Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 211642

Area Forecast Discussion
National Weather Service Sacramento CA
940 AM PDT Fri Oct 21 2016

Dry today with a little above normal temperatures. Cooling
Saturday with a chance of precipitation spreading over the
forecast area late Sunday through mid week with below normal


Upper level high pressure over the southwest U.S. will keep
Northern California under fair skies today. The upper ridge axis
will be shifting eastward today in response to an upper trough
forecast to dig into the eastern Pacific. High temperatures today
should come in around normal for this time of year or just a bit
cooler than Thursday highs. An increase in onshore flow and a slight
airmass cooling will bring still cooler temperatures on Saturday.

Models in fairly good agreement in bringing a disturbance across the
northwest corner of the state Sun afternoon or evening. This will
bring a threat of light precip across the northwest corner of the
state southward to about Chico Sunday night. A more defined frontal
band is forecast to push into the north state Monday afternoon
bringing precipitation to most of the forecast area by Monday
evening and overnight. The rain band is forecast to spread into the
I-80 corridor with the >.25" line north of Srn Lake Co to MYV to
Quincy. The northern mountains will see the greatest amount of
precipitation but nowhere near the amounts observed last week.
That said, this morning`s QPF more than tripled previous QPF (1" to
more than 3") over Shasta Co for the Sun-Wed time period. The NAEFS
mean precip anomaly shows a broader and longer duration moisture
plume affecting Norcal than earlier runs. This is likely due to the
persistent NErn Pac low maintaining the moist WSWly flow into Norcal
for the first part of next week. The digging trof and closed low
along 140w will then lift the frontal band to the N by midweek...
before moving inland with another round of wet wx late in the week
or early next weekend.   /JHM

Breezy southwest winds and still more cooling will also result.



Trough of low pressure currently in the northeast Pacific
continues to be on track to affect northern California throughout
the long term forecast period. Model consensus continues to depict
increased chances for rain and snow above 7500 feet for Tuesday
with below normal high temperatures in the 50s and 60s.

The upper level low center is anticipated to retrograde back into
the eastern Pacific on Wednesday as a stronger jet stream area
deepens the upper trough off the coast. As a result, temperatures
will warm slightly into the 60s and 70s with fewer chances for
precipitation, although some chances still exist for some rain
across the forecast area. Current forecast model tracks show the
upper low making landfall again late next week into the weekend,
which will bring better chances for rain again to northern



VFR conditions next 24 hours. Light winds will prevail across TAF


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