Area Forecast Discussion
FXUS66 KMTR [Monterey CA] 291727 AFDMTR ∨
FXUS66 KMTR 291727 AFDMTR [HEAD]
National Weather Service San Francisco Bay Area 10:27am PDT Sun May 29 2016 ∨
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA 1027 AM PDT SUN MAY 29 2016 [HEAD]
Synopsis. Slightly cooler weather is forecast for today, especially near the coast where there will be areas of low clouds and fog. A warming trend is then expected for Memorial Day and Tuesday. Warmer than normal temperatures will continue through the end of the week. Dry weather will persist. ∨
.SYNOPSIS...SLIGHTLY COOLER WEATHER IS FORECAST FOR TODAY, ESPECIALLY NEAR THE COAST WHERE THERE WILL BE AREAS OF LOW CLOUDS AND FOG. A WARMING TREND IS THEN EXPECTED FOR MEMORIAL DAY AND TUESDAY. WARMER THAN NORMAL TEMPERATURES WILL CONTINUE THROUGH THE END OF THE WEEK. DRY WEATHER WILL PERSIST. [DISC]
Discussion. As of 8:40am PDT Sunday… the first visible satellite images this morning reveal mainly clear skies across the North Bay region with patchy low clouds around the Bay. Along the coast stratus extends from the southern tip of Marin southward along the coast. Across the southern half of the forecast area low clouds have infiltrated well inland through coastal valleys under a deepening 2000 foot marine layer. The last few visible frames show stratus is beginning to erode over the southern Salinas Valley with further clearing expected in the next hour or two. Mainly sunny skies anticipated across the district by midday today with the exception of coastal areas south of San Francisco that will only see partial clearing. ∨
.DISCUSSION...AS OF 8:40 AM PDT SUNDAY...THE FIRST VISIBLE SATELLITE IMAGES THIS MORNING REVEAL MAINLY CLEAR SKIES ACROSS THE NORTH BAY REGION WITH PATCHY LOW CLOUDS AROUND THE BAY. ALONG THE COAST STRATUS EXTENDS FROM THE SOUTHERN TIP OF MARIN SOUTHWARD ALONG THE COAST. ACROSS THE SOUTHERN HALF OF THE FORECAST AREA LOW CLOUDS HAVE INFILTRATED WELL INLAND THROUGH COASTAL VALLEYS UNDER A DEEPENING 2000 FOOT MARINE LAYER. THE LAST FEW VISIBLE FRAMES SHOW STRATUS IS BEGINNING TO ERODE OVER THE SOUTHERN SALINAS VALLEY WITH FURTHER CLEARING EXPECTED IN THE NEXT HOUR OR TWO. MAINLY SUNNY SKIES ANTICIPATED ACROSS THE DISTRICT BY MIDDAY TODAY WITH THE EXCEPTION OF COASTAL AREAS SOUTH OF SAN FRANCISCO THAT WILL ONLY SEE PARTIAL CLEARING. [DISC]
Gradients at this hour continue to show a strong northerly gradient of 4.9 mb from ACV [Arcata/Eureka CA] to SFO [San Francisco CA] and an equally strong onshore gradient from SFO [San Francisco CA] to LAS [Las Vegas NV]. A deepening marine layer and a relatively strong onshore gradient will result in cooler temperatures along the coast and locally inland. Temperatures along the coast will experience a drop of up to 10°. Inland highs will only see a few degrees of cooling while the North Bay region sees very little, if any. ∨
GRADIENTS AT THIS HOUR CONTINUE TO SHOW A STRONG NORTHERLY GRADIENT OF 4.9 MB FROM ACV TO SFO AND AN EQUALLY STRONG ONSHORE GRADIENT FROM SFO TO LAS. A DEEPENING MARINE LAYER AND A RELATIVELY STRONG ONSHORE GRADIENT WILL RESULT IN COOLER TEMPERATURES ALONG THE COAST AND LOCALLY INLAND. TEMPERATURES ALONG THE COAST WILL EXPERIENCE A DROP OF UP TO 10 DEGREES. INLAND HIGHS WILL ONLY SEE A FEW DEGREES OF COOLING WHILE THE NORTH BAY REGION SEES VERY LITTLE, IF ANY. [DISC]
Warmer conditions are expected on Memorial Day and Tuesday as an upper level ridge of high pressure builds in over the region and a surface trough currently situated over the interior shift west along the coast. This will weaken the onshore gradient and thin out the marine layer resulting in a quicker clearing of low clouds in the morning and less marine influence. Patchy low clouds along the coast may still be possible. ∨
WARMER CONDITIONS ARE EXPECTED ON MEMORIAL DAY AND TUESDAY AS AN UPPER LEVEL RIDGE OF HIGH PRESSURE BUILDS IN OVER THE REGION AND A SURFACE TROUGH CURRENTLY SITUATED OVER THE INTERIOR SHIFT WEST ALONG THE COAST. THIS WILL WEAKEN THE ONSHORE GRADIENT AND THIN OUT THE MARINE LAYER RESULTING IN A QUICKER CLEARING OF LOW CLOUDS IN THE MORNING AND LESS MARINE INFLUENCE. PATCHY LOW CLOUDS ALONG THE COAST MAY STILL BE POSSIBLE. [DISC]
From previous discussion. The upper ridge axis is forecast to move to our east by midweek as an upper trough develops off the West Coast along 135°W [680 mi west of Montara]. This should result in slight cooling on Wednesday and Thursday. However, temperatures are expected to remain above normal through the week. And, the models indicate that temperatures will climb higher once again on Friday as the upper ridge to our east strengthens. The ECMWF [European Center for Medium-Range Weather Forecasts model] MOS [Model Output Statistics] indicates the most pronounced warming late in the week, with SFO [San Francisco CA] forecast to reach 82 on Friday and Livermore 102. ∨
FROM PREVIOUS DISCUSSION...THE UPPER RIDGE AXIS IS FORECAST TO MOVE TO OUR EAST BY MIDWEEK AS AN UPPER TROUGH DEVELOPS OFF THE WEST COAST ALONG 135W. THIS SHOULD RESULT IN SLIGHT COOLING ON WEDNESDAY AND THURSDAY. HOWEVER, TEMPERATURES ARE EXPECTED TO REMAIN ABOVE NORMAL THROUGH THE WEEK. AND, THE MODELS INDICATE THAT TEMPERATURES WILL CLIMB HIGHER ONCE AGAIN ON FRIDAY AS THE UPPER RIDGE TO OUR EAST STRENGTHENS. THE ECMWF MOS INDICATES THE MOST PRONOUNCED WARMING LATE IN THE WEEK, WITH SFO FORECAST TO REACH 82 ON FRIDAY AND LIVERMORE 102. [DISC]
The models agree that a weak upper low will develop off the Southern California coast late in the week and then lift gradually to the northeast next weekend. The GFS [Global Forecast System: global spectral model used primarily for aviation weather forecasts; provides guidance out to 384 hours at 00, 06, 12 and 18UTC.] forecasts precipitation across the southeast portion of our forecast area by Saturday morning as the low approaches. The ECMWF [European Center for Medium-Range Weather Forecasts model] maintains dry conditions in all areas until the following Monday night. Given these model differences and the fact that this precipitation potential is still out at day seven and beyond, will hold off on adding any explicit mention of shower chances to the forecast just yet. ∨
THE MODELS AGREE THAT A WEAK UPPER LOW WILL DEVELOP OFF THE SOUTHERN CALIFORNIA COAST LATE IN THE WEEK AND THEN LIFT GRADUALLY TO THE NORTHEAST NEXT WEEKEND. THE GFS FORECASTS PRECIP ACROSS THE SOUTHEAST PORTION OF OUR FORECAST AREA BY SATURDAY MORNING AS THE LOW APPROACHES. THE ECMWF MAINTAINS DRY CONDITIONS IN ALL AREAS UNTIL THE FOLLOWING MONDAY NIGHT. GIVEN THESE MODEL DIFFERENCES AND THE FACT THAT THIS PRECIPITATION POTENTIAL IS STILL OUT AT DAY SEVEN AND BEYOND, WILL HOLD OFF ON ADDING ANY EXPLICIT MENTION OF SHOWER CHANCES TO THE FORECAST JUST YET. [DISC]
Aviation. As of 10:27am PDT Sunday… low clouds persist over the Monterey Bay Area with KMRY [Monterey CA] and KSNS [Salinas CA] TAFs [Terminal Aerodrome Forecasts] expected to keep MVFR [Marginal Visual Flight Rules] ceilings for the next hour or so. VFR [Visual Flight Rules] is expected in the San Francisco Bay Area through today with low clouds spreading inland again overnight tonight. ∨
.AVIATION...AS OF 10:27 AM PDT SUNDAY...LOW CLOUDS PERSIST OVER THE MONTEREY BAY AREA WITH KMRY AND KSNS TAFS EXPECTED TO KEEP MVFR CIGS FOR THE NEXT HOUR OR SO. VFR IS EXPECTED IN THE SAN FRANCISCO BAY AREA THROUGH TODAY WITH LOW CLOUDS SPREADING INLAND AGAIN OVERNIGHT TONIGHT. [AVIA]
Vicinity of KSFO [San Francisco CA]… VFR [Visual Flight Rules] today. MVFR [Marginal Visual Flight Rules] ceilings returning tonight after midnight. ∨
VICINITY OF KSFO...VFR TODAY. MVFR CIGS RETURNING TONIGHT AFTER MIDNIGHT. [AVI2]
SFO [San Francisco CA] bridge approach… same as KSFO [San Francisco CA]. ∨
SFO BRIDGE APPROACH...SAME AS KSFO. [AVI2]
Monterey Bay terminals… MVFR [Marginal Visual Flight Rules] ceilings through 18–19Z [11am–12pm PDT]… VFR [Visual Flight Rules] this afternoon. IFR [Instrument Flight Rules]/MVFR [Marginal Visual Flight Rules] ceilings return early tonight. ∨
MONTEREY BAY TERMINALS...MVFR CIGS THROUGH 18-19Z...VFR THIS AFTERNOON. IFR/MVFR CIGS RETURN EARLY TONIGHT. [AVI2]
Marine. As of 8:20am PDT Sunday… high pressure over the eastern Pacific and low pressure inland will result in gusty northerly winds today and tonight. Winds will be strongest over the outer waters, especially north of Point Reyes [San Francisco CA]. Winds will gradually decrease on Memorial Day with weakening high pressure. A building southerly swell is anticipated to arrive early next week. ∨
.MARINE...AS OF 8:20 AM PDT SUNDAY...HIGH PRESSURE OVER THE EASTERN PACIFIC AND LOW PRESSURE INLAND WILL RESULT IN GUSTY NORTHERLY WINDS TODAY AND TONIGHT. WINDS WILL BE STRONGEST OVER THE OUTER WATERS, ESPECIALLY NORTH OF POINT REYES. WINDS WILL GRADUALLY DECREASE ON MEMORIAL DAY WITH WEAKENING HIGH PRESSURE. A BUILDING SOUTHERLY SWELL IS ANTICIPATED TO ARRIVE EARLY NEXT WEEK. [AVIA]
.MTR WATCHES/WARNINGS/ADVISORIES... .TDAY...SCA...PT ARENA TO PIGEON PT 10-60 NM SCA...PT ARENA TO PT REYES 0-10 NM SCA...SF BAY SCA...PIGEON PT TO PT PIEDRAS BLANCAS 10-60 NM [WARN]
Public Forecast: CW; Aviation: Sims; Marine: Sims ∨
PUBLIC FORECAST: CW AVIATION: SIMS MARINE: SIMS [CRED]
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29 May 11:35am PDT
This Afternoon Mostly sunny, with a high near 64°. South wind around 9 mph.
Tonight Patchy fog after 11pm. Otherwise, mostly cloudy, with a low around 52°. South wind 5 to 8 mph.
Memorial Day Patchy fog before 11am. Otherwise, mostly sunny, with a high near 63°. SSE wind 11 to 13 mph.
Monday Night Partly cloudy, with a low around 52°. SSW wind 5 to 8 mph.
Tuesday Mostly sunny, with a high near 63°. South wind 3 to 7 mph.
Tuesday Night Mostly cloudy, with a low around 53°.
Wednesday Partly sunny, with a high near 64°.
Wednesday Night Patchy fog after 11pm. Otherwise, mostly cloudy, with a low around 53°.
Thursday Patchy fog before 11am. Otherwise, mostly cloudy, with a high near 63°.
Thursday Night Partly cloudy, with a low around 53°.
Friday Mostly sunny, with a high near 64°.
Friday Night Mostly cloudy, with a low around 52°.
Saturday Partly sunny, with a high near 64°.
Mostly sunny, with a high near 64. South wind around 9 mph.
Patchy fog after 11pm. Otherwise, mostly cloudy, with a low around 52. South wind 5 to 8 mph.
Patchy fog before 11am. Otherwise, mostly sunny, with a high near 63. South southeast wind 11 to 13 mph.
Partly cloudy, with a low around 52. South southwest wind 5 to 8 mph.
Mostly sunny, with a high near 63. South wind 3 to 7 mph.
Mostly cloudy, with a low around 53.
Partly sunny, with a high near 64.
Patchy fog after 11pm. Otherwise, mostly cloudy, with a low around 53.
Patchy fog before 11am. Otherwise, mostly cloudy, with a high near 63.
Partly cloudy, with a low around 53.
Mostly sunny, with a high near 64.
Mostly cloudy, with a low around 52.
Partly sunny, with a high near 64.