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Area forecast discussion 
National Weather Service Sacramento California
351 am PDT Tuesday Jun 30 2015

Synopsis...
very hot weather across much of the region for the remainder of
the week. Some Sierra thunderstorms throughout the week, though
some may move into portions of the valley late in the week.

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Discussion...
main forecast concern continues to center around hot weather this
week. Heat Cranks up across the interior of norcal the next
several days as strong high pressure extends westward bringing a
hot airmass and suppressing any remaining coastal influence
inland. Highs the next 3 days across the northern half of the
Sacramento Valley will likely be in the 110 to 115 degree range
with overnight lows in the upper 70s to lower 80s, so the
excessive heat watch will continue for that area. Temperatures
won't be quite as hot across the remainder of the region, but the
warmest readings so far this Summer can be expected in many areas.

As the ridge axis shifts northward later in the week, there will
be an opportunity for the marine layer to once again deepen
Thursday beginning the process of spreading some cooling inland
late in the week.

Another item to keep an eye on will be moisture moving up from the
southeast around the periphery of the ridge. Despite a fair amount
of middle and upper level moisture, diurnal thunderstorms will
likely be fairly limited over the mountains the next couple of
days as middle-level temperatures warm. By Thursday and Friday, moisture is
forecast to increase with tpw of around 1.5 inches forecast by the
GFS, however, similar to last weekend, the moisture is mostly
concentrated above 500 mbs so the main thunderstorm threat will
remain over the mountains with the possibility of light showers or
sprinkles at the lower elevations. If any stronger lifting
mechanism appears in the southeast flow, then more widespread
thunderstorm chances will be possible.

&&

Extended discussion (saturday through tuesday)...
over the weekend, interior northern California sandwiched between
Four Corners upper high and offshore upper low. Southerly flow
aloft will continue to draw some monsoonal moisture into the area.
Main instability, and thus threat of showers and thunderstorms,
depicted over the mountains in the afternoons into early evenings.
Drier and more stable southwest flow aloft develops Monday into
Tuesday as downstream upper high progresses. Threat of afternoon
deep moist convection shifts east of the Sierra Nevada crest.

High temperatures through the extended forecast period will be
cooler. Maximum readings will range from the middle 80s in the Delta to
around 100 in the northern Sacramento Valley, with upper 70s to
around 90 for the mountains and foothills.

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Aviation...
upper high over rockies extends westward over norcal with southerly flow aloft. Mainly
VFR conds next 24 hours. Isolated thunderstorm poss near Sierra Nevada between 22z-02z.

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Sto watches/warnings/advisories...
excessive heat watch from Wednesday afternoon through Friday
morning for central Sacramento Valley-northeast
foothills/Sacramento Valley-northern Sacramento Valley.

&&

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