Forecast Discussions mentioning ACARS, received at FSL on 04/02/01

MARINE LAYER FAIRLY DEEP AND DEEPENING THIS EVENING. 00Z VBG SOUNDING SHOWED A DEPTH OF 2500 FEET AND NKX SHOWED 3500 FEET. ACARS OUT OF LAX SHOW 3200 FEET...BUT AT ONT THE MARINE LAYER IS 5000 FEET DEEP. GRADIENTS ARE VERY STRONGLY ONSHORE THANKS TO A 998 MB SFC LOW SITTING OVER DEATH VALLEY. LAX-DAG GRADIENT IS ALMOST 9 AND SMX-LAS IS 13. SATL SHOWING LOW CLOUDS PRESSING WELL INTO THE MTNS THIS EVENING. WOULD NOT BE SURPRISED TO SEE SOME CLOUDS SQUIRT OVER INTO THE ANTELOPE VALLEY...BUT DOWNSLOPE WINDS AND A DRIER ATMOSPHERE ON THAT SIDE OF THE MTNS SHOULD HELP TO MINIMIZE COVERAGE.

NO DOUBT THE SKY WILL REMAIN CLOUDY OVERNIGHT FROM THE MTNS TO THE BEACHES. HOWEVER WE HAVE NOTICED A RISE IN THE CEILINGS AND A SUBSEQUENT IMPROVEMENT IN SFC VSBYS AT COASTAL AND VALLEY LOCATIONS. FOG MAY NOT BE AS BIG AN ISSUE TONIGHT EXCEPT ON THE SLOPES WHERE THE CLOUD BASE INTERSECTS TERRAIN. DRIZZLE STILL POSSIBLE MOST AREAS DUE TO THE GENERAL LIFTING OF THE DEEP MARINE LAYER.

BROAD UPR TROUGH SETS UP OVER THE WEST COAST EARLY THIS PERIOD...FOLLOWED BY A MARKED SHARPENING AND DEEPENING OF THE TROUGH TUES. UPR LOW WILL TRY TO CUT-OFF FROM MAIN FLOW AND DROP SOUTH ALONG THE CA COAST WED...SPINNING OVER THE AREA THURSDAY AND LINGERING POSSIBLY INTO FRIDAY. THIS COLD CORE SYSTEM WILL BEAR WATCHING DUE TO THE LARGE AMOUNT OF INSTABILITY LIKELY TO BE ASSOC WITH IT.

CURRENT FCST CORRELATES WELL WITH LIMITED AMOUNT OF NEW DATA AVAILABLE SO FAR THIS EVENING. HOWEVER...CENT COAST MAY HAVE SOME PARTIAL CLEARING MONDAY AFTN AS COLDER AIR MIXES IN AND FLOW BECOMES MORE NORTHERLY. EDDY CIRCULATION APPEARS TO REALLY GET CRANKING BY TUESDAY MORNING WHICH COULD ACTUALLY ALLOW FOR TUESDAYS FCST IN VTU/LA COASTS/VALLEYS TO BE A LITTLE MORE CLOUDY THAN FORECASTED NOW. BUT...WILL LET MID SHIFT TAKE A MORE COMPREHENSIVE LOOK AT THAT SITUATION BEFORE MAKING ANY CHANGES.

LAX 1100. MOYER

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



ACARS SOUNDINGS INDICATING MARINE LYR DEPTH AROUND 3000 FEET THIS AFTERNOON. ONSHORE GRADIENTS TO DAG HAVE INCREASED TO ALMOST 8 MB. ALL THIS WITH A CATALINA EDDY CIRCULATION SPELLS GLOOMY WEATHER OVER SO CAL FOR THE NEXT 24 HOURS AT LEAST. MARINE LYR WILL DEEPEN OVERNIGHT TO BETWEEN 5000 AND 6000 FEET, PUSHING WELL UP THE COASTAL SLOPES AND MOUNTAIN PASSES. LOTS OF DRIZZLE ALREADY OCCURRING TODAY AND THIS WILL CONTINUE TONIGHT AND MONDAY, ESPECIALLY NEAR THE FOOTHILLS AND CSTL SLOPES. WINDS PICKING UP IN THE ANTELOPE VALLEY TODAY, AND THEY WILL BE EVEN STRONGER ON MONDAY.

A COLD FRONT WILL PASS THROUGH THE AREA LATER MONDAY. THE COLD AIR BEHIND THIS WILL WEAKEN THE INVERSION ENOUGH TO BREAK UP THE MARINE LYR MONDAY NIGHT AND TUESDAY, BUT SURFACE TEMPS WILL REMAIN COOL TUESDAY DESPITE THE REAPPEARANCE OF THE SUN. IT WILL BE BREEZY IN MANY AREAS MONDAY, AND ADVISORIES MAY BE NEEDED IN THE ANTELOPE VALLEY AND POSSIBLY EVEN ALONG THE CENTRAL COAST.

SKIES WILL BE PARTLY CLOUDY MOST AREAS TUESDAY AND WEDNESDAY WITH WELL BELOW NORMAL TEMPS. BY THURSDAY, THE MODELS ARE INDICATING A COLD UPR LOW WILL DROP SOUTH ALONG THE COAST. THIS ONE WILL BE SOMEWHAT LACKING IN MOISTURE, BUT WILL HAVE AN ABUNDANT AMOUNT OF COLD AND UNSTABLE AIR. WE WILL CERTAINLY HAVE TO KEEP AN EYE ON THE CONVECTIVE POTENTIAL FOR THURSDAY AS THIS COULD BE A VERY ACTIVE WEATHER DAY. FOR NOW, WILL INDICATE A CHANCE OF SHOWERS FOR THURSDAY, WITH DRYER AND WARMER CONDITIONS FOR THE WEEKEND.

LAX 1100. WOFFORD

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



SATELLITE IMAGERY SHOWS WEAK VORT MAX OVER WESTERN WASHINGTON AT 09Z WITH ANOTHER VORT MAX OFFSHORE NEAR 48N/134W. COLD AIR IN PLACE OVER WESTERN WASHINGTON WITH 500 MB TEMPS OF -33C AND FREEZING LEVEL NEAR 2000 FEET ON ACARS SOUNDINGS. 00Z MODELS INITIALIZED WELL BUT BY 06Z VORT MAX OFFSHORE WAS A LITTLE FURTHER WEST THAN THE MODELS INDICATE BUT BELIEVE THIS WILL NOT HAVE MUCH EFFECT ON WESTERN WASHINGTON WEATHER TODAY. VORT MAX MOVING INLAND WELL SOUTH OF WASHINGTON LATER TODAY LEAVING WESTERN WASHINGTON WITH A VERY COLD...UNSTABLE AMS OVER THE AREA. MODEL SOUNDINGS AROUND WESTERN WASHINGTON SHOW LI'S THIS AFTERNOON STILL NEAR 0 WITH CONVECTIVE TEMPERATURES IN THE LOWER TO MID 40S. FLOW ALOFT IS WEAK AND ACARS SOUNDINGS HAVE A VERY WEAK CAP AROUND 12000 FEET SO BELIEVE WE WILL NEED TO HAVE THE DAYTIME HEATING TO GET A CHANCE OF THUNDERSTORMS. WITH SOME AFTERNOON SUNBREAKS WILL KEEP MAX TEMPS IN THE UPPER 40S. SEA-TAC CAME CLOSE TO A RECORD LOW MAX ON SUNDAY UNTIL A LITTLE SUNSHINE IN THE MID AFTERNOON SPIKED THE TEMPERATURE UP TO 49. AMS REMAINING UNSTABLE INTO THE EVENING BUT AS THE TEMPERATURE COOLS EXPECT THE THREAT OF THUNDERSTORMS TO DIMINISH. MODELS CONSISTENT WITH LOW CONTINUING TO DIG ALONG THE WEST COAST. BY TUESDAY AFTERNOON NORTHERN HALF OF THE AREA UNDER DRYING NORTHEASTERLY FLOW ALOFT AS UPPER LEVEL RIDGE BUILDS INTO BC AND LOW CONTINUES TO DIG SOUTH. LOW STILL CLOSE ENOUGH TO KEEP THREAT OF SHOWERS/THUNDERSTORMS OVER SOUTHWEST WASHINGTON TUESDAY AFTERNOON. .EXTENDED...NEW MRF AS RETURNED TO THE SOLUTION OF TWO NIGHTS AGO WITH NEXT SYSTEM MOVING INTO THE AREA ON FRIDAY INSTEAD OF SATURDAY. CANADIAN AND EURO CONTINUE TO ADVERTISE AN EVEN FASTER SOLUTION. BEFORE THAT UPPER LEVEL RIDGE OVER BC ON WEDNESDAY MOVES SOUTH ON THURSDAY AS THE NEXT SYSTEM DEVELOPS NEAR THE QUEEN CHARLOTTES. WILL BE A LITTLE MORE PESSIMISTIC ON THE EXTENDED AND UP POPS OUT OF THE CHANCE CATEGORY FOR FRIDAY THROUGH SUNDAY. FELTON

UIL 842 SEA 743 OLM 854

.SEW...SMALL CRAFT COAST AND STRAIT.

.KATX...VCP21/CSR21...OPERATIONAL.