Area forecast discussion
National Weather Service Sacramento California
938 am PDT Thursday may 23 2013
Short term discussion...
A general upper level low pattern over the region looks like it
will be a persistent feature for the foreseeable future bringing
relatively cool temperatures. Reinforcing shortwaves will also
bring the possibility of precipitation at times...especially early
next week.
The upper level low is currently centered over the Pacific
northwest. A weak wave is rotating around the low over northern
California today. Satellite shows a limited enhanced area moving
from NE California into northwest Nevada. Radar indicates just a few
light returns over eastern Shasta...Lassen park and Plumas County.
Hrrr model suggests that just a few isolated showers will occur
through middle day with even clouds diminishing by afternoon. Will
update forecast to reduce cloud cover and coverage of showers for
the rest of today.
Will increase afternoon temperatures today a couple degrees over
the area...especially over the northern Sacramento Valley. Morning
temperatures in some spots are starting relatively cool but should
increase as heights rebound in the wake of the departing shortwave
trough. Cloud cover also looks like it will be a little more
limited over the northern portion of the forecast area and will
allow more solar heating. Temperatures at Redding are already 6
degrees warmer than yesterday.
Winds will generally be lighter today although there will be some
breezy north winds at times over the northern Sacramento Valley
this afternoon and up in the higher Sierra. Ek
&&
Extended discussion (monday through thursday)
A mean trough will linger over the West Coast through the weekend
and into the first part of next week. Several weak disturbances
will move through the longwave trough and brush far northern
California. Models are not in agreement however with the
amplitude and timing of these features. The European model (ecmwf) solution has
the least impact for US as it is less amplified with the longwave
trough and consequently keeps our area dry through the period.
The GFS and Gem meanwhile have compact shortwaves moving through
Saturday night and Monday night...with lingering mountain showers
in-between. The GFS is even showing some chance of convection
Saturday night for the coastal mountains and Lassen vicinity. With
limited certainty...have opted for a slight chance of showers
through the period over the mountains from around Red Bluff
northward. Have added a mention of thunder Sat afternoon/evening
to account for surface-based instability prognosticated by the GFS...which
also happens to match up well with neighboring forecast offices.
Regardless of which solution verifies...the only impact for the
Central Valley would be continued seasonal temperatures with
onshore flow and a few clouds. -Dvc
&&
Aviation...
VFR conditions continue next 24 hours for interior norcal taf
sites. North winds less than 15 knots today becoming variable to
10 knots after about 03z.
&&
Sto watches/warnings/advisories...
none.
&&
$$
