Scientific Forecaster Discussion
fxus66 ksto 121731
Area forecast discussion
National Weather Service Sacramento California
930 am PST Tue Nov 12 2019
dry weather pattern continues this week. Cooling trend this week,
but above normal high temperatures continue. Warmer this weekend.
the morning update: biggest change from 24 hrs is the -14 and -23
deg temp change at rbl and rdd, respectively at 16z. This is the
result of light winds this morning compared to the warming katabatic
winds of yesterday. With a strong ridge over the region it will
still be a mild day with Max temps mostly 8 to 15 deg above normal.
SAC (78 in 1990), sck (78 in 1995), and moderate (80 in 1989) will be
nearing record highs for the date, however, most areas will see a
degree or two of cooling from yesterday.
Still looks as if we have a cooling trend for the rest of the week,
with a warming trend for the weekend. Pacific trof forecast to move
inland Thu/Fri with synoptic cooling and thickening clouds into Fri
morning. This system will weaken drastically as it moves into the
strong ridge and may bring just a brief period of locally breezy
conditions to the NE SAC Vly fthls, and valley on Sat. Average gusts
in the low 20s miles per hour at rdd and rbl on the European model (ecmwf) ensembles.
The 8-10 day 500 mb hgts cluster suggests a trof will develop over
the Great Basin region which could bring some windy conditions to
our cwa, and much cooler wx and possible showers mainly over the
Partly cloudy skies (high clouds) cover the region early this
morning. Northerly surface pressure gradients have dropped off
considerably compared to 24 hours ago (kmfr-krdd currently around
1.5 mbs compared to over 6.5 mbs at this time monday) while the
easterly gradient krno-ksac is still around 5 mbs. Local northeast
wind gusts of 15-30 mph linger across the foothills and west
slopes of the northern Sierra. Current temperatures range from the
upper 20s in the mountain valleys to the upper 50s to lower 60s
across the warmer foothill and mountain thermal belts.
Strong ridging will gradually shift east later Wednesday into
Thursday as the closed low, presently near 30n/145w, weakens and
approaches the West Coast. The system will bring some cooling
along with mostly cloudy skies as it moves through Thursday into
Friday. High temperatures will remain above average.
Extended discussion (saturday through tuesday)...
upper level ridging will be in place for the start of the extended
period. This will result in a warming trend along with a decrease
in humidity. High temperatures will be around 5-15 degrees above
average for mid-November.
Upper level ridge flattens early next week as a trough digs into
the pacnw. Deterministic models keep the trough a bit further to
the west and pull in some moisture Tuesday/Wednesday but ensembles
are drier and further to the east with it. We will likely see
models shift to this scenario and have kept the forecast dry. If
ensembles are correct with the placement of the trough we could
see breezy north winds Tuesday continuing into Wednesday with low
relative humidity. -Cjm
VFR conditions the next 24 hours except local MVFR visibilities
from ksck southward 14z-18z Tuesday. Winds generally below 10 kts.