AREA FORECAST DISCUSSION
NWS SAN DIEGO
AFDSAN 330 AM PST THU MAR 18 2004
.SYNOPSIS...THE MARINE LAYER AND ONSHORE FLOW WILL CAUSE COASTAL LOW
CLOUDS AND FOG IN THE NIGHTS AND MORNINGS...EXTENDING LOCALLY INLAND.
OTHERWISE...HIGH PRESSURE ALOFT WILL KEEP THE WEATHER FAIR. WARMER
THIS WEEKEND AS THE HIGH BUILDS THEN COOLER NEXT WEEK AS THE HIGH
WEAKENS. SPRING BEGINS FRIDAY AT 1049 PM PST.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING
ORANGE...SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN
BERNARDINO COUNTIES.
ACARS REPORTS AND SATELLITE IMAGERY SHOW SOME DEEPENING OF THE
MARINE LYR FM 24 HOURS AGO WITH THE BASE OF A STRONG MARINE
INVERSION NR 1200 FT WITH THE TOP NR 1500 FEET. THOUGH THE MARINE
LYR IS DEEPENING SLOWLY AND THE STRATUS EXTENDS A LTL FARTHER INLAND
THAN 24 HOURS AGO...VISIBILITIES AND ESPECIALLY CEILINGS ARE STILL
FAIRLY LOW AT LWR ELEVATIONS CLOSE TO THE COAST. AS THE MARINE LYR
CONTINUES TO DEEPEN...IT WOULDN'T BE SURPRISING TO SEE SOME
IMPROVEMENT IN VISIBILITIES ALG THE COAST AROUND SUNRISE. DENSE FOG
ADVISORY IS IN EFFECT FOR THE SAME AREAS AS THE PAST TWO
MORNINGS...BUT LOCATIONS EXPERIENCING THE LOWEST VISIBILITIES MAY
SHIFT INLAND A BIT AROUND SUNRISE RELATED TO THE DEEPENING OF THE
MARINE LYR. ADDITIONAL DEEPENDING IS EXPECTED TONIGHT INTO FRI
MORNING AS A WEAK COASTAL EDDY CONTINUES. THIS SHOULD ALLOW STRATUS
TO SPREAD FARTHER INLAND INTO THE INLAND VALLEYS BY FRI MORNING AND
BRING GREATER COOLING TO THE VALLEYS FOR FRI.
WEAK HIGH PRESSURE BUILDS OVER SOUTHERN CALIFORNIA FOR THE WEEKEND.
THIS SHOULD BRING WARMING TO INLAND AREAS. THIS WILL ALSO STRENGTHEN
THE MARINE INVERSION. IN COMBINATION WITH A WEAKENING OF ONSHORE
FLOW...LOW CLOUDS MAY BE SLOW TO CLEAR AT SOME BEACHES FOR SATURDAY
AND SUNDAY AFTERNOONS.
FOR TUE THRU THU OF NEXT WEEK...A TROUGH OF LOW PRESSURE WILL MOVE
INLAND ALG THE WEST COAST TO THE NORTH OF SW CA. THIS WILL BRING
COOLING...A DEEPER MARINE LAYER...AND INCREASE IN ONSHORE FLOW.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
DENSE FOG ADVISORY...SEE LAXNPWSGX.
&&
$$
XXX666
AREA FORECAST DISCUSSION
NWS SAN DIEGO
AFDSAN 853 PM PST WED MAR 17 2004
.SYNOPSIS...THE MARINE LAYER AND ONSHORE FLOW WILL CAUSE COASTAL LOW
CLOUDS AND FOG IN THE NIGHTS AND MORNINGS...EXTENDING LOCALLY INLAND.
OTHERWISE...HIGH PRESSURE ALOFT WILL KEEP THE WEATHER FAIR. WARMER
THIS WEEKEND AS THE HIGH BUILDS THEN COOLER NEXT WEEK AS THE HIGH
WEAKENS. SPRING BEGINS FRIDAY AT 1049 PM PST.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING
ORANGE...SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN
BERNARDINO COUNTIES.
STRATUS IS SLOWLY PUSHING INLAND...MAINLY COASTAL AREAS. BASES HAVE
BEEN HIGH ENOUGH SO LITTLE IF ANY DENSE FOG HAS BEEN REPORTED EXCEPT
ALONG THE IMMEDIATE COAST IN THE AFTERNOON. ONSHORE PRESSURE
GRADIENTS RUNNING CLOSE TO 5 MBS TO THE LOWER DESERTS...BUT REMAIN
WEAKLY OFFSHORE TO THE GREAT BASIN. THE MIRAMAR SOUNDING AT 4 PM
SHOWED THE INVERSION HAD CHANGED LITTLE FROM 24 HR AGO...BUT AN EDDY
HAS REDEVELOPED OVER THE INNER COASTAL WATERS BASED ON LATEST
OBSERVATIONS...SO THE INVERSION MAY BE LIFTING A BIT.
MAIN FORECAST PROBLEM FOR THE NEAR TERM WILL BE FOG. HARD TO GET A
HANDLE ON HOW THE INVERSION WILL EVOLVE OVERNIGHT. IT IS MUCH LOWER
TO THE NORTH NEAR LA COUNTY THAN FARTHER S IN SAN DIEGO COUNTY.
LATEST IR/FOG LOOP SHOWS LOW CLOUDS SURGING NORTHWARD INTO SW LA
COUNTY. LOOKS LIKE THE FOG ADVISORY WILL HAVE TO BE MODIFIED TO
REMOVE SAN COASTAL AREAS FOR NOW. BASED ON VISIBILITIES AND CEILING
HEIGHTS THIS EVENING...THE FOG WILL NOT BE AS WIDESPREAD OR DENSE AS
LAST NIGHT. ACARS PROFILES FROM LINDBERGH FIELD AND JOHN WAYNE
AIRPORT SHOWED THE INVERSION LOWERING FROM NEAR 1100 FT AT KSAN...TO
850 FT AT KSNA. SO THE CLOUD LAYER MUST BE FAIRLY THIN TO ACCOUNT
FOR THE HIGHER BASES BEING REPORTED THIS EVENING. LOOKS LIKE AN EDDY
CIRCULATION OVER THE COASTAL WATERS AGAIN...COUPLED WITH BETTER
ONSHORE GRADIENTS TO THE LOWER DESERTS MAY ALSO BE LIFTING THE
INVERSION BASE A BIT IN SAN DIEGO COUNTY. IN ANY CASE WILL UPDATE
FOG ADVISORY TO REMOVE ZONE 43. WITH THE EDDY...LOOKS LIKE AT LEAST
SW PORTIONS OF THE INLAND EMPIRE MAY GET INVOLVED AS WELL...SO WILL
ADD ZONE 48.
00Z MODELS SHOW MINOR FLUCTUATIONS IN THE 500 MB HEIGHT FIELD OVER S
CALIFORNIA INTO FRIDAY BEFORE HEIGHTS RISE IN RESPONSE TO A BUILDING
UPPER RIDGE INLAND. THE 00Z MESO ETA IS STILL GENERATING A WEAK EDDY
THU NIGHT INTO FRIDAY WHICH PROPS UP THE MARINE LAYER FOR BETTER
INLAND STRATUS/FOG PENETRATION.
LOOKING AHEAD...MODELS SHOW STRONG REX BLOCK BREAKING DOWN OVER THE
E PACIFIC NEAR 150W LATE NEXT WEEK WITH INCREASED W FLOW OFF THE
PACIFIC INTO S CA. THIS SHOULD CAUSE SOME COOLING NEXT WEEK WITH A
DEEPER MARINE LAYER AND A CHANCE FOR SOME RAIN BY NEXT
WEEKEND...ESPECIALLY N AND CENTRAL CA. THESE BLOCKS CAN BE
TENACIOUS...BUT NCEP ENSEMBLE 500MB CHARTS OUT TOWARD THE END OF
NEXT WEEK DO SHOW SOME CONSISTENCY WITH TROUGHING ALONG THE W COAST
SO CANNOT BE IGNORED.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
DENSE FOG ADVISORY...SEE LAXNPWSGX.
&&
$$
JAD
AREA FORECAST DISCUSSION
NWS NORTHERN INDIANA
AFDFWA 645 AM EST THU MAR 18 2004
.AVIATION...
LIFR CONDITIONS BEGINNING TO IMPROVE AT SBN AS MID CLOUD DECK MOVG
OVER THE AREA LIMITING FURTHER RADIATIONAL COOLING AND WINDS ALOFT
AHEAD OF SHRTWV TO THE NW STARTING TO INCREASE. WENT WITH A RAPID
IMPROVEMENT AT SBN THIS MORNING AND A LITTLE SLOWER AT FWA. SNOW
OVER WI/MN ASSOCIATED WITH LOW OVER SE MN EXPECTED TO MOVE ACROSS
NRN IND THIS AFTN. RECENT ACARS FM FWA INDICATES TEMP PROFILE MOSTLY
BLO 0C WITH A SMALL AREA ABOVE AROUND 950MB. EXPECT EVAPORATIONAL
COOLING WILL RESULT IN MAINLY SNOW AT FWA/SBN CAUSING CONDITIONS TO
LOWER TO IFR AGAIN. AS THE LOW MOVES AWAY TONIGHT AND HIGH PRESSURE
BUILDS INTO THE AREA COULD SEE SIMILAR CONDITIONS AS THIS PAST NIGHT
WITH RADIATIONAL COOLING FOG.
&&
.SHORT TERM...
DENSE FOG A CONCERN EARLY THIS MORNING. ALTHOUGH FOG APPEARS TO BE
PATCHY WITH MANY SITES VSBYS GOING UP AND DOWN, SBN AND FWA BOTH
AOB 1/4SM ATTM. WITH LIGHT WINDS/LOW CLOUDS CLEARING AND HIGH
CLOUDS A LITTLE SLOWER THAN EARLIER ANTICIPATED TO SPREAD INTO THE
AREA, FOG MAY CONTINUE TO BECOME MORE WIDESPREAD INTO THE EARLY
MORNING COMMUTING TIME, SO HAVE ISSUED A DENSE FOG ADVISORY UNTIL
9AM.
LOW OVER SW MN EXPECTED TO TRACK RAPIDLY SE ACROSS THE AREA TODAY.
AREA OF PRECIP OVER MN/IA SHOULD SPREAD INTO THE CWA AROUND MIDDAY.
INCREASED POPS TO HIGH LIKELY ACROSS ALL OF THE CWA EXCEPT EXTREME
SW. FCST SOUNDINGS SUGGEST PRECIP WILL BE MAINLY SNOW NE AND RAIN SW
WITH A MIX IN BETWEEN. EXPECTING AN INCH OR LESS OF SNOW
ACCUMULATION WITH WARM GROUND RESULTING IN MELTING AS SNOW FALLS
OVER MUCH OF THE AREA WITH THE EXCEPTION OF SNOW COVERED SE. AS LOW
MOVES AWAY FROM THE AREA TONIGHT HIGH PRESSURE WILL MOVE OVER NRN
INDIANA BY 12Z FRI. LINGERING LOW LEVEL MOISTURE SHOULD RESULT IN
SLOW CLEARING AND MAY BE SOME FOG DEVELOP AGAIN LATE. FOR NOW WILL
CONTINUE WITH MOSTLY CLOUDY SKIES WITH JUST A CHC OF SOME LEFTOVER
S- IN THE FAR EAST IN THE EVENING.
&&
.LONG TERM...
ETA/GFS/GEM IN GOOD AGREEMENT WITH EACH OTHER AND WITH PREVIOUS RUNS
BRINGING A COLD FRONT ACROSS THE AREA SATURDAY. WITH ADDED
CONFIDENCE UPPED POPS A BIT BUT KEPT IN CHANCE CATEGORY. WENT AHEAD
AN INTRODUCED A SMALL CHANCE OF RAIN WELL AFTER MIDNIGHT FRIDAY
NIGHT IN THE NORTH AND WEST AS COLD FRONT REACHES THE EDGE OF THE
CWFA BY 12Z.
GFS TIME-HEIGHTS SHOWING SOME AVAILABLE LOW-LEVEL SYNOPTIC MOISTURE
SUNDAY AS DELTA T VALUES REACH INTO THE LOWER/MIDDLE TEENS WITH LOW
SHEAR NORTHWEST FLOW ACROSS LAKE MICHIGAN. DECIDED TO TOSS IN A
SMALL CHANCE OF LAKE EFFECT SHOWERS IN THE NORTHWEST SUNDAY.
MINIMUM TEMPERATURES FRIDAY NIGHT SHOULD OCCUR IN THE EVENING AND
THEN RISE SLOWLY OVERNIGHT IN WARM AIR ADVECTION AHEAD OF THE
APPROACHING FRONT.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...DENSE FOG ADVISORY FOR THIS MORNING FOR ZONES INZ003>009...
INZ012>018...INZ020...INZ022>027...INZ032>034.
MI...DENSE FOG ADVISORY FOR THIS MORNING FOR ZONES MIZ077>081.
OH...DENSE FOG ADVISORY FOR THIS MORNING FOR ZONES OHZ001>002...
OHZ004>005...OHZ015>016...OHZ024>025.
&&
$$