000
FXUS66 KSTO 212230
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
330 PM PDT Sat Jul 21 2018

.SYNOPSIS...
Near this weekend with the potential for isolated thunderstorms
in the mountains. Hot weather returns next week, peaking mid week.

&&

.DISCUSSION...
Mostly sunny weather today with temperatures near normal. It`s generally
a little cooler than yesterday, with onshore flow and a Delta
breeze. Monsoonal moisture is bringing some convection into the
northern Sierra, though most activity is focused east of the
crest. Lack of a shortwave to provide lift is the factor limiting
thunderstorm development.

Sunday will be similar to today, except that some
afternoon/evening thunderstorm activity may extend into the
northern Coastal Range and around Lassen Park and eastern Shasta
county as monsoonal moisture spreads northward. Monday and Tuesday
convection should be limited to the northern Sierra again.

Warmer temperatures return early next week as ridge of high
pressure strengthens and retrogrades westward. Locations over the
northern Sacramento Valley will likely exceed the century mark
early next week, reaching up to 105-108. Current trends suggest onshore
flow could limit significant daytime heating near the Delta-
influenced areas, with temperatures in the upper 90s to around
100 in the southern Sacramento and northern San Joaquin valleys.
An Excessive Heat Watch is in effect for the Valley and adjacent
foothills Tuesday through Thursday. At this point it appears the
most likely area for a possible Warning or Watch is to the north
of I80. EK

&&
.EXTENDED DISCUSSION (Wednesday THROUGH Saturday)
High pressure ridge that will be centered over the Great Basin
area early next week will begin to retrograde Wednesday through
late next week. Hot weather continues with temperatures topping
our at 100-110 degrees through the valley on Wednesday. Upper
level flow flattens out slightly over NorCal Thursday into the
weekend as the ridge continues to retrograde. This will allow
temperatures to fall somewhat, though still expect valley
temperatures to be warm. An excessive heat watch is still in
effect through Thursday night. Onshore flow is expected to
continue through late next week which will help keep overnight
temperatures in the 60s near the Delta region. Thunderstorm
chances will mostly remain east of the Sierra crest south of Lake
Tahoe through Thursday. HEC

&&

.AVIATION...
VFR conditions the next 24 hours. Isolated thunderstorms possible
northern Sierra Nevada and vicinity Mt Lassen 22Z-03Z. Southwest
winds 15-25 kts near the Delta with winds 10-15 kts elsewhere 22Z-
05Z. &&

.STO WATCHES/WARNINGS/ADVISORIES...
Excessive Heat Watch from Tuesday afternoon through Thursday
evening 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-Northern San Joaquin Valley-Shasta
Lake Area / Northern Shasta County-Southern Sacramento Valley-
Western Plumas County/Lassen Park.

&&

$$