Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Sacramento California
406 am PDT Tuesday Jul 28 2015
hot and dry weather continues this week as high pressure
strengthens. Increasing monsoon moisture may lead to a chance of
mountain thunderstorms by the end of the week.
clear skies across interior norcal early this morning. Temperatures are
milder across the northern Sacramento Valley and in the thermal
belts of the foothills and west slopes of the northern Sierra.
Northerly and easterly surface pressure gradients have increased
over the past 24 hours, but a weakening onshore gradient still
lingers between the coast and Sacramento providing a weak Delta
trickle at Travis AFB.
Hot weather returns in force to interior norcal the next several
days as high pressure builds. Additionally, the surface thermal
trough shifts to along or off the coast into Thursday resulting in
a prolonged period of offshore flow with locally breezy north to
east winds. More warming will occur today, but most areas of the
Central Valley will see the peak in temperatures reaching the 105
to 110 degree range Wednesday and Thursday along with very mild
overnight lows. However, portions of the Delta and South Valley
may see some some relief by Thursday as the Delta breeze returns.
Monsoonal moisture will return toward the end of the week bringing
an increase in middle and high clouds along with a chance of mainly
mountain showers and thunderstorms. A few storms may be possible
as early as late Thursday over the Sierra south of Lake Tahoe.
Extended discussion (saturday through tuesday)...
upper level ridging slowly weakens with a gradual cooling trend
continuing through the weekend into early next week. Temperatures
will cool a few degrees each day into early next week with highs
forecast to return to near normal for most of the area by Sunday
The main uncertainty with the extended period deals with the
spread of monsoonal moisture northward into the area. The GFS
continues to show this...while the European model (ecmwf) is still trending drier
with southwest flow. Have left a slight chance of late day showers
and thunderstorms over the higher mountains/Sierra crest. May need
to lower probability of precipitation if monsoonal moisture trends eastward. This would
also affect temperatures, which would not cool quite so much if
cloud cover is limited. Ek
VFR conditions next 24 hours for taf sites. Possible local visibility
restrictions near current fires (lowell, wragg) due to smoke.
Breezy northerly winds increasing after 17z with gusts to 25kts
possible through 01z for the northern and western side of the
Sacramento Valley. Ek