SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NWS LOS ANGELES/OXNARD CA
AFDLOX 300 AM PDT MON MAY 22 2000
IN SHORT TERM...SATELLITE/SURFACE OBS INDICATE EDDY IN PROGRESS...
GENERATING CATEGORICAL LOW CLOUDS/FOG ALONG THE COASTAL PLAIN SOUTH
OF PT CONCEPTION. WITH EDDY CIRCULATION...SOME MARINE LAYER HAS
EVEN REACHED COASTAL VALLEYS...WITH SOME LIGHT FOG REPORTED. 00Z
SOUNDINGS AND ACARS DATA INDICATE CONTINUED STRONG INVERSION...SO
WILL EXPECT LOW CLOUDS/FOG TO CLEAR TO THE BEACHES THIS AFTERNOON.
NORTH OF PT CONCEPTION...DO NOT EXPECT ANY MARINE LAYER THIS MORNING
DUE TO OFFSHORE GRADIENTS. SO WILL GO WITH MOSTLY SUNNY SKIES...DUE
TO SOME HIGH CLOUDS FLOATING OVERHEAD. OTHERWISE...WILL CONTINUE TO
HAVE LOCAL NORTHWEST TO NORTH WINDS ACROSS THE MOUNTAINS TODAY.
TONIGHT/TUESDAY...MODELS INDICATE LITTLE CHANGE SYNOPTICALLY...WITH
UPPER RIDGE MAINTAINING ITSELF OVER THE AREA. CLOSER TO THE GROUND
ONSHORE FLOW WILL CONTINUE. ALSO...LOOKS LIKE EDDY CIRCULATION WILL
CONTINUE...BRINGING LOW CLOUDS/FOG TO THE COASTAL PLAIN...WITH SOME
PATCHY STRATUS/DENSE FOG IN THE VALLEYS SOUTH OF PT CONCEPTION. NORTH
OF PT CONCEPTION...GRADIENTS SHOULD TURN WEAK ONSHORE TONIGHT...SO
SOME PATCHY STRATUS/FOG WILL DEVELOP ALONG THE CENTRAL COAST. BY
TUESDAY AFTERNOON...STRATUS/FOG WILL ONCE AGAIN CLEAR TO THE BEACHES.
BY TUESDAY AFTERNOON...MODELS DO INDICATE SOME MID/HIGH LEVEL
MOISTURE DRIFTS IN FROM THE SOUTHEAST-SOUTH. SO WILL MENTION PARTLY
CLOUDY AFTERNOON FOR THE MOUNTAINS...BUT WILL HOLD OFF ON ANY MENTION
OF PRECIP AT THIS TIME.
AS FOR TEMPS...CHALLENGING IS THE WORD. MODELS ALL INDICATE NO
THICKNESS CHANGES TODAY...WITH SOME SLIGHT FALLS ON TUESDAY. SO WILL
EXPECT PERSISTENCE TODAY AND A DEGREE OR TWO COOLING TUESDAY FOR THE
MOUNTAINS/DESERTS. TEMPS ON THE COASTAL PLAIN WILL HAVE SOME SLIGHT
COOLING THE NEXT COUPLE OF DAYS...AS MARINE INFLUENCE CONTINUES...
WITH TEMPS IN THE MID 60S TO MID 70S. BIG PROBLEM IS VALLEY TEMPS.
WITH PATCHY FOG REPORTED AT VNY/BUR...MARINE INFLUENCE IS OBVIOUS.
THIS SHOULD RESULT IN SOME NOTICEABLE COOLING TODAY FOR THE LA/VTU
COUNTY VALLEYS...WITH TEMPS GENERALLY IN THE UPPER 80S AND 90S...
ALTHOUGH SOME INLAND VALLEYS WILL STILL SHOULD REACH THE 100 MARK.
ON TUESDAY...WILL EXPECT SEVERAL MORE DEGREES COOLING AS MARINE
LAYER CONTINUES TO CREEP IN. INTERIOR VALLEYS OF THE CENTRAL COAST
WILL ONLY EXPERIENCE SLIGHT COOLING TUESDAY...PER SLIGHT THICKNESS
FALLS.
FOR EXTENDED...MODELS ALL APPEAR TO HAVE THE SAME GENERAL IDEA
WITH UPPER RIDGE BREAKING DOWN...AS WEAK UPPER LOW OPENS UP AND
MOVES ACROSS THE DISTRICT THURSDAY. BY FRIDAY...THE UPPER TROUGH
MOVES EAST...AS UPPER RIDGE BUILDS ONCE AGAIN OVER EASTERN PACIFIC.
THEREFORE...WILL EXPECT COOLING TEMPS FOR THE AREA WEDNESDAY AND
THURSDAY WITH H5 HEIGHT/THICKNESS FALLS AND CONTINUED MARINE LAYER.
ON FRIDAY...H5 HEIGHTS/THICKNESSES INCREASE...SO WILL EXPECT TEMPS
TO REBOUND SOMEWHAT.
LAX 000. THOMPSON.
.LAX...NONE.
AREA FORECAST DISCUSSION
NWS CHICAGO IL
AFDCHI 300 PM CDT SUN MAY 21 2000
LOOKING AT THE VELOCITY DISPLAY FROM THE DOPPLER RADAR THERE IS
VEERING OF WINDS AT 0758 UTC. SHOWERS HAVE DEVELOPED OVER NORTHEAST
ILLINOIS. THE ACARS SOUNDING SHOWS MORE POSITIVE AREA THAN NEGATIVE
AT ORD AT 0530 UTC. THE 700 MB ANALYSIS SHOWS A TROUGH OVER ILLINOIS
AT 0000 UTC. AS THIS TROUGH MOVES OVER NORTHEAST ILLINOIS WITH THE
SOMEWHAT UNSTABLE AIR AND STRONG WARM AIR ADVECTION SHOWERS
DEVELOPED.
WILL REMAIN WARM TODAY AND DEWPOINTS ARE EXPECTED TO SLOWLY INCREASE.
MOISTURE ADVECTION WAS NOTICED EVEN AT 0500 UTC SURFACE ANALYSIS...
ALTHOUGH IT WAS SMALL. PROFILE DATA SHOWS A 50 KNOT JET STREAK
ENTERING IOWA. THE MOVEMENT OF THE MAX WINDS WAS NOTICED ON THE
WATER VAPOR LOOPS. IR LOOPS SHOW SOME CLOUDINESS WITH THIS FEATURE
AND RADAR IS SHOWING RAIN IN WESTERN WISCONSIN AND EASTERN IOWA.
THIS TROUGH MAY BE THE RAIN PRODUCER THIS AFTERNOON. AGAIN WILL OPT
FOR LOW POPS OF AROUND 40 PERCENT. USE A COMBINATION OF THE NGM/AVN
FOR TIMING. TONIGHT WAVE AND MONDAYS SHOW UP IN THE EQUIVALENT
POTENTIAL TEMPERATURE FIELD AT 700 MB.
1000 TO 700 MB THICKNESS AND 500 MB HEIGHT FORECASTS INDICATE THE
WARMING TO CONTINUE TUESDAY. WILL STAY NEAR MOS FOR FORECAST
TEMPERATURES.
.CHI...NONE
WHW