Forecast Discussions mentioning ACARS, received at FSL on 05/06/00

CHAOTIC CLOUD PATTERN OVER THE FORECAST AREA TONIGHT...WITH AREAS OF LOWER MARINE LAYER CLOUDS/FOG BATTLING VARIABLE HIGH CLOUDS WHICH ARE STREAMING OVERHEAD. ACARS DATA AND EVENING SOUNDINGS INDICATE MARINE INVERSION BASE AT 2500 TO 3500 FEET. IR SATELLITE IMAGES INDICATE LARGE STREAM OF HIGH LEVEL MOISTURE LINED UP FOR SEVERAL HUNDRED MILES OFFSHORE. THIS WILL COMBINE WITH LOW CLOUDS FOR MOSTLY CLOUDY CONDITIONS THIS MORNING...BUT SUBSIDENCE MOVING ACROSS THE REGION THIS MORNING COMBINED WITH SLIGHTLY RISING HEIGHTS BETWEEN SHORTWAVE TROFS SHOULD ALLOW MOST OF THE LOW CLOUDS TO SCATTER OUT AND YIELD PARTLY CLOUDY SKIES FOR THE AFTERNOON.

00Z MODELS IN GENERAL AGREEMENT...WITH NEXT UPPER SHORTWAVE MOVING INTO CENTRAL AND NRN CA LATE TONIGHT AND SUNDAY MORNING. NGM IS SOMEWHAT WEAKER AND FURTHER NORTH THAN AVN/ETA. GIVEN SYSTEMS FAIRLY VIGOROUS APPEARANCE ON SATELLITE WILL GO WITH STRONGER AND FURTHER SOUTH SOLUTION. MODEL CROSS SECTIONS SHOW A GOOD DEAL OF LOW AND MID LEVEL MOISTURE ACCOMPANYING THIS FEATURE...WITH THE GREATEST MOISTURE FROM POINT CONCEPTION NORTHWARD. UVV IS LACKING HOWEVER...SO EXPECT LOTS OF CLOUDS...BUT NO PRECIP BEYOND SOME DRIZZLE FOR NORTHERN AREAS LATE SAT NIGHT AND SUNDAY MORNING. LOOKS LIKE CLOUDS WILL LINGER THROUGH MUCH OF THE DAY FOR MANY LOCATIONS SUNDAY... ESPECIALLY ALONG THE CENTRAL COAST. TEMPS ARE SOMEWHAT PROBLEMATIC... WITH BOTH FWC AND FAN MOS SHOWING A FEW DEGREES OF WARMING AT MANY LOCATIONS FROM SAT TO SUN...WHICH RUNS AGAINST WHAT WOULD BE EXPECTED...AS WELL AS THE PREVIOUS FORECAST. A LOOK AT THE ETA MSLP FIELDS SHOWS CONTINUED STRONG ONSHORE GRADS LAX-DAG...+6 MB OR BETTER BOTH THIS EVENING AND SUNDAY EVENING. WILL KEEP PREVIOUS FORECAST OF SLIGHT WARMING FOR TODAY FOLLOWED BY SLIGHT COOLING ON SUNDAY...BUT OUTCOME IS RATHER UNCERTAIN DEPENDING ON THE EXTENT OF CLOUD COVER.

EXTENDED...NEW MRF HAS RETREATED SOMEWHAT FROM ITS RIDGING SCENARIO FOR EARLY NEXT WEEK...NOW BUILDING A FLAT RIDGE IN FROM THE SW ON MONDAY... THEN FLATTENING IT AGAIN TUE AND WED AS TROFFING BEGINS TO SAG OFF THE PAC NW COAST. UK/CANDIAN IN GENERAL AGREEMENT WITH THIS SCENARIO. WILL FORECAST LESSENING MARINE INFLUENCE AND INCREASING TEMPS FOR MONDAY AND TUESDAY...THEN REVERSAL TO INCREASING MARINE LAYER AND COOLING TEMPS BEGINNING ON WEDNESDAY. LATER NEXT WEEK STILL LOOKS POSSIBLY INTERESTING AS MRF...AND TO SLIGHTLY LESSER EXTENT UKMET AND CANADIAN...CONTINUE TO ADVERTISE AMPLIFICATION OF A TROF ALONG THE WEST COAST. DO NOTE THAT THIS PROCESS IS DELAYED A DAY OR SO FROM YESTERDAYS RUN...SO CONFIDENCE IS LOW THAT THIS AMPLIFICATION WILL IN FACT OCCUR. 05/12Z ECMWF CONTINUES WEAK TROFFING TREND THROUGH NEXT WEEK...AND GIVEN RECENT HISTORY THIS MAY BE MORE REASONABLE.

LAX 000. JACOBSON

.LAX...SMALL CRAFT ADVISORY (SEE LAXCWFLAX).



INTERESTING MID-SPRING PATTERN SETTING UP FOR THE NEXT 48 HOURS WITH STRONG ZONAL FLOW PREVAILING OVER MUCH OF THE PACIFIC WITH APPROX 150KT JET PUNCHING EAST ALONG 40N. PLUME OF MOISTURE EXTENDS WEST TO AROUND 160E AND SSMI DATA SHOWS TPW/S APPROACHING 1.50 INCH ALONG AXIS. SEVERAL WAVES ARE EMBEDDED WITHIN FLOW WITH THE STRONGEST LOCATED AT APPROX 41N/145W AND MOVING RAPIDLY EWD AT AROUND 80KTS. GIVEN SMALLER SCALE AND RAPID MOVEMENT EVIDENT ON SAT PICS...MODELS APPEAR A BIT UNDERDONE AND TIMING REMAINS QUESTIONABLE SHOWING PRIMARY VORT REACHING NORCAL COASTLINE AROUND 00Z THIS EVE. ALTHOUGH PROGS SHOW PW AXIS LOCATED SOUTH OF LOW-MID LEVEL MOISTURE... WESTERLY FLOW WILL CONFINE BULK OF DYNAMICS AND DEEPEST MOISTURE OVER THE PAC NW AND NORCAL AS WAVES PUSH INLAND TONIGHT/SUN. THE ABOVE COMBINED WITH RELATIVELY HIGH HEIGHTS OVER THE CWA SHOULD RESULT IN A RATHER SHARP N-S MOISTURE GRADIENT DURING THE NEXT 48 HOURS. NEVERTHELESS...PROGGED X-SECTIONS SHOW ENOUGH MOISTURE AND UVM THROUGH 700MB TO CONT LIKELY POPS OVER HIGHER SIERRA ZONES NORTH OF KINGS WITH LOW CHANCES OVER NORTHERN PORTIONS OF THE CENTRAL SAN JOAQUIN. ALTHOUGH 00Z PROGS SHOW MOISTURE LINGERING THROUGH 00Z MON ...STRONGEST FORCING AND BEST PRECIP POTENTIAL SHOULD OCCUR BETWEEN 12-18Z SUN BEFORE WAVE AXIS SHIFTS EAST.

WESTERLY FLOW ALOFT WILL ALSO PREVENT ANY INTRUSION OF COLDER AIR INTO THE CWA WITH SNOW LEVELS REMAINING CONFINED TO HIGHEST ELEVS OF THE SIERRA AND LITTLE TEMP CHANGE ACROSS THE REMINDER OF THE DISTRICT. GRADS THROUGH MID LEVELS WILL ALSO CONT TO SUPPORT BREEZY TO WINDY CONDITIONS INTO SUN NIGHT WITH TYPICAL INCREASE IN SPEEDS DURING AFTN/EVE HOURS AS SURFACE PRESSURES FALL OVER INTERIOR DESERTS.

MEDIUM RANGE PROGS CONT TO DISPLAY DIFFERING SOLUTIONS FOR MON-WED. HOWEVER...FLAT RIDGE BUILDING OVER THE SOUTHERN HALF OF CA SHOULD PROVIDE SOME BOOST TO TEMPS EARLY NEXT WEEK.

.HNX...NONE.

FAT BE 079/057 078/055 083 88022 BFL AE 079/053 078/053 085 88000 YNP BW 071/051 068/045 075 88005

JSN



WET SPRINGTIME EVENT SETTING UP WITH IR SAT PIX IMAGERY SHOWING WELL-DEFINED MOISTURE PLUME EXTENDING FROM THE NORTHERN CALIFORNIA COAST WESTWARD ACROSS 3/4 THE PACIFIC. H20 VAPOR SAT PIX FURTHER DEFINES THIS AREA AND ITS EXTENSION INTO CHINA. COMPOSITE RADAR MOSAIC SHOWS LIGHT RETURNS ACROSS THE NORTHERN CWA. SURFACE OBS VERIFYING THAT ALL IS NOT ELEVATED. 00Z MODELS AS WELL AS DARKENING ON H20 VAPOR SAT PIX IMAGERY DEPICT A WEAK SHORT WAVE JUST ACROSS THE NORTHERN CA BORDER. USING THE 00Z ETA...THE H10-H7 Q VECTOR ANALYSIS AND THE 250 MB UPPER FLOW ALSO SHOWS A WEAK LOW LEVEL CONVERGENCE/UPPER LEVEL DIVERGENCE COUPLET. THIS COUPLET DIMINISHES BY ABOUT 12Z SATURDAY MORNING. LASTLY...BEFORE HIGHER CLOUDS MOVED INTO THE NORTHERN CWA THIS EVENING...LOWER CLOUDS WERE EVIDENT ON IR SAT PIX IMAGERY. ALL OF THE ABOVE HAVE COMBINED TO PRODUCE THE ABOVE MENTIONED LIGHT RADAR RETURNS AND SUBSEQUENT UPDATE. dPROG/dT ETA ANALYSIS DEPICTS A SIGNIFICANT CHANGE IN PRECIPITATION TIMING FOR TOMORROW/S EVENT. OVER THE LAST 3 MODELS RUNS...THE ONSET OF PRECIPITATION HAS BEEN FASTER. IF THIS TREND CONTINUES...RAIN/SNOW WILL BE IN HERE(ACROSS THE NORTH) BY EARLY AFTERNOON. WITH GOOD MOISTURE...PRECIPITABLE H20/S IN THE 1 TO 1.5 INCH RANGE 1500 MILES OFFSHORE...COMBINED WITH 45+ KT SW WINDS...1 TO 2 INCHES OF LIQUID LOOKS REASONABLE FOR THE WEST SLOPES OF THE SIERNEV WITH 3 INCHES NOT OUT OF THE QUESTION. WITH THE JET AND COLDER AIR STAYING MAINLY TO OUR NORTH...SNOW LEVELS WILL PROBABLY REMAIN NEAR PASS LEVELS SATURDAY NIGHT INTO SUNDAY MORNING. CURRENT THINKING...BASED ON SEASON AND WEEKS OF WARM TEMPERATURES...SNOW ACCUMULATION RATES WILL BE SLOWER THAN IN WINTER TIME CONDITIONS. THUS A WATCH WILL NOT BE ISSUED...ALTHOUGH A FOOT OR MORE OF SNOW IS POSSIBLE ABOVE 7000 FT IN A 24 HOUR PERIOD. WEEKEND MOUNTAIN RECREATIONALISTS BEWARE. AN SPS HAS BEEN ISSUED.

.STO...NONE

KRUZDLO



CONT FORECAST TRENDS. DEEP AND VARIABLE MARINE LAYER...ROUGHLY 3-4 THOUSAND FT DEEP...ALONG WITH PERSISTENT CLOUDINESS AND A BIT COOLER OVER THE WEEKEND.

SATELLITE SHOWS AREAS OF CLOUDS IN THE VALLEYS OF SOCAL...SOME BARELY VISIBLE PATCHY LOW CLOUDS ALONG CENTRAL CA COAST...AND THIN HIGH CLOUDS STREAMING OVERHEAD.

INCOMING MODELS SIMILAR TO PREVIOUS RUNS AND INDICATE W-NW ZONAL FLOW WILL PREVAIL FOR OUR DISTRICT. OCCASIONAL TROUGHS PASSING TO OUR NORTH WILL CAUSE LOCAL EFFECTS TO CLOUDS AND TEMPS ALL ALONG THE COAST. THE FLOW WILL BECOME MOIST ENOUGH BY SUN MORNING TO CAUSE LOCAL DRIZZLE OR VERY LIGHT RAIN NORTHWARD.

LAX 0000. SIMPSON.

.LAX...SMALL CRAFT ADVISORY (SEE LAXCWFLAX).



...SYNOPSIS...

ONSHORE FLOW AND THE MARINE LAYER WILL CONTINUE NIGHT AND MORNING LOW CLOUDS AND FOG WEST OF THE MOUNTAINS WITH ONLY PARTIAL AFTERNOON CLEARING NEAR THE BEACHES. OTHERWISE...FAIR THROUGH SUNDAY WITH LITTLE TEMPERATURE CHANGE. BUILDING HIGH PRESSURE WILL RESULT IN A DECREASING MARINE LAYER AND WARMER DAYS EARLY NEXT WEEK.

...DISCUSSION...

LOW CLOUDS MAINLY CONFINED TO COASTAL AREAS THIS EVE NOT VERY EXTENSIVE OFFSHORE. MODERATELY STRONG NW WINDS AROUND PT CONCEPTION AND SOME EVIDENCE OF WEAK EDDY OR AT LEAST CYCLONIC CURVATURE TO FLOW OVER COASTAL WATERS. 00Z NKX SOUNDING SHOWED INVERSION BASED NEAR 2400 FT...A LITTLE DEEPER THAN LAST NIGHT. GRADIENTS MODERATELY STRONG ONSHORE WITH ABOUT 7 MB SAN-IPL HELPING TO CAUSE SOME BREEZY WINDS IN MOUNTAINS/ DESERTS. SOME HI CLOUDS ALSO DRIFTING OVER IN W TO NW FLOW ALOFT.

MODELS SIMILAR TO PREVIOUS RUNS WITH UPPER TROUGH NEAR W COAST AND WEAK SHORT WAVES ROTATING THROUGH. ONLY MINOR CHANGES OR JUST SLIGHT INCREASE IN LOCAL HEIGHTS/ THICKNESS/850 MB TEMPS NEXT COUPLE OF DAYS. ALSO LITTLE CHANGE IN ONSHORE GRADIENTS WITH THE USUAL DIURNAL INCREASE TO AFTERNOON THERMAL LOW IN DESERTS. SMALLER SCALE MODELS INDICATE EDDY SPINNING UP TONIGHT AND EXPECT STRATUS WILL REDEVELOP AND BECOME MORE EXTENSIVE OVERNIGHT. INTERMITTENT WEAK EDDY LIKELY TO CONTINUE INTO SUN. SO EXPECT TO CONTINUE WITH NIGHT/MORNING LOW CLOUDS/FOG W OF MOUNTAINS WITH SLOW OR ONLY PARTIAL CLEARING NEAR BEACHES AND LITTLE TEMP CHANGE THROUGH SUN. OTHERWISE...FAIR IN DRY WLY FLOW ALOFT.

LONGER RANGE PROGS INDICATE UPPER HI BUILDING OFF COAST AND SLIDING OVER SW EARLY NEXT WEEK FOR LESS NIGHT/MORNING COASTAL LOW CLOUDS AND WARMING TREND. TROUGH DEEPENS IN E PAC DURING SECOND HALF OF WEEK FOR MORE CLOUDS AND COOLING TREND.

SAN 0000

.SAN...NONE.

ATKIN

BROAD UPPER TROUGH AXIS CONTINUES TO SWING INLAND WITH A FLAT FLOW PREVAILING OVER CALIFORNIA. NO SIGNIFICANT IMPULSES SLATED TO MOVE ASHORE IN THE NEAR TERM. THE FAST MOVING FLOW WILL CONTINUE TO MAKE TIMING OF THE NEXT IMPULSE FORECAST TO ARRIVE OVER THE WEEKEND TRICKY.

NO MAJOR CONCERNS IN THE NEAR TERM. GOES DATA SHOWS LOTS OF CIRRUS STREAMING ACROSS THE AREA WITH THE MAJORITY OF IT QUITE THIN. TEMPERATURES ARE RUNNING ANYWHERE FROM 3 TO 8 DEGREES COOLER THAN LAST EVENING AND DEW POINTS DOWN SEVERAL DEGREES AS WELL. THIS WILL TRANSLATE INTO OVERNIGHT MINS SEVERAL DEGREES COOLER THAN LAST NIGHT BUT HIGH CLOUDS AND WINDS WILL PREVENT IDEAL COOLING CONDITIONS. ONSHORE PRESSURE GRADIENTS TIGHTER BY A COUPLE OF MILLIBARS COMPARED TO 24 HOURS AGO PRODUCING SOME BREEZY CONDITIONS ACROSS THE FA WITH LOCALLY WINDY CONDITIONS THROUGH THE TEHACHAPI MOUNTAINS AND IN THE DESERT BELOW PASSES. UPPER SUPPORT FOR ANY SIGNIFICANT WIDEPSREAD WINDS IS LACKING PER LATEST MODEL AND RAOB DATA SO WINDS SHOULD STAY IN CHECK OVERNIGHT.

GOING ZONE PACKAGE LOOKS FINE. WILL UPDATE ONLY FOR ADJUSTMENT TO WORDING IN THE SECOND PERIOD OF SOUTH VALLEY ZONES.

.HNX...NONE.

TAL



SFC HIGH SHOULD CONTINUE TO WEAKEN ACROSS THE COASTAL WATERS TONIGHT AS UPPER LEVEL MOISTURE CONTINUES TO ENCROACH ON THE AREA. WE MAY SEE A FEW BRIEF BREAKS IN THE HIGH CLOUDS...BUT SATELLITE IMAGES SUGGEST THEY WILL BE SHORT LIVED. MODELS ALSO SUGGEST THAT BY MID MORNING SAT THE OVER RUNNING MOISTURE SHOULD PRETTY WELL BLOCK OUT THE SUN. WILL CONSIDER UPDATING ZONES TO INDICATE CLOUDIER CONDITIONS. OTHERWISE MODELS STILL LOCKING IN ON POWERFUL SPRING STORM TO ARRIVE AT NORTH COAST SAT NIGHT. PLUME OF MOISTURE WITH SUBTROPICAL ORIGIN STRETCHES ACROSS THE PACIFIC...WITH SSMI IMAGES SHOWING LONG STRETCH OF TPW VALUES OVER 1.5 INCHES BUMPING INTO 150W. MODELS AND SATELLITE BOTH SHOW 100+ KT JET ACROSS PACIFIC ALONG 40N. AND SSMI RAIN RATES IN WARM ADVECTION AHEAD OF PACIFIC LOW HAVE BEEN CONSISTENTLY AROUND .10 INCHES PER HOUR. MODELS ALSO SHOW FLOW ACROSS EPAC REMAINING ZONAL THROUGH SAT NIGHT AS STRONG SHORT WAVE MOVES TOWARD CAPE MENDOCINO. SO FOCAL POINT OF LANDFALL OF MOISTURE LOOKS TO BE NORTHERN CA AND SOUTHERN OR. AVN HAS BEEN SHOWING NOSE OF JET PUSHING INTO CA OVER SONOMA AND MENDOCINO COUNTIES...AS THETA-E AND PW RIDGES REMAIN A LITTLE FARTHER SOUTH. CURRENT SSMI RAIN RATE FIELD ALSO EXTENDS SOUTH TO AROUND 36 DEG N. SO UNSEASONABLY HEAVY RAIN SHOULD EXTEND OVER THE ENTIRE CWA...PART WAY UP THE OR COAST...AND SOUTH TO THE BAY AREA. EARLIER DISCUSSION OUT OF SATELLITE ANALYSIS BRANCH COMPARED CURRENT SYSTEM TO PREVIOUS LATE SPRING EVENTS WHICH BROUGHT OVER AN INCH OF RAIN IN 24 HOURS TO THE LOWLANDS...AND 3 TO 5 INCHES IN THE HILLS. CURRENT STRONGLY WORDED ZONES SHOULD COVER THIS EVENT FOR NOW. TJADEN

POPS CEC 07+7 EKA 07+7 UKI 0596. .EKA...NONE.



LOOKS LIKE ANOTHER NIGHT WITH VERY FEW LOW CLOUDS. THE FT ORD PROFILER SHOWS NO MARINE INVERSION DUE TO THE RELATIVELY COOL AIR ALOFT AND LOW LEVEL MOISTURE REMAINS SPARSE. THE STRONG ONSHORE FLOW ...3.1 MB SFO-SAC AT 03Z...WILL KEEP COOL AIR MOVING INLAND AND IT WILL BE A CRISP NIGHT IN MOST PLACES WITH ONLY AREAS OF HIGH CLOUDS TO INHIBIT RADIATIONAL COOLING.

THE NEW ETA FOLLOWS THE MRNG MODELS IN MAINTAINING A STRONG ZONAL FLOW INTO CA THRU THE WEEKEND...WITH A GOOD BATCH OF MOISTURE MOVING INTO THE N BAY SAT NIGHT. THE ETA FORECASTS A FAIRLY STRONG OMEGA FIELD TO MOVE INTO THAT AREA WITH RESPECTABLE OMEGA S TO SANTA CRUZ. HOWEVER...OTHER DYNAMICS ARE LACKING. THE MAIN JET IS FORECAST TO STAY N OF OUR FORECAST AREA THRU THE WEEKEND...WITH ONLY VERY SLIGHT UPPER LEVEL DIFFLUENCE SAT NIGHT AND NO THICKNESS DIFFLUENCE. COLD ADVECTION WILL ALSO BE WEAK OR NONEXISTENT. 500 MB HEIGHTS REMAIN FAIRLY HIGH TOO...THOUGH THE ETA DOES DROP THE 570 DM LINE AS FAR S AS SJC BY SUN MRNG. SATELLITE PIX SHOW A GOOD BAND OF CLOUDS WELL OFFSHORE HEADED RIGHT AT OUR REGION...BUT ITS HARD TO SAY WHAT WILL BE UNDER THEM WHEN THEY MAKE LANDFALL SAT NIGHT. ALL IN ALL...CANT RULE OUT RAIN FROM ABOUT MRY BAY N SAT NIGHT/SUN MRNG BUT AT THIS TIME OF YEAR ITS NOT A CERTAINTY ANYWHERE IN OUR CWA. WILL LEAVE FORECASTS AS THEY ARE...RAIN LIKELY IN THE N BAY SAT NIGHT WITH GRADUALLY DECREASING POPS FARTHER S.

THE EXTENDED OUTLOOK STILL CALLS FOR GRADUAL RIDGING AND DRYING LATE SUN INTO TUE. LOOKING AT THE MRF/EURO/NOGAPS/CANADIAN...THE MRF IS THE ODD MODEL OUT IN A COUPLE OF WAYS. THE OTHER 3 MODELS FORECAST LESS RIDGING MON-TUE...THOUGH ALL DO RAISE THE 500 MB HEIGHTS SIGNIFICANTLY AND END THE RAIN THREAT. AFTER THAT...THE MRF DROPS A DEEP...COLD TROF TOWARD OUR REGION STARTING ON WED AND PARKS IT OFFSHORE ON THU. THE OTHER MODELS ALSO LOWER HEIGHTS...BUT NOT AS MUCH. AND...THEY DEVELOP THE THU TROF IN THE GREAT BASIN INSTEAD OF OFFSHORE...WHICH OF COURSE WOULD BE A MUCH DRIER SOLUTION FOR OUR REGION THAN THAT OF THE MRF. AT ANY RATE...LOOKS LIKE WARMING INLAND BY MON...THEN COOLING AGAIN BY WED. STS 0275 SFO 0044 LVK 0033 SJC 0022 MRY 0011. MARKKANEN

.SFO...TNGT...SCA...PIGEON PT TO PT PIEDRAS BLANCAS.

N 

LITTLE CHANGE IN THE BROAD SYNOPTIC PATTERN...UPPER LOW TO REMAIN NEAR THE GULF OF ALASKA WITH FAST ZONAL FLOW OVER THE EAST PACIFIC AND WESTERN U.S. A FEW MINOR SHORT WAVES MOVING THRU AND THEN A SIGNIFICANT WAVE EXPECTED LATE SAT NIGHT INTO SUN. THE MODELS MIGHT HAVE SOME TROUBLE WITH TIMING AND STRENGTH OF THIS SYSTEM AND WILL NEED TO WATCH FOR CHANGES...HOWEVER THERE IS GOOD AGREEMENT FOR NOW AND FOLLOWED NEAR THIS CONSENSUS SOLUTION. BIGGEST FORECAST PROBLEM IS POPS FOR LATE SAT NITE/SUN. THE BEST LIFT IS PEGGED FOR NORCAL... HOWEVER A PERIOD OF MDT LIFT AND HEALTHY LOW TO MID-LEVEL MSTR ARE INDICATED FOR NORTHERN 1/3RD OF DISTRICT IN 12-18Z TIME WINDOW. GOING WITH LIKELY POPS FOR HIGHER TERRAIN OF SIERRA N OF KINGS CANYON AND CHANCE ELSEWHERE N OF KERN COUNTY LINE. IN SAN JOAQUIN VLLY H5 HGTS WILL BE RELATIVELY HIGH NEAR 5730M OR ABOVE AND AT THIS TIME WILL LIMIT TO SLIGHT CHANCES NORTH AND MENTION OF SPRINKLES FURTHER SOUTH...WITH A WATCHFUL EYE TO POTENTIAL LOW-MID LEVEL MSTR CONVERGENCE AND FORCING WHICH CONCEIVEABLY MIGHT BRING CHANCES FOR MEASURABLE LIGHT SHOWERS FURTHER TO S OF FRESNO.

GENERALLY COOLER TEMPS ON TAP FOR THE WEEKEND. SOLID COOLING TREND ALREADY HAS OCCURRED OVER THE CWA TODAY WITH TEMPS DOWN ANYWHERE FROM 5 TO 10 DEGF IN THE WAKE OF RECENT SHORT WAVE. EXPECT MINS TO DROP SVRL DEGREES FROM LAST NIGHT...THEN MAX TEMPS ON SAT SHOULD BE SIMILAR TO A BIT BELOW PERSISTENCE. OPAQUE HIGH CLOUDS SAT AFTN MAY CUT MAXES FOR NORTHERN SITES.

ANOTHER CONCERN WILL BE WINDS MAINLY LATE WEEKEND. CURRENT PROGS SUGGEST GRADIENTS WILL TIGHTEN BEST ON SUNDAY BRINGING SOME WINDY CONDS FOR PRONE AREAS TO W/NW FLOW. WINDS FOR EAST KERN COUNTY MAY REACH NEAR ADVISORY CRITERIA FOR SUNDAY AFTN/EVE WITH LOCAL STRONG GUST POTENTIAL THRU AND BELOW PASSES. OTHERWISE BREEZY TO LOCALLY WINDY THIS EVENING AND INCREASING AGAIN SAT AFTN INTO SAT NIGHT FOR HIER ELEVS AND KERN PASSES/DESERTS. IN THE EXTENDED OUTLOOK...MED RANGE MODELS TRY TO SLIDE THE UPPER CLOSED LOW CLOSER TO SOUTH BRITISH COLUMBIA COAST AND VANCOUVER ISL WHILE AT THE SAME TIME BUILDING A RIDGE POSITION NEAR 30N IN THE EAST PACIFIC AND ALLOWING FOR HGT/THICKNESS RISES OVER CNTRL CA. THINK TROUGHINESS AND ADDITIONAL SHORT WAVES IN ZONAL FLOW WILL LIKELY CONTINUE TO AFFECT THE REGION EARLY NEXT WEEK...RESULTING IN LESS...POSSIBLY MUCH LESS...OF WARMUP TREND THAN 00Z MRF INDICATED.

.HNX...NONE.

FAT BE 052/080 057/078 055 95001 BFL UE 050/079 052/079 053 95000 YNP BW 046/069 051/067 045 95004

LAVIS



...NEXT MAJOR WEATHER SYSTEM TO APPROACH ON SATURDAY...

DISC...SHORT RANGE MODELS SIMILAR WITH HANDLING AND TIMING OF APPROACHING SHORTWAVE. LATEST W/VAPOR IMAGERY SHOWS A LONG PLUME OF PACIFIC MOISTURE WITH BROAD WESTERLY FETCH BETWEEN 35-40N. THIS SHOULD BE ENOUGH FOR ONE MORE WIDESPREAD PRECIP EVENT ACROSS FROM LATE SATURDAY INTO SUNDAY.

PLENTY OF HIGH CLOUDS CURRENTLY ACROSS THE AREA...SO WILL WORD MOST ZONES AS "MOSTLY CLOUDY" EXCEPT FOR EXTREME SOUTHERN AREAS.

FOR SATURDAY...TIMING OF PRECIP A BIT TRICKY...BUT PROBABLY NORTHERN AREAS BY MID AFTERNOON...THEN TRENDING TOWARDS EVENING FARTHER SOUTH. MODELS HAVE BEEN TRENDING SLOWER WITH PRECIP ONSET...SO THIS WILL HAVE TO BE MONITORED WITH NEXT MODEL RUN.

SATURDAY NIGHT...WIDESPREAD RAIN EVENT...ESPECIALLY FROM SACRAMENTO NORTHWARD. 700 MB TEMPS MAINLY -2 TO -4C...SO THINKING OF SNOW LEVELS IN THE MOUNTAINS DROPPING FROM 8000 FT DOWN TO NEAR 7000 FT BY SUNDAY MORNING. MODEL QPF/S PROG OVER AN INCH OF PRECIP AT RDD...THEN TAPERING TO 0.25 TOWARDS SOUTHERN SACRAMENTO VALLEY. WENT CATEGORICAL IN NORTHERN AREAS...THEN LIKELY FARTHER SOUTH.

SUNDAY...WORDED A CHANCE OF LINGERING PRECIP FOR THE MORNING HOURS...BUT AGAIN IF THE MODEL TRENDS OF SLOWING THE SYSTEM CONTINUE THEN THIS MAY CHANGE. WORDED "VARIABLY CLOUDY" IN THE AFTERNOON TO INDICATE THAT ANY CLEARING WOULD BE GRADUAL.

WENT CLOSE TO MOS WITH TEMPS AND WIND.

...LONG RANGE...SOME RIDGING BEHIND THIS SYSTEM ON MON AND TUE SHOULD PROVIDE FAIR CONDITIONS. MRF AND UKMET SEEM FAIRLY SIMILAR WITH NEXT TROF DIGGING DOWN ACROSS THE AREA. WITH RECENT TRACK RECORD OF THE LONG RANGE MODELS...STAYED CONSERVATIVE WITH JUST A "CHANCE OF SHOWERS".

BASIL

.STO...NONE

BLU CE 042/050 042/050 042 77049 RBL EE 050/068 053/071 048 77049 SAC EE 051/071 052/073 049 77026

BASIL



UPPER LEVEL LOW PRESSURE CONTINUES OVER THE GULF OF ALASKA WITH ZONAL FLOW DEVELOPING ACROSS THE AREA TONIGHT PRODUCING MID AND HIGH LEVEL CLOUDINESS. ALSO...ONSHORE FLOW AT THE SURFACE WILL HELP THE LOW CLOUDS TO RETURN TO THE COASTAL AREAS. BY LATE IN THE DAY ON SATURDAY ANOTHER SHORTWAVE TROUGH WILL MOVE INTO THE AREA FOR THE POSSIBILITY OF RAIN IN THE NORTH BAY. THIS DISTURBANCE WILL MOVE TO THE EAST WITH A WEAK COLD FRONT SPREADING MOISTURE AND SCATTERED SHOWERS ACROSS THE REGION SATURDAY NIGHT AND SUNDAY. ALL THE SHORT RANGE MODELS ARE IN GOOD AGREEMENT WITH RESPECT TO TIMING AT THIS POINT WITH MINOR DIFFERENCES IN SOUTHWARD PROGRESSION OF THE RAIN. BUT...WITH EACH OF THE LAST FEW AVIATION MODEL RUNS THE SHORTWAVE HAS BECOME MORE SIGNIFICANT SO POPS HAVE BEEN INCREASED... ESPECIALLY NORTH. BY SUNDAY AFTERNOON WEAK RIDGING WILL DEVELOP FOR DECREASING CLOUDS.

FOR THE EXTENDED...THE MEDIUM RANGE MODELS ARE IN FAIRLY GOOD AGREEMENT THROUGH MONDAY BUT THEN DIVERGE QUICKLY ON TUESDAY. AT 12Z WEDNESDAY 500 MB HEIGHTS OVER SAN FRANCISCO RANGE FROM 5660 METERS ON THE NOGAPS MODEL TO 5780 METERS ON THE ECMWF MODEL. SO WITH THIS DIVERSE GROUP OF FORECASTS WILL TAKE A MIDDLE OF THE ROAD POSITION AND BRING RAIN INTO THE NORTHERN SECTIONS ON WEDNESDAY. OTHERWISE...MONDAY AND EARLY TUESDAY SHOULD EXPERIENCE FAIR WEATHER UNDER RIDGING CONDITIONS. STS 0275 SFO 0044 SJC 0022 MRY 0011 LVK 0033 EVANS

.SFO...TNGT...SCA...PIGEON PT TO PT PIEDRAS BLANCAS AND THE SFO BAY.



NW CALIFORNIA WILL REMAIN IN A BROAD 500 TROUGH WITH FLOW BECOMING MORE ZONAL WITH TIME. INDIVIDUAL WEAK SHORTWAVES MOVING THROUGH THE TROUGH WILL BE TOUGH TO TIME AND TO FORECAST PCPN. PCPN COULD BE IN THE FORM OF SHOWERS OR DRIZZLE. FIRST SHORTWAVE HAS MOVED THROUGH THE AREA EARLY THIS MORNING AND KICKED OFF A FEW SHOWERS. NEXT SHORTWAVE PASSES THROUGH SOUTHERN CWA LATE THIS AFTERNOON INTO THIS EVENING WITH VERY LITTLE MOISTURE TO WORK WITH. A STRONGER SHORTWAVE PUSHES ONTO THE COAST SATURDAY AFTERNOON AND NIGHT. OMEGA FIELDS ARE NEGATIVE FROM 00Z SUN ONWARD AT 1000...950...900 AND 850 MB ALONG WITH HIGH RH VALUES. WILL HAVE LIKELY POPS ON THE COAST IN THE AFTERNOON AND CHANCE POPS FURTHER EAST AND IN INTERIOR MENDOCINO COUNTY. THIS SHORTWAVE WILL HAVE MORE MOISTURE WITH IT AND WIDESPREAD RAIN AGAIN LOOKS LIKELY FOR THE CWA WITH LIGHTER AMOUNTS FURTHER SOUTH AND THE HEAVIEST AMOUNTS UP NEAR THE OREGON BORDER. WOULD NOT BE SURPRISED TO SEE .25 TO .75 INCH QPF OUT OF THIS WHOLE STORM FOR THIS WEEKEND. MIGHT HAVE TO WATCH FOR SOME THUNDERSTORMS ON SATURDAY NIGHT AND SUNDAY MORNING AS THERE IS A HINT OF A JET STREAK MOVING ACROSS THE OR/CA BORDER AND STEEPENING LAPSE RATES. WILL NOT PUT ANY THUNDERSTORMS IN THE FORECAST FOR NOW AS I WANT TO SEE HOW THIS WILL PLAY OUT LATER WITH THE LATER MODEL RUNS.

IN THE EXTENDED...NOT QUITE SURE WHAT TO BELIEVE...BUT BROAD UPPER LEVEL TROUGH WILL CONTINUE TO AFFECT THE AREA WITH A BROAD UPPER RIDGE NOT FAR AWAY. SHORTWAVE RIDGE AFFECTS CWA SUNDAY NIGHT AND MONDAY AND THE FAR SOUTHERN CWA FOR TUESDAY AND WILL GO WITH CHC PCPN FOR TUE AND WED NORTH OF THE CAPE AND CHC ONLY ON WED IN THE SOUTH. USED A BLEND OF THE MRF...CANADIAN...ECMWF AND UKMET FOR EXTENDED FORECAST.

POPS CEC 07+7 EKA 07+7 UKI 0596. .EKA...NONE.

MICHELS



MARINE LYR VERY STUBBORN TODAY AND ONLY PARTIAL CLEARING AT BEST SO FAR THIS AFTERNOON. WILL PROBABLY GET SOME MORE CLEARING LATER THIS AFTERNOON AND EVENING BUT CLOUDS SHOULD BECOME PRETTY WIDESPREAD AGAIN OVERNIGHT. MAIN DIFFERENCE TONIGHT IS THAT MODELS INDICATE A RATHER WIDE AREA OF SUBSIDENCE MOVING IN ALOFT WHICH THEORETICALLY SHOULD LOWER THE MARINE LYR. THIS IN TURN WILL MAKE FOR AN EARLIER CLEARING SAT AFTN AND SLIGHTLY WARMER TEMPS, ASSUMING ALL GOES AS PLANNED. HOWEVER, ZONAL FLOW ACROSS THE PACIFIC WILL LEAVE US SUSCEPTABLE TO THE TAIL END OF WEAK WEATHER SYSTEMS. THE FIRST OF WHICH WILL ARRIVE SAT NT AND SUN AND BRING THE POSSIBILITY OF SOME DRIZZLE OR MAYBE EVEN LIGHT RAIN IN THE NORTHERN ZONES SUN AM. FOR NOW, WILL JUST INDICATE AN INCREASE IN CLOUD COVERAGE AND SOME POSSIBLE DRIZZLE AND NOT MENTION ANY MEASUREABLE RAIN. FURTHER SOUTH, MAIN EFFECT WILL BE TO DEEPEN THE MARINE LYR AND I WOULDN'T BE SURPRISED IF WE GET SOME LOCAL DRIZZLE DOWN THIS WAY AS WELL. THIS WILL ALL RESULT IN COOLER TEMPS AGAIN SUN WITH MUCH LATER, IF ANY, CLEARING.

ON MONDAY, ONSHORE GRADIENTS WEAKEN SOMEWHAT WITH SLIGHT HEIGHT RISES SO EXPECT EARLIER CLEARING OF LOW CLOUDS AND SLIGHTLY WARMER TEMPS. DO NOT BUY INTO THE MRF FORECAST OF NEAR 90 DEGREES IN THE VALLEYS MON. PERHAPS LOWER 80S BUT THAT'S ABOUT IT. 12Z AVN IS CERTAINLY QUITE A BIT COOLER THAN LAST NIGHT'S MRF AND GIVEN THIS, HAVE VERY LITTLE CONFIDENCE IN THE REMAINDER OF THE MRF SOLUTION. IN FACT, MRF HAS BEEN QUITE AMPLIFIED LATELY INDICATING BIG RIDGES AND BIG TROFS THAT HAVEN'T MATERIALIZED. CURRENT PATTERN WOULD INDICATE MORE OF A ZONAL FLOW WITH FASTER, WEAKER SYSTEMS. FOR NOW, WILL INDICATE VERY LITTLE CHANGE IN THE 3-5 DAY FORECAST.

LAX 0000. WOFFORD

.LAX...SMALL CRAFT ADVISORY (SEE LAXCWFLAX).



...CORRECTION TO DAY AND DATE....

...SYNOPSIS...

MODERATE ONSHORE FLOW AND THE RESULTING DEEP COASTAL MARINE LAYER WILL ALLOW THE NIGHT AND MORNING LOW CLOUDS AND FOG TO CONTINUE WEST OF THE MOUNTAINS...WITH ONLY PARTIAL AFTERNOON CLEARING NEAR THE BEACHES. OTHERWISE...DRY WESTERLY FLOW ALOFT WILL KEEP FRONTAL SYSTEMS WELL NORTH OF SOUTHERN CALIFORNIA THROUGH SATURDAY. NEAR SEASONAL TEMPERATURES ARE EXPECTED THROUGH SATURDAY. BUILDING HIGH PRESSURE WILL RESULT IN A DECREASING MARINE LAYER AND WARMING TREND EARLY NEXT WEEK.

...DISCUSSION... A WEAK UPPER TROUGH MOVING THROUGH SOUTHERN CALIFORNIA HAS SIGNIFICANTLY DEEPENED THE MAINE LAYER TO SOMEWHERE AROUND 35 HUNDRED FEET. THIS SHOULD RESULT IN A PERSISTENT LOW CLOUD SCENARIO FOR TODAY.

ON SATURDAY...THICKNESS VALUES CONTINUE TO FALL...AND SHOULD RESULT IN LOWER MAXIMUM TEMPERATURES MOUNTAINS EASTWARD. SOME SURFACE AND UPPER SUPPORT FOR DESERT WINDS ALSO NOTED...AND CURRENT THINKING LOOKS TO BE OCCASIONAL GUSTS INTO THE LOWER 40S AT OUR FAVORED WEST WINDS LOCATIONS. SATURDAY TEMPERATURES WILL LIKELY BE NEAR FRIDAY VALUES.

ON SUNDAY...LOOKS LIKE THICKNESSES BOTTOM OUT...AND THE RIDGE BEGINS TO NOSE INTO SOUTHWESTERN CALIFORNIA...RELAXING THE ONSHORE GRADIENTS. AFTERNOON HIGH TEMPERATURES SHOULD BE AT OR SLIGHTLY ABOVE SATURDAYS TEMPERATURES.

MONDAY...RISING HEIGHTS...INCREASING THICKNESSES...AND RELAXED ONSHORE PRESSURE GRADIENTS SHOULD SIGNAL A WARMING TREND ALL AREAS. THE LOW CLOUDS SHOULD CLEAR A LITTLE EARLIER THAN NORMAL...AND TEMPERATURES ALL AREAS ARE LIKELY TO EXCEED NORMAL. THIS SHOULD BE THE CASE THROUGH WEDNESDAY.

THURSDAY AND FRIDAY THE LONG RANGE MRF IS INDICATING A TROUGH OVER THE WEST COAST...FOR STRONGER ONSHORE FLOW...DEEPENING MARINE LAYER...AND LOWER AFTERNOON HIGH TEMPERATURES.

ON SATURDAY...LATE NEXT WEEK...THERE SHOULD BE A SIGNIFICANT TROUGH ALONG THE COAST...AND WE COULD GET A BIT OF MOISTURE OUT OF IT. BUT FOR NOW I WILL ONLY THINK IN TERMS OF COASTAL MARINE LAYER DRIZZLE.

SAN 000

.SAN...NONE.

SMALL



...SYNOPSIS...

MODERATE ONSHORE FLOW AND THE RESULTING DEEP COASTAL MARINE LAYER WILL ALLOW THE NIGHT AND MORNING LOW CLOUDS AND FOG TO CONTINUE WEST OF THE MOUNTAINS...WITH ONLY PARTIAL AFTERNOON CLEARING NEAR THE BEACHES. OTHERWISE...DRY WESTERLY FLOW ALOFT WILL KEEP FRONTAL SYSTEMS WELL NORTH OF SOUTHERN CALIFORNIA THROUGH SATURDAY. NEAR SEASONAL TEMPERATURES ARE EXPECTED THROUGH SATURDAY. BUILDING HIGH PRESSURE WILL RESULT IN A DECREASING MARINE LAYER AND WARMING TREND EARLY NEXT WEEK.

...DISCUSSION... A WEAK UPPER TROUGH MOVING THROUGH SOUTHERN CALIFORNIA HAS SIGNIFICANTLY DEEPENED THE MAINE LAYER TO SOMEWHERE AROUND 35 HUNDRED FEET. THIS SHOULD RESULT IN A PERSISTENT LOW CLOUD SCENARIO FOR TODAY.

ON SATURDAY...THICKNESS VALUES CONTINUE TO FALL...AND SHOULD RESULT IN LOWER MAXIMUM TEMPERATURES MOUNTAINS EASTWARD. SOME SURFACE AND UPPER SUPPORT FOR DESERT WINDS ALSO NOTED...AND CURRENT THINKING LOOKS TO BE OCCASIONAL GUSTS INTO THE LOWER 40S AT OUR FAVORED WEST WINDS LOCATIONS. SATURDAY TEMPERATURES WILL LIKELY BE NEAR FRIDAY VALUES.

ON SUNDAY...LOOKS LIKE THICKNESSES BOTTOM OUT...AND THE RIDGE BEGINS TO NOSE INTO SOUTHWESTERN CALIFORNIA...RELAXING THE ONSHORE GRADIENTS. AFTERNOON HIGH TEMPERATURES SHOULD BE AT OR SLIGHTLY ABOVE SATURDAYS TEMPERATURES.

MONDAY...RISING HEIGHTS...INCREASING THICKNESSES...AND RELAXED ONSHORE PRESSURE GRADIENTS SHOULD SIGNAL A WARMING TREND ALL AREAS. THE LOW CLOUDS SHOULD CLEAR A LITTLE EARLIER THAN NORMAL...AND TEMPERATURES ALL AREAS ARE LIKELY TO EXCEED NORMAL. THIS SHOULD BE THE CASE THROUGH WEDNESDAY.

THURSDAY AND FRIDAY THE LONG RANGE MRF IS INDICATING A TROUGH OVER THE WEST COAST...FOR STRONGER ONSHORE FLOW...DEEPENING MARINE LAYER...AND LOWER AFTERNOON HIGH TEMPERATURES.

ON SATURDAY...LATE NEXT WEEK...THERE SHOULD BE A SIGNIFICANT TROUGH ALONG THE COAST...AND WE COULD GET A BIT OF MOISTURE OUT OF IT. BUT FOR NOW I WILL ONLY THINK IN TERMS OF COASTAL MARINE LAYER DRIZZLE.

SAN 000

.SAN...NONE.

SMALL