October 18, 2019 – Light showers are forecast for the northern mountains and far Northern Sacramento Valley overnight tonight and into the day Saturday. Otherwise, dry throughout the remainder of the forecast period. Below normal daytime temperatures this weekend will warm to above normal next week. Mid week could see slightly breezy north winds in the Valley.
Flat high pressure ridging over the state will bring dry conditions and daytime high temperatures a few to several degrees below normal. Models in good agreement in bringing a shortwave trough through the Pacific Northwest Saturday morning and through the day. Main precipitation threat will be over the mountains north of interstate 80 and over the far northern Sacramento valley but most of the CWA will see at least some cloud cover. High pressure begins rebuilding over the west coast as early as Saturday evening bringing an end to any precipitation threat. Surface high pressure building into the Pacific Northwest will bring breezy north winds on Sunday but not especially strong and with the reasonably moderate RH values expected, a significant increase in fire danger is not expected. Light northerly breezes continue into Monday as high pressure builds over the west coast with airmass warming bringing several degrees of warming. Daytime highs on Monday under fair skies are forecast to reach a few to several degrees above normal.
Extended Discussion (Tuesday through Friday)
Ensemble means support increasing heights across the region as EPAC upper level ridging strengthens and nudges inland. This should result in stable conditions and warm temperatures during the extended period. Models continue to indicate a period of locally breezy northerly to easterly flow Wednesday into Thursday as surface pressure gradient tightens. EPS shows elevated wind gust probabilities for the Valley and the Sierra foothills during this period. This, in combination with dry conditions and warm temperatures could bring fire weather concerns. Temperature readings will reach into the low and mid 80s in the Valley next week, which is 5 to 10 degrees above normal for late October.