Dec. 28 - Jan. 3 West (California) Winter Storm OBS, Last Minute Forecasts & OBS Options

[LALEO]

Things look to get again here in a few days...First in the series of storms is progged for Tuesday/Wednesday time frame for California, While there is a potential for a very large storm for Southern California around New Years.

Atm, Preliminary precip totals throughout the entire forecast period are around 4", However this is likely to change as the event unfolds and gets closer.

Here is the latest NWS discussion for LA/Oxnard.

.SHORT TERM (TODAY-TUE)...
ISSUED A NOWCAST EARLIER THIS MORNING FOR DENSE FOG IN THE LOW LYING
PORTIONS OF SLO AND WESTERN SBA COUNTIES. LATEST OBSERVATIONS AND
SATELLITE DATA SHOWS THAT CONDITIONS ARE IMPROVING...SO THE CHANCE
FOR ENCOUNTERING DENSE FOG CONDITIONS IN THE REGION ARE DIMINISHING
AS THE MORNING PROGRESSES.

LAST NIGHTS STORM WAS PRETTY MUCH AS EXPECTED. COASTS AND VALLEYS
RECEIVED WIDESPREAD RAINFALL AMOUNTS MOSTLY IN THE HALF TO 1 INCH
RANGE...WITH AMOUNTS LESS THAN A THIRD OF AN INCH REPORTED IN THE
ANTELOPE VALLEY. DUE TO THE WESTERLY TRAJECTORY OF THE WINDS...
THERE WAS LITTLE OROGRAPHIC EFFECT WITH THIS SYSTEM. SNOWFALL
AMOUNTS APPEARED TO BE RIGHT ON...WITH PINE MT CLUB REPORTING 4 TO 6
INCHES AND MT HIGH REPORTING 3 TO 7 INCHES OF SNOW...BUT WE WERE A
TAD HIGH ON THE SNOW LEVELS.

NORTHWEST WINDS WILL CONTINUE TO DIMINISH OVER THE MOUNTAINS TODAY
AS THE STORM MOVES FARTHER TO THE EAST...BUT A SIGNIFICANT NORTH TO
SOUTH GRADIENT SETS UP TONIGHT PRODUCING GUSTY NORTHERLY WINDS
THROUGH PASSES AND CANYONS OF THE MOUNTAINS. LOOK FOR THE STRONGEST
WINDS TO BE THROUGH THE I5 CORRIDOR WHERE GUSTS TO 35 MPH WILL BE
POSSIBLE. AT THIS TIME WE EXPECT THE WINDS TO REMAIN BELOW ADVISORY
LEVELS.

THE UPPER TROUGH THAT PASSED THROUGH THE REGION EARLIER TODAY IS
CURRENTLY OVER AZ. A WEAK RIDGE WILL BE OVER THE REGION TODAY...BUT
OVERNIGHT THIS IS REPLACED BY WEAK TROUGHING. IN 24 HOURS THAT
SECONDARY WEAK TROUGH MOVES OVER AZ AND A MORE SUBSTANTIAL RIDGE
BEGINS TO BUILD OVER THE REGION.

WITH WEAK TROUGHING MOVING IN ALOFT...LOOK FOR PARTLY CLOUDY
SKIES FOR THE NEXT 24 HOURS. WITH ALL THE RESIDUAL LOW LEVEL
MOISTURE...EXPECT THAT LOW LYING AREAS WILL SEE SOME FOG AGAIN
TOMORROW MORNING. MOS GUIDANCE IS CALLING FOR THE POSSIBILITY OF
DENSE FOG OVER PORTIONS OF SLO COUNTY. THIS COULD NUDGE INTO THE
WESTERN PORTIONS OF SBA COUNTY...AS WELL. YOU COULD ALSO EXPECT SOME
FOG IN THE MOUNTAIN VALLEYS...AND I WOULD NOT BE TOO SURPRISED TO
SEE SOME IN THE ANTELOPE VALLEY...ALSO...DUE TO THE AMOUNT OF LOW
LEVEL MOISTURE THERE.

ON MONDAY AND TUESDAY...A SLIGHTLY STRONGER RIDGE BUILDS INTO THE
AREA. IT WILL NOT BE STRONG ENOUGH TO DEFLECT HIGH CLOUDS...SO IT
WILL BE PARTLY CLOUDY. IT WILL ALSO NOT BRING MUCH IN THE WAY OF
WARMING. WHILE TEMPERATURES GO UP A FEW DEGREES EACH DAY...HIGHS
WILL STILL BE BELOW SEASONAL NORMS.

LAST NIGHTS STORM

.LONG TERM (WED-SAT)...
MEDIUM RANGE MODEL AGREEMENT IS GOOD THROUGH FRIDAY...THEN SOLUTIONS
START TO DIVERGE. BOTH MODELS BRING A STORM SYSTEM THROUGH THE
REGION ON WEDNESDAY. WHILE THE DETAILS ARE SLIGHTLY DIFFERENT...BOTH
MODELS SUGGEST THAT THIS SYSTEM WILL BE A QUICK HITTER WITH WEAK
OROGRAPHIC INFLUENCE...WHICH IS SIMILAR TO THE SYSTEM THAT PASSED
THROUGH OVERNIGHT. THEN STRONG NORTHWEST WINDS SET UP OVER THE
REGION ON THURSDAY AS A COLD UPPER LOW SETTLES INTO THE GREAT BASIN.
LOOK FOR BREEZY CONDITIONS WITH CLEARING SKIES ON THURSDAY...BUT
WITH TEMPERATURES RUNNING 5 DEGREES COLDER AT THE COASTS TO 15
DEGREES COLDER INLAND THAN WOULD BE NORMAL FOR THIS TIME OF YEAR. IT
WILL REMAIN COOL THROUGH FRIDAY. AT THIS TIME...THE WEEKEND LOOKS
UNSETTLED WITH THE CHANCE FOR ANOTHER WINTER STORM. HOWEVER...THERE
IS SUBSTANTIAL DISAGREEMENT ON THE DETAILS BETWEEN MODELS.

[LALEO]

Also temperatures look to be rather extreme for California, Nor Cal especially. This will also need to be monitored as any moisture around could make for some very low snow levels.

[Beck]

Thanks for making the new thread LALEO

This intensity of the rainfall for my area is uncertain at this point, but snow levels look to drop down to 4000ft!

[LALEO]

I think you are certainly going to be involved in these events Beck. Right now, It's a pretty safe bet.

[alxz310]

The WRF is showing a fair amount of precipitation on Wednesday, similar to last nights. About .5" - .75" within a 6 hour period or so. The New Year's storm is the one of most interest though. Interested to see what the 18Z GFS brings in comparison to the 06Z and 12Z runs.

[LALEO]

Think you guys could get a dusting out of this event Alex?

[Al.J]

LALEO, you need to add the subtopic at the bottom of this thread on your first post, thanks

18Z GFS should be initializing soon more updates to come.

Yeah, I'm not really sure about getting a dusting but certainly at the 1000ft mark they will. It will be interesting to see if Rancho Cordova will end up getting snow before my area does, it seems that it's been happening that way every time we get these cold outbreaks.

This post has been edited by Al.J: Dec 26 2010, 04:29 PM

[LALEO]

LALEO, you need to add the subtopic at the bottom of this thread on your first post, thanks

18Z GFS should be initializing soon more updates to come.

Done! I think...Did I do it right?

[Al.J]

Done! I think...Did I do it right?

Perfect.

[Beck]

I think you are certainly going to be involved in these events Beck. Right now, It's a pretty safe bet.

Oh yeah we'll be involved, snow levels down to 4000ft will be the lowest we've seen thus far in the season, but that's still not near the valley floor. It's enough to throw a sheet of snow on the mountains South and East of the valley here, so we'll get to see that. Really unsure about precipitation though

[wxrat01]

For the weekend...it looks like the 12z ECMWF is trying to get the same idea as the GFS and Canadian models with some type of cutoff low off the Central and Southern California coast.

Thankfully...I am off most of the week so I do not have to deal with the day-today changes in the forecast. However...it does look to be wet sometime next weekend.

Will the Rose Parade be dry?????

[Jet Developer]

EC models are predicting a ridge and offshore flow for next weekend

FOLLOWING THE EC MODEL...THE TROUGH AND ASSOCIATED SHORT-WAVES WOULD
BE E OF SOCAL BY NEXT WEEKEND. THIS WOULD SUPPORT BUILDING SURFACE
HIGH PRESSURE OVER THE INTERIOR WEST AND OFFSHORE FLOW HERE.

Source

This post has been edited by Jet Developer: Dec 26 2010, 04:56 PM

[wxrat01]

EC models are predicting a ridge and offshore flow for next weekend
Source

Well...the 12z ECMWF has an upper low off the NorCal coast Saturday morning where the 00z ECMWF only indicated a weak trough off the Pac NW. It is only one model run...but it could be the start of the ECMWF trending more and more towards the GFS idea.

Admittedly...this forecast will change at least 10 times during the week...but it is something to watch

[Al.J]

Well...the 12z ECMWF has an upper low off the NorCal coast Saturday morning where the 00z ECMWF only indicated a weak trough off the Pac NW. It is only one model run...but it could be the start of the ECMWF trending more and more towards the GFS idea.

Admittedly...this forecast will change at least 10 times during the week...but it is something to watch

It may not change though too much given that the storm rolls in tomorrow night, there is just not enough time left for the models to drastically change their forecasts

[Beck]

Nice day today. My camera made the sun look 50x larger than normal though

[Beck]

Sky is purely white here, with some grey every now and then.

[vb3347]

Sky is purely white here, with some grey every now and then.

Same out here, usually we enjoy clear blue skies. It's been a light grey high overcast all day.

BTW, I did manage to scrape together 0.01" last night.

This post has been edited by vb3347: Dec 26 2010, 06:48 PM

[LALEO]

It is downright ugly outside. No rain, Just extremely dark and ugly clouds outside and a pretty brisk wind kicking up. Certainly feels right for this time of year.

[Beck]

Same out here, usually we enjoy clear blue skies. It's been a light grey high overcast all day.

BTW, I did manage to scrape together 0.01" last night.

Yeah the front was weaker after it went through the LA Basin, we just got the leftovers.

It is downright ugly outside. No rain, Just extremely dark and ugly clouds outside and a pretty brisk wind kicking up. Certainly feels right for this time of year.

Ugly? It's beautiful, actually. Certainly comforting, for some reason.

[Al.J]

Yeah the front was weaker after it went through the LA Basin, we just got the leftovers.
Ugly? It's beautiful, actually. Certainly comforting, for some reason.

It certainly feels like the the end of DEC, with the fog around and the cold temps