A storm system is expected to bring strong winds, widespread heavy rainfall, and flooding concerns to the Hawaiian Islands through the weekend. Strong to severe thunderstorms are forecast from the Southern Plains to the Mid-Missouri Valley Thursday afternoon and evening. Large hail and strong winds are the primary threats. Read More >
| ZOA CWSU Discussion | KSFO TAF TDA | |
| AWAITING CWSU INPUT | TAF TDA KSFO/KSQL METAR METARArea PIREPs PIREP |
|
| Satellite | Webcams, Ceiling≤030 Prob | |
|
Webcams
|
||
| SIERRA 03 Hour Forecast | SIERRA 12 Hour Forecast | SIGMETs |
| TANGO 03 Hour Forecast | TANGO 12 Hour Forecast | |
| ZULU 03 Hour Forecast | ZULU 12 Hour Forecast | |
| Area Forecast Discussion | Forecast Maps |
|
853 FXUS66 KMTR 091240 CCA AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 517 AM PDT Thu Apr 9 2026 ...New AVIATION, MARINE... .KEY MESSAGES... Updated at 1159 PM PDT Wed Apr 8 2026 - Unsettled weather Thursday through the weekend - Thunderstorms are possible today through Sunday with the best chances Friday and Saturday && .SHORT TERM... Issued at 1159 PM PDT Wed Apr 8 2026 (Tonight through Friday night) A surface low near 38 N, -133 W in the Eastern Pacific Ocean will be the talk of the short term. Our area narrowly escaped thunderstorms Wednesday as steeper lapse rates just to our north and east yielded greater instability. We did have enough lift and moisture however to record measurable precipitation. With the over performance that occurred Wednesday, I would expect more of the same Thursday as the low slowly treks eastward. The best chances for thunderstorms on Thursday will be in the North Bay, Interior East Bay, and Eastern Santa Clara County - the same areas that were narrowly missed today. Rain showers on Thursday will be more efficient as the low-levels have become saturated; in fact, the April 9th 00Z sounding observed a PWAT value of 1.04" which is the second highest for the date and time behind 1.08" from 2016. The greatest chances for thunderstorms will be Friday as the low enters our waters and continues its journey inland. The exact location and timing will make all the difference as the center of the low will offer an area of convergence. Since it is associated with an upper-level cutoff low, the independence from the jet stream unfortunately makes the precision side of the forecast very difficult. Nonetheless, the best chances are across the Interior Bay Area. Thunderstorm hazards on Thursday and Friday include: lightning, locally heavy rainfall, erratic/gusty winds, and small hail. Aside from thunderstorms, southwesterly winds carrying moist, warm air from the tropics will increase ahead of the cold front with pre-frontal rain showers expected in the warm sector. The slow movement and training effect of the rain bands may lead to localized flooding if a heavier rain shower/thunderstorm were to develop, especially in poor drainage and/or urban areas. && .LONG TERM... Issued at 1159 PM PDT Wed Apr 8 2026 (Friday night through next Wednesday) An upper-level low in the Gulf of Alaska will dig down the West Coast Saturday, absorbing the first low as it does so. This second system is much more dynamic which will yield two noticeable differences: widespread rainfall instead of just rain showers and thunderstorms capable of rotating. The three thunderstorm ingredients of lift, instability, and moisture will be similar if not better than the first low. A surface low and its attendant cold front will be the primary lifting mechanism, cold air filtering in aloft (850 mb temperatures near freezing) will steepen lapse rates and increase instability as a result, and PWAT values will remain near the 90th percentile ahead of the cold front. The shear profiles will be very different between the vertically stacked first low and the progressive second low. The vertically stacked low will have low shear while the progressive low will have sufficient low-level shear to support rotation within thunderstorms. All of this to say, widespread rainfall with lingering thunderstorm chances are expected over the weekend with the best chances on Saturday. Moisture will be a limiting factor behind the cold front, but if the coldest conditions overlap with ample moisture, snow is possible in the mountain peaks Sunday morning with snow levels around 4,000 feet. Rainfall totals between Thursday and Sunday continue to trend higher with totals on the order of 0.50"-1.50" with up to 3.00" in the coastal ranges. Commercial and recreational fisherpeople are encouraged to use extreme caution now through the weekend with the unsettled weather moving in. Thunderstorms over the waters will be capable of producing: lightning, locally heavy rainfall, gale force gusts, small hail, and waterspouts. In the cold front`s wake we will be left with, you guessed it, cold air! Cold starts to the day can be expected as skies clear and dry air filters in. The warming and drying trend kicks off Monday and lasts at least until Wednesday as surface high pressure builds into the West Coast. && .AVIATION... (12Z TAFS) Issued at 517 AM PDT Thu Apr 9 2026 Surface pressures are gradually lowering c/o the approaching 500 mb cut-off low and upper level jet stream divergence. Weak cool air advection continues. All of these processes are now finally weakening the lower level thermal ridge (temperature inversion) over our forecast area. Stratus is mixing with fog /IFR-LIFR/ while higher clouds are advancing over the marine layer i.e., higher clouds decreasing nocturnal radiative cooling. It may then mostly be the aforementioned cooling processes resulting in the air reaching saturation, stratus and fog mix. Webcams show patchy coastal drizzle as well in the slowly cooling air mass. High resolution model forecasts indicate stratus and fog mixing out later in the morning and afternoon. Steady cool air advection today, tonight and Friday will continue to deepen and weaken the marine layer temperature inversion (thermal ridge aloft); full mix out occurs when lower level temperatures are about the same as (or cooler than) sea surface temperatures. In the current synoptic/meso pattern it`s more complicated, since the incoming low will bring higher cloud layers and eventually rain. Light rain is introduced in the 12z TAFs. Periodic light coastal drizzle/light rain today will increase in coverage by tonight and Friday. Will also have to watch for potential convection Friday, though at the moment model forecasts are presenting mixed solutions i.e. not a high confidence forecast for Friday. Vicinity of SFO...Stratus /MVFR-IFR/ lifting to VFR by early afternoon. Low clouds with light rain tonight and Friday morning. Winds onshore 5 to 15 knots. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...Variable conditions at the moment with stratus and fog /IFR-LIFR/. Patchy light drizzle is possible during the morning. Conditions improving to MVFR-VFR by late morning and afternoon. MVFR-VFR in low clouds and light rain then developing late tonight and Friday morning. Light and variable winds becoming onshore near 10 knots late morning and afternoon. Light and variable winds tonight and Friday morning. && .MARINE... (Today through Tuesday) Issued at 442 AM PDT Thu Apr 9 2026 A low pressure system approaching the coast from the west today through Friday will merge with an energetic low from Alaska by Saturday and Sunday. Expect rain possibly heavy at times and a chance of thunderstorms Thursday through Sunday. High pressure builds behind the system with fresh northwest winds developing Sunday through Monday. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...None. && $$ SHORT TERM...Sarment LONG TERM....Sarment AVIATION...Canepa MARINE...Canepa Visit us at www.weather.gov/sanfrancisco Follow us on Facebook, X, and YouTube at: www.facebook.com/nwsbayarea x.com/nwsbayarea www.youtube.com/nwsbayarea |
|
| Yesterday | ⇛Visible ⇛Nighttime ⇛GeoColor+GLM | Today | |
| 24-Hour Temp Change | 24-Hour RH Change | ||
⇛Visible ⇛Nighttime ⇛GeoColor+GLM
 |
|
Additional Links
National Airspace System Status
Other Webcams:
Alert California San Bruno Mountain
Alert California Sutro Tower 2
Alert California Coll of San Mateo Bldg36
Follow us on X
ZOA RSS Feed