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AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
458 AM PDT Thu Oct 23 2014

.Synopsis...
A weak Pacific cold front will drag slowly across NORCAL bringing
light precipitation north of about I-80 today and tonight. A brief
break Friday will be followed by another frontal passage on
Saturday with thunderstorms possible north of the Sacramento
area. Drying and warming most areas early next week then another
frontal system moving in around Tuesday. Weather model confidence
decreases by mid week but more light precip possible next Wednesday
and Thursday mainly north of Sacramento.

&&

A weak Pacific cold front dragging across the northwest corner of
the state is bringing light precipitation from about Chico
northward. The precipitation is forecast to continue moving very
slowly to the southeast with light precipitation reaching
southward to about the Sacramento area by 00z this afternoon.
Cloud cover and a slightly cooler airmass will bring slightly
cooler temperatures today. High pressure is forecast to rebound
northward over the western U.S on Friday limiting any
precipitation to the far northwest corner of the state. Clearing
skies and a warming airmass under the ridge will bring daytime
highs to near or a little above normal Friday. A Pacific low
pressure system approaching the coast will bring a threat of
precipitation inland Friday night with a chance of rain and high
elevation snow across the entire forecast area by Saturday
afternoon and evening. Precipitable water proggs show a moderate
amount of moisture associated with this system with moderate
dynamics but it will take mountain orograhics to squeeze out more
than light precipitation. 500 mb winds associated with the main
frontal passage early Saturday are progged to top 60 mph so
ridgetops may see some fairly gusty winds. Stability proggs show
enough instability behind the cold front for a threat of
thunderstorms Saturday afternoon and evening across the northern
CWA. As the upper trough passes through the Pacific Northwest
Saturday night and Sunday, winds will decrease and precipitation
will shift to the northeast. Daytime highs over the weekend will
remain well below normal under the cool airmass behind the front.

.Extended Discussion (Monday through Thursday)

Monday looks like a dry day with models rebuilding a ridge over
the eastern Pacific and west coast. Daytime highs may push back up
to near normal. A shortwave trough moving through the Paciiic
Northwest will flatten the west coast ridge on Tuesday bringing
clouds and cooler temperatures with a chance of precipitaton
across the northern mountains. After Tuesday...models really begin
to diverge so confidense in the day 6 plus forecast not real high.
GFS rebuilds a fairly strong ridge over the west coast Wednesday
and Thursday and has been doing so over the last couple of runs.
ECMWF and GEM dig the next upper trough into the eastern Pacific
Wednesday and Thursday bringing cooler temperatures and a
continued threat of precipitation especially across the northern
portions of the forecast area. Have leaned towards the more stable
ECMWF and GEM for now but will continue to watch model
developments in this time frame.

&&

.Aviation...

Cold front moving on shore today with increasing rain spreading
into the northern Sacramento Valley, peaking around 15z-21z. This
will bring some lcl visibilities reduced to MVFR levels, IFR in
the mountains. Local precipitation will stay mainly north of I80 today,
and will decrease in intensity by 00z. Mid level cloud cover will
increase over the rest of the area. Winds around 10 kt or less
expected today for TAF sites. EK

&&

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

$$

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