Scientific Forecaster Discussion
fxus66 klox 191132
Area forecast discussion
National Weather Service Los Angeles/Oxnard California
332 am PST Tue Feb 19 2019
It will be cold through the week with early morning temperatures
below freezing in many locations. There is a chance of light
precipitation and mountain snow late Wednesday through Thursday
otherwise conditions will be dry.
Short term (tdy-thu)...19/325 am.
Dry north flow will bring sunny skies to the area today. The clear
skies, light winds and a cool (554 dm) airmass is making for a
very cold start to the morning with most areas away from la urban
heat island will wake up to temps in the 30s or colder. Max temps
today, while warmer than ydy, will still struggle to reach 60
It will be a touch warmer tonight but the coastal vlys will likely
need another round of frost advisories.
Wednesday will start off partly cloudy but clouds will soon
increase as the next system arrives. A weak impulse will drop down
and move through the state. It will bring a chc of showers to
areas north of pt Conception in the morning and to slo/sba/vta
County during the afternoon. Snow levels will range from 3000 to
3500 feet. There will be little in the way rainfall or snow fall
since the very cold air cannot hold that much moisture and it will
entrain no extra moisture. Max temps will continue to be 12 to 15
degrees blo normal.
The shower activity will continue Wednesday night as weak positive vorticity advection
moves through the cold and unstable air. Snow levels will fall to
3000 feet and perhaps down to 2500 feet. There will be some snow
on all mtn roads. The only saving Grace will be that there will
not be that much snowfall.
Thursday looks to be the interesting day. A very cold upper low
that was spawned from the Canadian interior will move into the
state from Nevada (its overland Route means that the airmass will not
be modified by the relatively warm ocean waters) by afternoon the
upper low will be over Bishop and 534 dm hgts will be over lax
with 500 mb temps of -35 degrees celsius. These cold temps aloft
along with the weak positive vorticity advection associated with the upper low will keep
the shower threat going through the day. By afternoon the very
cold air aloft will destabilize the atmosphere enough to allow for
a slight chc of thunderstorm development. Snow levels could fall as low
as 1500 feet and will generally be near 2500 feet. Snow could fall
almost anywhere except for the coast. Again this will be a dry
system so it will not produce much in the way of snowfall or
rainfall totals. It will be yet another day where the coasts and
vlys will only see Max temps in the mid 50s.
Long term (fri-mon)...19/332 am.
A Little Ridge will pop up on Friday. It will be a sunny day but
still cool with Max temps still in the 50s.
On Sunday and continuing through Tuesday a cold stationary upper
low spinning Alberta Canada will extend its flow over the western
US. It will push the ridge away and bring cool dry northwest flow to
californian. Skies will be either mostly clear or partly cloudy.
Max temps will warm some but will still be 5 to 10 degrees blo
normal through the period.
At 11z at klax...there was no marine layer nor was there a sfc
High confidence in ceiling and visibility unlimited tafs. North winds will create turbulence
over and near to the mtns.
Klax...high confidence in the 12z ceiling and visibility unlimited taf. There is a 20% chance
of northerly cross winds of 15 to 20 kt through 15z.
Kbur...high confidence in the 12z ceiling and visibility unlimited taf. Lgt to ocnl MDT turbc
expected this morning near the Airport.
For the outer waters, moderate to high confidence in the
forecast. Small Craft Advisory level seas will continue today. Winds may drop below
Small Craft Advisory levels this morning, but should increase to Small Craft Advisory level again in
the afternoon. Then, Small Craft Advisory level winds and seas are likely through
Thu night, with seas possibly staying above Small Craft Advisory levels into Fri.
Small Craft Advisory level winds are expected across the southern outer waters Fri
afternoon and evening. There is a 30-40% chance of gale force
winds Wed afternoon thru Thu evening.
Across the northern inner waters, moderate confidence in the
forecast. There is a 20-30% chance of Small Craft Advisory level winds this
afternoon and evening. Small Craft Advisory conds are expected Wed afternoon
through Thu evening. Winds may drop below Small Craft Advisory levels late Wed
night/Thu morning but seas will likely remain at or above Small Craft Advisory
levels. There is a 20-30% chance of Small Craft Advisory level winds Fri.
For the sba channel and southern inner waters zone (pzz650, pzz655),
moderate to high confidence in the forecast. Small Craft Advisory level conds are
not expected through Wed morning. Small Craft Advisory level winds are likely Wed
afternoon through Thu evening. There is a 20-30% chance of gale
force winds gusts Wed evening, and during the afternoon and
evening hours Thu, mainly across western sections.
California...freeze warning in effect until 8 am PST this morning for
zones 34-35-44>46-88-547. (See laxnpwlox).
Wind Advisory in effect until 6 am PST early this morning for
zones 39-52. (See laxnpwlox).
Pz...Small Craft Advisory in effect until 3 am PST Friday for
zones 670-673-676. (See laxmwwlox).
Hazard potential outlook (thu-mon).
Low elevation snow is possible Thursday potentially creating
impacts on Interstate 5 and other roads through the mountains.
Near or sub-freezing temperatures are possible in many areas