Red Flag Warning 4, NWS San Francisco Bay Area, CA

547 
WWUS86 KMTR 120544
RFWMTR

URGENT - FIRE WEATHER MESSAGE
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
1044 PM PDT MON AUG 11 2014

.AN UPPER LOW OFF THE COAST WILL BRING A SLIGHT CHANCE FOR SHOWERS
AND THUNDERSTORMS AS IT MOVES INLAND OVERNIGHT. THE GREATEST
THREAT FOR THUNDERSTORMS WILL BE OVER NAPA COUNTY TONIGHT THROUGH
EARLY TUESDAY MORNING.

CAZ506-507-121200-
/O.CON.KMTR.FW.W.0004.000000T0000Z-140812T1200Z/
NORTH BAY INTERIOR VALLEYS-NORTH BAY MOUNTAINS-
1044 PM PDT MON AUG 11 2014

...RED FLAG WARNING REMAINS IN EFFECT UNTIL 5 AM PDT TUESDAY FOR
THUNDERSTORMS PRODUCING DRY LIGHTNING...

* AFFECTED AREA: FIRE ZONE 506 NORTH BAY INTERIOR VALLEYS... 
  FIRE ZONE 507 NORTH BAY MOUNTAINS.

* TIMING: THROUGH EARLY TUESDAY MORNING.

* THUNDERSTORMS: SLIGHT CHANCE FOR SHOWERS AND THUNDERSTORMS. 
  STORMS WILL BE A MIX OF DRY AND WET WITH DRY LIGHTNING 
  POSSIBLE.

* OUTFLOW WINDS: GUSTY AND ERRATIC WINDS TO 30 MPH WILL BE
  POSSIBLE.

* IMPACTS: LIGHTNING STRIKES CAN LEAD TO INCREASED FIRE STARTS 
  GIVEN THE VERY DRY FUELS.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A RED FLAG WARNING MEANS THAT CRITICAL FIRE WEATHER CONDITIONS
ARE EITHER OCCURRING NOW...OR WILL SHORTLY. A COMBINATION OF
STRONG WINDS...LOW RELATIVE HUMIDITY...AND WARM TEMPERATURES CAN
CONTRIBUTE TO EXTREME FIRE BEHAVIOR.

&&

$$


HTTP://WEATHER.GOV/SANFRANCISCO

256 
WWUS86 KMTR 121000
RFWMTR

URGENT - FIRE WEATHER MESSAGE
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
300 AM PDT TUE AUG 12 2014

CAZ506-507-121100-
/O.CAN.KMTR.FW.W.0004.000000T0000Z-140812T1200Z/
NORTH BAY INTERIOR VALLEYS-NORTH BAY MOUNTAINS-
300 AM PDT TUE AUG 12 2014

...RED FLAG WARNING IS CANCELLED FOR THUNDERSTORMS PRODUCING DRY
LIGHTNING FOR THE NORTH BAY INTERIOR VALLEYS AND MOUNTAINS...

THE NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA HAS CANCELLED
THE RED FLAG WARNING. 

THE THREAT FOR THUNDERSTORMS PRODUCING DRY LIGHTNING HAS GREATLY
DIMINISHED ACROSS THE REGION THIS MORNING DUE TO DRY MID-LEVEL
CONDITIONS. THUS...THE RED FLAG WARNING HAS BEEN CANCELLED.

$$


HTTP://WEATHER.GOV/SANFRANCISCO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
1045 AM PDT MON AUG 11 2014

.SYNOPSIS...THERE REMAINS A SLIGHT CHANCE OF THUNDERSTORMS ACROSS
THE EXTREME NORTHEASTERN PORTIONS OF THE REGION THIS EVENING
THROUGH EARLY TUESDAY MORNING AS AN UPPER LEVEL LOW MOVES INLAND.
OTHERWISE...TEMPERATURES WILL REMAIN NEAR SEASONAL AVERAGES
THROUGH MUCH OF THE WORKWEEK.

&&

.DISCUSSION...AS OF 10:09 AM PDT MONDAY...
UPDATES THIS MORNING ARE MINOR AND MAINLY TO ADDRESS CLOUD COVER
VS FORECAST. NOTING ON VISIBLE SATELLITE THAT MID LEVEL
INSTABILITY IS PRESENT ON THE EASTERN FRINGES OF THE FORECAST
AREA. FOCUS TODAY WILL BE ON THUNDERSTORM CHANCES TONIGHT AND THE
12Z MODELS ARE COMING TO A CONSENSUS ON THE HIGHEST THREAT OVER
THE EAST AND NORTH BAY TONIGHT. NOT DISCOUNTING THE
POSSIBILITY...ALBEIT LOWER...OF THUNDERSTORMS ALONG THE EASTERN
FRINGES OF THE FORECAST AREA DOWN THROUGH SAN BENITO COUNTY AS
WELL. WESTWARD PUSH OF MOISTURE REMAINS THE WILD CARD.

&&

.PREV DISCUSSION...AS OF 04:15 AM PDT MONDAY...THE CENTER OF A MID/UPPER
LEVEL LOW RETROGRADED FURTHER OFFSHORE OVERNIGHT AND CAN BE SEEN
ON WATER VAPOR SATELLITE THIS MORNING APPROXIMATELY 150 MILES WEST
OF POINT ARENA. MEANWHILE...MID-LEVEL MOISTURE CONTINUES TO BE
ADVECTED INTO SOUTHERN CALIFORNIA AND FAR EASTERN PORTIONS OF THE
STATE THIS MORNING WITH CONVECTION FIRING OVER THE SOUTHERN SIERRA
NEVADA. ACROSS THE SAN FRANCISCO BAY AREA AND CENTRAL COAST...A
DEEP MARINE LAYER ALLOWED COASTAL CLOUDS TO DEVELOP WELL INLAND
OVERNIGHT. IN ADDITION...WEAK SOUTHERLY FLOW HAS KEPT TEMPERATURES
MILD THIS MORNING WITH READINGS GENERALLY IN THE UPPER 50S TO
LOWER 60S.

THE AFOREMENTIONED MID/UPPER LEVEL LOW IS FORECAST TO PUSH BACK
TOWARD THE COAST TODAY AND MOVE INLAND ACROSS THE SAN FRANCISCO
BAY AREA LATE TONIGHT. WHILE THE LATEST NAM AND GFS SOLUTIONS DO
SHOW INCREASED MID-LEVEL INSTABILITY ACROSS THE NORTH AND EAST
BAY REGION LATE TONIGHT...THE MODELS GENERALLY AGREE THE NEEDED
MOISTURE WILL REMAIN EAST OF THIS REGION. HOWEVER...GIVEN THE
UNCERTAINTY WITH THESE TYPES OF CLOSED LOW PRESSURE SYSTEMS...WILL
KEEP A SLIGHT CHANCE OF THUNDERSTORMS ACROSS THE EASTERN PORTIONS
OF NAPA...CONTRA COSTA...SONOMA AND ALAMEDA COUNTIES AS THE UPPER
LOW MOVES INLAND OVERNIGHT. THE UPPER LEVEL SYSTEM WILL THEN
BECOME ABSORBED IN AN APPROACHING MID/UPPER LEVEL TROUGH ON
TUESDAY AND BRING AND END TO PRECIPITATION CHANCES ALL TOGETHER.

WITH A LINGERING TROUGH OVER THE PACIFIC NORTHWEST THROUGH
MIDWEEK...TEMPERATURES WILL REMAIN ON THE COOL SIDE OF NORMAL. A
SLIGHT WARMING TREND AND CONTINUED DRY WEATHER CONDITIONS ARE
EXPECTED FOR THE LATTER HALF OF THE WEEK INTO THE UPCOMING WEEKEND
WITH HIGH PRESSURE BUILDING BACK OVER THE REGION.

&&

.AVIATION...AS OF 10:44 AM PDT MONDAY...THE CURRENT VISIBLE
SATELLITE IMAGE IS SHOWING STRATUS RAPIDLY CLEARING OUT OF THE
FORECAST AREA THIS MORNING. ALSO EVIDENT ON THE VISIBLE SATELLITE
IMAGE IS A LOW PRESSURE SYSTEM SPINNING JUST OFF OF THE COAST.
THIS LOW WILL PROMOTE SOUTH TO SOUTHEASTERLY FLOW ALONG THE COAST
WHICH SHOULD SLOW THE RETURN OF STRATUS TO THE TERMINALS THIS
MORNING.

VICINITY OF KSFO...VFR IS EXPECTED TO PREVAIL INTO THE LATE
EVENING HOURS TONIGHT. THE FIRST GUESS OF STRATUS RETURN WILL BE
0900Z. WESTERLY WINDS WILL INCREASE TO 10 TO 15 KT WITH THE
AFTERNOON SEA BREEZE.

CONFIDENCE IS HIGH.

KSFO BRIDGE APPROACH...SIMILAR TO KSFO.

MONTEREY BAY AREA TERMINALS...VFR IS EXPECTED TO PREVAIL THROUGH
THIS AFTERNOON. FIRST GUESS OF STRATUS RETURN TO KMRY WILL BE
0500Z. WESTERLY WINDS ARE EXPECTED TO REACH 10 TO 15 KT WITH THE
AFTERNOON SEA BREEZE.

CONFIDENCE IS MODERATE.

&&

.MARINE...AS OF 10:09 AM PDT MONDAY...A LOW PRESSURE SYSTEM
POSITIONED OFF OF THE NORTHERN CALIFORNIA COAST WILL RESULT IN
LIGHT WINDS THROUGH TUESDAY. WINDS WILL INCREASE MIDWEEK AS THE
LOW MOVES INLAND AND HIGH PRESSURE REBUILDS OVER THE COASTAL
WATERS STRENGTHENING THE SURFACE PRESSURE GRADIENT. A MIXED SWELL
IS EXPECTED TO PERSIST INTO THE OVERNIGHT HOURS. A SMALL LONG
PERIOD WESTERLY WILL PUSH INTO THE WATERS TUESDAY NIGHT.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .TDAY...NONE.

PUBLIC FORECAST: JOHNSON
AVIATION: LARRY
MARINE: LARRY

VISIT US AT WEATHER.GOV/SANFRANCISCO

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HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
516 AM PDT MON AUG 11 2014

CAZ506-507-510-511-121200-
NORTH BAY INTERIOR VALLEYS-NORTH BAY MOUNTAINS-
EAST BAY INTERIOR VALLEYS-EAST BAY HILLS AND DIABLO RANGE-
516 AM PDT MON AUG 11 2014

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SAN FRANCISCO BAY AREA AND
MONTEREY BAY AREA.

.DAY ONE...TODAY THROUGH TONIGHT.

THERE IS A SLIGHT CHANCE OF THUNDERSTORMS ACROSS EXTREME
NORTHEASTERN PORTIONS OF THE AREA TONIGHT AND INTO EARLY TUESDAY
MORNING. ISOLATED CLOUD TO GROUND LIGHTNING STRIKES ARE POSSIBLE
EAST OF THE MAJOR URBAN AREAS AROUND THE SAN FRANCISCO BAY.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY.

NO HAZARDOUS WEATHER IS EXPECTED.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS PER STANDARD OPERATING PROCEDURES.