Area forecast discussion
National Weather Service Sacramento California
945 PM PDT sun may 19 2013
Short term discussion...
Temperatures currently running around 2 to 7 degrees warmer than 24
hours ago...except in the Solano Colorado area...along with decreasing northwest
winds from the afternoon. Enough northwest wind expected to continue lower
level mixing over most locales throughout the night elevating mins
from previous nites.
Upper low over the Yukon territory will be the dominating factor in
norcal weather this week...as it enhances ridging over norcal on Monday...
and then brings a cooling trend and windier weather to norcal for the
rest of the week as it drops southward into the Pacific northwest. Highs in the
valley are expected to climb into the lower 90s while the mountains
will be mainly in the upper 60s and 70s on Monday. Jhm
A major change toward cooler and breezier weather is forecast to
begin Tuesday as the upper trough presently over the goa drops
southeastward into the pacnw and closes off. The cold upper low is
forecast to be just offshore the mouth of the Columbia River by
later Tuesday...then only shifting slightly east by Wednesday.
Appears at this time that this system will be relatively dry for
norcal with shower chances mainly limited to the mountains north
of Redding while the main impacts will be much cooler temperatures
and breezy conditions for mid-week.
&&
Extended discussion (thursday through sunday)
Closed upper low over the Pacific northwest will impact our area from
midweek into the weekend as secondary vorticity maxes rotate around the
parent low and brush the northern reaches of our forecast area.
Although models are highly confident in placement of primary upper
low...confidence is much less in individual vorticity maxes pivoting
around it. The European model (ecmwf) continues to indicate one strong vorticity maximum
swinging through our area Thursday afternoon...with enough dynamics
to generate a few showers over the Sierra from around Tahoe
northward. The GFS meanwhile is much weaker with this feature...and
limits any chances of showers mountains from around Shasta County
northward. Have extended a slight chance of rain showers Thursday night
farther south along the Sierra south to around Blue Canyon since the
European model (ecmwf) has been more consistent. Either way...the main message is
still cooler temperatures through the end of the workweek.
By next weekend...the closed low weakens into an open wave along
the West Coast. Additional weak shortwaves look to move onshore to
norcal...bringing the possibility of isolated showers to the
mountains around the northern SAC valley. Temperatures should
moderate to around normal...with possible Delta breeze
modification in the SAC metropolitan area given onshore gradient. -Dvc
&&
Aviation...
VFR sky clear conditions continue over interior norcal next 24 hours. Northwest
winds 5-15 kts at taf sites through 00z Tuesday.
&&
Sto watches/warnings/advisories...
none.
&&
$$
