through Sunday afternoon, and the 18z NAM about 1.0 inch. A moderately strong mid-level southerly to southwesterly inflow should increase precipitation amounts in favored foothills and mountain locations.

Precipitation totals resulting from the passage of the second trough yesterday afternoon into this morning have ranged from about 0.25 to 0.75 inch in the Los Angeles area, with up to about 1.0 inch recorded at some locations. Here is an archived PDF of a NWS Public Information Statement with some preliminary rainfall totals as of 4:00 p.m. Isolated showers have continued to pop up around the Los Angeles area much of the day, but are forecast to be ending in most areas this evening.

Downtown Los Angeles (USC- KCQT) recorded 0.19 inches of rain Thursday, bringing the water year total (since July 1) to 12.84 inches. We're still at a deficit for the month of February, but remain above normal for the water year to date. Much of the February deficit may be erased by Monday. We'll see!

Following this series of systems, a ridge is forecast to build in, resulting in generally fair, Spring-like weather for at least several days. Today's NWS 6-10 Day and 8-14 Day Precipitation Outlooks for Southern California continues to indicate Below Normal precipitation.

More information concerning Southern California weather can be found using our WEATHER LINKS page.

Precipitation totals from the first of a series of shortwaves associated with a extended Pacific jetstream produced rainfall amounts ranging from about 0.1 to 0.25 inch in the Los Angeles area yesterday, with up to about 0.5 inch recorded in some mountain locations.

Downtown Los Angeles (USC- KCQT) recorded 0.14 inches of rain Wednesday, bringing the water year total (since July 1) to 12.27 inches -- still about 2.5 inches above normal for the date. Here is an archived PDF of a NWS Public Information Statement with some preliminary rainfall totals as of 4:00 p.m. yesterday afternoon.

There were a few sprinkles this morning, and Intellicast composite radar shows some shower activity around the area at 12:30 p.m. this afternoon. More general rain is expected to develop this afternoon or evening. Today's 12z NAM projects about 0.6 inch at Los Angeles between now and mid-morning Friday. Over that same period, a BUFKIT analysis of 12z NAM data for Van Nuys projects about 0.75 inch, but an analysis of 12z GFS data generates only about 0.25 inch.

A third system is forecast for the Saturday afternoon into Sunday timeframe and is expected to produce similar amounts of precipitation. However, the upper level flow will be transitioning to a more amplified pattern, so the computer models may have some difficulty with the forecast. We'll see!

Following this series of systems, a ridge is forecast to build in, resulting in generally fair, Spring-like weather for at least several days. Today's NWS 6-10 Day and 8-14 Day Precipitation Outlooks for Southern California are indicating Below Normal precipitation.

More information concerning Southern California weather can be found using our WEATHER LINKS page.

Today's trough was supposed to be an inside slider that stirred up some strong winds, and perhaps some drizzle. A more westward position of the upper low than forecast by yesterday's 18z GFS and NAM, has resulted in a more vigorous system that has produced rain in several areas of the Southland and snow in the mountains.

As of 11:00 a.m. the California Nevada River Forecast Center Los Angeles Area Precipitation Map shows 24 hour precipitation amounts ranging from 0.1 to 0.2 inch, generally south of the Los Angeles basin.

The last few runs of the GFS have been indicating a transition back to a wetter pattern around mid-week of next week, when a strong Pacific jet and a series of shortwave troughs are forecast to target the west coast. It appears that there is the possibility of a significant precipitation event in California, but it's too early to say where, when and how much rain may occur. We'll have to see how things develop over the next few days!

Today's NWS 6-10 Day and 8-14 Day Precipitation Outlooks for Southern California are indicating Above Normal precipitation.

More information concerning Southern California weather can be found using our WEATHER LINKS page.

Sunday's storm added more rain to Southern California's unexpectedly wet water year totals, and more snow to the Sierra snowpack. This rain season western storms have reduced drought classifications by as much as three steps in some areas of California and four in Arizona.

As of February 4, Downtown Los Angeles (USC- KCQT) has recorded 12.13 inches of rain since July 1-- about 4.5 inches above normal for the date. Here is an archived PDF of a NWS Public Information Statement with some preliminary rainfall totals for Sunday's storm.

Sierra snow course measurements for February 1 are coming in and manual measurements are confirming what automatic snow sensors have already reported -- that the Sierra snowpack is well above normal for the date.

Will the wet western weather continue? The GFS and ECMWF medium range models, and NCEP and PSD ensembles are forecasting a generally quiescent, rain free period for Southern California over the next several days, and into the extended period. Today's NWS 6-10 Day and 8-14 Day Precipitation Outlooks for Southern California are indicating Below Normal precipitation.

However, there are suggestions (see Atmospheric Insights) that sometime around February 15-20, the currently active MJO may more or less phase with the GWO, and amplify La Nina to produce a energetic, extended Pacific jet and west coast trough, similar to what occurred around January 3, 2008. We'll see!

More information concerning Southern California weather can be found using our WEATHER LINKS page.

According to NWS Preliminary Climatology Data (CF6), Downtown Los Angeles has recorded measurable rain on each of eight days from January 21 to January 28, 2008. This puts it in the top six of the station's wettest periods from 1921-2007.

Downtown Los Angeles (USC-KCQT) has recorded 5.78 inches of rain over the period, bringing its water year total to 11.73 inches -- nearly 5 inches above normal for the date. Even if Los Angeles were to receive no rain through the entire month of February, we would still go into the month of March ahead of normal.

And it doesn't look likely that we'll have no rain this February. Today's NWS 6-10 Day Precipitation Outlook for Southern California is Above Normal, and the 8-14 day outlook is Normal. We'll see!

Here is an archived PDF of a NWS Public Information Statement with some preliminary rainfall totals for our most recent storm -- from 4:00 p.m. Saturday to 10:00 a.m. this morning.

Update 01/29/08. Early this morning the NWS released a Public Information Statement (PDF) with the rainfall totals for the eight day period from January 21 to January 28.

More information concerning Southern California weather can be found using our WEATHER LINKS page.

Computer weather simulations can be impressive, but sometimes the models just don't get it. That was the case overnight and into this morning as the Los Angeles area was hit by thunderstorms, heavy rain, and hail. Rainfall totals around the area generally ranged from about 1.5 to 3 inches, with some foothill and mountain location recording much more. OPIDS Camp, near Mt. Wilson in the San Gabriel Mountains recorded 6.27 inches for the 24 hour period ending at 8:00 this morning.

As has been the case several times this rain season, the GFS provided a better rainfall guesstimate than the NAM, forecasting 1.5 inches at Los Angeles through today, compared to the NAM's paltry 0.5 inch. Here are a CNRFC graphic of 24 hour rainfall totals in the Los Angeles area, a PDF of some preliminary Los Angeles County rainfall totals, and another PDF of a NWS Public Information Statement with some preliminary rainfall totals for the ongoing rain event. Several stations have recorded more rain since Monday than during all of last year's rain season.

Now attention turns back to the large upper level low spinning off the coast. The extensive circulation around this low is forecast to interact with the southern branch of the jet stream and an associated plume of sub-tropical moisture, and draw the jet and moisture into Southern California overnight on Saturday. According to NAM, GFS and high resolution NMM and ARW, the strongest dynamics and precipitation are forecast for Northern and Central California, however heavy precipitation is also expected in Southern California.

The 12z NAM and GFS are in better agreement than in recent days, projecting about 2.5 inches at Los Angeles from early Saturday morning to early Monday morning, with peak rain rates around 1:00 a.m. on Sunday. A BUFKIT analysis of 12z VNY data shows a strong, saturated, veering, southeasterly to southerly inflow, turning southwest over a six hour period from about 9:00 p.m. Saturday to 3:00 a.m. Sunday. This could produce significant orographic enhancement of precipitation on favored foothill and mountain slopes. Wet antecedent conditions at the lower elevations, and the possibility of rain on snow at the middle elevations, could increase runoff.

Update 01/26/08. Today's models appear to be indicating stronger dynamics in the south with more embedded vorticity, more diffluence aloft, and more favorable jet stream dynamics, but the 18z NAM and GFS are still cranking out about 2.3 inches at Los Angeles, beginning this evening, continuing through Sunday night, and tapering off Monday morning. Strong southerly inflow could produce much more than this in the foothills and mountains, particularly on south facing slopes. As the upper level low moves onshore on Sunday afternoon, thunderstorms could produce very heavy rain in areas where the soil iis already saturated.

Here is a NWS Public Information Statement with the preliminary rainfall totals for the period 4:00 p.m. Monday afternoon, to 4:00 p.m. Friday afternoon.

Please refer to your local NATIONAL WEATHER SERVICE FORECAST OFFICE for official forecasts and warnings.

More information concerning Southern California weather can be found using our WEATHER LINKS page.