Area Forecast Discussion
Issued by NWS Sacramento, CA

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000
FXUS66 KSTO 240620
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
1015 PM PST Fri Jan 23 2015

.Synopsis...
Dry weather forecast with areas of night and morning valley low
clouds and fog through Monday. Temperatures expected to remain
well above normal through the early next week in fog free areas.
Potential for some light precipitation exists Tuesday into
Thursday of next week.

&&

.Discussion...
High clouds will temporarily mask the Stratus deck over Srn Sac Vly
this evening...but they should move SEwd later tonite yielding a
much clearer view of the Nrn portion of the ST deck that will spread
NNWwd overnite. At press time...the stratus had spread from the Ern
SJV and Srn Motherlode towards SMF and into SWrn Placer Co...and
Wwd into Solano Co at least into the SUU/Fairfield area.

The LAPS analysis shows SEly surface flow as far N as central Yolo
Co...to around Nicolaus and the ST deck is expected to spread at
least as far N as those locations by morning. The HR3 infers the
ST/low vsbys should spread as far N as about CIC/Orland by early Sat
morning. Nly flow forecast to the N of that area should keep the
ST/fog from advecting into the Nrn Sac Vly.

Tweaked the wording in the evening update for the expanding ST deck
and to raise the min temps in the far Nrn zones due to
warming/mixing from Nly flow.     JHM


.Previous Discussion...

Strong upper ridging building over Interior NorCal with clear skies,
light wind, and moist boundary layer resulted in extensive area of
dense fog in the Central Valley this morning. Satellite showing
the low clouds are eroding quickly and the CWA should be
relatively cloud free by early evening. Low clouds and fog are
expected to redevelop again tonight, initially in the Northern San
Joaquin Valley then expand northward into the Sacramento Valley
and west into the Delta. Dense fog advisory may be needed again
for Saturday morning.

Models similar in continuing to amplify strong upper ridge off the
West Coast and building it inland over NorCal through the weekend.
5H heights progged into the middle 580 DM Saturday. MOS guidance
bumping high temperatures into the mid 70s across the Northern
Sacramento Valley Saturday, which is approaching record values.
Extensive night and morning valley fog will continue to moderate
synoptic warming in the Southern Sacramento and Northern San Joaquin
Valleys, where upper 50s to lower 60s expected.

Upper ridge axis shifts through Interior NorCal Sunday with
continued night and morning valley fog and well above normal
temperatures in fog free areas. Locally breezy easterly wind
continues over the weekend into Monday morning for portions of the
eastern foothills/Motherlode and Sierra Nevada.

Models showing omega block over the Intermountain West Monday with
trapped closed low off the Baja coast. As upstream troughing
approaches the West Coast, this low is forecast to begin lifting
towards SoCal. Models spread some higher level cloudiness into the
area, from the south, Monday which, along with lower heights/
thicknesses will bring some minor cooling to the forecast area.

PCH

&&

.Extended Discussion (Tuesday through Friday)

Unfortunately dry pattern looks to continue across much of NorCal
into the long term. Only chance of precip looks to be mid week. Upper
ridge will be off to the east for the start of the long term as a
closed upper low off the Baja coast rotates eastward into the SW
CONUS. The low will then lift northward Tuesday into Wednesday into
the area. While guidance does indicate the arrival of some
subtropical moisture with this system, bulk of it will remain
removed to the east of the local area. Models continue with drier
trend with any precipitation likely occurring over the Sierra Tues
into Thursday. A few showers can`t be ruled out in the Valley
during this time frame but amounts will remain light. Have nudged
POPs down accordingly to mirror latest trends. Another cutoff low
then rotates offshore of SoCal for the end of the week but little
chance of any significant moisture making it this far north. High
pressure ridge then looks to build in again for the weekend with
dry weather and above normal temps continuing. CEO


&&

.Aviation...

Low clouds and fog will become widespread in the Valley again
tonight with IFR/LIFR conditions mainly from KMOD and Nwd towards
the KMYV/KCIC areas after 08-10z. Conditions will gradually improve
to MVFR/VFR Sat afternoon.

&&

.STO Watches/Warnings/Advisories...
None.
&&

$$









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