 |
Forecast Discussion:NW Oregon - SW Washington
830 PM PDT SUN SEP 07 2008SYNOPSIS
AN UPPER RIDGE OVER THE EASTERN PACIFIC WILL BE THE PERSISTENT LARGE SCALE FEATURE THROUGH MUCH OF THE COMING WEEK. THERE WILL BE SOME WEAK UPPER LEVEL DISTURBANCES RIDING OVER THE RIDGE AND DOWN INTO THE ROCKY MOUNTAIN REGION THAT WILL AFFECT THE ONSHORE FLOW AND MARINE LAYER AT TIMES. ONE DISTURBANCE TO OUR NORTH WILL TURN THE FLOW ONSHORE MONDAY NIGHT AND TUESDAY AS AN UPPER TROUGH CARVES OUT OVER THE ROCKY MOUNTAIN REGION AGAIN. THE UPPER RIDGE WILL THEN REBUILD WEDNESDAY AND THURSDAY FOR ANOTHER WARMING PERIOD BEFORE THE NEXT DISTURBANCE RETURNS ONSHORE FLOW TO THE AREA AT THE END OF THE WEEK. &&
SHORT TERM
CLEAR SKIES WILL CONTINUE OVER THE REGION TONIGHT INCLUDING THE COASTAL WATERS...BUT THERE COULD BE SOME MINOR FOG PATCHES NEAR THE COASTLINE TOWARD DAYBREAK MON. THE SURFACE THERMAL TROUGH WILL REMAIN CLOSE TO THE COAST TONIGHT AND EARLY MON...FOR ANOTHER PLEASANT WARM LATE SUMMER DAY IN THE NW. INLAND TEMPS WILL BE CLOSE TO THOSE TODAY. THE THERMAL TROUGH SHIFTS EAST LATE MON AND REACHES E OF THE CASCADES MON EVENING AS A WEAK UPPER DISTURBANCE MOVES IN FROM THE NW... TURNING THE LOW LEVEL FLOW ONSHORE AND DEVELOPING A MARINE LAYER ON THE COAST THAT WILL PUSH INTO THE COASTAL GAPS OVERNIGHT MON NIGHT. THE MODELS ARE SHOWING A FAIR AMOUNT OF LOW CLOUDS INLAND TUE MORNING FOR THE VALLEYS...LOWER COAST RANGE AND FOOTHILLS...THAT WILL TAKE SOME TIME TO BREAK UP IN THE AFTERNOON. THE CASCADES AND HIGHER COAST RANGE PEAKS APPEAR TO REMAIN ABOVE THE CLOUDS ALTHOUGH TEMPS WILL BE LOWER IN A COOLER AIR MASS. CLOUDS MAY PERSIST ON THE COAST AND NEAR THE MOUNTAINS THROUGH MUCH OF THE DAY AS THE WESTERLY ONSHORE FLOW REMAINS STRONG ALL DAY. WILL NEED TO WATCH WHETHER WE CAN GET SOME DRIZZLE ON THE COAST EARLY TUE. CLOUDS WILL CONTINUE TUE NIGHT AND WED MORNING...THEN CLEAR WED AFTERNOON AS HIGHER PRESSURE BEGINS TO BUILD BACK INTO THE PAC NW. RW
LONG TERM
NO CHANGES. PREVIOUS DISCUSSION FOLLOWS... HIGH PRESSURE BUILDS OVER THE PACIFIC NORTHWEST WEDNESDAY NIGHT INTO THURSDAY FOR CLEARING SKIES AND SOME WARMING ON THURSDAY. THIS WILL BE SHORT-LIVED HOWEVER AS AN UPPER LEVEL TROUGH MOVING INTO BRITISH COLUMBIA FLATTENS THE RIDGE THURSDAY NIGHT INTO FRIDAY. ONSHORE FLOW SHOULD RETURN FRIDAY THROUGH THE WEEKEND...FOR CLOUDY CONDITIONS AND A RETURN TO MORE NORMAL TEMPERATURES FRIDAY AND SATURDAY. LATEST MODEL RUNS INDICATE A REBUILDING OF THE RIDGE TO BEGIN NEXT WEEK...WILL HAVE TO WAIT FOR FURTHER RUNS TO SOLIDIFY THIS SOLUTION. BROWN &&
AVIATION
HIGH OFFSHORE EXTENDING INTO NORTHERN ROCKIES TONIGHT. THERMAL TROUGH ALONG COAST SHIFTS OFFSHORE OVERNIGHT. THERMAL TROUGH SHIFTS TO CENTRAL OREGON MONDAY AFTERNOON. NORTHERLY FLOW THIS EVENING BECOMES LIGHT OFFSHORE LATER TONIGHT AND MONDAY MORNING. NORTHWEST FLOW INCREASES MONDAY AFTERNOON AS THERMAL TROUGH SHIFTS EAST. VFR CONDITIONS OVER ALL THE AREA TONIGHT. A FEW FOG PATCHES ARE POSSIBLE ALONG THE COAST LATE TONIGHT AND EARLY MONDAY WITH LOCAL IFR CONDITIONS. CONDITIONS WILL REMAIN VFR ON MONDAY. KPDX AND APPROACHES...VFR CONDITIONS IN THE KPDX AREA TONIGHT AND MONDAY. &&
MARINE
STRONG HIGH PRESSURE OFFSHORE TONIGHT AND MONDAY. THERMAL TROUGH ALONG COAST SHIFTS OFFSHORE LATER TONIGHT. THERMAL TROUGH SHIFTS BACK ASHORE MONDAY MORNING THEN MOVES FURTHER INLAND MONDAY AFTERNOON. SMALL CRAFT WINDS WILL RETREAT TO THE OUTER WATERS AFTER MIDNIGHT. SMALL CRAFT WINDS WILL GRADUALLY PUSH TO BEACHES MONDAY AS THE THERMAL TROUGH SHIFTS EASTWARD. SEAS WILL REMAIN BELOW 10 FEET TONIGHT AND MONDAY. HAZARDOUS SEAS DUE TO CHOPPY SEAS FROM WIND GENERATED WAVES WILL OCCUR OVER THE CENTRAL COAST TONIGHT AND MONDAY MORNING AND OVER ALL THE WATERS MONDAY AFTERNOON. &&
PQR WATCHES/WARNINGS/ADVISORIES
OR/WA...SMALL CRAFT ADVISORY FOR WINDS CAPE SHOALWATER TO FLORENCE THROUGH MON NIGHT. SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS CASCADE HEAD TO FLORENCE TONIGHT THROUGH MON NIGHT. SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS CAPE SHOALWATER TO CASCADE HEAD MONDAY AFTERNOON AND MONDAY NIGHT. &&
PRELIMINARY POINT POPS (PROBABILITY OF MEASURABLE PRECIPITATION)