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AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
920 AM PDT MON AUG 3 2015

.SYNOPSIS...A SUBTLE COOLING TREND IS FORECAST TO CONTINUE THROUGH
TUESDAY AS ONSHORE FLOW AND THE MARINE INFLUENCE INCREASES. MODEST
WARMING IS THEN FORECAST FOR WEDNESDAY AND THURSDAY. ASIDE FROM
PATCHY COASTAL DRIZZLE AND FOG DURING THE OVERNIGHT AND EARLY
MORNING HOURS...DRY WEATHER CONDITIONS ARE EXPECTED TO PERSIST
THROUGH THE FORECAST PERIOD.

&&

.DISCUSSION...AS OF 09:11 AM PDT MONDAY...THE MARINE LAYER REMAINS
DEEP...YET SOMEWHAT DISORGANIZED THIS MORNING AND SHOULD GIVE WAY
TO CLEARING SKIES THAT WILL PERSIST THROUGH THE AFTERNOON. OVERALL
WEATHER CONDITIONS AND TEMPERATURES FOR THE REMAINDER OF THE DAY
WILL BE SIMILAR TO THIS WEEKEND AS ONSHORE FLOW PERSISTS AND THE
PATTERN ALOFT CHANCES LITTLE. THE ONGOING FORECAST APPEARS TO BE
ON TRACK AND NO UPDATES ARE NEEDED AT THIS TIME.

&&

.PREV DISCUSSION...AS OF 03:02 AM PDT MONDAY...INTERESTING
SATELLITE IMAGERY OVERNIGHT...ASIDE FROM PASSING HIGH CLOUDS AND
HOT SPOTS FROM WILDFIRES A DISORGANIZED MARINE LAYER/STRATUS DECK
REMAINS ALONG THE COAST. BEST COVERAGE OF CLOUDS IS PRIMARILY FROM
THE SAN MATEO COAST NORTHWARD. BASED ON LATEST TRENDS AND HI-RES
MODELS DO EXPECT SOME MORE FILLING IN OF STRATUS ALONG THE COAST
BY SUNRISE. HOWEVER...COVERAGE WILL NOT BE AS EXTENSIVE AS SUNDAY
MORNING. AFTER A SOME WHAT CLOUDY START FOR SOME AREA...AFTERNOON
SUNSHINE SHOULD PREVAIL FOR MUCH OF THE BAY AREA TODAY. SLIGHT
COOLING TODAY AND TUESDAY AS SEMI-FLAT FLOW DEVELOPS ALOFT WITH
HIGH PRESSURE MOVING EAST AND AN UPPER LOW REMAINING NEARLY
STATIONARY W OF 130W. NIGHT AND MORNING CLOUDS WILL REMAIN DURING
THIS TIME PERIOD AS WELL. ONE POTENTIAL AREA OF CONCERN IS TUESDAY
EVENING/NIGHT. AN EMBEDDED SHORTWAVE TROUGH IS FORECAST TO MOVE
OVER THE NORTH BAY TUESDAY. TO ENHANCE LIFT EVEN FURTHER...THE
NOSE OF A JET MOVES OVERHEAD AS WELL. LASTLY...LAPSE RATES ALOFT
ARE DECENT AND GREATER THAN 7 C/KM. THE MISSING INGREDIENT IS
MOISTURE...MODELS DO NOT BRING MUCH MOISTURE OVERHEAD.
THEREFORE...WILL CONTINUE TO KEEP THE FORECAST DRY AT THIS TIME
FOR TUESDAY EVENING/NIGHT.

BY WEDNESDAY...THE UPPER LOW WEST OF 130W BEGINS TO MOVE EASTWARD.
DOWNSTREAM OF THE LOW WE GET A LITTLE SHORTWAVE RIDGING OVERHEAD
LEADING TO A SLIGHT WARM UP WEDNESDAY AND THURSDAY. DESPITE THE
SLIGHT WARM UP...WE WILL STILL EXPERIENCE NIGHT AND MORNING
CLOUDS.

TEMPERATURES DROP AGAIN ON FRIDAY AS THE UPPER LOW FINALLY MAKES A
MOVE INLAND OVER THE NORTH BAY. THE INSTABILITY AND DYNAMICS
ASSOCIATED WITH THE UPPER LOW ARE BETTER THAN THE TUESDAY
SHORTWAVE...BUT ONCE AGAIN THE MISSING INGREDIENT IS MOISTURE.
LATEST MODEL FORECAST SHOWS SOME MOISTURE ALOFT...BUT NOT MUCH.
THE BEST MOISTURE AND LIFT STILL REMAIN NORTH OF THE NORTH BAY.
WILL KEEP FORECAST DRY FOR NOW. HOWEVER...AS MENTIONED ON PREVIOUS
DISCUSSIONS WILL HAVE TO WATCH THIS CLOSELY AS IT COULD HAVE MAJOR
IMPACTS ON FIRE WEATHER CONCERNS LOCALLY AND OTHER PARTS OF THE
STATE WHERE FIRES ARE ALREADY ONGOING. THE BIGGEST CONCERN WOULD
BE THUNDERSTORMS.

&&

.AVIATION...AS OF 5:00 AM PDT MONDAY...STRATUS HAS SPREAD INTO THE
SFO BAY AREA FROM THE NORTHWEST. SOME HOLES IN THE STRATUS ARE
SEEN IN THE SOUTH BAY BUT THESE MAY BE FILLING IN AS WELL.
EXTENSIVE CLOUDS SUPPORTS A LATE BURNOFF BUT GIVEN THAT THE CIGS
ARE AROUND 2000 FEET THE CLOUD DECK IS A LITTLE SHALLOWER AND THUS
COULD CLEAR OUT EARLIER. FORECAST CALLS FOR CLEARING AFTER 18Z AT
SFO BUT COULD HOLD OFF UNTIL CLOSE TO 19Z. A WEAK SHORTWAVE
TROUGH MOVING INTO NORTHERN CALIFORNIA THIS MORNING MAY SQUEEZE
OUT PATCHY MORNING DRIZZLE.

VICINITY OF KSFO...MVFR CIGS THROUGH 18-19Z. WEST WINDS GUSTING TO
20-22 KT AFTER 20Z.

KSFO BRIDGE APPROACH...MVFR CIGS THROUGH 19Z. 
 
MONTEREY BAY AREA TERMINALS...STRATUS IS NOT WELL ORGANIZED WITH
SOME HOLES IN THE STRATUS OVER THE NORTHERN MRY BAY AND IN THE
SALINAS VALLEY. THIS SUPPORTS SLIGHTLY EARLIER CLEARING. MVFR
CIGS CLEARING AFTER 18Z AT MRY AND 17Z AT SNS.

&&

.MARINE...AS OF 09:12 AM PDT MONDAY...LIGHT WINDS AND SEAS ARE
FORECAST THROUGH TUESDAY AS A WEAK SYSTEM LINGERS OFFSHORE. THE
STRONGEST WINDS WILL BE ACROSS THE NORTHERN SAN FRANCISCO BAY
TODAY... ESPECIALLY THROUGH THE GOLDEN GATE AND NEAR ANGEL ISLAND.
WINDS INCREASE AND SHIFT TOWARDS THE NORTHWEST MIDWEEK.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .TDAY...SCA...SF BAY FROM 3 PM

&&

$$

PUBLIC FORECAST: RGASS
AVIATION: W PI
MARINE: DRP


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