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000
FXUS66 KSTO 172229
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
329 PM PDT Mon Jun 17 2019

.SYNOPSIS...
A warming trend is expected early this week, peaking on Tuesday,
followed by less hot weather. Isolated mountain thunderstorms are
possible this afternoon and evening, mainly over the higher
elevations of the Sierra Nevada.

&&

.DISCUSSION...
A broad negatively-tilted trough continues to dip southward
fostering the development of isolated showers and thunderstorms
over the Sierra crests. Vertical shear is quite weak so storms
that do spawn will be short-lived. However, a brief heavy
downpour, small hail, and lightning are all possible with any of
the afternoon convection. While cumulus fields have been observed
up and down the Sierra, areas south of I-80 have contained much
stronger updrafts (per lightning activity). Thus, expect any
thunderstorms threat to remain south of I-80 through this evening
before convection wanes given the loss of diurnal heating.

On the temperature side, readings will remain above average given
the eastern extent of an offshore ridge moves overhead. Current
temperatures are quite warm today, especially over the northern
Sacramento Valley (i.e., Redding and Red Bluff), generally up to
the low 100s. With numbers expected to rise further tomorrow, a
Heat Advisory has been placed over sections of the
northern/central Sacramento Valley on Tuesday. Highs are forecast
to max out around 105 degrees which may affect those sensitive to
excessive exposure to the heat. Fortunately, a gradual cooling
trend is in store although conditions will still feel rather hot
through mid-week. The shift in the pattern is by an amplified
trough dropping down into the Pacific Northwest and upper
Intermountain West on Thursday.

Overall wind fields should vary throughout the week, but will be
dry and gusty in nature through Tuesday to the north of
Sacramento. These should quiet by the following day as synoptic
gradients gradually relax. Farther south, the Delta breeze kicks
up each day but its more eastward influence does not really take
shape until mid-week. This ultimately brings a conclusion to the
brief period of excessive heat. ~BRO
&&


.EXTENDED DISCUSSION (Friday THROUGH Monday)

A cooling trend is expected for this weekend and into next week. Ensemble
guidance is in good agreement a trough will dip down into the
Western U.S. by this weekend, bringing cooler, near normal
temperatures to the forecast region. Breezy, northerly winds
combined with low relative humidities could create some fire
weather concerns for portions of the Sacramento Valley late in the
work week. Early next week, the Delta breeze is expected to
strengthen as the flow becomes more onshore bringing cooler temps
to Delta influenced areas. High temps across much of the valley
are only expected to reach into the mid to upper 80s Monday, with
mountain highs in the 60s to 70s. SLL
&&

.AVIATION...

VFR conditions expected for interior northern California for the
next 24 hours. Isolated mountain showers and thunderstorms
possible this afternoon and evening, mainly south of I-80.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from 9 AM to 10 PM PDT Tuesday for Central
Sacramento Valley-Clear Lake/Southern Lake County-Motherlode-
Mountains Southwestern Shasta County to Northern Lake County-
Northeast Foothills/Sacramento Valley-Northern Sacramento Valley-
Shasta Lake Area / Northern Shasta County-Southern Sacramento
Valley.

&&

$$