765
FXUS66 KPQR 062118
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
218 PM PDT SUN JUL 6 2025
SYNOPSIS
WEAK HIGH PRESSURE ALOFT WITH ONSHORE FLOW AT THE
SURFACE. WARMING TEMPERATURES THROUGH TUESDAY WITH MODERATE
HEATRISK IN THE INLAND LOWLANDS MONDAY AND TUESDAY. COOLER ON
WEDNESDAY AND THURSDAY AS A BROAD LOW ALOFT MOVES NORTHWARD.
FOR THE LATTER PART OF THE WEEK WARMING RETURN AS HIGH PRESSURE
ALSO RETURNS.
SHORT TERM...TONIGHT THROUGH TUESDAY NIGHT
BROAD AREA OF
HIGH PRESSURE BUILDS THROUGH THE START OF THE WEEK. AT THE SAME
TIME, AN UPPER LEVEL LOW WILL PARK OVER NORTHERN CALIFORNIA
THROUGH TUESDAY. WITH RIDGE OF HIGH PRESSURE POLE-WARD ALONG
WITH AN UNDERCUTTING LOW, THIS CREATES A REX BLOCKING PATTERN.
NOW, THIS BLOCKING PATTERN IS VERY WEAK, GIVEN THAT THE UPPER
LEVEL RIDGE IS NOT VERY ROBUST. HOWEVER, THIS PATTERN WILL BRING
ABOUT A WARMING AND DRYING TREND FOR THE FORECAST AREA THROUGH
TUESDAY NIGHT. DAYTIME HIGHS AT THIS TIME ARE FORECASTED TO BE
IN THE UPPER 80S TO LOW 90S FOR INLAND LOCATIONS AND INTO THE
UPPER 60S TO LOW 70S ALONG THE COAST. HIGHEST TEMPERATURES ARE
EXPECTED ON MONDAY. ON TUESDAY, THE UPPER LEVEL LOW THAT IS
FORMING THE REX BLOCK, WILL START TO MEANDER NORTHWARD ALONG THE
CALIFORNIA COAST. AS THAT UPPER LEVEL LOW MOVES NORTHWARD, THE
GREAT BASIN SURFACE LOW WILL ALSO RESULT IN A TIGHTENING OF THE
PRESSURE GRADIENT ALONG THE CASCADES AND COULD SEE GUSTS UP TO
30 MPH FOR THE CENTRAL AND EASTERN PARTS OF THE COLUMBIA RIVER
GORGE ON TUESDAY.
MONDAY AND TUESDAY WILL ALSO HAVE MODERATE HEATRISK FOR THE
WILLAMETTE VALLEY, CLARK COUNTY LOWLANDS AND THE GORGE. THOSE
SENSITIVE TO HEAT SHOULD TAKE PRECAUTIONS AND EVERYONE SHOULD
REMAIN HYDRATED. /42
LONG TERM...WEDNESDAY THROUGH SATURDAY
AS WEDNESDAY
APPROACHES, THE REX BLOCK WILL CONTINUE TO BREAK DOWN AS BOTH
THE UPPER LEVEL RIDGE BECOMES MORE ZONAL AND THE UPPER LEVEL LOW
CONTINUES TO PUSH EASTWARDS TOWARDS EASTERN OREGON. THIS
PATTERN CHANGE WILL ALSO BRING ABOUT RELATIVELY COOLER AND
MOISTER AIR INTO THE REGION. 850 MB TEMPERATURES WILL DROP FROM
16-18 DEG C ON TUESDAY TOWARD 8-10 DEG C ON WEDNESDAY AND
THURSDAY. ONE NEWER FEATURE THAT HASN'T BEEN REALIZED YET IN
PREVIOUS MODEL RUNS IS A WEAK MESO-LOW AND SHORTWAVE TROUGH AT
THE MID-LEVELS FORMING OVER WASHINGTON. THE ADDED INSTABILITY
COMBINED WITH MOISTER AIR AND COOLING TEMPERATURES IS BRINGING A
SLIGHT CHANCE (LESS THAN 25%) OF VERY LIGHT PRECIPITATION TO
SOUTHWEST WASHINGTON, AND LESS THAN A 10% CHANCE OF ISOLATED
SHOWERS ALONG THE CENTRAL OREGON CASCADES. CONFIDENCE IS VERY
LOW THOUGH AS THE PATTERN COULD EASILY SHIFT IF THE LOW TRACKS A
BIT FURTHER NORTH. OVERALL, MOST PLACES SHOULD REMAIN DRY. WITH
ALL THAT SAID, ANY PRECIPITATION THAT DOES FALL WILL BE LIGHT,
BRIEF AND RESULT IN LITTLE TO NO ACCUMULATIONS.
THURSDAY WILL BE DRY ONCE AGAIN WITH NEAR NORMAL HIGH
TEMPERATURES IN THE 80S INLAND. AS THE LATTER PART OF THE WEEK
AND THE WEEKEND APPROACHES, MODELS ARE SHOWING A BROAD, UPPER
LEVEL RIDGE RETURNING TO THE EASTERN PACIFIC. SOME MODELS ARE
ALSO SHOWING A MESO-LOW DEVELOPING AGAIN NEAR NORTHERN
CALIFORNIA. EITHER OF THESE SCENARIOS LOOK TO BRING BACK A
WARMING PATTERN FOR THE REGION AND COULD EASILY BE A REPEAT (OR
VERY SIMILAR) OF MONDAY AND TUESDAY. AS A RESULT, DAYTIME HIGHS
COULD WARM RIGHT BACK INTO THE UPPER 80S TO LOW 90S FOR INLAND
LOCATIONS, WHILE THE COAST WARMS INTO THE 70S. THE FORECAST WILL
CONTINUE TO EVOLVE THROUGH THE WEEK AND WILL LIKELY CHANGE AS
DETAILS BECOME MORE CLEAR. /42
AVIATION
CLEAR SKY VFR CONDITIONS ACROSS THE REGION TODAY AS
HIGH PRESSURE BUILDS OVERHEAD. GUIDANCE DEPICTS MARINE STRATUS
RETURNING TO COASTAL TERMINALS 04-08Z MON, WITH A 30-50% CHANCE
FOR MVFR CONDITIONS OR LOWER AT KAST A 50-70% CHANCE ALONG THE
IMMEDIATE COASTLINE INCLUDING KONP. INCREASING SUBSIDENCE AND THE
SHALLOW NATURE OF THE MARINE LAYER SUGGEST PROBABLE IFR CIGS WITH
THE POTENTIAL FOR SOME PATCHES OF LIFR FOG ALONG THE CENTRAL COAST
NEAR KONP, BREAKING OUT TOWARDS VFR AGAIN 16-18Z MON. OTHERWISE,
VFR WILL PREVAIL THROUGH THE PERIOD AT THE INLAND TERMINALS. WINDS
WILL CONTINUE TO FOLLOW A DIURNAL TREND, WITH N-NW WINDS
INCREASING TO 10-15 KT WITH GUSTS TO 20-25 KT 20-23Z SUN. WINDS
WILL DIMINISH BACK TO AROUND 5 KT AFTER 06Z MON.
PDX AND APPROACHES...VFR PREVAILS THROUGH THE PERIOD UNDER CLEAR
SKIES. NW WINDS 10-12 KT WITH GUSTS TO AROUND 20 KT, EASING TO
AROUND 5 KT AFTER 06Z MON. /CB
MARINE
A TYPICAL SUMMERTIME PATTERN PERSISTS THROUGH MUCH OF
THE COMING WEEK AS SURFACE HIGH PRESSURE OFFSHORE MAINTAINS NORTH
TO NORTHWEST WINDS ACROSS THE COASTAL WATERS. INLAND HEATING WILL
DRIVE A STRENGTHENING COASTAL PRESSURE GRADIENT THROUGH MONDAY,
WHICH IS IN LINE WITH CURRENT OBSERVATIONS SHOWING GUSTS
INCREASING TO 20-25 KT OVER THE WATERS. SMALL CRAFT ADVISORIES
REMAIN IN EFFECT THROUGH MONDAY EVENING AS WIND GUSTS INCREASE A
BIT MORE TO 25 TO 30 KT LATER TODAY INTO MONDAY. EXPECT THE
STRONGEST GUSTS SOUTH OF CAPE FALCON, WHILE CONDITIONS WILL BE
MORE MARGINAL TO THE NORTH ACROSS THE MOUTH OF THE COLUMBIA RIVER
AND THE SOUTH WASHINGTON COASTAL WATERS. SEAS WILL REMAIN IN THE
4-6 FT RANGE, COMPRISED MAINLY OF SHORT PERIOD WIND-DRIVEN WAVES
AND A MODEST, MID-PERIOD WESTERLY SWELL. /CB
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 10 PM PDT MONDAY FOR PZZ251>253-
271>273.
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