EXTREME SOUTHWESTERN CALIFORNIA AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
AFDSAN 300 AM PDT FRI MAY 4 2001
...SYNOPSIS...
HIGH PRESSURE WILL BUILD OVER THE INTERIOR WEST THROUGH THE WEEKEND
BRINGING A WARMING TREND TO THE MOUNTAINS AND DESERTS. A COASTAL
EDDY WILL BRING INCREASING NIGHT AND MORNING LOW CLOUDS AND FOG TO
THE COAST...EXTENDING LOCALLY INTO THE INLAND VALLEYS DURING THE
WEEKEND INTO NEXT WEEK.
...DISCUSSION...
IN THE NR TERM...THU EVENING ACARS SOUNDINGS SHOWED THE BASE OF THE
MARINE INVERSION NR 1200 FT NRN ORANGE COUNTY TO 2000 FT SRN CA
COUNTY. SOUNDINGS FM ONT SINCE 09Z SHOWED WINDS IN THE LOWEST 5000
FT HAVE BECOME WK WLY. WL REMOVE ANY REMAINING OFSHR WINDS FM ZONES.
OFSHR WINDS AND ASSOCD LOW LVL DRYING OCCURRED AS FAR S AS SRN
ORANGE COUNTY THU WITH CSTL DRYING NOT EXTENDING INTO SAN COUNTY.
WITH CSTL EDDY IN PLACE...STRATUS HAS STARTED TO REDEVELOP ALG THE
SAN COUNTY CST...BUT DEVELOPMENT FARTHER N ALG THE ORANGE COUNTY CST
WL BE A STRUGGLE THIS MORNING FOLLOWING THE DRYING THAT OCCURRED
THU. HOWEVER...RAPID RECOVER NOTED IN SNA DEWPOINTS THE PAST FEW
HOURS PORTENDS AT LEAST PATCHY STRATUS COVERAGE ALG THE ORANGE
COUNTY CST FOR THIS MORNING. WK DIURNAL EDDY WL CONTINUE THRU THE
WEEKEND. STRATUS SHOULD DEVELOP OVERNIGHT ALG MUCH OF THE SAN COUNTY
CST...SAN COUNTY CST EARLIER AND ORANGE COUNTY CST AND LWR SAN
COUNTY VLYS LATE.
EXTENDED...ECMWF PREFERRED. TEMPERATURES WILL WARM FM THE MTNS
INLAND THE NEXT TWO DAYS...THEN CHANGE LTL THRU THE MIDDLE OF NEXT
WEEK. PROGRESSION OF SHORTWAVES INTO NRN CA AND THE PAC NW WL KP A
GREATER MARINE INFLUENCE FOR CSTL SXNS THAN SHOW BY THE AVN/MRF WITH
HIGH TEMPERATURES W OF THE MTNS CORRESPONDINGLY COOLER THAN SHOWN BY
THE MRF MOS GUIDANCE.
SAN 000
.SAN...NONE.
MARTIN
AREA FORECAST DISCUSSION
NWS CHICAGO IL
AFDCHI 300 AM CDT FRI MAY 4 2001
THE FRONT LIES FROM KANKAKEE TO BELLEVUE ILLINOIS. THE ACARS
SOUNDING FROM RFD SHOWS A REASONABLY DEEP LAYER OF MOISTURE WITH TWO
DRY LAYERS AROUND 900 AND 820 MB. RADAR SHOWS THE THUNDERSTORMS AND
SHOWERS MOVING VERY SLOWLY EAST AT THE WESTERN EDGE OF THE FORECAST
AREA. ALTHOUGH THE IR LOOPS SHOW WARMING CLOUD TOPS WILL KEEP AN EYE
ON THE SHOWERS AS THEY ARE MOVING IN TRAIN LIKE FASHION OVER THE
SAME AREA. SO FAR RAIN AMOUNTS HAVE BEEN BELOW FLASH FLOOD GUIDANCE.
THE FRONT WILL SLOWLY TILT EAST AS THE SHORT WAVE TROUGH AT 500 MB
MOVE EAST ACROSS WISCONSIN AND MICHIGAN THROUGH SATURDAY MORNING.
WILL PUT LIKELY POPS IN THE WEST PART OF OUR FORECAST AREA OF
NORTHEAST ILLINOIS AND NORTHWEST INDIANA. THEN HAVE CHANCE POPS FOR
CHICAGO AND OUR SOUTH AREAS INCLUDING KANKAKEE AND OTTAWA FOR TODAY.
AS THE FRONT TILTS EAST THIS WILL BRING WARMER AIR ON SUNDAY AS
WELL. THE NEXT VORTICITY MAXIMUM AND SHORT WAVES IS FORECASTED TO
MOVE INTO THE AREA SUNDAY NIGHT. THIS IS USING A TIMING OF THE
CIRCULATION OUT WEST FROM IR LOOPS AND AN AVERAGE BETWEEN THE ETA
AND AVN MODELS. WILL RELY ON THE AVN GUIDANCE FOR TEMPERATURES AND
MAY BE GO A LITTLE WARMER FOR HIGHS AND LOWS.
.CHI...NONE
$$
WHW