Forecast Discussions mentioning ACARS, received at FSL on 03/31/00

...SYNOPSIS... A DEEP MARINE LAYER WILL GRADUALLY GIVE WAY TO DRY OFFSHORE FLOW THIS AFTERNOON AS SURFACE HIGH PRESSURE BUILDS INTO THE GREAT BASIN. SANTA ANA WINDS ARE EXPECTED TO REACH SAN BERNARDINO COUNTY THIS BY THIS EVENING...AND THEN SPREAD SOUTH ACROSS THE REGION TONIGHT AND FRIDAY.

...DISCUSSION... ACARS SOUNDINGS SHOW A 4500 FT DEEP MARINE LAYER STILL FIRMLY ENTRENCHED WEST OF THE MOUNTAINS. THIS LAYER WILL GRADUALLY ERODE FROM NORTH TO SOUTH THIS AFTERNOON AS DRY NORTHERLY FLOW SPREADS SOUTH. SATELLITE IMAGERY INDICATES SCATTERED CLOUDS SBD/RIV AND ORANGE CNTIES. PERSISTENT CLOUD DECK REMAINS OVER SAN DIEGO COUNTY WEST OF THE MOUNTAINS. MEANWHILE...THE BEGINNINGS OF THE SANTA EVENT ARE EVIDENT IN THE UPPER DESERTS WHERE YUCCA VALLEY REPORTED NORTH WINDS 11 KNOTS GUSTING TO 17 KNOTS AT 16Z.

SYNOPTICALLY SPEAKING...THE 500 MB LOW OVER UTAH THIS MORNING WILL MOVE SOUTHWEST AND BE OVER LAS VEGAS BY 12Z FRIDAY. CONDITIONS STILL LOOK FAVORABLE FOR A SANTA ANA EVENT TONIGHT AND FRIDAY WITH A 90 KT 300MB JET MAX...A STRONG 850 MB THERMAL GRADIENT...AND SURFACE HIGH PRESSURE BUILDING INTO THE GREAT BASIN.

THE ETA AND AVN OFFER SLIGHTLY DIFFERENT SOLUTIONS FRIDAY NIGHT AND SATURDAY. BUT THE HIGH AMPLITUDE UPPER AIR PATTERN SUGGESTS LITTLE MOVEMENT OF THE SURFACE FEATURES THROUGH SATURDAY...AND WITH MODERATELY STRONG OFFSHORE PRESSURE GRADIENTS IT APPEARS THE STRONG WIND EVENT WILL CONTINUE THROUGH SATURDAY.

SAN 000

.SAN...HIGH WIND WATCH FOR INLAND EMPIRE AND SANTA ANA MTS...SEE NPWSAN.

MOEDE

12Z DATA SHOW LEADING EDGE OF UPPER JET ALONG THE PACIFIC NORTHWEST COAST. AIRCRAFT/SATELLITE WINDS INDICATE A 150KT MAX READY TO ROUND THE RIDGE AND HEAD SOUTH, SUGGESTING SHORT WAVE TROF, CURRENTLY OVER THE GREAT BASIN, WILL DIVE WELL SOUTH AS PER ALL SHORT RANGE PROGS. THIS WILL LEAD TO A GENERAL SOUTH TO SOUTHWEST FLOW ALOFT OVER THE FORECAST AREA. MEANWHILE, SURFACE HIGH PRESSURE IS EXPECTED TO DEVELOP SOUTH WITH TIME BEHIND STRONG NORTHERN BRANCH SHORT WAVE TROF, LEADING TO A PERSISTENT NORTH TO NORTHEAST FLOW AT LOW LEVELS. THIS TYPE OF SETUP IS FAVORABLE FOR PRECIPITATION, WITH POSSIBLE LOCALLY HEAVY RAIN DEPENDING ON LOCATION OF LOW LEVEL BAROCLINIC ZONE, STRENGTH OF WARM ADVECTION/ISENTROPIC LIFT, AND QUALITY OF MOISTURE RETURN. ANY THUNDERSTORMS IN THIS SITUATION ARE TYPICALLY ROOTED IN THE HIGHER THETAE ON TOP OF THE NEAR-SURFACE COOL AIR, WITH LIMITED POTENTIAL FOR BEING SEVERE. WILL HAVE TO WATCH FOR THE POSSIBILITY OF STORMS TO THE SOUTHWEST ADVECTING INTO THE AREA BY LATE FRIDAY AFTERNOON AND FRIDAY NIGHT, ESPECIALLY IF LOW LEVEL BOUNDARY IS NOT AS FAR SOUTH AS EXPECTED. WILL CARRY MENTION OF RAIN 2ND THROUGH 4TH PERIODS, TAPERING OFF THEREAFTER. NOT MUCH DIURNAL TEMPERATURE RANGE EXPECTED THROUGH SUNDAY.

PRELIMINARY: FRIONA/TULIA 38/49/38/49 2576 CHILDRESS 42/57/42/55 -576 BROWNFIELD/LUBBOCK 41/53/44/53 2576 ASPERMONT 46/59/47/57 -477

.LBB...NONE.



STILL WAITING FOR HIGH WINDS TO DEVELOP ACROSS THE DISTRICT THIS MORNING. RAWS OBS SO FAR HAVE GUSTS IN THE 40S ACROSS THE MOUNTAINS... AND NORTH WIND GUSTING TO 22 KT AT VNY IS GOOD SIGN. INHIBITING FACTORS ARE LINGERING MARINE INVERSION ALONG THE COAST...LESS THAN IDEAL PRESSURE GRADIENT PATTERN...AND BEST SUBSIDENCE STAYING TO THE EAST OF THE DISTRICT SO FAR. RECENT ACARS SOUNDINGS DO SHOW 25-30 KT AT 850 MB...QUITE AN INCREASE FROM THE 00Z SOUNDINGS. STILL EXPECT WINDS TO INCREASE SUBSTANTIALLY ACROSS VTU/LA MOUNTAINS AND VALLEYS...FIRST ACROSS THE MOUNTAINS...THEN INTO THE VALLEYS AFTER SUNRISE AS MIXING OCCURS.

00Z MODELS CONTINUE TREND WHICH STARTED ON THE 30/12Z CYCLE OF TAKING UPPER LOW CENTER FURTHER EAST. ALL MODELS KEEP THE 500 MB CENTER OVER AZ THRU SAT MORNING...NEVER CROSSING THE COLORADO RIVER. THIS IS QUITE DIFFERENT FROM LAST NIGHTS SOLUTION WHICH HAD THE LOW CENTER FURTHER WEST OVER EXTREME SRN CA. MODELS DIVERGE SOME AFTER 24 HOURS WITH THE AVN STARTING TO ELONGATE AND WEAKEN THE SYSTEM...WITH THE ETA KEEPING IT STRONGER AND FURTHER SW...WITH THE NGM IN BETWEEN. MODELS ALSO DIFFER QUITE A BIT ON THE FORECAST STRENGTH OF THE 850 MB WINDS... WITH AVN CONSIDERABLY STRONGER THAN ETA. AFOREMENTIONED ACARS SOUNDINGS SUPPORT STRONGER AVN SOLUTION...AT LEAST FOR THIS MORNING. AVN GIVES 35-40 KT AT 850 MB BY 18Z WITH STRONG SUBSIDENCE WHICH WOULD LIKELY BE SUFFICIENT TO CAUSE WARNING LEVEL WINDS ACROSS AT LEAST THE LA/VTU MOUNTAINS AND POSSIBLY THE VALLEYS AS WELL. NEGATIVES WILL BE THE RELATIVELY WEAK SURFACE GRADIENT PATTERN ALONG WITH POTENTIAL LACK OF BEST DOWNWARD MOTION...IF BEST SUBSIDENCE STAYS TO OUR EAST OVER ERN CA/WRN AZ. WILL KEEP ALL HIGH WIND WARNINGS POSTED THROUGH 9 PM TONIGHT INTACT FOR NOW...BUT LATER SHIFTS MAY HAVE TO DOWNGRADE DEPENDING ON DEVELOPMENTS LATER THIS MORNING. WILL ALSO ISSUE WIND ADVISORY FOR ANTELOPE VALLEY THROUGH THIS EVENING.

NEXT FORECAST PROBLEM IS A POSSIBLE CONTINUATION OF HIGH WINDS INTO TONIGHT AND SATURDAY. AVN IS VERY AGRESSIVE WITH ITS 850 MB PATTERN... DEPICTING 50-55 KT WINDS AT THIS LEVEL ACROSS LA/VTU COUNTIES BY 12Z SATURDAY MORNING. THIS SEEMS A BIT STRANGE GIVEN ITS WEAKER AND SOMEWHAT SHEARED OUT 500 MB LOW FORECAST FOR THIS TIME. ETA IS QUITE A BIT WEAKER WITH ONLY 25-30 KT WINDS AT 850 MB AT THE SAME TIME. SURFACE PATTERN FORECAST FOR SATURDAY MORNING IS NOT PARTICULARLY FAVORABLE. WITH SOME UNCERTAINTY AS TO WHETHER HIGH WIND WARNING WILL VERIFY FOR FIRST PERIOD...AM NOT ANXIOUS TO EXTEND IT INTO THE LATE 2ND AND 3RD PERIODS. WILL KEEP WINDY WORDING IN THE FORECAST THRU SATURDAY BUT WILL CONFINE WARNING TO 1ST AND EARLY 2ND PERIODS FOR NOW.

TEMPS WILL BE TRICKY TODAY AND WILL BE LARGELY DEPENDENT ON HOW STRONG THE OFFSHORE FLOW AND COLD ADVECTION IS AT EACH LOCATION. SIMILAR SITUATION SATURDAY FOR COASTS AND VALLEYS ALTHOUGH MOUNTAINS/DESERTS SHOULD WARM SOMEWHAT AS COLD ADVECTION SHUTS OFF. SHOULD SEE BIG WARMUP ON THE CENTRAL COAST AS IS USUALLY THE CASE WITH OFFSHORE FLOW.

EXTENDED IS VERY QUESTIONABLE...AS MODELS ARE IN SEVERE DISAGREEMENT. NEW MRF HAS 585 RIDGE BY 120 HOURS AT ALMOST THE SAME LOCATION WHERE THE NEW UK/CANADIAN AND OLD EC MODELS KEEPS CLOSED LOW LINGERING THROUGH THE PERIOD. WILL GENERALLY BROADBRUSH EXTENDED PERIODS WITH FEW CHANGES FROM PREVIOUS FORECAST AND HOPE THAT THE MODELS COME INTO BETTER AGREEMENT WITH TIME.

LAX 000. JACOBSON

.LAX...HIGH WIND WARNINGS/WIND ADVISORY (SEE LAXNPWLAX).