Dry weather with a warming trend the rest of the week and into the weekend. Periods of breezy north to east winds into the weekend. Dry weather pattern continues through the middle of the month.
Discussion
Yesterday’s short wave and associated high cloud cover have dropped south of our CWA as the short wave continues to parallel the Srn half of the CA coast. Residual Nly winds in the wake of this short wave will be slackening today as the Ern Pac ridge tilts positively into Norcal behind the Sly dropping short wave along the CA coast and ahead of the upstream NErn Pac trof. Simulated satellite imagery indicates this upstream trof will spread a lot of high cloudiness over Norcal beginning late tonight and into Sat as it moves through the Pac NW.
Precip will remain well north of CA due to the strong Ern Pac ridge building Nwd along the W Coast and into NorCal with a dry and warmer air mass. Max temps into the low to mid 70s are likely across the Nrn Sac Vly and well into the 60s in the Srn Sac/Nrn SJ Valleys.
The clouds will clear out Sat night over NorCal as the trof moves into the mid section of the USA carving out a long wave trof and allowing the Pac ridge to push inland a little farther prompting additional warming Sun. Surface high pressure over the Great Basin will continue to cause late night/early morning katabatic winds with the NAM 925 mbs winds suggesting Sat night/Sun morning will see the stronger winds in the low 30s kts in those areas prone to downsloping winds.
The combination of adiabatic warming from the katabatic winds and a 2+ positive 850 mbs temp anomaly setting up over the NWrn portion of CA, including our Nrn/central Sac Vly with 850 mbs temps in the low to mid teens deg C, suggests some unseasonably mild temps for our CWA Sun and Mon.
Granted we don’t see the downward momentum transfer with the Feb sun angle, but this would equate to max temps in the low to mid 80s in the spring/summer months. Subtracting a conservative 10 deg puts temps in the 70s in the Valley which is not uncommon in Feb.
Since 2001, 16 times the monthly highest max temp has exceeded 70 deg F at DTS. Remembering Feb of 2006, DTS recorded 8 consecutive days of max temps >=70 F from the 7th thru the 14th (inclusive). (And BTW, KRDD topped out at 80 deg F on the 8th in Feb 2006 and had 7 consecutive days where the max temp exceeded 70 F from the 7th through the 13th). NBM Viewer shows a 30% chance of RDD seeing 80F Tue through Fri, increasing to near a 50% chance Thu. Chances of KSAC seeing 70F increase to 25-50% from Tue and the rest of next week as strong and persistent high pressure dominates the region.
Extended Discussion (Tuesday through Friday)
There is high confidence in ensemble guidance that the upper level ridge will remain through next week, strengthening over the West Coast through mid to late week. Dry weather and offshore flow will prevail under this pattern. Temperatures will increase through late week with daytime temperatures 10-20 degrees above normal.
Widespread 70s are forecast across the Valley by Wednesday, with upper 70s to near 80 in the northern Sacramento Valley.
Foothills could see upper 60s to low 70s, and the mountains 40s to low 60s. For reference, normal daytime temperatures at this time of year are right around 60 degrees in the Valley, mid 50s in the foothills, and 40s in the mountains. Overnight temperatures will also warm to near to above seasonal normal.