RAIN CHANCES THIS WEEKEND

A few showers are possible on Saturday, though it won't be a washout. A sprinkle or two could linger into Sunday, but most of the day looks dry. New Year's Eve and New Year's Day both look dry and cool.

WEATHER OUTLOOK FOR CHRISTMAS & NEW YEAR'S

We will have a chance for some showers Sunday into Monday (Christmas Eve), then Christmas looks dry and cool. A better chance for rain should arrive by the middle of next week (Wednesday). A cold blast of air will follow behind for the end of next week (Thursday, Friday). I'm also watching for the possibility of more rain for the end of the month (Sunday 12/30), however, it looks like New Year's Eve and New Year's Day will be dry.

SOME MORE RAIN HEADED THIS WAY

A few showers will pass the area tonight and into Tuesday. Most of the rain should be gone tomorrow afternoon and evening. Some light rain could return for the upcoming weekend as well, though there are some uncertainties on the strength of this next system.

RAIN TOTALS FRIDAY & SATURDAY 12/14/2012 TO 12/15/2012

SAN DIEGO COUNTY RAINFALL TOTALS, THURSDAY DECEMBER 13, 2012

A passing shower is still possible tonight, however, it won't amount to much. Here are the totals from earlier today - many areas received over an inch of much needed rainfall.

 

 

UPDATE: THURSDAY 7:30 AM

A round of widespread moderate to heavy rain showers will continue to drift east over the next couple hours (8-10 AM). An isolated shower or thunderstorm could bring a quick downpour in the afternoon and evening, however, the rain will not be nearly as widespread as it was this morning. Rain chances then diminish by Friday morning.

It looks like this weekend's rain chance has moved into Saturday instead of Sunday. Some light rain is also possible for the middle of next week.

ACTIVE WEATHER AHEAD

We will see a couple storm systems in the near future. These will bring SoCal our first threat for some real rainfall. A few showers will arrive late Wednesday and intensify into early Thursday. Another chance for rain will arrive Sunday and possibly again by the middle of next week.

WINTER OUTLOOK 2012-2013

 

 

SUMMARY

The past couple months have been warm and dry in San Diego. Given the overall state of the atmosphere and Pacific Ocean, I think this trend will continue through the winter of 2012-2013. Average rainfall during meteorological winter (December, January and February) is 5.78". I'm expecting 2 to 5". The average high temperature for December, January and February is 64.7, 65.1 and 65.0 respectively. I'm expecting average highs to hover 1 to 2 degrees above these values. It is important to remember that these are averages - there will still be cold rainy days this winter.

The areas to watch this year will be the Pacific Northwest for flooding rains, and the northern Ohio River Valley into New England for potentially heavy snow events. In addition, I'm expecting drought conditions to continue/worsen for the High Plains and parts of the northern Midwest. The Southeast could also see increasing drought conditions.

For my snow-loving friends in Richmond, there should be several chances for a big snow this winter. For this reason, I'm going for above-average total accumulations for December through February (9 to 14"). 

MASSIVE RAIN AMOUNTS EXPECTED FOR NORCAL

Here is an interesting link about Atmospheric Rivers and forecasting heavy rain events.

 

http://www.esrl.noaa.gov/psd/atmrivers/

 

Northern California is going to get hard with heavy rains (look at the 7-day computer forecast to the left). However, I'm only expecting a few showers here in San Diego on Thursday, Friday and Sunday.

WARM & DRY...BUT CHANGES AHEAD?

The next four days look fantastic! In fact, Friday and Saturday will be warm with highs inland approaching the low 80s. Although morning fog will loom, I'm not expecting any rain.

You can see on the image to the left that a massive high pressure ridge hovers over most of the western United States.

EL NINO PROBABLY A NON-FACTOR THIS WINTER

The lastest imagery continues to show neutral conditions along the equatorial Pacific. This trend will probably persist for the next couple months. The winter forecast will be a challenge this year! I plan on posting my outlook by December 1st.

 

SLIGHT CHANCE FOR RAIN THIS WEEKEND

A passing light shower or drizzle will be possible on-and-off through Saturday and into Saturday night. Not a washout - rain totals only 0.1" or less. It shouldn't be a major concern if you plan to be outside. In fact, I will be riding my bike to Ocean Beach tomorrow and will only bring my wind breaker. Rain chances will completely diminish early Sunday morning. Have a great weekend!

UPDATE ON RAIN CHANCES FOR FRIDAY, SATURDAY & SUNDAY

An isolated light shower will be possible Friday, otherwise, most of the day looks dry. A few showers are still possible Saturday into early Sunday. It doesn't look like a lot of rain, but you will want to keep your umbrella handy if you plan to be outdoors. As you can see on the image to the left, the vast majority of rain will hit the Central Coast and especilly Northern California. Snow levels will stay well above 5000 feet, so only the tallest mountains will see any accumulations.

SLIGHT CHANCE FOR RAIN FRIDAY, SATURDAY, SUNDAY

FIRST BIG FRONT OF THE SEASON

Now that rain season is about to start, I think it is time to dust off this blog and provide some updates.

Big Warm Up For Southern California This Upcoming Weekend

Today and tomorrow will be warm, then a cold front will bring some mild air to the area for Wednesday through Friday. Afterwards, we are headed towards a major shift in the weather pattern starting this weekend. We should see several days with high temperatures in the upper 70s to possibly mid 80s inland and mid to lower 70s along the coast. I don't see any rain for at least the next 10 days.

UPDATE ON WEEKEND STORM SYSTEM IN SOUTHERN CALIFORNIA

I'm about a week late in posting this, but I've been insanely busy at the brewery training for my new position.

Showers should arrive early tomorrow morning, then we will see periods of moderate to heavy rain in the afternoon and evening. The chance for rain will persist into Sunday, but showers will be more widely scattered as the trough axis (storm's core) shifts east. An isolated shower could linger into Monday, but most of the rain will be gone.

Rain totals will be impressive with this system. Most of San Diego County could see 1 to 2" with higher amounts in the mountains.

Snow levels will start at 5000 to 7000 feet early Saturday. They will then drop to 4000 to 5000 feet Saturday night. Snow levels could dip as low as 3000 to 4000 feet on Sunday. Accumulations will be impressive with this system. Big Bear down to Mount Laguna could see around 6 to 12" of new snow!

This is going to be a massive snow storm for the Central Sierra. Check out these snow totals!

MONDAY SNOW IN VIRGINIA

Latest data shows an impressive shift northward with the track of this storm. As I said before, you have to be careful with these type of systems. They can sneak up on you! I'm going to include the Richmond metro in the 1 to 3" category and put Emporia in the 1" or less category.

I've posted the computer forecasts below. Good luck tomorrow!

COMMENTS ON MONDAY SNOW IN VIRGINIA

You always have to be wary of a clipper system that is strengthening as it heads your way. I've been burned many times by these type of storms because they usually bring more snow than expected. Although surface temperatures will be above freezing, they will quickly drop once the precip starts. The air is very dry, so there will be major evaporative cooling.

I think the NAM does a pretty good job with this event. It won't be a 10:1 snow-to-liquid ratio, so the map below is overdone:

The next map uses the Kuchera algorithm and seems more plausible. Richmond should see 1" or less, though an area from Petersburg to Emporia could see 1 to 3".

VERIFICATION - WINTER OUTLOOK

Meteorological spring starts today, so it is time to verify my winter outlook. Obviously snow can still occur across most of the U.S. during this time of the year, but my forecast was for December through February. Last November, I typed up this summary:

San Diego - Last winter was cooler and wetter than average. This December-February should have below average temperatures and slightly above average precipitation. The southern stream will be weak, so we might not see any major rain events (exceeding 2"). Instead, I expect occasional moderate events through the winter. This could eat away at snow totals in the mountains, but colder air in the upper atmosphere could compensate a little.

Richmond - Last winter was cooler than average (cool Dec-Jan, warm in Feb) and drier than average (Dec was wet, Jan-Feb dry). Snow last year was *just* below average with a total of 10.7". I expect December-February temperatures to stay slightly above average and precipitation to hover near or slightly below average. There should be two to three cold blasts, though I don't think there will be any prolonged cold weather (over two weeks). After watching the storm track over the past couple months, I wouldn't be surprised if there will be a couple threats for a significant snow storm. Regardless, snow totals should stay near or below average at roughly 6 to 12".

Here were my forecast maps:

Here is what actually happened:

Although I'm generally happy with my temperature forecast in San Diego and California, I had a significant miss on the precip outlook. In retrospect, I should have known better considering the lack of a strong southern stream.

I'm very happy about my Richmond outlook (I've had more practice with Mid-Atlantic weather). 

I had a major bust with temperatures in the Northern Plains and New England. The handwriting was on the wall, in fact, I even talked about it during my discussion on the Arctic Oscillation and NAO. 

Lastly, I wish I would have extended my heavy precip area down into Texas. I drew my precip outlook two or three times. Each time I seriously considered putting Texas into the "above average" category. Instead, I stuck with persistence. Anyway, I'm glad I was wrong...Texas needed that moisture!

STORMY MONDAY FOR SOUTHERN CALIFORNIA

Scattered rain showers will overspread the area by midday tomorrow. Periods of rain will persist into Monday night and then will taper early Tuesday morning. Most of San Diego County will see a half inch or less. Monday will also be a blustery day with winds gusting up to 35 mph. Mountain winds will gust as high as 60 mph.

Snow levels will start off at 4500-5500 feet early Monday and then drop to 3500-4500 feet by Monday night. This storm system is moving fast and doesn't have much moisture, so I'm expecting 2 to 4" above 3500 feet and 3 to 6" above 4500 feet. Isolated areas could get more. Definitely good news for Bear Mountain! In addition, parts of the central Sierra will easily see over a foot of new snow.

I've posted the snow outlook from two computer forecasts. The first one is from the RPM, which I think is accurate, while the second one (NAM) is too dry.

CALIFORNIA WEATHER OUTLOOK FOR THE REST OF FEBRUARY 2012

The weather should remain warm through Saturday, then we will see some cool changes next week. Unfortunately, I don't see much rain with this current pattern. I've posted two maps below which show temperature anomalies and precipitation anomalies over the past 30 days. It has been very dry and warm for most of the state.

The weather pattern will be dominated by northwest flow in the jet stream for the next several days. This means we will see a prolonged period of slightly cooler than average weather with an occasional warm day. I'm leaving the forecast dry through the end of February. We might eventually see a storm system sneak into our area by the first week of March.

VERIFICATION

ECMWF did an excellent job with the track of this storm. It showed hints of this storm eight days before it happened! I based my forecast on this model and did not waiver when the other models flip-flopped.

Within 48 hours, NAM generally did a good job with snow accumulations, though it was too ambitious with snow-to-liquid ratios (as expected). In addition, it was too far north in the early runs (as expected). RPM also did well within 36 hours. GFS was the worst.

I have to admit, there was definitely some luck mixed in with skill while making this forecast. I'm glad it panned out!

Here are the snow totals:

LAST UPDATE MID-ATLANTIC SNOW - SUNDAY MORNING

RPM always does very well during the day of a storm, and to be honest, I like this solution the best. I've gone for 3 to 6" in the Richmond metro all along, so there is no reason to change it now. Be sure to check with your local meteorologist for the latest with this storm.

As expected, the NAM shifted back north. I still think it's too far south though. All in all a somewhat plausible solution.

GFS...well...we'll see if this happens...doubt it.

UPDATE ON MID-ATLANTIC SNOW - SATURDAY NIGHT

The latest data is significantly different than earlier today. The NAM still shows the most plausible precip field. It shows the persistent band of snow reaching all the way to the coast. However, it has shifted the snow band about 50 miles south. Although I anticipated a southerly trend, this is again too much. 

I would shift this map up about 20 miles. I would also take a couple inches off the totals in Central Virginia. I'm not expecting a 10:1 snow-to-rain ratio for the entire event (warm ground and surface temps and the possibility of some sleet).

I want to also mention that I think it's odd how the NAM/GFS MOS data keep dew points near 30 all day tomorrow, yet when it starts raining, they keep surface temps in the lower 40s. That's nonsense! Temps will rapidly fall at the onset of precipitation from evaporative cooling. Dew points tonight are in the mid 20s, so the models are already wrong...just food for thought.

I might as well stick with my 3 to 6" forecast in the Richmond metro area. Isolated areas will pick up more.

RPM also shifted south.

GFS is either going to be hailed as the best model ever or it's going to be considered the ultimate bust machine. This model stands alone with its' forecast in Central Virginia...1" or less. Wow! I still can't think of a reason why the snow band would completely dissipate as the storm system strengthens. It just doesn't make sense. If the GFS is right, I will gladly eat crow on Monday. Again, I would rather get people prepared for this storm than downplay it.

WEATHER UPDATE ON MID-ATLANTIC SNOW - SATURDAY AFTERNOON

After looking at the latest data, I still like the NAM solution to this event. It generally matches what the ECMWF has been showing all along. With that said, the maps below represent a 10:1 snow-to-liquid ratio. Parts of this event will have a lower ratio due to wet snow, warm ground temperatures and the possibility of some sleet. I would take off a couple inches from the NAM totals for Central and Eastern Virginia.

I'm keeping with my 3 to 6" forecast for Richmond. Isolated areas in Central Virginia will get more.

RPM also shows a plausible solution, though I'm sad that the 12Z data is unavailable. The 15Z data shows an explosion of 6 to 8" of snow in Central Virginia. This is probably caused by the rapid strengthening of the storm as it moves off the coast. Precipitation rates will increase and bring colder air down from aloft. 

The GFS continues to change its' solution each run. The key here is the strength of the storm. GFS never has the central pressure dropping below 1000 MB unlike the NAM and ECMWF, which have the pressure dropping to 996 MB. A weaker storm means weaker cold air advection - both horizontally and vertically.

I'm not buying this solution. This storm "over-achieved" what the models predicted here along the West Coast, so the same could occur farther east. I think it's better to be prepared for a snow event than to be surprised Monday morning with 6" of snow on the ground. Worst case scenario...GFS is right and I'm eating crow Monday morning.

WEATHER UPDATE ON MID-ATLANTIC SNOW - FRIDAY NIGHT

Here are some brief thoughts on the latest data:

• GFS is out to lunch. How can the band of snow magically disappear once it moves into the eastern half of VA? However, if it continues to show the same scenario for tomorrow's 12Z and 00Z runs, I might be a little worried.
• What happened to the NAM? I expected a slight shift south, but this is ridiculous. I expect a dramatic shift back northward tomorrow morning.
• ECMWF has shifted *slightly* northward. Wobbling is to be expected as the storm approaches. ECMWF ensemble never ceases to amaze me when it comes to these type of storms. It's the best medium to long range forecasting tool.
• RPM snow accumulations match the ECMWF storm track. It has the best solution this evening.

Right now I'm keeping with my 3 to 6" forecast for Richmond. Here are factors that can ruin my forecast: 

1. Surface temperatures
2. Ground temperatures
3. Prolonged period of sleet
4. Shift in the track of the storm

The data tomorrow will be more reliable, so don't get too excited (or sad) until then.