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White Christmas?

Tracking latest odds and possible events for the holidays


December 5-7, 2018 | Storm

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I know we don't have many left coasters  but thought I'd start a topic just in case. 

Looks like a good dose of precipitation can be expected for much of California.   I'm sure this is welcomed by many in drought stricken areas, let's just hope it doesn't come with and landslides. 

The driver is a cutoff like that is slowly making its approach to the west coast. 


Drought map


NAM precip 


San Diego disco 



  Surface high pressure over the Great Basin will bring periods of 
  gusty east winds to around 25 mph near the coastal slopes of the 
  mountains through Tuesday. 
  A low, closed pressure system will move to a position off the  
  California coast on Tuesday, then move slowly toward the southeast 
  on Wednesday and Thursday with the center of the low pressure  
  moving inland through southern California and northern Baja  
  Thursday night. Given the track of the system, the more  
  significant rainfall is expected to remain over the coastal waters 
  extending locally into coastal areas. With the lower level flow  
  out of the south to southeast, orographic enhancement will mostly  
  be limited to south facing mountain slopes. Precipitation from the 
  cold front is expected around Wednesday followed by periods of  
  showers through Thursday night or early Friday. 
  Rainfall amounts for Wednesday through Thursday night... 
  Coast.........1.5 to 2 inches 
  Valleys.......1 to 1.5 inches 
  Mountains.....1 to 1.5 inches (locally 2 to 3 inches on south  
  facing slopes)  
  High desert...0.5 to 0.75 inch  
  Low desert....0.25 to 0.50 inch 
  The snow level will be near 6000 to 6500 feet with several inches 
  of snowfall possible above 7000 feet. 
  The stronger winds for Wednesday, mostly out of the south to  
  southeast are expected across the coastal waters with less inland. 
  As the low pressure system moves on to the east, dry weather with 
  a warming trend is expected for next weekend. 



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...more wet weather moving into the West Coast...the Bay Area is already clouding up as the next system approaches from the west...light rainfall expected in the Bay Area with light snows in the Sierras...great to see early season snows build our watershed and snowpacks in water challenged California...large storm in the Aleutians will send several 'fronts' towards the west after this first 'wave' moves through...beautiful 'baroclinic leaf' profile (as noted in NWS outlook) to the wonderful satellite views...


FXUS66 KMTR 040010

Area Forecast Discussion
National Weather Service San Francisco Bay Area
410 PM PST Mon Dec 3 2018

.SYNOPSIS...Dry and seasonably cool weather is forecast through this
afternoon. Unsettled weather conditions return late tonight into
Tuesday as a storm system approaches the central California coast.
Periods of rain are expected through Thursday before dry conditions
return by Friday. Light rain will again be possible over the North
Bay this weekend with another chance of widespread rainfall early
next week.


.DISCUSSION...as of 01:46 PM PST Monday...Tricky few days ahead
as offshore flow and easterly flow complicate precip chances.
Drier weather late in the work week with another chance for precip
over the weekend.

Pretty spectacular GOES 17 image over the EPAC - nice baroclinic
leaf and easily identifiable frontal structure. This system will
be the rain maker over the next 24-48 hrs. The forecast trend over
the last 12 hours has been to slow the onset of precip across the
Bay Area. This makes sense given the deepening low and easterly
flow/offshore flow over land. Have trended forecast slightly dry
and slower through Tuesday afternoon. If the local WRF is correct
current forecast is too wet as WRF keeps most precip off the coast
through Tuesday afternoon. None the less, official forecast will
have light precip developing late tonight/early Tuesday and then
gradually filling in through Tuesday afternoon. Precip will
continue (light to moderate) through Thursday as the low slowly
moves to the coast and eventually southward. Rainfall amounts
generally 0.25-0.75"...locally higher in the terrain favored spots
of 1-3". One potential limiting factor will be prevailing easterly
flow - dampening upslope potential and limiting shadow effect.

Speaking of easterly winds - winds will increase tonight and
Tuesday as the sfc low approaches. Strongest winds over the waters
and near the coastline. Gusty winds will also be possible over
the higher peaks and inland valley (Salinas/Santa Clara Valleys).
A little atypical for the valleys, but SE flow can get funneled
through the valleys. There could even be some gusty winds along
the Santa Mateo coast in the gaps and passes. Given the peak gusts
will be more isolated in nature will not issue a wind advisory at
this time.

Slight ridging on Friday as one low exits to the south and
another approaches from the NW. Another round of precip will be
possible over the weekend into next week, but medium range models
have been trending weaker with this front and slowing the timing
as well.






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Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
251 PM EST Tue Dec 04 2018

Valid 00Z Wed Dec 05 2018 - 00Z Fri Dec 07 2018

...Storm system to bring rain  and mountain snow to California beginning

Changes are coming however, at least for California, as a slow moving upper level disturbance nears
the West Coast tonight. While the track of the system will keep the
heaviest rain/wind near the coast or offshore, wind gusts up to 50 mph
will be possible for the southern Sierra Nevada Mountains into the
Transverse Ranges of southern California through Wednesday morning as the
associated frontal boundary nears the area. Rain and higher elevation snow
will also begin to impact the Golden State by Wednesday morning with
locally heavy rain possible for the Channel Islands into portions of the
southern California coast through the day on Wednesday. There will be
possible runoff concerns where heavy rain overlaps with sensitive burn
scar locations. Higher elevation snow for the mountains of southern
California and the Sierra Nevada range can also be expected, although
accumulations should remain fairly light as a whole, as the slow moving
storm system continues to impact southern portions of California through
much of Thursday.



heavy rains in S Cali could cause flooding and mud slides

WeatherStory1 (1).png

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Heavy showers came into the Santa Clara Valley late last night...lasting well into the wee hours...one quarter to one half inch of rain fell in most South Bay Area locations overnight...right now it is scattered clouds with a development coming in from Big Sur moving S to N

Clearing should gradually develop N to S into Thursday with some residual showers as low pressure(now centered off Pt. Conception) slowly continues south and east...wraparound showers will effect the Bay Area overnight as a small vortice spins just to our north ...

Southern California is hunkering down as the main rainfall bands have not yet reached their areas...especially noted is the Malibu Canyon areas up towards Thousand Oaks(fire-ravaged areas) as these areas have a large southern exposure and orographic augmentation of rainfall totals in these areas could make mud slides, debris flows and run-off issues a problem in the next two days...otherwise California has held up well during these first few storms in what could be the prelude to wet to very wet winter...esp. if El-Nino arrives in '19

...more on the way next week?...see the 96hr OPC for hints...




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