Area Forecast Discussion
Issued by NWS Los Angeles, CA

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000
FXUS66 KLOX 211202
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
402 AM PST Sun Jan 21 2018

.SYNOPSIS...
Clear skies and generally light winds will lead to below normal
temperatures this morning with areas of frost for colder coastal
areas. A warming trend is expected through early next week as
weak ridging builds aloft. A weakening cold front will likely push
through the region later in the week, bringing wind and cooler
conditions and possibly widespread rain and mountain snow showers.

&&

.SHORT TERM...(TDY-TUE)

Latest IR satellite imagery showed southern California sandwiched
between a departing trough of low pressure pushing east along the
front range of the Rockies and a deeper low pressure system slowly
spiraling east into British Columbia. Breezy north winds continue
across mainly across the mountains this morning but should
continue to weaken as they turn offshore and thus have allowed the
wind advisory to expire at 3 am. The weak offshore flow and
remnant cold air from the previous system will support freezing
conditions once again for many interior areas and at higher
elevations. Frost and freeze conditions area also likely for some
coastal and valley areas especially north of Point Conception and
wind sheltered valleys (such as Ojai). Have decided to cancel the
frost advisory for eastern Ventura Valleys as most temperatures
remain in the low to mid 40s in this area this morning. May also
cancel the Freeze warning focused across the Ojai Valley as
temperatures remain near 40 this past hour. the See the latest
NPW for associated frost and freeze products.

Continued moderation of the airmass in place coupled with weak
offshore flow will bring 3-6 degrees of warming for many areas
South of Point Conception today. Several degrees of warming is
also likely for the Central Coast into adjacent coastal valleys.
Increasing mid to high level clouds through the day will lead to
mostly skies by Sunday evening north of Point Conception and
partly cloudy skies to the south.

A rapidly weakening cold front is expected to push into the
Central Coast Sunday night into early Monday morning. It may hold
together just long enough to bring light rainfall to northwest
San Louis Obispo County. Impacts are expected to be minimal except
across lower elevations of the interior valley (such as near Paso
Robles) where wet bulb temperatures (a measure of how low
temperatures may fall with persistent rainfall) are expected to
hover near freezing during the early morning hours. Have left the
mention of freezing rain or drizzle out of the forecast for now
given the low odds of occuring. However, even a little freezing
drizzle can have significant travel impacts so this situation will
be watched closely. The front is expected to wash out along the
Central Coast Friday afternoon with clearing skies.

A ridge of high pressure aloft is will nose in from southwest
of the region Tuesday with H5 heights peaking at around 574 dm.
This combined with mostly clear skies and some increase in
offshore flow will bring a nice jump in temperatures with
widespread highs in the 60s to 70s, warmest coast and coastal
valleys south of Point Conception. Offshore winds in the morning
may approach advisory levels for wind prone areas.

.LONG TERM...(WED-SAT)

Above normal model agreement and confidence in the forecast exists
during the extended period.

A deepening trough of low pressure diving south from the Gulf of
Alaska to just off the Pacific Northwest Coast will push the weak
ridging out of the region by late in the day Wednesday with weak
offshore in the morning turning weakly onshore by the evening
hours (especially north of Point Conception). At this time, the
transition to onshore flow will be delayed just enough for another
warm day especially for coastal valleys and further inland.
Coastal areas, especially north of Point Conception may see
several degrees of cooling due to the switch to onshore flow. Mid
and high level clouds will likely be on the increase by late in
the day ahead of the next frontal system. Low clouds may also
develop for some coastal areas by Wednesday night.

A cold front is currently expected to push through the region
sometime Thursday. Although, in recent runs model guidance has
been trending slower by up to 12 hours. Would not be surprised if
this trend continued a bit longer. The trough associated with the
cold front does not currently look quite as deep or as far south
as the one that passed through the region Friday into Saturday.
However, the associated cold front with the upcoming potential
storm looks to have slightly better southerly flow out ahead of
hit. This might improve the chances of holding the front and
associated rain chances together as it moves south of Point
Conception into Ventura and Los Angeles counties. Like the
aforementioned storm, this one will also likely have a significant
pool of cold air aloft to work with. If this is the case, it would
likely bring gusty winds, especially to the mountains and southern
Santa Barbara County along and behind the cold front later
Thursday into Friday. The cold air could also support periods of
snow showers as low as 3000 to 4000 feet during this time period
(similar snow levels as the previous storm).

A warming and drying trend is likely heading into next weekend
with similar if not warmer conditions to that experienced earlier
in the week. Warmer valleys may break 80 degrees for high
temperatures by next Sunday.

&&

.AVIATION...21/1140Z

At 1105Z at KLAX, there was no marine layer nor was there a sfc
based inversion.

High confidence in CAVU TAFs.

KLAX...High Confidence in CAVU TAF.

KBUR...High Confidence in CAVU TAF.

&&

.MARINE...21/300 AM

Across the southern outer waters zones (PZZ673, PZZ676). SCA
conds for seas are then likely this morning, and possibly much of
the time Mon through Tue night due to a combination of winds and
seas.

Across the northern outer waters zone (PZZ670) SCA conds for
seas will last through this morning. SCA conds are then likely
again Mon thru Mon night due to seas.

For the inner waters SCA conds are possible again Mon and Mon
night due to high seas.

Across the SBA Channel and the southern inner Waters, SCA conds
are not expected until Thu.

Another long period NW swell will arrive in the water late Sunday
night, rising to 10 to 13 feet by Monday.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Frost Advisory in effect until 9 AM PST this morning for
      zones 34-35. (See LAXNPWLOX).
     Freeze Warning in effect until 9 AM PST this morning for zone
      44. (See LAXNPWLOX).
PZ...Small Craft Advisory for hazardous seas in effect until 9 AM
      PST this morning for zones 670-673-676. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK...(TUE-SAT)
Strong and impactful winds are possible Thursday and Friday over
the mountains and southern Santa Barbara County. Snow and travel
delays are possible over the Tejon Pass/Grapevine area late
Thursday into Friday.

&&

$$

PUBLIC...Munroe
AVIATION...Rorke
MARINE...ASR
SYNOPSIS...Munroe

weather.gov/losangeles


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