SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NWS LOS ANGELES/OXNARD CA
AFDLOX 915 PM PDT TUE APR 3 2001
EDDY CIRCULATION STILL IN PROGRESS THIS EVENING ACROSS SOUTHERN
CALIFORNIA. SOUNDINGS AND ACARS DATA SHOWING VERY DEEP MARINE LAYER
IN PLACE...GENERALLY ABOVE 6000 FEET. AS A RESULT OF THIS DEEP
MARINE LAYER...REVERSE CLEARING PATTERN TOOK PLACE THIS
AFTERNOON...WITH THE COASTAL AREAS CLEARING FAIRLY WELL...WHILE
CLOUDS HUNG IN ACROSS MUCH OF THE VALLEYS AND MOUNTAINS OF LA/VTU
COUNTIES. FROST ADVISORY POSTED FOR INTERIOR VALLEYS OF SLO/SBA
COUNTIES DUE TO LESS CLOUDS AND LIGHTER WINDS EXPECTED OVERNIGHT
ACROSS THESE AREAS.
BROAD UPPER LOW OVER WEST COAST NOW CENTERED OVER EXTREME NORTHERN
CALIFORNIA. AS THIS UPPER LOW SLIDES SOUTHWARD OVER THE NEXT 24
HOURS...CYCLONIC FLOW WILL CONTINUE ACROSS SOUTHERN CALIFORNIA...
HELPING TO REINFORCE THE EDDY CIRCULATION AND DEEP LOW LEVEL MOIST
LAYER. LOW LEVEL COLD ADVECTION IS EXPECTED TO FILTER IN ACROSS THE
ENTIRE FORECAST AREA...WHICH COULD CONTINUE TO WEAKEN THE MARINE
INVERSION AND CAUSE A CHAOTIC MARINE LAYER PATTERN.
BY WEDNESDAY NIGHT...COLD UPPER LOW WILL BE CENTERED OFF THE COAST
OF POINT CONCEPTION. BECAUSE THE LOW CENTER WILL MOVE RIGHT ALONG
THE COAST...MOST OF THE MOISTURE AND DYNAMICS WILL SWING OFFSHORE
AND TO THE SOUTH OF OUR AREA. NONETHELESS...THE COLD CORE WILL MOVE
RIGHT OVER THE FORECAST AREA...BRINGING THE THREAT OF SHOWER AND
THUNDERSTORM ACTIVITY. 500 MB TEMPERATURES OF -30 DEGREES CELSIUS
AND LIFTED INDICES OF -2 TO -4 STILL WARRANT THREAT OF
THUNDERSTORMS ACROSS SOUTHERN CALIFORNIA ON THURSDAY.
LAX 0003. GOMBERG
.LAX...SMALL CRAFT ADVISORY (SEE LAXCWFLAX).
AREA FORECAST DISCUSSION
NWS BURLINGTON VT
AFDBTV 247 AM EDT WED APR 4 2001
HIGH AND DRY. LOOKS LIKE DECENT MODEL AGREEMENT THOUGH THE FORECAST.
MAX TEMPS YESTERDAY RANGED FROM 37 TO 45 (40 BTV) WITH 850 MB
TEMPERATURES ABOUT -8 ON LATE NIGHT ACARS SOUNDINGS INTO BTV AND
YUL AND -5 INTO SYR AND ROC WHERE MAXS WERE AROUND 50 WITH LACK
OF SNOW COVER.
TODAY 850 TEMPERATURES FORECAST TODAY ARE A BIT WARMER THAN
YESTERDAY ABOUT -5 SO TEMPERATURES SHOULD BE IN THE 40S JUST ABOUT
EVERYWHERE AND SHORT WAVE RIDGE MEANS LOTS OF SUNSHINE.
WEAK VORT 00-06Z TONIGHT WITH SOME WEAK QG FORCING FOR LIFT BUT
LITTLE IN THE WAY OF MOISTURE. RESULT = MOSTLY CLEAR SKIES. EXPECT
WIDE RANGE OF MIN TEMPERATURES.
THURSDAY SOME COLD ADVECTION WITH 850 MB TEMPS A FEW DEGREES COOLER
SO EXPECT MAX TEMPS MORE LIKE YESTERDAY. AVN CRANKS OUT A FEW CENTS
WORTH OF PRECIP AND SEEMS TO BE LINKED TO UPSLOPE FORCING FROM
INCREASING LOW LEVEL NW FLOW BUT LACK OF MOISTURE FROM SOURCE REGIONS
WOULD NOT SEEM TO SUPPORT THIS. NONE ON ETA OR NGM. POPS NIL.
FRIDAY...BAROCLINIC ZONE GETS CLOSER WITH PRECIP FORECAST ACROSS
WESTERN NY...POSSIBLY GETTING INTO EXTREME S AND W ZONES LATER
IN THE DAY. WILL JUST GO WITH PARTLY CLOUDY WITH MAINLY HIGH CLOUDS
EXPECTED.
FRIDAY NIGHT INTO SATURDAY NIGHT...AVN SHOWS MULTIPLE SHORT WAVES
TRAVELING OVER THE RIDGE. BEST QG FORCING FOR ASCENT NOT OVER OUR
FORECAST AREA UNTIL SATURDAY AFTERNOON FOR CHANCE OF SHOWERS.
...MODEL TRENDS CONTINUE SHOW SIGNIFICANT WARM UP BY SUNDAY...
AVN/ECMWF SHOWS 850 TEMPERATURES REACHING +10 BY SUNDAY. IF THIS IS
INDEED THE CASE...NORMALLY WOULD MEAN 70 DEGREES....BUT WITH SNOW
COVER PROBABLY NOT THE CASE. AVN SURFACE TEMP FORECAST SHOWS MID 60S
NY, BUT WITH COOLER MARITIME FLOW INTO E VT TEMPERATURES ONLY MID
40S. THIS IS USUALLY THE CASE IN THE SPRING WITH THESE KINDS OF
SITUATIONS. MOST ENSEMBLE MOS MEMBERS FROM YESTERDAY INDICATE A MORE
CONSERVATIVE WARM UP IS THE MOST LIKELY SCENARIO AND THIS IS WHAT WE
CURRENTLY HAVE AND WILL CONTINUE WITH IT. IF CORRECT, SURFACE DEW
POINTS FORECAST INTO THE 45 TO 55 DEGREE RANGE AND OVERNIGHT LOWS IN
THE 40S THIS COULD MEAN QUITE A SNOWMELT SITUATION BEGINNING SAT
NIGHT AND CONTINUING INTO TUESDAY.
.BTV...NONE.
SISSON