textproduct: San Francisco Bay Area

KEY MESSAGES

- Warming and drying trend will bring widespread moderate to major HeatRisk through Thursday

- Cooler temperatures, closer to normal, Friday into the weekend

SHORT TERM

(Today through Friday)

A northward intrusion of mainly mid and high level tropical moisture from the remnants of Marie continues through the North Bay Area with more filling in overnight. Warm temperatures will continue tonight with the incoming cloud layers greatly reducing radiative cooling. Sub- cloud layer dry air does at times tend to stay land- locked over the highly varied terrain of CA, until diurnal mixing, diffusion, wind transport and/or precipitation get going to thoroughly mix in the higher humidity to ground level. The radar KMUX currently shows showers moving by about 70 miles offshore. This bears close monitoring in the nearest term.

No changes to the forecast at this time. A Heat Advisory remains in effect for the entire forecast area until 10 PM Thursday. Strong high pressure will result in warm morning low temperatures and daytime highs in the 90s to lower 100s over much of the forecast area. Along the immediate coastline an afternoon sea breeze may help nudge temperatures back down. This is a complex pattern, please stay tuned for the latest updates. Cooler, more seasonal temperatures are expected by Friday.

From the earlier forecast discussion:

Please remember these tips to help mitigate impacts from heat exposure:

-Suspend unnecessary outdoor activities during the extreme heat, but if you must be outdoors, take frequent breaks in the shade or AC and drink cool water. -Know the signs and symptoms of Heat Exhaustion vs. Heat Stroke! Heat Stroke can be deadly if not treated immediately by a medical professional. Call 911 if you suspect someone is suffering from Heat Stroke. -Wear a life jacket, swim near a lifeguard, and check conditions before entering the water if going to a river or ocean to cool off. Rivers and the ocean are extremely cold, and Cold Water Shock can turn into paralysis and drowning if you are not careful. -Use a cool and damp towel on your body if you do not have AC and are feeling hot. Or, take a cool shower or bath. -Do not leave kids or pets in a parked car. -Ensure pets and livestock have access to shade and water.

LONG TERM

(Saturday through next Wednesday)

The main concern is the short term.

A weekend cooling trend remains in the forecast. The strong ridge over our forecast area will weaken. Dry weather is forecast.

AVIATION

(18Z TAFS)

VFR conditions are expected to continue as mid to high clouds continue through the region. Light offshore flow will continue to disrupt the marine layer today. These factors are both contributing to the high confidence VFR forecast across the terminals today. An afternoon sea breeze will easily overpower the offshore gradient, with a moderate to fresh breeze expected in the afternoon and evening. More consistent onshore flow is expected to return by Thursday, bringing low clouds back into play.

Vicinity of SFO...High confidence in VFR conditions through the TAF period. Winds are currently light and variable, but the NW sea breeze will take hold this afternoon. Gusty NW winds potentially up to 15 kts could occur this afternoon.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR conditions are anticipated to persist through the TAF period with mid to high clouds returning overnight. Light drainage winds in the morning will flip to a moderate onshore breeze in the afternoon.

MARINE...as of 11:41 AM PDT Wednesday

A moderate NW breeze and moderate seas will continue through Thursday. By Friday, a tighter pressure gradient will cause a steady increase in wind speed through the weekend, with a strong NW breeze expected Saturday and Sunday. A moderate SW swell from distant tropical cyclones will continue through the week.

MTR WATCHES/WARNINGS/ADVISORIES

.Tngt...Heat Advisory...CAZ006-502>506-508>510-512>518-528>530 Coastal Flood Advisory...CAZ006-506-508-529-530