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FXUS66 KSTO 132320

Area Forecast Discussion
National Weather Service Sacramento CA
320 PM PST Wed Nov 13 2019

Dry weather pattern continues this week with a cooling trend. 
Warmer this weekend with well above normal high temperatures. 


Temps mostly trending a little cooler and likely reached their 
maximum earlier in the afternoon due to increasing high cloud cover 
ahead of the Pacific trof with the low center near 35N/135W. This 
trof is forecast to move inland Thu/Fri with synoptic cooling and 
continued thickening clouds into Fri morning. The 700-500 RH prog 
suggests the cloud cover will be thicker (more prevalent and opaque) 
tonight into Fri morning than the past couple of days for "cloudy" 
or "mostly cloudy" sky conditions. 

The trof will weaken drastically as it moves inland and into the 
strong ridge. The high resolution REFs from the NAM 3km keep radar
echoes (precip) to the WNW of our CWA, and will opt for the lower
(dry) PoPS on Fri. Behind the trof, a brief period of locally 
breezy conditions is possible over the NE Sac Vly Fthls, and 
Valley late Fri nite and into Sat morning. The average gusts are 
forecast in the 20-25 mph range at RDD and RBL on the ECMWF 
ensembles. Although temps will cool through Fri, they will 
continue to run above normal for the middle of Nov. 

As this trof passes over the ridge and digs into the Great Basin and
4-Corners area an Omega-Rex Blocking pattern will develop along the 
W Coast of NOAM this weekend. Anticyclonic flow from the 
repositioning of the strong ridge will return warmer temps to the 
CWA. Valley and Foothill max temps will warm into the 70s on Sat 
(low 80s far N on Sun). These temps are some 6 to 17 deg above 
normal on Sat, and some 9 to 21 deg above normal on Sun, with the 
greatest departures from normal over the Nrn Sac Vly. Probabilities 
are quite high that max temp records for the dates (Nov 16 & 17) 
will be equaled, if not exceeded, in the North Valley including 
RDD and RBL. 

The Day 7 500 mb heights Cluster suggests a positively tilted 
trof will develop over the Great Basin region which could bring 
some windy conditions to our CWA, and much cooler wx and possibly 
a few light showers mainly over the mtns. This 5H Cluster would 
support the retrograding solution of the ECMWF and closed low 
developing over Socal later next week.   JHM 



High pressure will be the dominate feature this weekend as it 
brings warmer and drier air back to the region. Temperatures are 
forecast to peak in the mid 70s to low 80s for the Valley on 
Sunday, while those in the mountainous terrain can expect highs 
ranging from the mid 50s to the low 70s. Relative to climatology, 
this is roughly 10 to 20 degrees above average. With a daily 
record high in Redding of 83 degrees (dating back to 1893), would 
not be surprised to see this either tied or broken. Well above 
average readings will continue into Monday given the ridge lingers
yet another day.

From Tuesday into later in the week, the upper ridge will finally
have advanced into the Rockies. A seasonably strong trough enters
the picture while accelerating through the Pacific Northwest early
Tuesday. While a few ensemble members support the trough taking a
farther west track bringing some scattered showers to the region,
a vast majority carry the system through the Central Great Basin
instead. The latter scenario would favor an uptick in northerly
gradients which lowers humidities and enhances wind fields. Given
this trough remains nearly a week out, it will need to be closely
monitored for any notable impacts. In the meanwhile, high 
temperatures from Tuesday onward should be noticeably cooler, but 
still roughly 3 to 6 degrees above average. ~BRO/KR



VFR conditions the next 24 hours except local MVFR visibilities 
from KSAC southward 12Z-17Z. Winds generally below 10 knots.



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