Area Forecast Discussion
Issued by NWS Sacramento, CA
FXUS66 KSTO 151009
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
309 AM PDT Mon Sep 15 2014
Cooler temperatures for much of this work week. Valley sprinkles
and mountain showers and isolated thunderstorms will be possible
for parts of the area today, and again Wednesday and Thursday.
Skies are mostly clear across the region early this morning. Early
morning temperatures remain mild and are similar to readings of 24
hours ago ranging from the upper 40s in the colder mountain
valleys to the upper 60s and 70s in the Central Valley.
Temperatures will remain rather hot across the interior of NorCal
today as high pressure begins to shift east ahead of a low
pressure system in the eastern Pacific, but the marine layer
remains shallow (around 1000 ft deep) and onshore gradients are
not overly strong. Not expecting much synoptic cooling today
(maybe a degree or so C at 850 mbs) and any cloudiness will likely
not be around all day. Most areas will only see a few degrees of
cooling compared to Sunday while Delta-influenced locales will
see around 4-8 degrees of cooling.
Initial closed low near 40N/130W will open up and lift northward
today. It appears that the strongest lift ahead of this feature
will be across far northern California later today, so the best
chance of deep convection later today appears to be up along the
Oregon border and over northeast California. Blended TPW satellite
product does indicate some deeper TPW approaching an inch
approaching the southern portion of the forecast area, so cannot
completely rule out some sprinkles this morning across much of the
region if the short-wave provides enough lift.
More substantial cooling forecast to gradually develop into mid-
week as the upper ridge shifts further east as a deeper trough
approaches NorCal. Appears there will be sufficient moisture and
dynamics with the system for a chance of showers across much of
the region later Wednesday into Friday along with continuing
breezy conditions over the mountains.
Models then diverge heading into the weekend with placement of
omega upper ridge and associated trapped low. 00Z GFS is more
progressive keeping the ridge axis farther downstream while 00Z
GEM and ECMWF-HiRes keep it along the central California coast.
Forecast becomes increasingly difficult as models handle placement
of trapped closed low poorly. Have introduced some low POPS for
the southeast corner of the forecast area over the weekend with a
little warmer temperatures across the area.
Generally VFR conditions expected the next 24 hours as an upper
level low approaches the coast. Mid and high clouds will move
through the area with a slight chance of thunderstorms over the
Burney Basin and Lassen Park area this afternoon. Local southwest
surface wind gusts to 35 kts possible over mountains and in the
Delta this afternoon and evening.