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FXUS66 KMTR 250704
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA CA
1200 AM PDT TUE AUG 25 2009
.DISCUSSION...AS OF 9:00 PM PDT MONDAY...MUCH WARMER WEATHER FOR THE
REMAINDER OF THE WEEK ESPECIALLY FOR INLAND LOCATIONS.
TYPICAL EVENING SETUP FOR THE SF/MONTEREY BAY FORECAST AREA AS A
NEARLY 3 MB WESTERLY/ONSHORE FLOW IS COMBINING WITH A MARINE LAYER
OF AROUND 1800 FEET. THIS IS LEADING TO CLOUDS SPREADING ACROSS
ALMOST ALL OF THE COASTAL AREAS AND INTO BOTH BAYS. ONE INTERESTING
FEATURE IS THE NORTHERLY COMPONENT IS EVEN STRONGER AT 3.2 MB.
THIS WILL HELP TO LIMIT SOME OF THE CLOUDS FOR THE NORTHERN THIRD OF
THE CWA AND PRODUCE COPIOUS AMOUNTS UP AND DOWN THE ENTIRE SALINAS
VALLEY. LOWS SHOULD BE MOSTLY IN THE 40S AND 50S.
MAIN STORY FOR THE REST OF THE WEEK WILL BE A SIGNIFICANT WARM-UP
AS A RIDGE OF HIGH PRESSURE OFF TO THE SOUTHEAST BUILDS WHILE
TEMPERATURES ALOFT WARM 4-7C AT 850MB. HIGHS ARE EXPECTED TO
INCREASE 3-5F EACH DAY OVER MANY INLAND SPOTS OVER THE NEXT THREE
DAYS WITH MANY INTERIOR SPOTS FORECAST TO HIT THE 90S BY FRIDAY AND
LOWER 100S IN THE WARMEST LOCATIONS. BIGGEST QUESTION MARK APPEARS TO
BE HOW MUCH IT WILL WARM-UP. THREE PIECES ARE GOING AGAINST THIS
BEING A WIDE-SPREAD RECORD-SETTING EVENT. ONE...500 MB HEIGHTS ARE
FORECAST TO "ONLY" BY 594 MB INSTEAD OF THE 598-600 MB RANGE THAT
WOULD BE NEEDED. TWO...TEMPERATURES AT 850 ARE NOT FORECAST TO WARM
ABOVE 27C EXPECT IN SPOTS THAT ARE ALWAYS THE WARMEST IN THE CWA SUCH
AS INTERIOR MONTEREY. THREE...ALL OF THE MODEL GUIDANCE KEEPS AN
ONSHORE/WESTERLY FLOW GOING WHICH WILL KEEP THE COAST MUCH COOLER AND
SHOULD ALSO ACT AS A BARRIER TO RECORD HEAT. THIS WILL ALSO HELP TO
KEEP CLOUDS GOING AT THE COAST AND ELEVATIONS UNDER 1500 FEET AT
ADJACENT SPOTS. OBVIOUSLY IF THE TREND STARTS TO MOVE MORE TOWARD A
TROUGH OFF THE COAST AND HIGHER HEIGHTS AND TEMPERATURES...THE
FORECAST HIGHS AND LOWS WILL BE INCREASED. AT THIS TIME...THAT DOES
NOT APPEAR LIKELY. MODELS HAVE ALSO BEEN HINTING AT SOME MOISTURE
BEING BROUGHT IN FROM THE SOUTHEAST AS AN UPPER WAVE OVER THE PACNW
ON FRIDAY KICKS OFF TO THE NORTHEAST. THIS LOOKS VERY UNLIKELY SO
POPS WERE KEPT AT 10 PERCENT OR LESS.
&&
.AVIATION...AS OF 11:00 PM PDT MONDAY...SATELLITE IMAGERY SHOWS ONLY
A THIN STRIP OF STRATUS CLINGS TO THE NORTH COAST TONIGHT. THIS IS A
DIRECT RESULT OF THE INCREASING NORTHERLY PRESSURE GRADIENT FROM ACV-
SFO. MEANWHILE THE FORT ORD PROFILER IS CURRENTLY SHOWING A STEADY
2000 FOOT MARINE LAYER. STRATUS IS ANTICIPATED TO FILL IN OVER MOST
TERMINALS OVERNIGHT WILL A SLIGHTLY LATER BURN OFF TUESDAY MORNING
AS A RESULT OF THE DEEPER MARINE LAYER.
VICINITY OF KSFO...MVFR-VFR CONDITIONS EXPECTED TO DEGRADE TO IFR
CONDITIONS OVERNIGHT. BKN-OVC 007-009 DECKS WILL SCATTER OUT
BETWEEN 17Z-18Z TUESDAY MORNING. WINDS WILL REMAIN LIGHT THEN
INCREASE TO AROUND 15 KT AFTER 20Z TUESDAY.
KSFO BRIDGE APPROACH...VFR CONDITIONS EXPECTED TO DEGRADE TO IFR-
MVFR (BKN 009-010) AFTER 10Z EARLY TUESDAY MORNING. STRATUS WILL
SCATTER OUT AROUND 17Z.
MONTEREY BAY TERMINALS...IFR-MVFR (OVC 007-010) CONDITIONS WILL
PERSIST THROUGH 18-19Z TUESDAY MORNING. WINDS WILL REMAIN LIGHT.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
.TNGT...SCA...PT ARENA TO PIGEON PT 10 TO 60 NM
SCA...PT ARENA TO PT REYES TO 10 NM
&&
PUBLIC FORECAST: BELL
AVIATION/MARINE: CW
$$
NWS ON THE WEB AT WEATHER.GOV/SANFRANCISCO
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