Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 232125
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
225 PM PDT Wed Apr 23 2014

.Synopsis...
Milder temperatures are forecast into Thursday, then another weather
system will bring a chance of widespread precipitation along with
cooler temperatures late Thursday into early Saturday. Thunderstorms
are possible Friday.

&&

.Discussion...
Weak upper ridging moving into the Great Basin as upstream Pacific
storm system approaches. Some overrunning WAA precip showing up radar
along the NW coast attm could spread into portions of the Coastal
and Shasta mountains overnight into Thursday. Associated cold
front then brings more widespread precip over the CWA Thursday
night into Friday. Significantly colder and unstable air is
ushered into the area Friday for the threat of showers and
thunderstorms. Cold pool aloft (5H temps around -28 to -30 deg C)
moves over Interior NorCal Friday...steepening lapse rates and
providing potential for thunderstorms, possibly with hail.
Isolated severe thunderstorms cant be ruled out, although shear
profiles don`t look real favorable. Snow levels will lower from
6000 to 7000 feet late Thursday to 4500 to 5500 feet Friday and
down to 3500 to 4500 feet Friday night into Saturday morning.
Models continuing to show significant differences in QPF,
especially in the Eastern Shasta, Western Plumas and Northern
Sierra Nevada mountains. Oper GFS nearly double the QPF of the NAM
in the NE mountains and almost three times compared to the ECMWF-
HiRes. Both the GFS/NAM are about double the amount of the Euro in
the Northern Sierra Nevada. QPF values in the Central Valley
generally about half an inch or less with the GFS showing high
amounts towards the eastern foothills. Potential for winter
weather advisory criteria in the higher Trans-Sierra, but given
differences in model QPFs, will issue an SPS for now. Potential
exist though for up to a foot or more of snow in the higher
mountain terrain. High temperatures on Friday likely to be 10 to
20 degrees lower than Thursday with upper 50s to lower 60s in the
Central Valley and upper 30s to 50s for the mountains and foothills.

Lingering showers may be possible over the mountains through the
weekend but in general weak short wave ridging progged over Interior
NorCal. AMS warms slightly with high temps returning to near normal
by Sunday.

PCH

&&

.Extended Discussion (Sunday through Wednesday)

A weak wave moves through the Pacific Northwest on Sunday for
possible showers...especially over the mountains. Temperatures on
Sunday are expected to be in the upper 60s to low 70s in the
Valley and 40s and 50s in the mountains which is a few degrees
below normal for this time of year. Temperatures will warm up to
near to above normal with dry weather Monday into Wednesday with
the ridge building over the area. Temperatures on Tuesday
expected to be in the low to mid 80s in the valley and upper 50s
to low 70s in the mountains, which is a few degrees above normal
for this time of year. The GFS has the ridge shifting to the east
with a trough moving into the Pacific Northwest on Wednesday which
could bring a little precipitation to the far north and a little
cooling. The ECMWF keeps the ridge over the area on Wednesday.
The forecast leans toward the ECMWF with a dry forecast and
similar temperatures on Wednesday.


&&

.Aviation...

VFR conditions continue for the next 24 hours. Winds generally
light up to 12 kts. Some moderate gusts in the KSCK-KMOD vicinity
up to 20 kts between now and 03z.  JBB


&&

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

$$







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