Area Forecast Discussion
FXUS66 KMTR [Monterey CA] 232107 AFDMTR ∨
FXUS66 KMTR 232107 AFDMTR [HEAD]
National Weather Service San Francisco Bay Area 2:07pm PDT Thu Oct 23 2014 ∨
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA 207 PM PDT THU OCT 23 2014 [HEAD]
Synopsis. A stalled out frontal boundary just to the north should keep most precipitation out of the region through Friday. Rain chances increase region-wide Friday night through Saturday morning as a stronger system pushes a cold front into central California. Chances for precipitation will diminish Sunday into Monday with near seasonal temperatures. ∨
.SYNOPSIS...A STALLED OUT FRONTAL BOUNDARY JUST TO THE NORTH SHOULD KEEP MOST PRECIPITATION OUT OF THE REGION THROUGH FRIDAY. RAIN CHANCES INCREASE REGION-WIDE FRIDAY NIGHT THROUGH SATURDAY MORNING AS A STRONGER SYSTEM PUSHES A COLD FRONT INTO CENTRAL CALIFORNIA. CHANCES FOR PRECIPITATION WILL DIMINISH SUNDAY INTO MONDAY WITH NEAR SEASONAL TEMPERATURES. [DISC]
Discussion. As of 02:04pm PDT Thursday… a weak frontal boundary stalled just north of Sonoma and Napa Counties should keep most precipitation north of the region tonight. However… with the possibility of this deeper moisture and frontal boundary sagging southward… have kept chances for precipitation over portions of the North Bay. Overall… any rainfall amounts should remain light across the North Bay region overnight. This boundary is forecast to lift northward on Friday and will likely keep dry weather conditions and mild temperatures over the entire region. The main forecast challenge for Friday morning will be the development of coastal stratus. Have increased cloud cover over the coastal waters and along the coast overnight tonight through Friday morning as boundary layer moisture is expected to rapidly return. Already seeing some stratus offshore below the high clouds on visible satellite. ∨
.DISCUSSION...AS OF 02:04 PM PDT THURSDAY...A WEAK FRONTAL BOUNDARY STALLED JUST NORTH OF SONOMA AND NAPA COUNTIES SHOULD KEEP MOST PRECIPITATION NORTH OF THE REGION TONIGHT. HOWEVER...WITH THE POSSIBILITY OF THIS DEEPER MOISTURE AND FRONTAL BOUNDARY SAGGING SOUTHWARD...HAVE KEPT CHANCES FOR PRECIPITATION OVER PORTIONS OF THE NORTH BAY. OVERALL...ANY RAINFALL AMOUNTS SHOULD REMAIN LIGHT ACROSS THE NORTH BAY REGION OVERNIGHT. THIS BOUNDARY IS FORECAST TO LIFT NORTHWARD ON FRIDAY AND WILL LIKELY KEEP DRY WEATHER CONDITIONS AND MILD TEMPERATURES OVER THE ENTIRE REGION. THE MAIN FORECAST CHALLENGE FOR FRIDAY MORNING WILL BE THE DEVELOPMENT OF COASTAL STRATUS. HAVE INCREASED CLOUD COVER OVER THE COASTAL WATERS AND ALONG THE COAST OVERNIGHT TONIGHT THROUGH FRIDAY MORNING AS BOUNDARY LAYER MOISTURE IS EXPECTED TO RAPIDLY RETURN. ALREADY SEEING SOME STRATUS OFFSHORE BELOW THE HIGH CLOUDS ON VISIBLE SATELLITE. [DISC]
The next mid/upper level trough is forecast do deepen over the eastern Pacific and approach the Pacific Northwest late Friday night. With this… rain chances will increase over the coastal waters and North Bay as moisture advects across the region ahead of the frontal boundary. With increased mid/upper level support as the front moves into the region… isolated thunderstorms will be possible Saturday morning/afternoon across our northern coastal waters inland into the North Bay. Further south… showers will increase along the boundary and bring rain to much of the San Francisco Bay Area down along then Central Coast. At this time… the greatest rainfall amounts appear to occur over the North Bay and along the west/southwest facing slopes down the coastline. Cannot rule out some locations picking up one-quarter to nearly one inch of rainfall Friday night through Saturday. With increased clouds and precipitation chances… temperatures will be noticeably cooler on Saturday. ∨
THE NEXT MID/UPPER LEVEL TROUGH IS FORECAST DO DEEPEN OVER THE EASTERN PACIFIC AND APPROACH THE PACIFIC NORTHWEST LATE FRIDAY NIGHT. WITH THIS...RAIN CHANCES WILL INCREASE OVER THE COASTAL WATERS AND NORTH BAY AS MOISTURE ADVECTS ACROSS THE REGION AHEAD OF THE FRONTAL BOUNDARY. WITH INCREASED MID/UPPER LEVEL SUPPORT AS THE FRONT MOVES INTO THE REGION...ISOLATED THUNDERSTORMS WILL BE POSSIBLE SATURDAY MORNING/AFTERNOON ACROSS OUR NORTHERN COASTAL WATERS INLAND INTO THE NORTH BAY. FURTHER SOUTH...SHOWERS WILL INCREASE ALONG THE BOUNDARY AND BRING RAIN TO MUCH OF THE SAN FRANCISCO BAY AREA DOWN ALONG THEN CENTRAL COAST. AT THIS TIME...THE GREATEST RAINFALL AMOUNTS APPEAR TO OCCUR OVER THE NORTH BAY AND ALONG THE WEST/SOUTHWEST FACING SLOPES DOWN THE COASTLINE. CANNOT RULE OUT SOME LOCATIONS PICKING UP ONE-QUARTER TO NEARLY ONE INCH OF RAINFALL FRIDAY NIGHT THROUGH SATURDAY. WITH INCREASED CLOUDS AND PRECIPITATION CHANCES...TEMPERATURES WILL BE NOTICEABLY COOLER ON SATURDAY. [DISC]
While lingering showers will be possible Saturday evening in wake of the frontal passage… most locations will begin to dry out Saturday night into Sunday. With a cooler and drier air mass aloft… surface temperatures will remain on the cool side of normal Sunday and Monday. Early next week… the forecast models differ on the upper level pattern across the state. Cannot rule out light precipitation returning to the North Bay Tuesday as another plume of moisture spreads into Northern California. However… will keep most areas dry through early next week until the forecast models diverge on a more concise solution. ∨
WHILE LINGERING SHOWERS WILL BE POSSIBLE SATURDAY EVENING IN WAKE OF THE FRONTAL PASSAGE...MOST LOCATIONS WILL BEGIN TO DRY OUT SATURDAY NIGHT INTO SUNDAY. WITH A COOLER AND DRIER AIR MASS ALOFT...SURFACE TEMPERATURES WILL REMAIN ON THE COOL SIDE OF NORMAL SUNDAY AND MONDAY. EARLY NEXT WEEK...THE FORECAST MODELS DIFFER ON THE UPPER LEVEL PATTERN ACROSS THE STATE. CANNOT RULE OUT LIGHT PRECIPITATION RETURNING TO THE NORTH BAY TUESDAY AS ANOTHER PLUME OF MOISTURE SPREADS INTO NORTHERN CALIFORNIA. HOWEVER...WILL KEEP MOST AREAS DRY THROUGH EARLY NEXT WEEK UNTIL THE FORECAST MODELS DIVERGE ON A MORE CONCISE SOLUTION. [DISC]
Aviation. As of 10:50am PDT Thursday… large area of mid and high clouds streaming across the northern half of the Bay Area as a low moves into the Pacific Northwest. Current expectations are that the rain will not make it to any terminals so have not mentioned any rain in the TAFs [Terminal Aerodrome Forecasts]. Lower clouds will develop late tonight especially towards the 12Z [5am PDT] Friday time frame. These lower ceilings will persist through most of the remaining TAF [Terminal Aerodrome Forecast] period. ∨
.AVIATION...AS OF 10:50 AM PDT THURSDAY...LARGE AREA OF MID AND HIGH CLOUDS STREAMING ACROSS THE NORTHERN HALF OF THE BAY AREA AS A LOW MOVES INTO THE PACIFIC NORTHWEST. CURRENT EXPECTATIONS ARE THAT THE RAIN WILL NOT MAKE IT TO ANY TERMINALS SO HAVE NOT MENTIONED ANY RAIN IN THE TAFS. LOWER CLOUDS WILL DEVELOP LATE TONIGHT ESPECIALLY TOWARDS THE 12Z FRI TIME FRAME. THESE LOWER CIGS WILL PERSIST THROUGH MOST OF THE REMAINING TAF PERIOD. [AVIA]
Vicinity of KSFO [San Francisco CA]… VFR [Visual Flight Rules] conditions with just mid and high clouds. Increasing low level moisture will produce reduced ceilings after 07Z [12am PDT]. This will persist through the end of the TAF [Terminal Aerodrome Forecast] period. Low-moderate confidence. ∨
VICINITY OF KSFO...VFR CONDITIONS WITH JUST MID AND HIGH CLOUDS. INCREASING LOW LEVEL MOISTURE WILL PRODUCE REDUCED CEILINGS AFTER 07Z. THIS WILL PERSIST THROUGH THE END OF THE TAF PERIOD. LOW- MODERATE CONFIDENCE. [AVI2]
KSFO [San Francisco CA] bridge approach… similar to KSFO [San Francisco CA]. ∨
KSFO BRIDGE APPROACH...SIMILAR TO KSFO. [AVI2]
Monterey Bay Area terminals… VFR [Visual Flight Rules] conditions expected all day with just some mid level clouds moving in. MVFR [Marginal Visual Flight Rules]-IFR [Instrument Flight Rules] conditions develop after 06Z [11pm PDT] and worsen around 13Z [6am PDT] Friday and persist through end of TAF [Terminal Aerodrome Forecast] period. ∨
MONTEREY BAY AREA TERMINALS...VFR CONDITIONS EXPECTED ALL DAY WITH JUST SOME MID LEVEL CLOUDS MOVING IN. MVFR-IFR CONDITIONS DEVELOP AFTER 06Z AND WORSEN AROUND 13Z FRI AND PERSIST THROUGH END OF TAF PERIOD. [AVI2]
Marine. As of 02:04pm PDT Thursday… a weak ridge of high pressure continues over Southern California coast while low pressure will strengthen to our west over the next few days. This is bringing light winds to the area today which will become southerly and increase Friday and Saturday as the low pressure system strengthens off the Oregon coast. High pressure will build off the California coast Sunday and Monday after the low moves inland. ∨
.MARINE...AS OF 02:04 PM PDT THURSDAY...A WEAK RIDGE OF HIGH PRESSURE CONTINUES OVER SOUTHERN CALIFORNIA COAST WHILE LOW PRESSURE WILL STRENGTHEN TO OUR WEST OVER THE NEXT FEW DAYS. THIS IS BRINGING LIGHT WINDS TO THE AREA TODAY WHICH WILL BECOME SOUTHERLY AND INCREASE FRIDAY AND SATURDAY AS THE LOW PRESSURE SYSTEM STRENGTHENS OFF THE OREGON COAST. HIGH PRESSURE WILL BUILD OFF THE CALIFORNIA COAST SUNDAY AND MONDAY AFTER THE LOW MOVES INLAND. [AVIA]
.MTR WATCHES/WARNINGS/ADVISORIES... .TNGT...NONE. [WARN]
Public Forecast: Rgass; Aviation/Marine: Johnson ∨
PUBLIC FORECAST: RGASS AVIATION/MARINE: JOHNSON [CRED]
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1:50pm PDT Oct 23 2014
This Afternoon. Mostly cloudy, with a high near 66°. WNW wind around 7 mph.
Tonight. Mostly cloudy, with a low around 58°. NNW wind 5 to 7 mph becoming calm in the evening.
Friday. Increasing clouds, with a high near 67°. East wind 6 to 9 mph becoming SSW in the afternoon.
Friday Night. A 30% chance of rain after 11pm. Mostly cloudy, with a low around 57°. South wind 13 to 21 mph, with gusts as high as 26 mph.
Saturday. Showers likely, mainly before 11am. Mostly cloudy, with a high near 64°. Breezy, with a SW wind 18 to 23 mph, with gusts as high as 29 mph. Chance of precipitation is 60%.
Saturday Night. A 30% chance of showers. Partly cloudy, with a low around 56°.
Sunday. Mostly sunny, with a high near 61°.
Sunday Night. Mostly clear, with a low around 54°.
Monday. Sunny, with a high near 61°.
Monday Night. Mostly clear, with a low around 55°.
Tuesday. Mostly sunny, with a high near 64°.
Tuesday Night. Mostly cloudy, with a low around 57°.
Wednesday. Mostly sunny, with a high near 66°.