EXTREME SOUTHWESTERN CALIFORNIA AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
AFDSAN 310 AM PDT MON APR 10 2000
...SYNOPSIS...
AN UPPER LEVEL LOW PRESSURE SYSTEM OVER SOUTHERN NEVADA WILL MOVE
INTO ARIZONA TODAY BRINGING GUSTY WINDS TO THE MOUNTAINS AND DESERTS
OF SOUTHWEST CALIFORNIA. WEAK HIGH PRESSURE BUILDING OVER CALIFORNIA
WILL BRING A WARMING TREND TO SOUTHWEST CALIFORNIA TUESDAY AND
WEDNESDAY. A COASTAL EDDY WILL BRING NIGHT AND MORNING LOW CLOUDS
AND FOG TO COASTAL AREAS THROUGH TUESDAY MORNING.
...DISCUSSION...
WATER VAPOR IMAGERY SHOWS THE UPR LOW OVR SRN NV CONTINUING TO TRACK
SOUTHEASTWARD TOWARD AZ. YESTERDAYS PREFERRED STRONGER AVN SOLUTION
IS VERIFYING NICELY WITH OTHER SHORT RANGE MDLS NOW IN AGREEMENT
WITH THE STRONGER AVN SOLUTION. GUSTY NORTHWEST WINDS ACROSS THE
DESERTS AND NRN MTNS SHOULD DECR LATER TODAY...BECOME NLY TONIGHT...
AND WK NELY TUE. CSTL EDDY VERY MUCH IN EVIDENCE THIS MORNING AS
EXPECTED WITH CSTL LOW CLOUDS CONTINUING TO EXPAND NORTHWARD. 00Z
RAOB FM NKX SHOWED AN INVERSION BASE OF 1300 FT WITH A HIGH
RESOLUTION ACARS SOUNDING FM LAX AT 03Z SHOWING AN INVERSION BASE OF
1700 FT. OBSERVED CEILING HEIGHTS SUGGEST THE INVERSION BASE AT 09Z
IS BETWEEN 1500 AND 2000 FT. THIS DEPTH IS SUFFICIENT FOR AT LEAST
PATCHY LOW CLOUDS AND DENSE FOG TO SPREAD INTO THE INLAND EMPIRE BY
MORNING.
AS THE UPR LOW MOVES EASTWARD FM AZ TUE...HEIGHTS AND THICKNESS OVR
SRN CA WL BUILD TUE INTO WED WITH A WARMING TREND FOR ALL OF SW CA.
HIGHER RESOLUTION MDLS AND SYNOPTIC PATTERN SUGGEST THE POTENTIAL
FOR A WKR CSTL EDDY TONIGHT INTO TUE MORNING. DEVELOPING N FLOW
OVERNIGHT SHOULD RESULT IN THE NRN EXTENT OF THE STRATUS FOR TONIGHT
THRU TUE MORNING BEING A LTL LESS THAN THIS MORNING WITH FASTER
CLEARING FOR TUE.
EXTENDED...MDLS CONTINUE TO BE IN LESS THAN PERFECT AGREEMENT WITH
HANDLING THE EASTWARD MOVEMENT OF THE CLOSED UPR LOW PRESENTLY OVR
THE ERN PAC BETWEEN 140W AND 150W. BLEND OF MDLS WOULD BRING LWRG OF
HEIGHTS/THICKNESSES AND AN INCR IN ONSHR LOW LVL FLOW TO SRN CA FOR
WED THRU FRI WITH A COOLING TREND FOR ALL OF SW CA...BREEZY
CONDITIONS IN THE MTNS AND DESERTS...AND INCRG NIGHT AND MORNING
CSTL LOW CLOUDS EACH DAY. THIS IS HANDLED WELL IN THE CURRENT
PACKAGE WITH ONLY MINOR ADJUSTMENTS TO HIGH TEMPERATURES.
SAN 000
.SAN...NONE.
MARTIN
AREA FORECAST DISCUSSION
NWS SEATTLE WA
AFDSEW 230 AM PDT MON APR 10 2000
NEW PROGS CONT TREND OF BLDG UPR RDG OVR PACNW AND MOVG H5 RDG AXIS
EWD TO WA CST TDY. OFSHR UPR LOW NR 40N/145W IS STILL FCST TO DIG
FURTHER S...FORMING SRN PART OF REX BLOCK...THEN MOV EWD TO 38N/130W
BY WED AFTN. THIS PUTS NEW AVN/MRF SOLN A MORE LIKE 00Z CANADIAN GEM
MDL...THOUGH CANADIANS ARE FASTER AND HAVE NRN UPR RDG FURTHER W. SEE
EXTENDED DISCUSSION BELOW.
SHORT TERM PROBLEM IS HOW LONG TO HOLD STRATUS IN OVR W WA TDY. PER
MULTI-SPECTRAL SAT IMGRY...STRATUS IS FILLING IN OVR N INTR AND
SHOULD ENGULF KBLI-KFHR BY 12Z. CNTRL PGTSND ALREADY SWALLOWED
UP...AFT CLRG LAST EVENING. MORE WORRISOME IS HOW QUICKLY STRATUS WL
ERODE FM S. CLDS HAVE BEEN CLEARING RAPIDLY OVR ALL BUT EXTREME N
PTNS OF W OREGON. THIS TREND WL MAKE IT EASIER FOR SW WA TO CLR MORE
QUICKLY TDY. PGTSND CLD TOPS ABT 4000 FT AND 4C/39F THIS MORNING PER
ACARS SNDGS...WHICH WOULD NORMALLY REQUIRE ABT A 60F SFC TEMP TO MIX
OUT LATE THIS AFTN. HOWEVER...WARMG OF LOW LVL AMS FM DVLPG OFSHR
FLOW SHOULD HASTEN THE MIX-OUT. WL LV AFTN SUNSHINE IN CURRENT FCSTS
AS IS.
SFC THERMAL TROUGH MAKES IT UP ALG WA CST TUE...BUT THEN WITH OFSHR
UPR LOW MOVG IN TO 130W...SFC HI BLDS OFSHR B.C....AND LOOKS LIKE A
WEAK NW PUSH IS PSBL TUE NIGHT. UPR RDG DOESN'T BLD AS MUCH AS PVSLY
FCST AND CROSS CASCD OFSHR FLOW ISN'T TOO STRONG...SO WARM-UP WL ONLY
BE MODEST. WL UNDERCUT MOS MAX TEMPS SLGTLY.
EXTENDED...WITH NEW AVN/MRF MORE LIKE CANADIAN GEM SOLN. THIS SPELLS
SIGNIFICANT CHANGE IN THU/FRI FCST. DEFORMATION ZONE FM UPR LOW MOVS
UP FM SW OREGON WED AFTN TO NW OREGON THU MORNING ALG WITH
MSTR/INSTABILITY. THIS INTERACTS WITH TROF AXIS OVR SRN B.C. WITH BIG
PCPN BULLSEYE OVR PDX THU AFTN. WL ADD CLDS TO THU FCST AND CHC SHWRS
TO MAINLY SRN ZONES. FRI IS CLDY BUT NOT FM MARINE PUSH...VORT MAX IN
NRN BRANCH MOVS ACRS W WA...WL ADD CHC SHOWERS. KAM
UIL 100 SEA 100 OLM 100
.KATX...VCP32/CSR32...OPERATIONAL.
.SEW...NONE.
N