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

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS66 KMTR 300408
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
908 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.

&&

.FROM PREVIOUS DISCUSSION...AS OF 2:26 PM PDT TUESDAY

.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.

.DISCUSSION...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 04:30 PM PDT TUESDAY...SOLID STRATUS FIELD JUST
OFFSHORE IS STARTING THE INITIAL PUSH INLAND THIS AFTERNOON. THE
MARINE LAYER REMAINS COMPRESSED AROUND 1000 FEET DEEP AND THE
ONSHORE GRADIENT RELATIVELY MILD. MODEL GUIDANCE INDICATES
STRATUS PATTERN WILL BE SIMILAR TO LAST NIGHT WITH LIMITED
COVERAGE AROUND SF BAY.

VICINITY OF KSFO...VFR THIS AFTERNOON. COMPRESSED MARINE LAYER
UNLIKELY TO AFFECT THE TERMINAL TONIGHT.

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

MONTEREY BAY AREA TERMINALS...VFR THIS AFTERNOON. CIGS TO RETURN
THIS EVENING AND LOWER TO IFR OVERNIGHT.

&&

.MARINE...AS OF 10:48 AM PDT TUESDAY...SLIGHT CHANCE OF SHOWERS
POSSIBLE THIS MORNING AS MONSOON MOISTURE REMAINS OVER THE REGION.
OTHERWISE...NORTHERLY WINDS WILL PREVAIL OVER THE COASTAL WATERS.
MODERATE TO LOCALLY STRONG NORTHERLY WINDS WILL BE POSSIBLE NORTH
OF POINT REYES THIS EVENING 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 FROM 9 PM
             SCA...PT ARENA TO PT REYES 0-10 NM FROM 3 AM
             SCA...SF BAY NORTH OF THE BAY BRIDGE UNTIL 9 PM

&&

$$

PUBLIC FORECAST: BLIER/LARRY
AVIATION/MARINE: AC

VISIT US AT WEATHER.GOV/SANFRANCISCO

FOLLOW US ON FACEBOOK, TWITTER, AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSBAYAREA
WWW.TWITTER.COM/NWSBAYAREA
WWW.YOUTUBE.COM/NWSBAYAREA




USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.