Area Forecast Discussion
Issued by NWS Los Angeles, CA

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

FXUS66 KLOX 221843

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
1143 AM PDT Thu Mar 22 2018

.SYNOPSIS...22/705 AM.

The temperatures will be below normal into Friday. A significant
precipitation storm, isolated thunderstorms and breezy winds is
forecast into early Friday. The storm should make an exit on
Friday. Then skies will began clearing on Sunday with a warming
trend into Wednesday.


.SHORT TERM (TDY-SAT)...22/906 AM.

The last hurrah from this storm is today and this evening. For
today we`ve seen a significant increase in south winds below 850mb
which is enhancing rainfall rates on south facing slopes. Minimal
lightning so far but with the increase in orographic enhancement
we could easily see rainfall rates in excess of a half inch per
hour. In fact we`ve already seen that at a few rain gauges in
Ventura and SB Counties this morning.

We`ll transition from a steady moderate to locally heavy rain to
a showery environment later this afternoon and evening with
possible thunderstorms as the cold front moves through. Models
show pretty good instability with that front and still ample
moisture to generate some very heavy downpours and possible
lightning. Rain rates with thunderstorms could easily reach an
inch per hour. Because of this the current flash flood watch may
need to be extended through the evening for western counties.

***From previous discussion***

Rainfall rates over SLO/SBA/VTA will range from .50 TO 1.00
inches per hour with rates in excess of 1 inch per hour under
TSTMs. LA county rainfall rates will range from a third to two
thirds inch per hour with rates of 1 inch per hour under TSTMS.

Rainfall amounts today will range from .75 to 1.5 inches across
the flatter coasts with 2 to 4 inches across the coastal slopes.
The interiors will see a half inch to an inch of rain and the
Antelope Vly will see a quarter to a half inch of rain.

Due to the potential convection of this system the entirety of both
SLO and SBA counties are now under a flash flood watch not just
the burn areas.

Due to the jet placement there will be good shot of south winds
with this system. The winds will be strongest over the higher
terrain and a wind advisory is in affect for all the mtns and the
interior vlys behind the mtns.

The rain will end from northwest to southeast late this afternoon
through early Friday morning. But it still looks like there will
be decent amount of shower activity south of Point Conception
through this evening.

No real snow today but this evening the snow level will drop and
three inches or so might fall above 6000 feet.

Look for decreasing clouds on Friday with the only real chc of
additional shower activity across the north slopes of the mtns. It
will be a little warmer than today but not much with coastal and
vly highs only in the mid 60s.

Both the GFS and the EC show a trof moving through northern two
thirds of the state on Saturday. It will bring partly to mostly
cloudy skies to the area and a slight chc of light rain showers to
SLO and SBA counties. It will also bring in more cool air and max
temps will actually drop a few degrees from Friday`s already cool
max temps.

.LONG TERM (SUN-WED)...22/329 AM.

Both the EC and the GFS agree that Saturday`s trof will slowly
move over the state on Sunday. It will be dry but with hgts
falling to 552 DM it will be cool in fact Sunday looks like it
will be the coolest day of the next 7 with max temps 10 to 15
degrees blo normal.

On Monday the trof will stall over UT/NV/AZ and will begin to cut
off. At the same time a ridge will begin to nose into the Pac NW.
North flow will develop over the area but nothing close to
advisory levels.

On Tuesday the trof will evolve into a cut off low and then in
will spin in place through Wednesday. The upper flow will be
favorable for some NE offshore flow. At the sfc there will be
offshore flow but it will not be that strong from the east and
only moderate from the north. So there will likely be some gusty
winds but nothing to huge. Max temps will warm some each day and
may even approach normal by Wednesday.inland.



At 1718Z, there was no marine inversion at KLAX.

Low confidence in 18Z TAF package. High confidence in moderate to
locally heavy rain with associated MVFR to LIFR conditions
through this afternoon, but low confidence in timing of flight
category changes.

Additionally, there is the slight chance of TSTMs for all sites
through this afternoon with gusty/erratic winds and heavy rain.

KLAX...Low confidence in 18Z TAF. MVFR/IFR conditions likely
through this evening with moderate/locally heavy rainfall, but low
confidence in timing of flight category changes. There is a 20%
chance of TSTMs especially this afternoon/evening. Winds likely to
occasionally drift back to the south for the next couple of hours,
but no easterly component. By late this afternoon (22z), the
cold front will move through, bringing southwest to west winds
for good.

KBUR...Low confidence in 18Z TAF. MVFR/IFR conditions likely
through this evening with moderate/locally heavy rainfall, but low
confidence in timing of flight category changes. There is a 20%
chance of TSTMs especially this afternoon/evening.


.MARINE...22/931 AM.

Marginal small craft advisory remains in effect for much of the
coastal waters as a cold frontal boundary approaches the waters.
Isolated thunderstorms are possible at times across the waters
through this evening. Brief gusty and erratic winds with an
isolated waterspout is possible near any thunderstorm.

Small Craft Advisory winds are likely again from Friday through
this weekend across the Northern and Outer Waters with a 30
percent chance of reaching the inner waters at times. There is
also a 20 percent chance of Gale force winds across the Outer
Waters by Sunday.


CA...Flash Flood Watch in effect until 5 PM PDT this afternoon for
      zones 34>37-39-40-44-51>53. (See LAXFFALOX).
     Flash Flood Watch in effect through late tonight for zones
      41-46-54-88-547. (See LAXFFALOX).
     Wind Advisory in effect until 8 PM PDT this evening for zones
      53-54-59. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 3 AM PDT Friday for zone
      673. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 PM PDT this afternoon
      for zone 676. (See LAXMWWLOX).



No significant hazards expected.



SYNOPSIS...STu is the U.S. government's official web portal to all federal, state and local government web resources and services.