Scientific Forecaster Discussion
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Area forecast discussion
National Weather Service Sacramento California
330 am PDT sun Aug 25 2019
above normal temperatures through midweek, peaking Tuesday, then
returning to near to slightly above normal by the weekend. Dry
high pressure over norcal will continue dry weather with above
normal temperatures. Marine layer has shrunk to around 1000 feet
and is hindering cooling impact of Delta breeze into the Central
Valley. As a result, morning temperatures are running about 2 to 5
degrees warmer than 24 hours ago. Afternoon highs expected to be
near to slightly above what they were Saturday with triple digit
heat again in the northern Sacramento Valley. Strong subsidence
and dry air mass will hinder mountain deep moist convection today.
Heights and thicknesses slowly trend up into early next week as
desert SW upper high builds towards the northwest. 850 mb temps
top out Tuesday, climbing into the mid to upper 20s deg c in the
afternoon. Bought dry adiabatically to the surface results in Max
temperatures Tuesday around the century mark for much of the
Central Valley. Hottest readings expected in the northern SAC
valley with around 107 forecast at Redding. Overnight lows
forecast to cool into the 60s for most valley locations providing
some relief. Exception will be portions of the northern and
central Sacramento Valley and thermal belts within the foothills
where lows will be in the 70s.
Upper ridge axis shifts into the intermountain west Wednesday as
a pair of mesoscale upper troughs move into the County Warning Area. This will
result in some synoptic cooling midweek with increased onshore
flow. Highs temps lower about 2 to 4 degrees Wednesday and again
Thursday, returning to slightly above normal by that time.
Extended discussion (thursday through sunday)...
ensemble models show upper ridge over the western U.S. With
troughing digging in off the coast through the extended period.
Southwest flow aloft will keep monsoon moisture south and east of
the forecast area while ridging keeps any Pacific moisture north
of the region. Therefore, extended period is expected to remain
dry through next weekend. Development of upper trough off the
coast will bring continued onshore flow and slightly cooler
temperatures Thursday through Sunday although daytime highs are
expected to remain a few degrees above normal. May see breezy
winds at times over the Sierra and through the Delta but otherwise
winds are expected to remain relatively light under the ridge.
VFR conditions next 24 hours. Sustained surface winds generally
below 15 knots. Local gusts 15-25 kts in the Delta.