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

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000 FXUS66 KMTR 272346 AFDMTR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA 346 PM PST THU NOV 27 2014 ...PERIODS OF RAIN FORECAST FROM LATE FRIDAY THROUGH THE MIDDLE OF NEXT WEEK... ...POTENTIAL HEAVY RAIN...HYDRO CONCERNS...AND STRONG AND GUSTY WINDS NEXT WEEK... .SYNOPSIS...HIGH PRESSURE WILL MAINTAIN DRY AND MILD WEATHER THROUGH TODAY. RAIN WILL DEVELOP IN THE NORTH BAY BY LATE FRIDAY AND PRESS SOUTH THROUGH MOST OF THE REST OF THE REGION FRIDAY NIGHT INTO SATURDAY. PERIODS OF RAIN ARE EXPECTED TO CONTINUE INTO SUNDAY. MORE RAIN...POSSIBLY HEAVY...IS THEN LIKELY AROUND THE MIDDLE OF NEXT WEEK. && .DISCUSSION...AS OF 01:45 PM PST THURSDAY...ACTIVE WEATHER PATTERN THROUGH THE ENTIRE FORECAST AS A SERIES OF DISTURBANCES ARE FORECAST TO IMPACT THE BAY AREA. MOIST WESTERLY FLOW ALOFT CONTINUES TO STREAM MID-HIGH LEVEL CLOUDS OVER THE BAY AREA. DESPITE THE FILTERED SUNSHINE TEMPERATURES AROUND THE REGION ARE SOMEWHAT MILD FOR THIS TIME OF YEAR. IN FACT...PINNACLES IS CURRENTLY SITTING AT 85 DEGREES. SYNOPTICALLY SPEAKING...HIGH PRESSURE OVER SOCAL CONTINUES TO WEAKEN AND FLATTEN OUT AS A TROUGH DIGS DEEPER OVER THE EPAC. THE DEEPENING TROUGH WILL BE THE FIRST STORM TO BRING RAIN TO THE REGION. FARTHER UPSTREAM...ANOTHER TROUGH/LOW PRESSURE IS SLOWLY DEVELOPING NEAR THE ALEUTIAN ISLANDS. THIS DEVELOPING SYSTEM WILL BE THE RAIN MAKER SUNDAY INTO NEXT WEEK. SHORT TERM(TONIGHT-SUNDAY)... THE COLD FRONT TO THE WEST WILL MARCH TOWARD THE BAY AREA INCREASING CLOUDS TONIGHT AND FRIDAY. MODELS REMAIN IN PRETTY GOOD AGREEMENT IN DEVELOPING RAIN OVER THE NORTH BAY INITIALLY FRIDAY AFTERNOON/EVENING AND THEN SLOWLY MOVING SOUTHWARD TOWARD SF FRIDAY NIGHT/SATURDAY MORNING. MONTEREY BAY AREA SOUTHWARD WILL SEE RAIN LATE SATURDAY MORNING INTO SATURDAY AFTERNOON. RAINFALL AMOUNTS WITH THE COLD FRONT ARE EXPECTED TO BE 1-2" OVER THE NORTH BAY WITH GENERALLY 1/4"-3/4" FOR MOST URBAN AREAS AND SOUTHERN AREA. THINGS GET INTERESTING SATURDAY NIGHT IF YOU BELIEVE THE GFS/ECMWF. THE IMPULSE NEAR THE ALEUTIANS REALLY DEEPENS OFF THE MONTEREY/BIG SUR COAST POINTING A DECENT MOISTURE PLUME TOWARD THE COAST. PWATS ARE NEAR 1.25 INCHES...NOT BAD AT ALL. THAT BEING SAID...A DECENT PUSH OF MODERATE TO POTENTIALLY HEAVY RAIN WILL BE POSSIBLE SOUTH OF SF OVER THE SANTA CRUZ MTS THROUGH THE BIG SUR COAST. RAINFALL AMOUNTS WILL BE ON THE ORDER OF 1/2-1" FOR MANY URBAN SPOTS WITH 1.5-2.5" AROUND THE SANTA CRUZ MOUNTAINS PLUS COASTAL RANGES IN MONTEREY COUNTY. IF THE FORECAST PANS OUT...THIS WILL HAVE TO BE WATCHED AS IT MAY CAUSE HYDRO CONCERNS AROUND THE PFIEFFER BURN SCAR NEAR BIG SUR. THE BULK OF THE RAIN WILL END BY SUNDAY EVENING...BUT A FEW LINGERING SHOWERS WILL BE POSSIBLE. IN ADDITION...LOCALLY GUSTY SOUTHERLY WINDS CAN BE EXPECTED THROUGH THE WEEKEND. STRONGEST WINDS WILL BE ALONG THE COAST AND HIGHER TERRAIN. LONG TERM(MONDAY-THURSDAY)... LOTS OF UNCERTAINTY REMAINS FOR THE LONG TERM AS MEDIUM RANGE MODEL DISAGREEMENT REMAINS. AS STATED ON THE PREVIOUS DISCUSSION...THE GFS IS STILL THE WETTEST AND MOST PROGRESSIVE EARLY NEXT WEEK. THE ECMWF ON THE OTHER HAND IS DRIER AND BRINGS IN THE RAIN ALMOST 24-36 HRS LATER (TUESDAY NIGHT INSTEAD OF MONDAY NIGHT). GIVEN THE DRY VS WET FORECAST...WILL NOT CHANGE CURRENT FORECAST AND HOPE THAT MODEL CONSENSUS INCREASES BETWEEN NOW AND THEN. CURRENT FORECAST WILL KEEP THE CHANCE OF RAIN MONDAY THROUGH WEDNESDAY. REGARDLESS OF TIMING DIFFERENCES NEXT WEEK...RAINFALL TOTALS THROUGH THE ENTIRE EVENT LOOK PRETTY DECENT. DEFINITELY NOT A DROUGHT BUSTER...BUT MUCH NEEDED RAINFALL ANYWAY. RAINFALL TOTALS ARE EXPECTED TO RANGE FROM 4-7" OVER THE NORTH BAY PLUS COASTAL RANGES OF MONTEREY AND SANTA CRUZ COUNTIES WITH GENERALLY 1.5"-3.5" FOR MANY URBAN AND VALLEY LOCATIONS. LOCALLY HIGHER AMOUNTS ARE POSSIBLE IN BOTH CASES. && .AVIATION...AS OF 3:40 PM PST THURSDAY...DRY AIRMASS CONTINUES OVER THE AREA THROUGH THE REMAINDER OF THURSDAY. UPPER LOW WILL PUSH ONSHORE LATER FRIDAY AND BRING -RA AND DETERIORATING CIGS FROM NORTH TO SOUTH BEGINNING AROUND 00Z SAT FOR THE NORTH BAY. VICINITY OF KSFO...VFR. HAZY CONDITIONS TODAY WITH LIGHT WINDS. KSFO BRIDGE APPROACH...SIMILAR TO KSFO. MONTEREY BAY AREA TERMINALS...VFR. && .MARINE...AS OF 03:40 PM PST THURSDAY...WEAK HIGH PRESSURE OFF THE SOUTHERN CALIFORNIA COAST WILL PERSIST WITH LIGHT WINDS EXPECTED ACROSS THE COASTAL WATERS THROUGH TONIGHT. SOUTHERLY WINDS WILL DEVELOP FRIDAY AS A FRONTAL SYSTEM APPROACHES THE AREA. THESE SOUTHERLY WINDS WILL INCREASE SUNDAY OR MONDAY AS ANOTHER STORM SYSTEM APPROACHES CALIFORNIA. && .MTR WATCHES/WARNINGS/ADVISORIES... .TNGT...NONE. $$ PUBLIC FORECAST: MM AVIATION: DRP MARINE: SIMS 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

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