AREA FORECAST DISCUSSION
NWS SEATTLE WA
AFDSEW 915 AM PDT MON APR 2 2001
LATEST IR AND WATER VAPOR SATELLITE IMAGERY INDICATES UPPER LOW
CENTER NEAR S CENTRAL PART OF WA. SEVERAL VORTICITY LOBES ROTATING
AROUND UPPER LOW...ONE OF WHICH IS ALONG THE WA COAST AND MOVING S
THIS MORNING. THE FIRST FEW VISIBLE SATELLITE PICTURES SHOWS CLEARING
TO THE NORTH OF THIS SHORT WAVE VORT LOBE...OVER W VANCOUVER ISLAND
AND ALONG THE NW COAST.
ETA AND AVN INITIALIZED PRETTY WELL THIS MORNING AND KEEP THE UPPER
LOW OVER E WA THRU TUE MORNING THEN DROP THE LOW S OVER OREGON BY TUE
AFTERNOON/EVENING WITH THE LOW OFF N CALIF BY WED MORNING. THE AIR
MASS WILL VERY SLOW DRY OUT OVER W WA SINCE SIGNIFICANT N AND
OFFSHORE GRADIENTS WILL BE SLOW IN DEVELOPING THROUGH
TONIGHT...ESPECIALLY IN PUGET SOUND INTERIOR. HIGH POPS WILL DECREASE
TO CHANCE POPS TONIGHT AND FURTHER DECREASE ON TUE. MENTION OF
THUNDERSTORMS WILL BE LEFT IN AFTERNOON FORECAST DUE VERY UNSTABLE
AIR MASS BUT FORCING LACKING AND PREVAILING CLOUDS WILL INHIBIT MUCH
HEATING THIS AFTERNOON.
MORNING SNOW LEVELS DIPPED TO 400 TO 500 FEET THIS MORNING IN COLD
SHOWERS...BUT ACARS SHOW FREEZING LEVEL AROUND 2000 FEET. SPS AND NOW
FORECAST HAVE COVERED THE SITUATION. 500 MB TEMP OF AROUND -35 C IS
VERY COLD FOR APRIL...SO A MIXTURE OF WET SNOW/SMALL HAIL POSSIBLE
THRU AFTERNOON AND TONIGHT.
MINOR ADJUSTMENTS TO CURRENT FORECASTS.
UIL 642 SEA 743 OLM 854
.SEW...SMALL CRAFT COAST FOR OUTER WATERS.
.KATX...VCP21/CSR21...OPERATIONAL.