AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
235 AM PDT TUE JUN 1 1999
.OVERVIEW...A STRONG SURFACE AND UPPER LEVEL RIDGE ALONG 150W AND IN
THE ERN/CENTRAL US IS RESULTING IN SHORT WAVE ENERGY DROPPING SE INTO
THE PACIFIC NW FROM THE NORTHERN GULF OF ALASKA. WHILE THE SHORT TERM
MODELS... PARTICULARLY THE AVN...APPEAR WELL INITIALIZED OVER THE ERN
PAC PER ACARS DATA...THE STRONG RIDGING ALONG 150W APPEARS TO PRODUCE
A GOOD DEAL OF CONSISTENCY PROBLEMS WITH THE MODELS. THIS IS
PARTICULARLY APPARENT WITH THE VARIOUS GLOBAL SPECTRAL MODELS
(ECMWF/UKMO/MRF/CANADIAN)...SPECIFICALLY WITH REGARD TO THE AMPLITUDE
OF THE FLOW IN THE EXTENDED PERIOD. WITH THE OVERALL PATTERN OF A
STRONG LONG WAVE RIDGE ALONG 150W AND A TROF IN THE WEST...I WOULD
THINK THAT THE MORE AMPLIFIED MRF WOULD VERIFY BEST.
.SHORT TERM...THE WEATHER OVER WRN WA THRU WED WILL BE DOMINATED BY
AN UPPER LOW THAT IS DROPPING SE FROM QUEEN CHARLOTTE SOUND THIS
MORNING. THIS LOW IS EXPECTED TO BE SITUATED OVER THE FORECAST AREA
TONIGHT...LINGER NEARBY TIL WED NIGHT...THEN DROP S INTO NRN NV/NRN
CA THU. EXPECT RATHER WIDESPREAD PRECIPITATION OVER MOST OF THE CWFA
TODAY AS THIS LOW APPROACHES FROM THE NW...BUT WILL STAY WITH NEAR 50
POPS AT KSEA TODAY AS WLY FLOW OFF THE OLYMPICS PROVIDES CONVERGENCE
ZONE DOMINATED PRECIPITATION AND LOCAL DOWNSLOPE CONDITIONS SOUTHERN
PGTSND. POPS WILL BE RATHER HIGH TONIGHT AND WED AS THE UPPER LOW
COMES OVERHEAD THEN DROPS JUST TO OUR SOUTH BRINGING DEFORMATION BAND
MOISTURE INTO THE AREA. THE NGM LOOKS MUCH TOO DRY AND WARM. COOLING
MID LEVEL TROPOSPHERIC TEMPERATURES...PVA...LOW LEVEL
CONVERGENCE...AND A FEW BREAKS IN THE CLOUDS WITH DESTABILIZATION
SUGGEST THE NEED FOR A CHANCE OF THUNDERSTORMS THIS AFTERNOON AND
EVENING...PARTICULARLY PGTSND AREA.
.EXTENDED...MODELS ARE INTERNALLY CONSISTENT BUT THE MRF IS THE MOST
AMPLIFIED OF THE BUNCH. THE MRF APPEARS TO BE VERIFYING BEST OF LATE
SO WILL FOLLOW IT. LOOKS LIKE IMPROVING CONDITIONS THU AS THE UPPER
LOW DROPS S...UPPER CLOUDS BUT RATHER DRY CONDITIONS FRI WITH FLAT
RIDGE...THEN CHC PCPN WITH NEXT UPPER LOW SAT. TEMPERATURES WILL
LIKELY CONTINUE TO AVERAGE A COUPLE OF DEGREES BELOW NORMAL WITH
CLOUDS AND PREDOMINATELY ONSHORE FLOW.
UIL 877 SEA 577 OLM 677 ALBRECHT
.KATX...VCP21/CSR21...OPERATIONAL.
.SEW...GALE WARNING STRAIT OF JUAN DE FUCA.
SCA COAST AND CAMANO ISLAND TO PT ROBERTS.