Forecast Discussions mentioning ACARS, received at FSL on 02/21/00

SATELLITE IMAGERY SHOWS SPLIT STILL INTACT OFF PACIFIC NORTHWEST COAST NEAR 135W. MAJORITY OF THE ENERGY ASSOCIATED WITH CURRENT SYSTEM MOVING ONSHORE GOING INTO CALIFORNIA. CLOUD TOP TEMPERATURES ARE WARMING OVER NORTHERN CALIFORNIA AS THE SYSTEM GETS PULLED APART WITH UPPER LEVEL TROUGH DIGGING OFF CALIFORNIA COAST. FORECASTS LOOK ON TRACK HERE WITH SOUTHERLY FLOW ALOFT BRINGING AN INCREASE IN THE HIGH CLOUDS THIS AFTERNOON. MAX TEMPS ALSO LOOK ON TRACK WITH ACARS SOUNDINGS INDICATING MID TO UPPER 50S HIGHS AFTER WEAK INVERSION BREAKS. WHAT IS LEFT OF THE FRONT MOVING THROUGH TOMORROW. WILL LEAVE LIKELY POPS FOR NOW BUT WITH SYSTEM WEAKENING MIGHT DROP POPS BACK TO CHANCE CATEGORY IN AFTERNOON PACKAGE. WILL WAIT FOR ALL THE MODELS TO COME IN. STRONG OFFSHORE GRADIENTS WITH GAP FLOW ALONG WEST SLOPES OF THE CASCADES GIVING BREEZY CONDITIONS TODAY WILL WEAKEN TONIGHT. LITTLE CHANGE TO CURRENT PACKAGE. FELTON

UIL 277 SEA 136 OLM 136

.KATX...VCP32/CSR31...OPERATIONAL.

.SEW...SCA COAST...W ENTRANCE STRAIT JDF.

SYNOPSIS...A STRONG PACIFIC STORM WILL MOVE INTO ARIZONA TONIGHT AND MONDAY. EXPECT PERIODS OF RAIN AND SNOW SPREADING FROM WEST TO EAST ACROSS ARIZONA EARLY MONDAY THROUGH TUESDAY. AFTER A BREAK LATE TUESDAY AND EARLY WEDNESDAY...UNSETTLED WEATHER WITH PERIODS OF RAIN AND SNOW WILL RETURN TO THE NORTHLAND THROUGH THE END OF THE WEEK.

DISCUSSION...THE BIG STORY CONTINUES TO BE THE TROUGH CENTERED NEAR 38N 132W. UPPER AIR DATA...AIRCRAFT OBSERVATIONS AND SATELLITE DATA ARE SHOWING A SOMEWHAT DEEPER SYSTEM THAN THE 12Z MODEL RUNS WERE INDICATING WITH A 250 MB 150-170 KNOT JET CORE ON THE BACK SIDE OF THE TROUGH. THE AVN REMAINS THE MODEL OF CHOICE. IN ANY CASE...THE EXIT REGION OF THE 250 MB JET WILL APPROACH ARIZONA FROM THE WEST TONIGHT AND MONDAY MORNING. AS IT PROPAGATES EAST OF THE TROUGH AXIS AND ENTERS ARIZONA THIS WILL RESULT IN PROLONGED AND SIGNIFICANT LARGE SCALE UPWARD MOTION...ESPECIALLY DURING THE DAY MONDAY. COMBINED WITH 30 TO 40 KNOT SOUTHERLY FLOW AT THE 700 MB LEVEL AND PLENTY OF LOW TO MID LEVEL MOISTURE IT LOOKS LIKE MONDAY COULD BE A SNOW PACKED DAY FOR ELEVATIONS ABOVE THE 6500 FOOT LEVEL (850-500 MB THICKNESS VALUES OF APPROXIMATELY 415 DM). THERE WILL BE ENOUGH INSTABILITY FOR A FEW ISOLATED THUNDERSTORMS AS WELL. AT THIS TIME LOOKS LIKE THE MAIN IMPACT FROM SNOW WILL BE THE HIGHER ELEVATION LOCATIONS OF THE WESTERN HALF OF THE CWA WITH THE STORM FILLING AND LIFTING AS IT ENTERS THE EASTERN PORTION OF THE STATE. WILL KEEP THE WINTER STORM WATCH UNCHANGED EXCEPT FOR DELAYING THE ONSET OF HEAVIER SNOW A FEW HOURS. THE MAIN IMPACT IN TERMS OF TIMING ACROSS THE EASTERN ZONES WILL BE MONDAY NIGHT. MODELS IN GENERAL AGREEMENT ON MOVING THE TROUGH EAST OF ARIZONA ON TUESDAY BUT RESIDUAL SHOWERS COULD LINGER FOR A GOOD PORTION OF THE DAY OVER THE FAR EAST.

EXTENDED...THE EXTENDED MODELS IN GENERAL AGREEMENT IN SETTING UP A GENERAL TROUGH OVER THE SOUTHWEST UNITED STATES IN THE LATE WEDNESDAY THROUGH FRIDAY TIME FRAME. A SERIES OF JET MAXES WILL MOVE THROUGH THE BASE OF THE TROUGH WITH UNSETTLED WEATHER THROUGH INTO THE WEEKEND.

MCCOLLUM

.FGZ...WINTER STORM WATCH AZZ004-006-007-008-015-016 MONDAY AND MONDAY NIGHT ABOVE 6500 FEET...



CONTINUING TO WATCH AN AREA OF SHSN MOV OUT OF THE MTNS. THIS AREA LUKS AS THOUGH...DESPITE SUM DOWNSLOPE...THAT IT MAY MAKE THE CST (21/00Z KGYX RAOB...AS WELL AS ACARS SOUNDINGS FROM PWM AND MHT... SHOW THE DRY ADIABATIC LAPSE RATE STILL INTACT THROUGH 800 MB). COVERING ATTM WITH NOWCASTS.

SFC CDFNT OVER S CNTRL QUEBEC LUKS TO MOVE INTO THE NRN PTN OF THE FA AFT 04Z...AND TO THE CST BY 08-10Z. AHEAD OF IT...KCXX AND CANADIAN COMPOSITES SHOW SUM ACTIVITY...BUT THIS DOES NOT APPEAR TO BE AS IMPRESSIVE AS THE BATCH NOW ON RADAR. CAA RIGHT BHND THE FNT IS IMPRESSIVE...AND THE LAPSE RATES ARE SUFFICIENT TO ALLOW FOR THE REDEVELOPMENT OF SN SHOWERS. WL CONT THE MENTION OF 3 INCHES FOR THE TOP NUMBER FOR THE MTNS.

FOR THE FOOTHILLS...WL PROBABLY BE ABLE TO CONT WITH THE MENTION OF HI CHC...BUT WL CONT TO MONITOR. MODEL SOUNDINGS SUGGEST A MIXING DEPTH OF 4-5KFT...AND WITH ONLY A BIT LESS MOISTURE TO WORK WITH THAN THIS AFTN...MAY BUMP THESE AREAS UP TO LO LIKELY AND MENTION AN INCH.

FURTHER S...WL ADD A POP FOR PTNS OF ME AWAY FM THE CST FOR A SNOW SHOWER...GIVEN THE AMT OF MIXING JUST BEFORE AND WITH THE FNT. AT THE CST...WL LEAVE THE NON-POP EVENT INTACT.

AS FOR CLDS...WL LEAVE THE CST AND SRN NH/SWRN ME WITH P/CLDY...BUT WL PROBABLY GO WITH M/CLDY FOR THE FOOTHILLS...BASED ON THE EXPECT MIXING AND AVAIL MOISTURE.

MINS SEEM IN THE BALLPARK...SINCE MOS AND ETA 2M DWPTS ARE CLOSE. MAY EDGE TEMPS IN THE MTNS UP A BIT...SINCE THE COLDEST OF THE AMS DOES NOT GET IN THERE UNTIL NEARLY 4 AM.

NO CHANGES TO THE REMAINDER OF THE FCST.

ON THE COASTAL WATERS...WINDS STILL BLO SCA...BUT THIS WL CHANGE WITH THE PASSAGE OF THE CDFNT LATE TNGT. LUKING AT THE MIXING DEPTH AND LAPSE RATES OVER THE CSTL WATERS MON...WUDN'T BE SURPRISED TO SEE MDRM1 AND MISM1 GUST INTO THE L3OS DURING THE MRNG HRS.

PRELIM WRKZFP/WRKCWF AVBL. AS ALWAYS...COMMENTS/OPINIONS WELCOME.

.GYX...SCA.

HAYES