Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA

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000
FXUS66 KMTR 300532
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
1032 PM PDT TUE JUL 29 2014

.UPDATE AS OF 8:55 PM PDT TUESDAY...BASED ON COMBINATION OF
RECENTLY DEVELOPING ACCAS OVER THE NORTH BAY EVIDENT IN AREA
WEBCAMS AND LATEST VIS AND IR SATELLITE IMAGERY...APPROACHING TAIL
END OF WEAK UPPER LEVEL DISTURBANCE MOVING TO THE NNE APPROX 170
MILES WEST OF THE GOLDEN GATE...AND ANALYSIS OF ELEVATED
CONVECTIVE PARAMETERS AND MODEL OUTPUT SOUNDINGS FROM JUST REC`D
NEW 00Z RUN OF THE NAM...AM UPDATING THE FORECASTS TO ADD IN A
SLIGHT CHANCE OF DRY THUNDERSTORMS NORTH OF THE GOLDEN GATE FOR
THE 9-HR PERIOD 06Z TONIGHT THROUGH 15Z WEDNESDAY. EVERYTHING FROM
DETAILS OF TIMING TO EXACT BOUNDARIES OF AREA AT POTENTIAL RISK
ARE INTRINSICALLY FUZZY GIVEN THAT THE MODELS HAVE BEEN DOING A
POOR JOB LATELY WITH BOTH INITIALIZATION AND FORECASTS OF
EVOLUTION OF SUBTROPICAL MOISTURE PLUMES MOVING THROUGH OUR
DISTRICT. BUT WANT TO GET THE MESSAGE OUT THAT BELIEVE THERE IS
SOME RISK AND THIS IS BEST CURRENT ESTIMATE OF TIMING AND AREA OF
FOCUS.

WILL ALSO NEED TO KEEP AN EYE ON FAR SE PORTION OF OUR CWA...AS
PRIMARY STREAM OF MOISTURE DETRAINING FROM THE REMNANT LOW OF
FORMER TROPICAL STORM HERNAN IS NOW CLIPPING THROUGH SE MONTEREY
COUNTY...AND HAS THUS SHIFTED A BIT FARTHER NORTHWARD THAN MODELS
WERE PREDICTING.

&&

.SYNOPSIS...MONSOON/SUBTROPICAL MOISTURE WILL CONTINUE TO FILTER
IN OVER THE FORECAST AREA TONIGHT AND TOMORROW. THIS WILL RESULT
IN PARTLY CLOUDY SKIES AND A RELATIVELY WARM NIGHT DUE TO EXTRA
HUMIDITY IN THE AIR. THE AIRMASS WILL BEGIN TO DRY TOMORROW
EVENING SO EXPECT SLIGHTLY COOLER LESS HUMID NIGHTS. OTHERWISE...DRY
CONDITIONS AND NEAR NORMAL TEMPERATURES CAN BE EXPECTED THROUGH
THE REMAINDER OF THE WEEK.

&&

.PREV DISCUSSION...AS OF 2:26 PM PDT TUESDAY...MOSTLY CLEAR SKIES ARE
PRESENT OVER THE FORECAST AREA THIS AFTERNOON WITH STRATUS
APPARENT OVER THE COASTAL WATERS. THE CURRENT SATELLITE WATER
VAPOUR IMAGE IS SHOWING MOISTURE STREAMING INTO SOUTHERN
CALIFORNIA AND PORTIONS OF OUR FORECAST AREA. SATELLITE BLENDED
TOTAL PRECIPITABLE WATER IS SHOWING VALUES 1.0 TO 1.25 INCHES
AROUND THE CENTRAL CALIFORNIA WHICH IS ABOUT 110 TO 120 PERCENT OF
NORMAL. THIS MOISTURE WILL PRIMARILY RESULT PARTLY CLOUDY SKIES
AND A WARM HUMID NIGHT TONIGHT.

THE 1200Z ECMWF AND GFS40 HAVE INITIALIZED WELL WITH THE CURRENT
SYNOPTIC PATTERN. BOTH FORECAST MODELS BEGIN TO MOVE THE
MONSOON/SUBTROPICAL MOISTURE OUT OF THE FORECAST AREA WEDNESDAY.
THIS WILL RESULT IN CLEARING SKIES AND LOWER HUMIDITY
VALUES...SLIGHTLY COOLER EVENING TEMPERATURES. OTHERWISE LOOKS
LIKE RELATIVELY MILD WEATHER THROUGH THE BEGINNING OF NEXT WEEK
WITH NEAR NORMAL TEMPERATURES EXPECTED.

&&

.AVIATION...AS OF 10:30 PM PDT TUESDAY...THE MARINE LAYER REMAINS
COMPRESSED AT AROUND 1000 FEET AND THE ONSHORE GRADIENT MILD.
STRATUS HAS BEGUN TO WORK ITS WAY INTO THE BAYS THIS EVENING
HOWEVER THE INLAND PUSH WILL BE LIMITED BY THE SHALLOW MARINE
LAYER DEPTH.

VICINITY OF KSFO...VFR THROUGH TOMORROW AFTERNOON. STRATUS NOT
EXPECTED TO IMPACT THE TERMINAL OVERNIGHT.

KSFO BRIDGE APPROACH...PATCHY CIGS TOMORROW MORNING COULD BRIEFLY
IMPACT APPROACH EARLY. OTHERWISE SIMILAR TO KSFO.

MONTEREY BAY AREA TERMINALS...STRATUS NOW IN MRY AND FORECAST TO
REACH SNS WITHIN THE NEXT COUPLE OF HOURS. CIGS TO BURN OFF EARLY
TOMORROW DUE TO SHALLOW MARINE LAYER.

&&

.MARINE...AS OF 02:14 PM PDT TUESDAY...NORTHERLY WINDS WILL
PREVAIL OVER THE COASTAL WATERS. MODERATE TO LOCALLY STRONG
NORTHERLY WINDS WILL BE POSSIBLE NORTH OF POINT REYES TONIGHT AND
WEDNESDAY. SEAS WILL GENERALLY BE GENTLE THROUGH THE REMAINDER OF
THE WEEK.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .TNGT...SCA...PT ARENA TO PT REYES 10-60 NM

&&

$$

PUBLIC FORECAST: BLIER/LARRY
AVIATION: AC
MARINE: JOHNSON

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