727 
fxus66 ksto 211659 
afdsto 


Area forecast discussion 
National Weather Service Sacramento California 
900 am PST Sat Nov 21 2009 


Discussion... 
clearing skies have developed across much of interior northern 
California in the wake of fridays system. Snow reports from 
yesterday are starting to filter in from yesterday...over a foot of 
snow fell near the Sierra crest with widespread swaths of 5 to 10 
inches of snow. Snow managed to accumulate to around half an inch as 
low as nearly 3000 feet elevation. 


The main concern in the immediate short term is widespread fog. Two 
swaths of fog are evident on visible satellite...one narrow area 
along I-5 from Redding to around Corning. The other is a bit more 
extensive running from Willows through the Sacramento metropolitan area to 
just north of Stockton. The fog should disperse in the middle to late 
morning hours as we start to see some more mixing. 


A brief period of dry weather is expected today before the next 
system moves towards the area. This next wave is a fair bit quicker 
than the last and most of its energy will remain north towards 
Oregon. However...warm advection processes will allow some light 
precipitation to develop across the region mainly to the north of 
I-80 late tonight and continue into midday Sunday. Not a whole lot 
of moisture with this system and snow levels should remain 
relatively high...so only light snow accumulations are expected over 
higher elevations. Not expecting any updates to the current forecast 
package at this time. Dang 


Previous discussion... 
more substantial ridging is forecast to develop over the eastern 
Pacific and northern California early next week and continue much of 
the week. Much milder temperatures are forecast to return to the 
foothills and mountains...while milder valley temperatures will 
depend on how strong offshore flow gets during the week and whether 
it provides enough mixing to realize some of this warming at the 
lower elevations. All medium range models indicate another system 
weakening as it moves into the ridge later Thanksgiving or Friday 
with the European model (ecmwf) faster on the timing of either the GFS or Gem. 


&& 


Aviation... 
IFR/LIFR conds in fog/St until around 18z in SAC valley and extreme northern 
sj valley otherwise VFR conds through 06z sun. Warm front and associated upper 
trough move into norcal tonight into sun. For Central Valley after 06z 
sun...areas of MVFR/IFR conds mainly north of I-80 in -ra/br. For 
fthls/mountains after 06z sun...widespread IFR and local LIFR conds obscrg terrain 
developing from north-S overnight Sat into Sun morning. Snow levels generally 045-055 mean sea level. 
Areas westerly surface wind gusts to 30 kts or gtr over hyr mountain terrain after 06z sun. 


Taf sites: ksmf and ksac are both in center of southern SAC valley fog 
area. Fog has now advected southeast over kmhr...keeping ksmf...ksac and 
kmhr in similar conds. Krdd and krbl are within narrower band of 
fog...so it may thin out a bit sooner. Jmc 


&& 


Sto watches/warnings/advisories...none. 


&& 


$$