Forecast Discussions mentioning ACARS, received at FSL on 03/23/01

MARINE LAYER STILL RATHER DEEP THIS EVENING. ALL SOUNDINGS AND ACARS DATA SHOW THE DEPTH TO BE BETWEEN 3000 AND 4000 FEET. WITH GOOD ONSHORE GRADIENTS EVEN AT 03Z (+5.9 MB LAX-DAG) MARINE LAYER CLOUDS SHOULD FORM IN MOST COASTAL AND VALLEY AREAS OVERNIGHT...WITH SOME LOW CLOUDS TO THE LOWER COASTAL SLOPES. LATEST FOG PRODUCT IMAGES SHOW THE LOW CLOUDS NOT VERY ORGANIZED. LARGEST AREA OF LOW CLOUDS EXTENDED FROM VTU/SBA COUNTIES SOUTHWARD OFF THE COAST. NOT MUCH IN THE WAY OF LOW CLOUDS FOR LAX OR SBP COUNTIES. AGAIN...LOOKS LIKE THOSE AREAS WITHOUT CLOUDS WILL BECOME MOSTLY CLOUDY OVERNIGHT.

WEAK UPPER RIDGE IS FORECAST TO BUILD OVER THE DISTRICT ON FRI. THIS SHOULD HELP TO LOWER THE MARINE LAYER AND WARM TEMPS UP A FEW DEGREES OVER INLAND AREAS. FORECAST TEMPS IN VALLEY ZONES FOR FRI MAY BE SLIGHTLY HIGHER THAN WHAT MAY OCCUR...BUT WILL LET MID SHIFT DETERMINE IF FORECAST TEMPS FRI SHOULD BE LOWERED SLIGHTLY OR NOT. THE UPPER RIDGE THEN MOVES EAST FRI NIGHT AND SAT WITH MORE OF A BROAD SOUTHWEST FLOW ALOFT SETTING UP OVER SOCAL AS A LARGE UPPER LOW POSITIONS ITSELF WELL OFF THE PAC NW COAST. 950 MB TEMPS WARM UP A FEW DEGREES FOR FRI...THEN A FEW MORE DEGREES FOR SAT. MESO-ETA CROSS SECTIONS SHOW THE MARINE INVERSION NOT VERY EVIDENT BY SAT AFTERNOON...WHICH SUGGESTS LOW CLOUDS SHOULD DISSIPATE FASTER ON SAT. WARMER DAY STILL IN THE OFFING FOR SAT WITH WIDESPREAD 70S POSSIBLE IN THE VALLEYS.

CURRENT ZONES LOOK REASONABLE. DO NOT EXPECT A ZONE UPDATE THIS EVENING.

IN THE EXTENDED...GENERALLY A ZONAL FLOW WILL PREVAIL OVER SOCAL...WITH ONE WEAK UPPER DISTURBANCE MOVING THROUGH THE FLOW OVER THE REGION SUN NITE AND MON. DRY WEATHER WILL CONTINUE SUN THRU TUE...WITH MORE NIGHT AND MORNING LOW CLOUDS AND FOG FOR THE COAST AND ADJACENT VALLEYS. TEMPS THRU THE PERIOD ARE EXPECTED TO BE RATHER SEASONAL FOR THIS TIME OF YEAR.

LAX 0000. SIRARD.

.LAX...NONE.



.OVERVIEW... A STRONG SHORT WAVE TROUGH SE OF THE ALEUTIANS IS SHOWING SIGNS OF SHUNTING A DEEP CUT OFF LOW NOW NEAR 37N/149W EWD ABOUT 10 DEG. IN THE MEAN TIME DEEP ARCTIC AIR WITH A SURFACE HIGH NEAR 1052 MB AT 18Z OVER THE NRN YUKON AND NW TERRITORIES IS SHOWING SIGNS OF DROPPING ESE INTO CENTRAL CANADA. THE COMBINED MOVEMENT OF THESE FEATURES IS FINALLY ALLOWING RIDGING ALOFT TO TAKE PLACE OVER THE NW. 12Z MODELS ARE RATHER WELL INITIALIZED...ALTHOUGH ABOUT 20 KT TOO WEAK PER AIRCRAFT DATA WITH THE NWLY 300MB JET STREAK ASSOCIATED WITH THE KICKER SE OF THE ALEUTIANS. THE MESOETA AND AVN ARE SHOWING REMARKABLE RUN-TO-RUN CONTINUITY. WHILE THE CONTINUITY OF THE AVN/MRF SUITE CONTINUES QUITE GOOD THRU THE 7 DAY FORECAST PERIOD...THE ECMWF/CANADIAN MODELS AND A VAST NUMBER OF ENSEMBLE MEMBERS GO OUT OF PHASE WITH THE MRF/AVN CONCERNING SHORT WAVES PASSING THROUGH THE PAC NW TUE AND BEYOND. THE UNCERTAINTY APPEARS TO BE RELATED TO AN INCREASING ZONAL INDEX OVER THE PAC AND DIFFICULTIES IN TIMING SHORT WAVES. WILL USE THE MESOETA/AVN SOLUTIONS THRU TUE...THEN ENSEMBLE MEANS WED/THU.

.SHORT TERM... NICE SPRING WEATHER TONIGHT THRU FRI NIGHT. TEMPERATURES IN THE 60 TO 65 RANGE LOOK GOOD FRI. THE RECORD HIGH AT KUIL OF 65 MAY BE THREATENED FRI...BUT ELSEWHERE RECORDS IN THE UPPER 60S AND LOWER 70S SHOULD STAND. INTERESTING TO NOTE THAT THIS MORNING WITH RADIATIONAL COOLING KOLM HAD A RECORD LOW OF 24.

SATURDAY IS A TRANSITION DAY AS A STRONG NEG TILT SHORT WAVE... THE SHORT WAVE NOW INTERACTING WITH THE OFFSHORE CUT OFF LOW...MOVES IN FROM THE SW. THE 18Z MESOETA SOLUTION IS A COUPLE OF HOURS FASTER THAN THE AVN IN BRINGING THIS WAVE NNEWD THRU THE FORECAST AREA. THIS WOULD KEEP AFTN TEMPERATURES MUCH COOLER AND REDUCE CHANCES FOR CONVECTION. BUT FOR NOW WITH LOW LEVEL FLOW INITIALLY OFFSHORE AND THE AIR MASS RATHER UNSTABLE...WILL STAY WITH AFTN TEMPS NEAR 60...INCREASING SHRA CHANCES THRU THE DAY...AND BRINGING IN A CHANCE OF AFTN TSTMS AS CONVECTIVE TEMPERATURES FALL FROM 70 DEG AT 15Z TO 55 DEG BY 00Z. LATER SHIFTS CAN REFINE BASED ON NEW GUIDANCE. NOTE THE AVN MOS THAT SHOWS A 40 PCT CHANCE OF TSTMS SAT AFTN.

.EXTENDED... WILL INCLUDE A SAT NIGHT PERIOD FOR SHOWERS AND A CHANCE OF EVENING TSTMS. BUT THEN THE BROAD BRUSH FORECAST FOR THE SUN THRU TUE PERIOD LOOKS GOOD. A SERIES OF SHORT WAVE TROUGHS ROTATE AROUND THE OFFSHORE TROUGH SUN AND MON...FOLLOWED BY THE MAIN TROUGH PASSAGE TUE. GIVEN UNCERTAINTY WILL PLACE CHANCE PCPN WORDING WED AND THU UNTIL MODEL TIMING BECOMES MORE CERTAIN.

UIL 0016 SEA 0016 OLM 0017 ALBRECHT

.SEW...NONE. .KATX...VCP31/CSR31...OPERATIONAL.



.OVERVIEW... A STRONG SHORT WAVE TROUGH SE OF THE ALEUTIANS IS SHOWING SIGNS OF KICKING EWD AND OPENING UP A DEEP CUT OFF LOW NOW NEAR 37N/151W. IN THE MEAN TIME DEEP ARCTIC AIR WITH A SURFACE HIGH NEAR 1054 MB AT 12Z OVER THE NRN YUKON AND NW TERRITORIES IS SIGNS OF DROPPING ESE INTO CENTRAL CANADA. THE COMBINED MOVEMENT OF THESE FEATURES IS FINALLY ALLOWING RIDGING ALOFT TO TAKE PLACE OVER THE PAC NW. MODELS ARE RATHER WELL INITIALIZED...ALTHOUGH ABOUT 20 KT TOO WEEK PER AIRCRAFT DATA WITH THE NWLY 300MB JET STREAK ASSOCIATED WITH THE KICKER SE OF THE ALEUTIANS. THE MESOETA AND AVN ARE SHOWING REMARKABLE RUN-TO-RUN CONTINUITY. WHILE THE CONTINUITY OF THE AVN/MRF SUITE CONTINUES QUITE GOOD THRU THE 7 DAY FORECAST PERIOD...THE ECMWF AND CANADIAN MODELS GO OUT OF PHASE WITH SHORT WAVES PASSING THROUGH THE PAC NW TUE AND BEYOND.

.SHORT TERM... NICE WEATHER THRU FRI. WARMING ALOFT AND LIGHTER NW GRADIENTS SHOULD PROVIDE 3 DEG WARMING OVER WED...THEN TEMPS GO INTO THE UPPER 50S TO UPPER 60S ON FRI...NICE. CURRENT FORECASTS LOOK GREAT.

.EXTENDED...WITH NEG TILT SHORTWAVE ENERGY ROTATING NEWD AROUND THE OFFSHORE UPPER LOW...IT APPEARS THAT THERE IS LITTLE CHANCE FOR A SIGNIFICANT MARINE PUSH FRI NIGHT. THE 12Z MESOETA SHOWS THIS LACK OF MARINE PUSH WELL. FORECAST CHALLENGES BEGIN SAT AS A NEGATIVE TILT SHORT WAVE TROUGH ROTATES AROUND THE PROGRESSIVE TROUGH BRINGING A COLD FROPA...INCREASING RA CHANCES...AND A THREAT OF CONVECTION. BUT AT THIS TIME CONVECTIVE CHANCES APPEAR LOW OVER NW WA AS CLOUD COVER AND SOME -RA 18-00Z WOULD KEEP THE LOWER LEVELS STABLE. AT THIS POINT CAPES NEVER EXCEED 300J/KG OVER THE FORECAST AREA. HIGH CAPES AND LOW LIS WITH BEST UPPER LEVEL DIFFLUENCE REMAIN OVER SE WA SWWD INTO THE CENTRAL OREGON COASTAL AREAS.

SUN-MON LOOK SHOWERY AND SEASONALLY COOL WITH ONSHORE FLOW AND SW FLOW ALOFT. THE EXTENDED MODELS DIVERGE TUE AND BEYOND BUT FOR NOW WILL STICK WITH CONSISTENT MRF.

UIL 000 SEA 000 OLM 000 ALBRECHT

.SEW...NONE. .KATX...VCP31/CSR31...OPERATIONAL.



DEEP MARINE LAYER ACRS THE FCST AREA THIS A.M....WITH SOUNDINGS AND ACARS DATA INDICATING THE BASE OF THE MARINE INVERSION BETWEEN 3500 AND 4000 FT. INVERSION WAS QUITE WK...MUCH MORE SO THAN PAST COUPLE OF MORNINGS...AND WITH N-S GRADS BEGINNING TO INCRS... XPCT FASTER BURN OFF ACRS THE FCST AREA TODAY. HWVR...06Z ETA KEEPS QUITE A BIT OF MSTR AT LOW LVLS ACRS THE AREA TODAY. WITH SAT IMAGERY INDICATING A RATHER LARGE MASS OF LOW CLDS OFF THE CST NOW ENTERING SLO/SBA COUNTIES...AND FLOW REMAINING ONSHR TODAY...BLV LOW LVLS WL REMAIN RATHER MOIST...AND WL KEEP PTLY CLOUDY SKIES IN MOST AREAS INTO THE AFTERNOON. WITH SMALL RISES IN THICKNESSES...H85 AND H95 TEMPS...XPCT A COUPLE OF DEGS OF WARMING IN MOST AREAS TODAY...BUT TEMPS WILL STILL REMAIN BELOW NORMAL.

WK RIDGE WILL BUILD INTO THE AREA LATER TODAY AND TONIGHT. MARINE INVERSION WL PROBABLY RE-FORM TONIGHT...LIKELY AT A SIGNIFICANTLY LOWER LVL...BUT LACK OF STG WARMING ALF SUGGESTS THAT INVERSION SHOULD REMAIN RATHER WK. XPCT LESS WDSPRD LOW CLOUD COVERAGE TONIGHT/EARLY SAT...ESPECIALLY IN THE VLYS AS ONSHR PUSH WKNS.

BROAD UPR TROUGH SWINGING THRU ERN PAC WILL LIFT NEWD TOWARD THE PAC NW CST LATE SAT AND SAT NIGHT. SOME CLOUDS ON THE SRN FRINGES OF THE SYSTEM MAY PUSH INTO AREA N OF PT CONCEPTION AS EARLY AS LATE SAT AFTERNOON...SO WL ADD PTLY CLOUDY IN THOSE AREA FOR SAT AFTERNOON. OTHERWISE...XPCT FASTER CLRG OF LOW CLOUDS SATURDAY...AND WITH ADDITIONAL RISES IN THICKNESSES AND MORE SIGNIFICANT WARMING FCST AT 950 MB...XPCT A FEW DEGS OF WARMING MOST AREAS.

AS UPR SYSTEM PULLS EWD INTO THE NWRN STATES SUN AND SUN NIGHT...IT WL CAUSE HGTS ACRS THE AREA TO FALL. ALTHOUGH THE DYNAMICS ASSOCD WITH THE MAIN SYSTEM WILL REMAIN FAR TO THE N OF THE FCST AREA...A WK S/WV WL APCH THE AREA IN WLY FLOW ALF. THIS SHOULD HELD SUSTAIN A TRAILING BAND OF LOW LVL MSTR...AND KEEP THINGS QUITE CLOUDY ON SUNDAY ACRS SLO AND SBA COUNTIES. WOULD NOT BE SURPRISED TO SEE A FEW SHWRS ACRS SLO AND NRN SBA COUNTIES FOR SUN...BUT FOR NOW...WL ONLY MENTION LCL DRIZZLE IN CSTL SXNS. WL ADD SLGT CHC SHWRS TO THE MTNS OF SLO/SBA COUNTIES FOR SUNDAY...AND FOR VTU/L.A. COUNTIES SUN NIGHT/EARLY MONDAY...BUT REALLY DO NOT EXPECT ANY WDSPRD RAINFALL. WK TROUGH WL DEEPEN A BIT AS IT MOVES TO THE E OF THE AREA MONDAY...AND NWLY FLOW WL INCREASE. COULD GET RATHER WINDY MONDAY...ESPECIALLY ACRS SLO/SBA COUNTIES AND IN THE MTNS. SKIES SHOULD BEGIN TO CLEAR LATE MONDAY...AND WITH RIDGE BLDG INTO THE AREA TUE ALG WITH DRIER NLY FLOW...XPCT MOSTLY CLEAR AND SOMEWAT WARMER WEATHER ACRS THE AREA.

LAX 000. BRUNO.

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



...SYNOPSIS... COASTAL NIGHT AND MORNING LOW CLOUDS AND FOG WILL CONTINUE INTO NEXT WEEK. BUILDING WEAK HIGH PRESSURE WILL BRING SOME WARMING TO SOUTHWEST CALIFORNIA TODAY AND SATURDAY. A DEVELOPING WEAK TROUGH OF LOW PRESSURE OVER THE SOUTHWEST STATES WILL BRINGER COOLER TEMPERATURES TO SOUTHEST CALIFORNIA SUNDAY INTO EARLY NEXT WEEK ALONG WITH BREEZY CONDITIONS IN THE MOUNTAINS AND DESERTS.

...DISCUSSION... IN THE NR TERM...ETA/AVN PREFERRED. THU EVENING ACARS SOUNDINGS SHOWED THE BASE OF THE MARINE INVERSION NR 3000 FT AT THE CST TO 3500 FT FAR INLAND VLYS. THE TOP OF THE INVERSION WAS NR 4000 FT. INVERSION STRENGTH WAS VERY WK VCNTY LAX AND STRONGER TO THE E AND S OF LOS ANGELES...EXPLAINING THE PATCHIER STRATUS COVERAGE FAR NW PORTIONS OF THE FORECAST AREA AND MORE WIDESPREAD COVERAGE ELSEWHERE W OF THE MTNS THU EVENING. CLRG SHOULD OCCUR SOMEWHAT FASTER TODAY THAN THU AND FASTER STILL ON SAT WITH SAT THE WARMEST DAY W OF THE MTNS. MTN AND DESERT TEMPERATURES SHOULD BE SIMILAR BOTH DAYS IN THE MTNS AND DESERTS.

EXTENDED...AVN/MRF HAS TRENDED TOWARD THE ECMWF IN HAVING A WK UPR TROUGH OVR THE SW STATES SUN INTO EARLY NEXT WEEK. THIS IS ALSO SUPPORTED BY THE UKMET. FOR NOW...WL FOLLOW THE WKR ECMWF AS THE AVN/MRF HAS A TENDENCY TO OVERAMPLIFY SYSTEMS AT LATER TIME PDS. EITHER WAY...IT WILL BE COOLER FOR ALL OF SW CA...WITH BREEZY CONDITIONS AT TIMES IN THE MTNS AND DESERTS. WITH THE MORE AMPLIFIED AVN/MRF SOLN...THERE MIGHT BE A CHANCE OF SHOWERS OVR THE SBD/RIV COUNTY MTNS FOR SUN AND MON BUT WL NOT ADD AT THIS TIME.

SAN 000

.SAN...NONE.

MARTIN