EXTREME SOUTHWESTERN CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
850 AM PDT FRI MAY 14 1999
...SYNOPSIS...
A BROAD UPPER TROUGH WILL REMAIN ACROSS THE WEST THROUGH SUNDAY WITH
A COASTAL EDDY EACH NIGHT AND MORNING FOR SOUTHERN CALIFORNIA. THIS
WILL CONTINUE THE EXTENSIVE NIGHT AND MORNING LOW CLOUDS WEST OF THE
MOUNTAINS WITH BREEZY CONDITIONS IN THE MOUNTAINS AND DESERTS.
...DISCUSSION...
ONLY MINOR CHANGES IN THE PATTERN AFFECTING SRN CA THE NEXT TWO DAYS
AS THE BROAD UPPER TROUGH CONTINUES OVR THE WRN U.S. WITH LOW LVL
FLOW/PRESSURE GRADIENTS OVR SRN CA FAVORABLE FOR A CSTL EDDY NIGHT
THRU MORNING HOURS THRU SUN MORNING. AS THE UPR TROUGH AXIS
SHARPENS AND MOVES EAST ON SUN AND MON...SHORTWAVE RDGG ALF AND LOW
LVL FLOW UNFAVORABLE FOR EDDY DEVELOPMENT SHOULD FINALLY RESULT IN A
DECRG MARINE INFLUENCE W OF THE MTNS SUN NIGHT AND MONDAY.
ACARS SOUNDINGS THIS MORNING SHOW THE MARINE LYR DEEPENED SLIGHTLY
IN THE PAST 24 HOURS TO AROUND 4500 FEET THIS MORNING...UP FM 4000
FT THU MORNING. PAST TWO RUNS OF THE COAMPS MDL
(HTTP://205.67.220.5/TAMS/) HAVE SHOW THE EDDY CRCLN DRIFTING S AND
DISSIPATING DURG THE DAY TODAY (NORMAL DIURNAL DECAY OF THE EDDY)
WITH WK ONSHR W TO NW FLOW DEVELOPING THIS AFTERNOON AT LOW LVLS
AS OPPOSED TO THE PERSISTENT S FLOW ALG THE CST YESTERDAY AFTERNOON.
03Z ETA 850 MB RH SHOWS A DECR IN 850 MB RH W OF THE MTNS TODAY.
THIS...IN COMBINATION WITH THE DECAY OF THE EDDY...SHOULD ALLOW FOR
FASTER...GREATER CLEARING W OF THE MTNS. HOWEVER...WITH MDT ONSHR
LOW LVL FLOW CONTINUING AND WITH THE REDEVELOPMENT OF THE EDDY
TONIGHT...LOW CLOUDS SHOULD SPREAD QUICKLY INLAND TO THE LOWER CSTL
SLOPES THIS EVENING.
DEEP MARINE LYR...INCR IN ONSHR FLOW...AND LIFT PROVIDED BY A
SHORTWAVE MOVG ACROSS SRN CA SAT NIGHT...COULD BE SUFFICIENT FOR
MEASURABLE DRIZZLE OR LIGHT RAIN TO DEVELOP ALG AND W OF THE MTNS
FM THE INLAND EMPIRE AND ORANGE COUNTY S. WL TAKE A CLOSER LOOK AT
THIS FOR THE AFTERNOON ISSUANCE.
SAN 000
.SAN...NONE.
MARTIN
ILLINOIS STATE FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO IL
234 PM CDT FRI MAY 14 1999
MAIN CONCERNS THIS FCST PKG INCLUDE PSBL RETURN OF CLOUDS FROM SE
TNGT...AND PCPN CHCS LATE SAT/EARLY SUN.
MEAN TROF OVR WRN US...WITH WEAKENING UPR RDG IN THE EAST. PESKY UPR
LOW THAT AFFECTED IL ON WED DRIFTING SE OVR THE CAROLINAS. MODELS
FAIRLY CONSISTENT IN CONTG TO WKN ERN RDG...AND EJECTING SEVERAL
WEAK IMPLUSES OUT OF POS TILT WRN TROF INTO THE PLAINS NEXT SVRL
DAYS.
VIS SAT IMGRY SHOWING SC/AC CLOUD DECK S OF UIN-SPI-SBN LINE AT 18Z.
SOME CONCERN THAT THESE CLOUDS WOULD ADVECT BACK TO THE NW THIS
AFTERNOON...INTO NRN IL. 1835Z ACARS SOUNDING OUT OF ORD CONFIRMS
MODEL FCSTS OF FLOW BECOMING MORE SERLY FROM ABOUT H85 ON UP...BUT
SUBSIDENCE ASSOCIATED WITH ADVANCING UPR RDG AXIS AND DRY NERLY SFC
FLOW HELPING TO ERODE NRN EDGE OF CLOUD DECK. AS FLOW BECOMES MORE
SRLY TONIGHT COULD SEE CLDS MOVE BACK INTO NRN IL. MODEL TIME SCTNS
SHOW INCRS IN LOW LVL RH OVRNGT...SO SOME AMNT OF CLOUDS TNGT
REASONABLE. MID/HIGH CLDS TO MOV INTO IL SAT...FROM CONVECTION OVR
PLAINS TO OUR WEST LTR TONIGHT.
S/WV SEEN IN WV IMGRY LIFTING TO NORTHEAST OUT OF CO THIS AFTERNOON
WL BRING BEST UPR DIVERGENCE AND 850-500MB Q VECTOR CONV TO PTNS OF
CNTRL AND NRN PLNS TNGT. SCND S/WV FCST BY ETA TO LIFT OUT A BIT
FARTHER TO EAST SATURDAY NIGHT...WITH DECENT H85 WAA AND 40KT LO LVL
JET ORIENTED MORE TOWARD ERN IA/NWRN IL BY 12Z SUN. H85 WRMFNT THEN
LIFTS TO THE NORTH ON SUNDAY...WITH BEST PCPN CHCS ENDING SUN AM.
THUS WL CONT CHC POPS FOR SAT NGT INTO EARLY SUN.
TEMP WISE...FAN/FWC NUMBERS VERY CLOSE...AND WL FOLLOW CLOSELY. MAY
GO A BIT ABOVE GUIDANCE SUNDAY...AS PROGGED H85 TEMPS WOULD SUGGEST
PSBLY BREAKING THE 80 DEG MARK. OF COURSE...CHI AREA COOLER DUE TO
LK BREEZE.
.CHI...NONE.
RATZER