AREA FORECAST DISCUSSION
NWS SEATTLE WA
AFDSEW 845 AM PDT FRI APR 27 2001
.OVERVIEW...
A RATHER HIGH ZONAL INDEX IS DEVELOPING OVER THE PACIFIC WITH A MEAN
TROUGH NEAR 140W. FAST MOVING SHORT WAVE SYSTEMS MOVING THROUGH THE
MEAN OFFSHORE TROUGH PROMISE TO BRING COOL AND UNSETTLED CONDITIONS
THROUGH MID WEEK NEXT WEEK. SATELLITE IMAGERY AND AIRCRAFT DATA SHOW
VARIOUS SHORT WAVE FEATURES AND THE STRENGTH OF THE JET WELL
INITIALIZED. MODELS SHOW GOOD CONSISTENCY AND CONTINUITY THROUGH
ABOUT WED OF NEXT WEEK.
.SHORT TERM...
IR/VISIBLE SATELLITE IMAGERY SHOW A WEAK FRONT MOVING SLOWLY EWD
THROUGH THE OFFSHORE WATERS...NOW NEARING 127W. EXTRAPOLATION OF THIS
FEATURE MOVES IT ONTO THE COAST ABOUT 00Z AND THROUGH THE INTERIOR BY
06Z. QPF WITH THIS FRONT VERY LIGHT. THEN ONSHORE GRADIENTS INCREASE
BEHIND THE FRONT AND THE AIR MASS DESTABILIZES AS COLD AIR ALOFT
MOVES IN. BY SAT EXPECT SHOWERS WITH ISOLATED THUNDERSTORMS. THE
ETA/MESOETA SOLUTIONS APPEAR TO BE UNDER-FORECASTING CAPE VALUES IN
THE INTERIOR SAT AFTN. THEY SHOW CAPES IN THE COASTAL WATERS NEAR 700
J/KG LATE TONIGHT JUST OFFSHORE THEN TAPER OFF TO 300-400J/KG AS THE
COLD AIR ALOFT MOVES INLAND. THIS IS TOO LOW GIVEN MAX TEMPS IN THE
MID 50S INLAND WITH SUN BREAKS. WILL KEEP CURRENT FORECAST WORDING
AND FORECASTS. THEN A STRONG FRONT NOW AT 168W MOVES THROUGH DURING
THE DAY SUN WITH PREFRONTAL GALES POSSIBLE ON THE COAST. NO CHANGES
FOR SUNDAYS FORECAST AT THIS POINT.
.EXTENDED...
ALL EXTENDED MODELS NOW SHOW POSSIBLE SHORT WAVE RIDGING WED TIME
FRAME. BUT THIS IS FOLLOWED BY YET ANOTHER STRONG SHORT WAVE TROUGH
THU. GIVEN SPEED OF JET WILL NOT MAKE CHANGES YET.
UIL ++8 SEA 467 OLM 467 ALBRECHT
.SEW...SMALL CRAFT ADVISORY COAST FOR ROUGH BAR CONDITIONS.
.KATX...VCP31/CSR31...OPERATIONAL