Forecast Discussions mentioning ACARS, received at FSL on 02/20/00

FCST PROBLEMS FOR THE UPDATE INCLUDE SKY COVER...CHC OF --SHSN FOR THE SRN ZNS...AND MIN TEMPS. FOR THE MOST PART...NO SIG CHANGES TO THE PRVS PACKAGE.

IR LOOP SHOWS THAT THE NERN PTN OF THE FCST HAS CLEARED...AND TEMPS ARE ALREADY STARTING TO RESPOND. SUM PLACES GETTING TWD FCST MINS NOW...AND WL LIKELY NEED A BUMP DOWNWARD.

FURTHER S AND W...LUKS LIKE MOIST IS TRAPPED UNDER THE INVERSION OVER SRN NH. HOWEVER...BOTH THE 20/00Z GYX RAOB AND 19/2352Z ACARS OBS FM MHT SUGGEST THAT THE INVERSION IS LIFTING...AND THIS IN ITSELF WUD BRING BREAKS FURTHER S AND W.

ANY BREAKS WUD BE SHORT LIVED...AS A S/W MOVG INTO WRN PA IS KICKING OFF SUM SCT --SHSN ACTIVITY...AS WELL AS MID LEVEL CLDS. GIVEN THE AMT OF DRY AIR ABV THE INVERSION...WUD EXPECT MOST OF THIS ACTIVITY TO DRY UP...BUT WL LEAVE THE --SHSN WHERE IT IS NOW.

FURTHER N...ACRS NRN NH...IR LOOP SHOWS SUM CLDS...BUT THE METARS SHOW IT IS ABT THE LEVEL OF THE INVERSION. ALTHOUGH IT IS TUFF TO TELL THE EXTENT OF THE CLDS TO THE E ACRS WRN ME...WUD EXPECT THE MTNS ARE SEEING SUM OF THIS CLD SHEET AS WELL. WL WATCH THE TREND... BUT P/CLDY OR BECOMING P/CLDY MAY YET WORK. MODEL SOUNDINGS SHOW THIS AREA SLOW TO CLEAR.

ALL OF THIS WL HAVE A MAJOR IMPACT ON MINS. WHERE IT IS CLR...TEMPS ARE ALREADY AT THE TOP OF THE MIN RANGE. SINCE THE LOWER CLDS ARE PROBABLY MAKING THEIR MAX APPEARANCE NOW...WUD EXPECT THESE AREAS TO REMAIN P/CLDY AT WORST. WL PROBABLY DROP MINS IN THE ERN ZNS (SINCE TEMPS TO THE E ARE ALREADY IN THE SINGLE NUMBERS).

OVER THE MTNS...TEMPS IN THE SINGLE NUMBERS ON EITHER SIDE OF THE CLD SHEET...SO WL PROBABLY MODIFY THE MINS HERE ONLY SLIGHTLY...AND MAY HAVE TO CHANGE SPLITS BASED ON CLDS AT PRESS TIME.

FOR SRN ZNS...WHERE CLDS SHUD REMAIN MOST OF THE NGT...WL KEEP MINS WHERE THEY...SINCE THEY AGREE WITH THE ETA 2M DWPTS AT 00Z (FOR THE MOST PART). CLDS SHUD KEEP THE MINS FM REACHING THE TEENS.

NO CHANGES TO THE REMAINDER OF THE PUBLIC FCST.

ON THE COASTAL WATERS...WINDS ARE DROPPING BLO SCA...AND WUD EXPECT THIS TREND TO CONT. HOWEVER...SEAS ARE WELL ABV SCA CRITERIA...AND THE WAM MODEL SUGGESTS THAT THIS WL BE THE CASE FOR THE REST OF THE NGT.

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

.GYX...SCA

HAYES



SYNOPSIS...A WEAK SUB-TROPICAL DISTURBANCE WILL BRING MOSTLY CLOUDY SKIES TO THE REGION TODAY WITH A CHANCE FOR MAINLY RAIN SHOWERS FROM FLAGSTAFF WESTWARD. A MUCH STRONGER SYSTEM WILL FOLLOW THIS SUNDAY NIGHT. EXPECT PERIODS OF RAIN AND SNOW SPREADING FROM WEST TO EAST 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...CURRENT FORECAST IN GOOD SHAPE WITH NO UPDATES. FOR TODAY...TROUGH MOVING INTO ARIZONA FROM THE SUB-TROPICS IS PRODUCING WIDESPREAD THUNDERSTORMS IN SOUTHERN CALIFORNIA. IT WILL WEAKEN AS IT MOVES INTO ARIZONA BUT BRING QUITE A BIT OF MOISTURE TO THE WESTERN CWA. THE CURRENT FORECAST HANDLES THIS WELL. LOW LEVEL PRESSURE GRADIENTS CONTINUE TO STRENGTHEN WITH BREEZY CONDITIONS ON TRACK FOR TODAY. ALSO...WILL HAVE TO KEEP AN EYE ON WET BULBING IF PRECIPITATION STARTS TODAY. THE POTENTIAL IS TO BRING THE SNOW LEVEL DOWN TO AROUND THE 7000 FOOT LEVEL. THE BIG STORY CONTINUES TO BE THE TROUGH CENTERED NEAR 38N 132W. MORNING UPPER AIR DATA AND AIRCRAFT OBSERVATIONS ARE SHOWING A DEEPER SYSTEM THAN THE 00Z MODEL RUNS WERE INDICATING WITH A 250 MB 150-170 KNOT JET CORE (QUITE A BIT STRONGER THAN FORECAST) ON THE BACK SIDE OF THE TROUGH. THE AVN REMAINS THE MODEL OF CHOICE ALTHOUGH THE 00Z RUN WAS NOT DEEP ENOUGH. IN ANY CASE...THE EXIT REGION OF THE 250 MB JET WILL APPROACH ARIZONA FROM THE WEST TONIGHT. AS IT PROPAGATES EAST OF THE TROUGH AXIS AND ENTERS ARIZONA THIS WILL RESULT IN PROLONGED AND SIGNIFICANT LARGE SCALE UPWARD MOTION. COMBINED WITH 30 TO 40 KNOT SOUTHERLY FLOW AT THE 700 MB AND PLENTY OF LOW TO MID LEVEL MOISTURE IT LOOKS LIKE MONDAY COULD BE A SNOW PACKED DAY FOR ELEVATIONS ABOVE THE 6000 FOOT LEVEL. AT THIS TIME LOOKS LIKE THE MAIN IMPACT WILL BE THE HIGHER ELEVATION LOCATIONS OF THE WESTERN HALF OF THE CWA WITH THE STORM WEAKENING SOME AS IT ENTERS THE EASTERN PORTION OF THE STATE.

MCCOLLUM

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



SHORT TERM DISCUSSION: HEALTHY BATCH OF HIGH LEVEL MOISTURE STREAMING NORTHEASTWARD AHEAD OF UPPER LOW OFF OF SOUTHERN CALIFORNIA. LEADING EDGE OF THICKER MOISTURE TIMED TO REACH DENVER AROUND SUNRISE. IR LOOP INDICATES A FEW BREAKS...AND NO SIGN OF ANY MOUNTAIN WAVE ENHANCEMENT AND DONT EXPECT ANY EITHER WITH PROGGED STABILITY PROFILE. THUS...PARTLY CLOUDY SHOULD SUFFICE. DROPPED MENTION OF PRECIP IN MOUNTAINS SINCE MID LEVEL MOISTURE DOES NOT REACH AREA TIL AFTER 00Z.

TEMPS SHOULD RESPOND NICELY TO WARM ADVECTION. LAST THREE HOURS OF ACARS PLOTS SHOW GOOD WARM ADVECTION FROM 700 MB ON UP. WITH WESTERLY COMPONENT TO WINDS AND LIMITED SUNSHINE...TEMPS SHOULD REACH THE 55 TO 60 DEGREE RANGE MOST AREAS. LITTLE COLDER OVER THICKER SNOW FIELD STRETCHING ACROSS NORTHERN WASHINGTON COUNTY.

BARJENBRUCH

LONG TERM DISCUSSION: FIRST UPPER LOW NOW OVER SOUTHERN CALIFORNIA SHEARS SUBSTANTIALLY AS IT PULLS OUT SO DYNAMICS ALSO EXPECTED TO WEAKEN CONSIDERABLY. DESPITE UNSTABLE AIRMASS...MOISTURE LOOKS LIMITED AND SOUTHWEST FLOW ALOFT NOT GOOD FOR OROGRAPHIC SNOWS IN NORTH CENTRAL MOUNTAINS. THUS...SCATTERED POPS SHOULD BE THE RULE TONIGHT AND MONDAY.

ON THE PLAINS...CONTINUED DRY AND WARM THROUGH MONDAY WITH SOUTH/ SOUTHWEST FLOW AND WARM MID LEVEL TEMPS. CLOUD COVER MAY BE CONSIDERABLE ESPECIALLY BY MONDAY AFTERNOON AS NEXT STRONGER STORM BEGINS TO SPREAD HIGH LEVEL MOISTURE SHIELD THIS WAY.

AT THIS TIME...I'M NOT IMPRESSED WITH THE MODELS HANDLING OF THIS NEXT STRONGER STORM. BASED ON WATER VAPOR TRENDS...LOOKS LIKE ALL MODELS ARE TOO FAR NORTH TO START. SO A DEEPER EVOLUTION THAN EVEN THE AVN MAY OCCUR. EVEN THE CONSISTENTLY MORE PROGRESSIVE NOGAPS IS LEANING DEEPER. TIME WILL TELL...BUT STILL LOOKS LIKE A DECENT CHANCE OF RAIN/SNOW OVER THE CWA TUESDAY...EXTENDING INTO EARLY WEDNESDAY OVER THE EASTERN PLAINS. TEMPS WARM ENOUGH FOR MOSTLY RAIN ON THE PLAINS.

BARJENBRUCH

.DEN...NONE.