August 24, 2016 – Dry weather pattern with near to slightly below normal temperatures for the rest of the week.
Short term discussion (Today through Saturday)
Relatively benign wx pattern continues into the weekend for Norcal with temps near to slightly below normal and a lack of convection/ thunderstorms over the mountains in our CWA. Seasonably deep upper low over Saskatchewan will be moving Ewd today…but will maintain some troffiness back to the SW today and Thu keeping high pressure cells over the North Pacific and vcnty 30N/125W from making much Ewd progress and warming interior Norcal.
Onshore pressure gradients remain strong enough for a moderate to strong Delta Breeze to significantly cool the Solano Co area some 6-12 degrees below normal. This is expected to continue in that area for the next couple of days…with the breeze perhaps decreasing over the weekend as high pressure begins to build-in from the south. The stratus scheme came out negative due to the marine layer depth 1200-1700 ft and wide T/Td spreads. However, the strength of the Breeze suggests a thin strip of stratus may develop in the Srn Sac Vly briefly this morning.
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A review of the NAM dProg/dt for 18z Thu illustrates the “backdoor” short-wave from ID which brushes NErn CA (NE Plateau area) will be moving into Nrn NV a little faster than in recent runs. There were some C-G strikes in ID yesterday with this feature…but the elevated instability progs maintain a rather dry/stable/low TT values over our CWA. Only the NAM prog showed minor/isolated areas of instability in our CWA…but nothing that made a convincing argument to include a chance of thunder in our CWA (Lassen NP vcnty) at this time. For now…we would expect some cumulus cloud development is possible from late morning into afternoon on Thu in that area given the current trends.
Extended discussion (Sunday through Wednesday)
Model differences with synoptic features in the extended forecast period. GFS/GEM suppress upper high to south as upper troughing moves through the PacNW Sunday into Tuesday. GFS showing deeper system than GEM while ECMWF maintains more ridging over the area. Models show a secondary wave moving through midweek but differ on timing and track. All solutions have limited available moisture and forecast looks dry through the period. Slightly below normal temperatures expected Sunday into Monday, returning to near or slightly above normal by the middle of next week.