River Flood Warning 31, NWS Seattle, WA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
939 AM PDT SAT MAR 22 2014

.SYNOPSIS...A WEAK WARM FRONT WILL BRUSH BY NORTHWEST WASHINGTON
TODAY AND THIS EVENING. AN UPPER LEVEL RIDGE ACCOMPANIED BY LOW
LEVEL OFFSHORE FLOW WILL BRING MILD WEATHER SUNDAY AND MONDAY. THE
RIDGE WILL SHIFT EAST MONDAY NIGHT WITH THE NEXT FRONTAL SYSTEM
ARRIVING ON TUESDAY.

&&

.SHORT TERM...A SMALL SHORTWAVE SCOOTING ACROSS SRN B.C. TODAY WILL
BRING MODEST WARM ADVECTION AND AN INCRS IN MOISTURE TODAY...WITH
SOME LIGHT RAIN POSSIBLE ACROSS THE NRN THIRD OR HALF OF THE FCST
AREA. CURRENTLY HAVE LIKELY POPS THIS AFTN FOR THE NW OLYMPIC
PENINSULA...THE NORTH CASCADES...AND NEAR BLI. HAVE NO PRECIP IN THE
FCST OVER THE INTERIOR FROM SEATTLE ON SOUTH. THE FORECAST AND THE
WEATHER SETUP SEEM TO MATCH VERY WELL...SO NO FORECAST UPDATES THIS
MORNING.

AN UPPER RIDGE WILL AMPLIFY OUT NEAR 130W TONIGHT AND SUNDAY
MORNING. THE NW FLOW ALOFT WILL PUSH SOMEWHAT COOLER AIR INTO ERN WA
AND HELP INITIATE LOW-LEVEL OFFSHORE FLOW OVER WRN WA. THE UPPER
RIDGE AXIS WILL CROSS WRN WA ON MON MRNG...REACHING ERN WA ON MON
AFTN. WITH LOW-LEVEL OFFSHORE FLOW CONTINUING ON MON AND FLOW ALOFT
BECOMING SOUTHERLY...LOOKS LIKE A GOOD SETUP FOR ONE OF THE WARMER
DAYS SO FAR THIS YEAR. COULD SEE QUITE A FEW LOWLAND TEMPS REACHING
THE MID 60S...THAT IS IF THICKENING MID-UPPER LEVEL CLOUDS DO NOT
BLOT OUT TOO MUCH OF THE SUN'S WARMING RAYS.

HOWEVER...THE GFS BRINGS SOME LIGHT RAIN ON MON NEAR THE CANADIAN
BORDER...AT THE NOSE OF THE WARMING LOW-LEVEL AIR MASS. THE 12Z NAM
KEEPS PRECIP NORTH OF THE BORDER. COULD EASILY ENVISION INTRODUCING
LOW POPS NEAR THE CANADIAN BORDER ON MON WITH THE RELEASE OF THE
AFTN FCST PACKAGE.      HANER

.LONG TERM...FROM PREVIOUS DISCUSSION...A FRONTAL SYSTEM WILL MOVE
THROUGH THE AREA MONDAY NIGHT THROUGH TUESDAY NIGHT...BRINGING RAIN
AT TIMES TO THE AREA. A BAGGY UPPER TROUGH WILL REMAIN OVER THE AREA
WEDNESDAY AND THURSDAY FOR COOL SHOWERY WEATHER. BOTH THE ECMWF AND
GFS ARE NOW SUGGESTING AN ATMOSPHERIC RIVER EVENT AT THE END OF NEXT
WEEK. THE CURRENT FORECAST DOES NOT HAVE THIS. LATER SHIFTS WILL
PROBABLY NEED TO BOOST POPS AND QPF IF MODELS CONTINUE TO TREND IN
THIS DIRECTION. SCHNEIDER

&&

.HYDROLOGY...RIVER FLOODING IS NOT EXPECTED FOR THE NEXT 7 DAYS.

&&

.AVIATION...A WEAK UPPER LEVEL SHORT WAVE TROUGH WILL CLIP THROUGH
SOUTHERN B.C. TODAY. THE FLOW ALOFT IS NORTHWESTERLY. EXPECT
INCREASING CLOUDS ACROSS WESTERN WASHINGTON WITH LIGHT RAIN MAINLY
NEAR THE CANADIAN BORDER. VFR CONDITIONS WILL PREVAIL. AN UPPER
LEVEL RIDGE WILL BUILD OFFSHORE TONIGHT AND SUNDAY FOR DRY/STABLE
WEATHER. 33

KSEA...VFR CONDITIONS TODAY WITH LIGHT NORTHERLY FLOW AT THE
SURFACE. 33

&&

.MARINE...A WEAK FRONTAL SYSTEM WILL PASS INTO SOUTHERN BRITISH
COLUMBIA TODAY. HIGH PRES WILL BUILD OVER THE REGION ON SUNDAY FOR
GENERALLY LIGHT WINDS. OFFSHORE FLOW WILL INCREASE ON MON...WITH
SMALL CRAFT ADVISORY WINDS POSSIBLE OVER THE COASTAL WATERS AND
WESTERN STRAIT OF JUAN DE FUCA. A COLD FRONT WILL MOVE INLAND ON
TUE. 33

&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...NONE.

&&

YOU CAN SEE AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML