198 FXUS66 KPQR 101000 AFDPQR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PORTLAND OR 300 AM PDT MON AUG 10 2015 .SYNOPSIS...A LOW PRESSURE SYSTEM CENTERED OFF THE WASHINGTON COAST ALONG 130W EARLY THIS MORNING WILL CONTINUE MOVING SOUTHWARD OFF THE COAST...REACHING WEST OF THE NORTHERN CALIFORNIA COAST TUESDAY... THEN LIFTING OUT TO THE NORTHEAST AND THROUGH THE PACIFIC NORTHWEST THURSDAY AND FRIDAY. LOOK FOR OCCASIONAL SHOWERS OR THUNDERSTORMS IN THE AFTERNOONS AND EVENINGS DURING THE WEEK THAT MAY DRIFT OUT INTO THE VALLEYS AND THE COAST RANGE AT TIMES IN THE EVENINGS AND OVERNIGHT PERIODS. THE BEST CHANCE OF MORE WIDESPREAD SHOWERS OR THUNDERSTORMS IS LATER THURSDAY INTO FRIDAY AS THE LOW MOVES ONSHORE AND INLAND. WARMER AND DRY WEATHER IS EXPECTED TO RETURN NEXT WEEKEND. && .SHORT TERM...AS ADVERTISED...A CLOSED UPPER LOW WAS LOCATED OFF THE WASHINGTON COAST EARLY THIS MORNING CENTERED ALONG 130W. THE LOW WILL CONTINUE TO MOVE SOUTHWARD AND WILL BE CENTERED OFF THE OREGON COAST THIS AFTERNOON. THIS WILL CAUSE THE FLOW ALOFT TO BACK TO MORE SOUTHERLY TODAY...WARMING THE AIR MASS SOME. A BAROCLINIC OR FRONTAL ZONE HAS DEVELOPED OVER THE COASTAL WATERS BUT WILL HAVE TROUBLE MAKING MUCH INLAND PROGRESSION TODAY DUE TO THE SOUTHERLY FLOW ALOFT. THE COAST MIGHT GET BRUSHED WITH A FEW SHOWERS THOUGH. TEMPS INLAND TODAY WILL BE IN AT LEAST THE MID 80S AND POSSIBLY THE UPPER 80S. THE MODELS ALSO INDICATE THAT CONVECTION WILL DEVELOP OVER THE CASCADES AND FOOTHILLS THIS AFTERNOON AS A SHORT WAVE LIFTS NORTH ALONG THE EASTERN PERIPHERY OF THE OFFSHORE LOW...AND POSSIBLY EVEN OVER THE VALLEY OR INTO THE COAST RANGE LATER TODAY OR TONIGHT. THERE IS SOME UPPER JET SUPPORT FOR THIS CONVECTION TODAY AND THIS EVENING...AND SOME OF THE THUNDERSTORMS THAT DO DEVELOP COULD BE STRONGER THAN WHAT WE NORMALLY SEE. AS THE LOW CONTINUES TO MOVE SOUTH TONIGHT INTO TUESDAY...THE UPPER FLOW TURNS SOUTHEASTERLY AND WILL CAUSE ANY RESIDUAL ACTIVITY TO DRIFT OUT OVER THE VALLEYS AND TOWARD THE COAST RANGE TONIGHT. THINGS SHOULD SETTLE DOWN BY TUESDAY MORNING AS THE LAST OF THE MOISTURE DRIFTS OUT OVER THE COASTAL WATERS AND WEAKENS. THE LOW WILL CONTINUE TO MOVE SOUTH AND BE CENTERED SOUTH OF 40N AND WEST OF 130W OFF THE NORTHERN CALIFORNIA COAST BY LATER TUESDAY. THERE IS AGAIN A CHANCE OF THUNDER OVER THE CASCADES TUESDAY AFTERNOON THAT COULD DRIFT OUT OVER THE VALLEYS TUESDAY NIGHT UNDER PREVAILING SOUTHEAST FLOW ALOFT. THE AIR MASS WILL CONTINUE TO BE QUITE WARM TO THE EAST AND NORTHEAST OF THE LOW ON TUESDAY...AND INLAND TEMPS MAY APPROACH 90 ON TUESDAY. THE LOW MEANDERS OFF THE NORTHERN CALIFORNIA COAST WEDNESDAY. THE MODELS SUGGEST THAT AFTER THE RESIDUAL CONVECTIVE ACTIVITY FROM TUESDAY NIGHT DRIFTS NORTHWEST AND AWAY FROM OUR AREA WEDNESDAY MORNING...THAT ACTIVITY WILL BE LESS WEDNESDAY AFTERNOON AND EVENING. HAVE KEPT A SLIGHT CHANCE OF AFTERNOON AND EVENING THUNDER OVER THE CASCADES. THE MODELS SHOW OUR CURRENT SOUTH WINDS ALONG THE COAST THIS MORNING TURNING NORTHERLY IN THE WAKE OF THE LOW LATER TODAY AND TONIGHT. THE WINDS THEN TURN BACK TO SOUTHERLY AGAIN WEDNESDAY AS A SOUTHERLY WIND REVERSAL AND STRATUS SURGE MOVES UP THE COAST IN RESPONSE TO SHORT WAVE MOVING NORTH ALONG THE COAST. THIS SHOULD BUILD THE MARINE LAYER ALONG THE COAST AND IS THE FIRST STEP IN STARTING TO INCREASE THE ONSHORE FLOW. WE MAY SEE SOME PATCHY DRIZZLE IN THIS STRENGTHENING MARINE LAYER. THE SOUTHERLY WINDS THAT DEVELOP ALONG THE COAST WEDNESDAY MAY BE A BIT BREEZY AS WELL. TOLLESON .LONG TERM...THE LOW THAT DROPPED SOUTH ALONG THE COAST DURING THE EARLY PART OF THE FORECAST IS EXPECTED TO APPROACH THE OREGON COAST THURSDAY AND MOVE NORTHEAST ACROSS SOUTHWEST WASHINGTON AND NORTHWEST OREGON THURSDAY NIGHT AND EARLY FRIDAY. THIS WILL BRING AN INCREASED CHANCE OF SHOWERS...WITH A FEW THUNDERSTORMS POSSIBLE DUE TO INSTABILITY FROM THE COLD POOL ALOFT WITH THE UPPER LOW. THIS WILL ALSO BRING A STRONG SOUTHWEST MARINE PUSH TO OUR FORECAST AREA WITH WIDESPREAD CLOUDS AND COOLER TEMPS THROUGH FRIDAY. THE MODELS ARE THEN GENERALLY DRY FOR THE WEEKEND BUT DIFFER ON HOW WARM IT WILL BE...AND HAVE OPTED FOR A BLEND OF THE MODELS FOR NOW AS NORTHWEST FLOW ALOFT PREVAILS. THE MODELS HINT AT ANOTHER TROUGH DROPPING DOWN FROM THE NORTHWEST EARLY NEXT WEEK...BUT THE GFS IS STRONGER AND DIGS IT MORE SOUTHWARD WHILE THE ECMWF KEEPS THE MAIN PART OF THE TROUGH SLIDING BY TO OUR NORTH. HAVE OPTED TO STAY DRY FOR NOW BUT WITH SOME ONSHORE FLOW CONTINUING/INCREASING. TOLLESON && .AVIATION...VFR CONDITIONS WITH CIGS BETWEEN 10K-25K FT WILL GENERALLY PERSIST NEXT 24 HRS FOR INLAND SITES. MVFR AND IFR CIGS ALONG THE COAST WILL CONTINUE TONIGHT UNDER SOUTH-SOUTHWEST FLOW...BUT CIGS APPEAR TO BE RISING PARTICULARLY ALONG THE N OR COAST. EXPECT MOSTLY MVFR CIGS ON THE COAST THROUGH MORNING. FOR MON...CHANCE OF TSRA FROM THE COAST RANGE EASTWARD IN THE LATE AFTERNOON AND EVENING BUT WITH DISAGREEMENT AMONG MODELS...WILL LEAVE OUT MENTION FOR NOW. KPDX AND APPROACHES...VFR NEXT 24 HOURS. SLIGHT CHANCE SHRA OR TSRA MAINLY AFTER 00Z. BOWEN && .MARINE...NOT MUCH CHANGE TO THE FORECAST WITH WINDS BELOW ABOUT 15 KTS AND SEAS AROUND 4 FT THROUGH MUCH OF THE WEEK. WEAK SURFACE LOW CURRENTLY SITS OFF THE WASHINGTON COAST OVER THE OFFSHORE WATERS BUT BIGGEST IMPACT WILL BE VARIABLE WIND DIRECTION WITH A VARYING DEGREE OF SOUTH OR WEST COMPONENT IN THE WIND AS THE LOW SLOWLY DRIFTS THROUGH THE REGION OVER THE NEXT 48 HOURS. SURFACE HIGH PRESSURE BUILDS OVER THE NE PACIFIC STARTING MIDWEEK AND ESPECIALLY INTO LATE WEEK. THE NEXT THREAT FOR SMALL CRAFT ADVISORY STRENGTH WINDS LOOKS TO BE AROUND FRIDAY AS THERMAL LOW PRESSURE DEEPENS ALONG THE N CALIFORNIA/SW OREGON COAST. HOWEVER MODELS HAVE AT LEAST TEMPORARILY BACKED OFF ON WINDS LATE WEEK. BOWEN && .PQR WATCHES/WARNINGS/ADVISORIES... OR...RED FLAG WARNING FROM NOON TODAY TO 11 PM PDT TUESDAY FOR CENTRAL OREGON CASCADE FOOTHILLS-MT. HOOD NATIONAL FOREST WEST OF CASCADE CREST-NORTH OREGON CASCADE FOOTHILLS- WILLAMETTE NATIONAL FOREST. WA...FIRE WEATHER WATCH FROM 1 PM PDT THIS AFTERNOON THROUGH LATE TONIGHT FOR EXTREME SOUTH WASHINGTON CASCADES AND FOOTHILLS. PZ...NONE. && $$ INTERACT WITH US VIA SOCIAL MEDIA WWW.FACEBOOK.COM/NWSPORTLAND WWW.TWITTER.COM/NWSPORTLAND THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS COMMONLY REFERRED TO AS THE FORECAST AREA.