textproduct: Sacramento

KEY MESSAGES

- Cooler and more seasonable weather through Saturday before a return to hot and dry conditions Sunday through next week.

- Elevated fire weather conditions are anticipated due to the potential for elevated mountain thunderstorms and gusty thunderstorm outflow winds.

DISCUSSION

Conditions across the area this afternoon show mostly sunny skies with temperatures in the 80s to mid 90s for daytime highs. Warmest temperatures are expected in the northern Sacramento Valley. Upper level pattern has a weak shortwave moving along the California coast and shifting inland through the early part of the weekend. Moisture influx and instability increase as the shortwave moves onshore. HIRES guidance has indicated the potential for isolated thunderstorm activity within the Sierra for this afternoon and evening (along and south of I80), with soundings indicating modest moisture in the low levels along and west of the crest. There is a potential for a few isolated dry thunderstorms mainly in the Sierra and along the crest this afternoon/evening. Probabilities are 20 percent for occurrence as the soundings indicate sufficient moisture content. None the less, this brings the elevated fire weather concerns for today.

Chances for continued isolated showers and thunderstorms overnight and into Friday, with coverage increasing along the northern and northeastern section of the forecast area Friday morning. This would include the southern Cascades into portions of the coastal range near Shasta county. As the center of shortwave moves onshore, initiation of thunderstorms start in the southern Cascades and coastal range through Shasta county. Some dry air is noted in the latest HIRES atmospheric soundings showing slight inverted V structures at times. Elevated fire weather concerns are anticipated from isolated to scattered dry thunderstorms during the morning and afternoon hours on Friday. Main threats from the dry thunderstorms would be new fire starts and gusty outflow winds.

Uncertainty arises with the coverage of the dry thunderstorms and how much dry air is near the surface through 700mb. As of right now the probabilities of thunderstorms is around 30 percent with the highest in the southern Cascades. This is where the CAMS have picked up the highest chances for initiation of thunderstorms as the short wave moves onshore. Because of the remaining uncertanity in coverage and nature of thunderstorms, we do not anticpated the need for a Red Flag Warning at this time. We will conitnue to monitor the latest trends and if the need arises for the increased messaging for fire weather concerns.

Around the mid to late afternoon hours, chances for storms begin to dwindle as the wave moves further east. Concerns for fire weather start to dwindle by the evening and overnight hours.

Moving into the weekend and beyond we will start to heat back up into the 90s across the area, with the potential for lower 100s as we move into the new work week. Conditions will start to dry out quickly and RH values begin to drop. Confidence is increasing in the potential for breezy conditions at times next week on top of the drier conditions. We will continue to monitor the fire weather conditions for next week.

AVIATION

VFR conditions are expected through the TAF period. Winds are light and variable, but increase out of the west for the Sacramento sites this afternoon and evening. Sustained winds up to 15kts are possible. Periods of gusts of 20-25kts for Sacramento sites this evening. RDD and RBL will see southerly winds this afternoon and evening, while SCK and MOD see WNW to NW winds. Winds do go light and variable overnight and into tomorrow morning. Otherwise, higher terrain isolated showers and thunderstorms will be possible this afternoon and evening.

STO WATCHES/WARNINGS/ADVISORIES

Red Flag Warning from 5 AM to 7 PM PDT Friday for Burney Basin- E. Shasta /S. Cascades Above 3000 ft-Shasta County Foothills 1000-3000 ft-Shasta Lake Area & 1-5 1000-3000 ft-Shasta Metro-W. Shasta County 1000-3000 ft-W. Shasta County Above 3000 ft.