AREA FORECAST DISCUSSION
NWS SEATTLE WA
AFDSEW 900 AM THU MAR 9 2000
WATER VAPOR IMAGERY SHOWS THAT OLD LOW W OF PACNW CST HAS WEAKENED
INTO NW-SE ORIENTED UPR TROF AXIS ALG THE CNTRL OREGON CST. NWD
MOVEMENT IS ABT 20KTS WHICH FITS NEW 12Z ETA...PUTTING IT ALG KAST-
KPDX LINE ARND MIDDAY AND ACRS SW WA THIS AFTN. THUS WITH UPR TROF
AXIS STILL APCHG DON'T SEE ANY MECHANISM FOR STABILIZATION.
AMS OVR W WA THIS MORNING IS MOIST AT LOW LVLS AND SOMEWHAT
UNSTBL...WITH VSBL IMGRY SHOWING SOME BREAKS IN CLD CVR. KUIL
SOUNDING HAD -1 LIFTED INDEX THIS MORNING AND PGTSND ACARS SNDGS HAVE
SMLR PROFILE. MODIFIED 12Z ETA SNDG FOR 00Z SHOWS POTENTIAL LFC/LCL
NR 2500 FT WITH EL JUST ABV FL200. WL ADD SCT SHWRS TO FCST FOR THIS
AFTN/EVENING...AND WITH SNOWLVL NR 3000 FT WL MENTION SOME ICE
PELLETS. WOULDN'T SURPRISE ME TO SEE SOME LGTNG EITHER...BUT WL HOLD
OFF FROM TSTM WORDING FOR NOW.
12Z AVN/ETA HAVE TROF AXIS MOVG THRU THIS EVENING WITH BRIEF UPR RDG
OVR W WA THRU MIDDAY FRI AS DVLPG WAVE 40N/140W APCHS. THIS WAS OLD
FULL LATITUDE OCCLUSION YDA AND APCHG UPR TROF IN SRN BRANCH WLYS HAS
CAUSED A BAROCLINIC LEAF TO DVLP. AVN/ETA VRY SMLR THRU 48HRS IN
BRINGING A NEG TILT FRONT TO WA CST FM THE SW FRI AFTN THEN A
TRAILING UPR TROF AND CD POOL ALF FM W ON SAT. FCSTS ON TRACK AND
MDLS ACCEPTED. WL TREND POPS FM SW ON FRI WITH LIKELY CST/SW INTR
DURG AFTN AND CHC ELSEWHERE. KAM
UIL 338 SEA 434 OLM 436
.KATX...VCP21/CSR21...OPERATIONAL
.SEW...NONE.
N