SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NWS LOS ANGELES/OXNARD CA
AFDLOX 200 PM PDT TUE SEP 7 1999
LATEST SATELLITE/SURFACE OBS INDICATE SUNNY SKIES ACROSS THE AREA
EXCEPT FOR SOME PATCHY STRATUS/FOG NEAR THE BEACHES. AREA OF
SUBSIDENCE...ASSOCIATED WITH UPPER TROUGH OFFSHORE...HAS HELPED
CLEAR THE STRATUS/FOG OVER THE OCEAN. POSSIBILITY EXISTS THAT THE
ATMOSPHERE MIGHT BE MIXED UP ENOUGH TO LIMIT MARINE LAYER FORMATION
TONIGHT. HOWEVER...WITH DECENT ONSHORE FLOW AND GOOD INVERSION
PRESENT...BELIEVE STRATUS/FOG WILL EVENTUALLY DEVELOP OVERNIGHT.
LATEST ACARS DATA...FROM LA BASIN...INDICATES SUBSIDENCE HAS HELPED
SQUASH MARINE INVERSION WITH BASES AROUND 1000-1500 FEET. WITH THE
BASE OF THE INVERSION THAT LOW...STRATUS/FOG MAY HAVE SOME TROUBLE
REACHING THE VALLEYS TONIGHT...SO WILL ONLY MENTION PATCHY MARINE
LAYER FOR VALLEY ZONES. OTHER THAN MARINE LAYER CLOUDS...SKIES
SHOULD BE CLEAR OVERNIGHT ACROSS THE DISTRICT.
FOR WEDNESDAY THROUGH THURSDAY...MODELS ARE IN GOOD AGREEMENT WITH
OVERALL SYNOPTIC PATTERN. UPPER LOW...CURRENTLY SOUTHWEST OF THE
AREA...WILL GRADULLY LIFT NORTHEASTWARD INTO CENTRAL CALIFORNIA.
AS THE UPPER LOW LIFTS...H5 HEIGHTS WILL GRADUALLY INCREASE AND
ONSHORE FLOW WILL WEAKEN SLIGHTLY. THEREFORE...WILL EXPECT SLIGHT
SHRINKING OF MARINE LAYER THROUGH THURSDAY...WITH STRATUS/FOG
CONFINED TO THE COAST. OTHER THAN MARINE LAYER...HAVE SOME SLIGHT
CONCERN ABOUT SOUTHERLY FLOW ALOFT BRINGING IN SOME MOISTURE FROM
HURRICANE GREG. AT THIS POINT...DO NOT THINK WILL GET ANYTHING MORE
THAN SOME MID/HIGH CLOUDS FROM GREG...WHICH WILL BE COVERED BY
MOSTLY SUNNY/MOSTLY CLEAR WORDING.
AS FOR TEMPS...THICKNESSES SHOW ONLY MINOR FLUCUATIONS THROUGH
THURSDAY. THEREFORE...MOUNTAIN/DESERT TEMPS SHOULD CHANGE LITTLE
WEDNESDAY AND THURSDAY. HOWEVER...COASTAL AND VALLEY TEMPS SHOULD
WARM A COUPLE OF DEGREES WEDNESDAY AND THURSDAY...AS MARINE LAYER
INFLUENCE DIMINISHES.
LAX 0000. THOMPSON.
.LAX...NONE.
AREA FORECAST DISCUSSION
NWS GREEN BAY WI
AFDGRB 200 PM CDT TUE SEP 7 1999
SFC COLD FRONT NEAR INL TO ATY AT 18Z. IT IS PRODUCING CLOUDS AHEAD OF
IT BUT NOT MUCH IN THE WAY OF PCPN. FURTHER AHEAD OF THE FRONT IS A
BROKEN LINE OF RW AND TRW IN NW WI AND E MN. THIS NOT ASSOCIATED WITH A
SFC OR UPR FEATURE...BUT WITH STRONG LOW LVL JET. THIS JET WAS ESCAPING
THE PROFILER NETWORK AT 18Z...AS BLUE RIVER WISCONSIN AND WHITE LAKE
MINNESOTA BOTH REPORTED SW WINDS AT 15 KNOTS AND SLATER IOWA HAD 25 KTS.
ACARS AIRCRAFT SOUNDING (ACWEB.FSL.NOAA.GOV FOR NOAA OFFICES) FROM MSP
AT 1753Z SHOWED 50 KT WINDS AT 850MB. MODELS HAVE ABT 40 KNOT WINDS AT
850MB. ETA/NGM/AVN HAVE TROUBLE WITH THIS CONVECTION OUT AHEAD OF FRONT,
BUT LAST NIGHT'S MESO ETA RUN DID AN EXCELLENT JOB. IT/S 850MB
CONVERGENCE ACCURATELY DEPICTED WHERE THE TRW STARTED EARLY THIS
MORNING. IT LIFTS THIS AREA TO THE NORTHEAST THIS EVENING AND WEAKENS
IT. 12Z MODELS ALSO SHOW 850MB JET LIFTING INTO CANADA. SO EXPECT TRW
NOW IN NW WI TO MOVE EAST AND FIZZLE OUT AS LOW LVL JET LIFTS TO THE
NORTHEAST. WILL KEEP LIKELY POPS IN NW ZONES BUT KEEP CHC POPS FURTHER S
AND EAST AS WE/LL HAVE TO RELY ON SFC FRONT TO PRODUCE PCPN THERE. WITH
STG PRESSURE RISES OVER PLAINS THIS AFTERNOON THE FRONT SHOULD BEGIN
ACCELERATING THIS EVENING. AS FRONT MOVES THROUGH AND 500MB LOW HEADS
TWDS GREAT LAKES 500MB TEMPS COOL TO NEAR -20C THURSDAY. THINK THERE
MIGHT BE INSTABILITY RW SO WILL KEEP THAT IN FORECAST.
.GRB...NONE.
RDM
RDM
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