000
FXUS66 KMTR 051758
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA CA
1058 AM PDT SAT JUL 5 2008

.DISCUSSION...AS OF 10:30 AM PDT SATURDAY...BUSY START TO THE DAY SO
A QUICK UPDATE.

LATEST VIS PICS DO SHOW SOME CLEARING ALONG THE IMMEDIATE COAST...
ESP NORTH OF PT REYES AND NEAR SANTA CRUZ. ELSEWHERE...STRATUS IS
STILL HANGING ON ALONG THE SAN MATEO COAST AND MTR PENINSULA.
PROFILERS AND SOUNDINGS PUT THE MARINE LAYER 1100-1600 FEET.  EXPECT
ANY REMAINING STRATUS TO GRADUALLY CLEAR OUT DURING THE AFTERNOON.
CLEARING SKIES WILL ALLOW FOR A GRADUAL WARM UP INLAND AND SLOWLY
MAKING ITS WAY TO THE COAST TODAY.  OTHERWISE...NO UPDATE WITH THE
CURRENT FORECAST.

MOST OF THE AFTERNOON PACKAGE WILL CONTINUE TO FOCUS ON THE
UPCOMING HEAT WAVE. 12Z MODELS ARE ALL IN AGREEMENT WITH A BUILDING
AREA OF HIGH PRESSURE WITH 500 MB HEIGHTS IN EXCESS OF 590 DAM WITH
850 MB TEMPS IN THE MID 20S.  THIS WILL SPELL WELL ABOVE NORMAL
DAYTIME TEMPERATURES WITH MANY INLAND LOCATIONS ABOVE 100
DEGREES. IN ADDITION...THERMAL BELTS WILL LIKELY BECOME ESTABLISHED
OVERNIGHT WITH HIGHER ELEVATIONS SEEING LITTLE COOLING/RECOVERY.
PEAK DAYS WILL LIKELY BE WED/THUR.  GUIDANCE IS HINTING AT
FLATTENING THE RIDGE BY FRIDAY...BUT MODELS TYPICALLY BREAK DOWN THE
RIDGE TOO QUICKLY.  WILL SEE HOW THIS PLAYS OUT OVER THE NEXT FEW
MODELS RUNS.  MEDIUM RANGE MODELS ALSO SUGGEST SOME SUB-TROPICAL
MOISTURE POOLING IN FROM THE SE TO S MID WEEK UNDER THE RIDGE. FOR
NOW...TSTORM THREAT SEEMS MINIMAL BUT WILL MONITOR OVER THE NEXT
FEW DAYS.

PREVIOUS DISCUSSION...
VERY ROBUST WARMING IS FORECAST TO OCCUR FROM MONDAY THROUGH
WEDNESDAY AS THE UPPER RIDGE STRENGTHENS OVERHEAD AND THE FLOW BEGINS
TO TREND OFFSHORE. BOTH THE GFS AND ECMWF HAVE BACKED OFF SLIGHTLY ON
THE STRENGTH OF THE UPPER RIDGE WITH THE LATEST MODEL RUN. HOWEVER...
RECENT MODEL RUNS...OF THE GFS IN PARTICULAR...ARE INDICATING MORE
IN THE WAY OF OFFSHORE LOW LEVEL FLOW BY TUESDAY AND WEDNESDAY.
THIS WOULD SUGGEST THAT VERY WARM TEMPERATURES WILL DEVELOP ALL
THE WAY TO THE COAST BY TUESDAY AND ESPECIALLY WEDNESDAY OF NEXT
WEEK. MOS GUIDANCE TYPICALLY UNDER-FORECASTS HEAT EVENTS SUCH AS THE
ONE COMING NEXT WEEK...AT LEAST MORE THAN A FEW DAYS OUT ANYWAY.
LATEST MOS NUMBERS ARE PROBABLY TOO COOL FROM MONDAY THROUGH
WEDNESDAY...PARTICULARLY FOR AREAS NEAR THE COAST. HAVE DECIDED TO GO
WITH WARMER TEMPERATURES THAN MOS FOR MOST OF OUR FORECAST AREA NEXT
WEEK...BOTH FOR HIGHS AND OVERNIGHT LOWS. THE NAM IS SHOWING ALMOST
NO TENDENCY TOWARDS OFFSHORE FLOW NEXT WEEK...AT LEAST THROUGH
TUESDAY MORNING. BOTH THE NAM AND GFS FORECAST THE UPPER RIDGE AXIS
TO BE JUST OFFSHORE NEXT TUESDAY...AN UPPER LEVEL PATTERN MOST
CONDUCIVE TO DEVELOPMENT OF OFFSHORE SURFACE FLOW. SO...WILL FAVOR
THE GFS SURFACE PATTERN NEXT WEEK AND GO WITH RAPIDLY WARMING TEMPS
NEAR THE COAST FROM MONDAY THROUGH WEDNESDAY. LOOKS LIKE BEST
OFFSHORE FLOW CONDITIONS WILL OCCUR TUESDAY NIGHT INTO WEDNESDAY
MORNING AND SO WEDNESDAY SHOULD BE THE WARMEST DAY NEAR THE OCEAN.
INLAND AREAS WILL CONTINUE HOT INTO THURSDAY. WIDESPREAD MID
TO UPPER 90S ARE FORECAST FOR INLAND AREAS NEXT TUE-THU...WITH THE
WARMER INLAND AREAS EXPECTED TO WARM PAST 100 AND PERHAPS AS HIGH AS
110 IN PLACES LIKE PINNACLES NATIONAL MONUMENT AND NEAR LAKE
BERRYESSA. COASTAL TEMPS WILL LIKELY CLIMB INTO THE 80S BY TUESDAY
AND POSSIBLY PAST 90 BY WEDNESDAY.

HEAT ADVISORIES ARE A GOOD POSSIBILITY BY TUESDAY AND WE MAY NEED AN
EXCESSIVE HEAT WARNING BY TUESDAY OR WEDNESDAY. SINCE THE HOTTEST
WEATHER IS STILL THREE DAYS AWAY...WILL CONTINUE WITH AN EXCESSIVE
HEAT OUTLOOK FOR NOW (UNDER SPECIAL WEATHER STATEMENT) AND CONSIDER
TRANSITION TO A WATCH PRODUCT WITHIN THE NEXT 24 HOURS.

BOTH THE GFS AND ECMWF INDICATE THE UPPER RIDGE WILL RAPIDLY BREAK
DOWN LATE NEXT THURSDAY INTO FRIDAY AS A TROUGH MOVES INTO THE PAC
NW. THIS WILL RESULT IN MUCH COOLER WEATHER BY THE END OF NEXT
WEEK.

&&

.AVIATION...AS OF 11:00 AM PDT FRIDAY...LATEST VISIBLE IMAGE SHOWING
MOSTLY CLEAR SKIES OVER THE SAN FRANCISCO BAY. STRATUS IS HANGING
ALONG THE COASTLINE. VFR CONDITIONS ARE EXPECTED TO PREVAIL THROUGH
MIDNIGHT AFTER-WHICH THE STRATUS WILL RETURN WITH IFR CIGS EXPECTED.
WINDS WILL GENERALLY BE WESTERLY REACHING 15 TO 20 KT WITH
OCCASIONAL GUSTS TO 30 KT AT SFO THIS AFTERNOON.

.MONTEREY BAY AREA TERMINALS...VISIBLE IMAGE SHOWING STRATUS
RAPIDLY ERODING OUT OF THE SALINAS VALLEY. STRATUS IS LINGERING
AROUND THE MONTEREY AIRPORT BUT IS LIFTING AND SHOULD SCATTER OUT
BY 1900 OR 2000 UTC. VFR WILL PREVAIL THROUGH THIS EVENING. EXPECT
CONDITIONS TO DEGRADE SUBSTANTIALLY AFTER MIDNIGHT WITH DRIZZLE IN
THE EARLY MORNING HOURS.
.



&&

.FIRE WEATHER...AS OF 4:30 AM PDT SATURDAY...BIGGEST CONCERN
CONTINUES TO BE WEATHER CONDITIONS NEAR THE BASIN COMPLEX...BOTH IN
THE SHORT TERM (LOCALLY GUSTY NORTH-NORTHEAST WINDS) AND ALSO
AS WE MOVE INTO THE FIRST HALF OF NEXT WEEK (VERY WARM AND DRY
CONDITIONS WITH OFFSHORE FLOW). FOR MOST OF THE AREA...THE WIND FLOW
REMAINS OUT OF THE NORTHWEST...BUT LOCAL NORTH-NORTHEAST WINDS HAVE
DEVELOPED AT THE PORTABLE RAWS STATION NEAR THE BASIN COMPLEX BURN
SITE. THAT RAWS STATION...AT AN ELEVATION OF 2500 FT...CURRENTLY
INDICATES A NNE WIND OF 18 MPH WITH GUSTS TO 27 MPH. ALSO RH
RECOVERIES AT THAT LOCATION HAVE BEEN VERY POOR OVERNIGHT...REMAINING
BELOW 30 PERCENT. LATEST HIGH RESOLUTION WRF MODEL OUTPUT INDICATES
MODERATE NE WINDS WILL PERSIST AT THE BASIN COMPLEX BURN SITE
THROUGH THE MORNING WITH WINDS SUBSIDING SLOWLY IN THE AFTERNOON. THE
MARINE LAYER WILL REMAIN SHALLOW AT 1000 FEET OR LESS AND THUS MOST
OF THE FIRE WILL REMAIN IN THE WARM AND DRY AIRMASS ABOVE THE
INVERSION. NOT MUCH CHANGE IS EXPECTED TONIGHT AND SUNDAY MORNING
WITH A CONTINUED SHALLOW MARINE LAYER AND LOCALLY GUSTY NORTHERLY
WINDS. WINDS SHOULD EASE SUNDAY AFTERNOON INTO MONDAY...BUT
TEMPERATURES WILL WARM UP. HOT TEMPERATURES WITH VERY LOW HUMIDITIES
ARE EXPECTED TO DEVELOP EARLY NEXT WEEK AS A STRONG HIGH PRESSURE
MOVES IN ALOFT. TEMPERATURES WILL WARM WELL INTO THE 90S DURING THE
FIRST HALF OF NEXT WEEK AND PROBABLY OVER 100. IN ADDITION...
INDICATIONS ARE THAT WIDESPREAD OFFSHORE WINDS WILL DEVELOP AS EARLY
AS SUNDAY NIGHT AND LIKELY BY MONDAY NIGHT. AT THIS POINT IT APPEARS
THAT OFFSHORE WINDS WILL MOSTLY BE LIGHT...BUT LOCALLY STRONGER WINDS
ARE POSSIBLE. RH RECOVERIES WILL BE VERY POOR AT NIGHT THROUGH MOST
OF NEXT WEEK. RELIEF FROM THE HOT AND DRY CONDITIONS PROBABLY WON`T
COME UNTIL THURSDAY NIGHT.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .TDA...SCA...ALL COASTAL WATERS EXCEPT PIGEON PT TO PT PINOS
                  0 TO 20 NM
            SCA...SFO BAY

$$

PUBLIC FORECAST: MEHLE/DYKEMA
AVIATION/MARINE: LARRY
FIRE WEATHER: DYKEMA

NWS ON THE WEB AT WEATHER.GOV/SANFRANCISCO

NWS MTR Office Area Forecast Discussion