Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 301729
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
929 AM PST FRI JAN 30 2015

.SYNOPSIS...A BUILDING UPPER RIDGE AND OFFSHORE FLOW SHOULD PRODUCE
RELATIVELY MILD TEMPERATURES...WITH AREAS OF VALLEY FOG AND EAST
WINDS NEAR THE MOUTH OF THE COLUMBIA RIVER GORGE THROUGH SATURDAY
NIGHT. A DECENT SHOT OF RAIN IS EXPECTED IN SOUTHWEST WASHINGTON AND
NORTHWEST OREGON SUNDAY INTO SUNDAY EVENING AS A PACIFIC FRONT MOVES
THROUGH. ANOTHER GOOD SHOT OF RAIN APPEARS LIKELY ON MONDAY AS
ANOTHER PACIFIC LOW AND FRONT MOVES BY. SOME MORE RAIN IS POSSIBLE
MID WEEK FROM A WARM FRONT THOUGH CONFIDENCE IN THE DETAILS IS LOW. A
SERIES OF WETTER COLD FRONTS IS LIKELY LATE NEXT WEEK INTO NEXT
WEEKEND. SIGNIFICANT SNOWS AT CASCADE PASS LEVEL APPEAR UNLIKELY
DURING THE NEXT WEEK.
&&

.SHORT TERM...TODAY THROUGH SUNDAY...THE PATTERN OF FOG AND LOW
CLOUDS IS PRETTY MUCH WHAT WE SAW THURSDAY AFTERNOON JUST BEFORE IT
ALL CLEARED...WITH IT FAVORING THE EASTERN SECTIONS SOUTHWARD IN THE
WILLAMETTE VALLEY...AND ALONG INTERSTATE 5 NORTH OF PORTLAND...BUT
LESS NEAR THE GORGE FROM THE EAST WINDS. EXPECT SIMILAR CLEARING
THIS AFTERNOON AS ON THURSDAY AFTERNOON AS THE EAST WINDS HIT THE
EAST SLOPES OF THE COAST RANGE AND ARE DEFLECTED SOUTH ALONG THE
WILLAMETTE VALLEY. TEMPS THIS AFTERNOON MAY BE PRETTY CLOSE TO WHAT
WE SAW THURSDAY AFTERNOON AS WELL.

THE GRADIENT THROUGH THE GORGE DOES NOT CHANGE MUCH TONIGHT AND
SATURDAY...PERHAPS A LITTLE WEAKENING TONIGHT AND EARLY SATURDAY...
SO WILL NOT STRAY TOO MUCH FROM THE FOG AND LOW CLOUDS PATTERN OF THE
LAST TWO DAYS. IF ANYTHING...PERHAPS THERE WILL BE A BIT MORE
COVERAGE SATURDAY MORNING AND A BIT SLOWER CLEARING SATURDAY
AFTERNOON.

THE GRADIENT THROUGH THE GORGE INCREASES SATURDAY NIGHT AS THE HIGH
PRESSURE EAST OF THE CASCADES STRENGTHENS SOME DUE TO THE PASSAGE OF
A WEAK SYSTEM WELL TO OUR NORTH AND EAST. THIS MAY AFFECT THE FOG
FORMATION SOME NEAR PORTLAND AND VANCOUVER...BUT THE REST OF THE
VALLEY AREAS SHOULD SEE MORE FOG AGAIN OVERNIGHT SATURDAY NIGHT.

THE MODELS ARE SHOWING THE NEXT FRONTAL SYSTEM APPROACHING THE NORTH
COASTAL AREAS LATE SATURDAY NIGHT AND MOVING THROUGH SOUTHWEST
WASHINGTON AND NORTHWEST OREGON SUNDAY AND EARLY SUNDAY EVENING. HAVE
SPED THE ARRIVAL OF THE PRECIPITATION UP A TOUCH AND RAISED POPS. WE
SHOULD SEE A DECENT SHOT OF QPF FROM THIS SYSTEM...WITH THE HIGHER
TERRAIN SEEING A HALF INCH OR MORE AND THE VALLEYS A QUARTER TO A
THIRD OF AN INCH. A BIT WETTER SYSTEM IS EXPECTED MONDAY...WITH
AMOUNTS A BIT HIGHER THAN ON SUNDAY. MAY SEE SOME BREEZES ON THE
COAST MONDAY AS A 1005 MB SURFACE LOW HEADS TOWARD VANCOUVER ISLAND.
TOLLESON

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...
SUNDAY NIGHT THROUGH THURSDAY...MODELS HAVE BACKED OFF ON THE IDEA
THAT SHORTWAVE RIDGING WOULD BUILD INTO THE AREA QUICKLY ON TUESDAY.
INSTEAD...ADDITIONAL SHORTWAVE TROUGHS RIDING EASTWARD IN THE ZONAL
PATTERN MAY BRING ANOTHER ROUND OR TWO OF RAINMIDWEEK...BUT
CONSIDERABLE DIFFERENCES IN THE EVOLUTION AND TIMING OF THESE SYSTEMS
REMAIN. AS A RESULT...POPS WERE GENERALLY KEPT IN THE CHANCE RANGE
MIDWEEK. EITHER WAY...THESE SYSTEMS LOOK TO BE RELATIVELY WARM SO
SUBSTANTIAL CASCADE SNOWS APPEAR UNLIKELY. HOWEVER...SNOW LEVELS MAY
END UP BEING A TOUCH LOWER ACROSS THE SOUTH WASHINGTON CASCADES WHERE
COLD AIR DAMMING COULD ALLOW HIGHER SNOW TOTALS TO FALL DEPENDING ON
HOW THESE SYSTEMS PLAY OUT. A MORE SUBSTANTIAL FRONTAL STORM SYSTEM
APPEARS AS THOUGH IT WILL ARRIVE LATER IN THE WEEK. SNOW LEVELS WILL
ONCE AGAIN BE RELATIVELY HIGH WITH THIS SYSTEM AND IT APPEARS
UNLIKELY TO HELP OUR PITIFUL MOUNTAIN SNOWPACK. /NEUMAN
&&

.AVIATION...LITTLE CHANGE IN OVERALL PATTERN TODAY. LIGHT OFFSHORE
FLOW CONTINUES...WITH VFR CONDITIONS. PATCHY LOW CLOUDS AND FOG STILL
HUGGING COASTAL BAYS...BUT MORE FOG/LOW CLOUDS INLAND ALONG THE
COLUMBIA AND COWLITZ VALLEYS. TOPS GENERALLY AROUND 200 TO 500
FEET...SO MOST OF THIS WILL BURN OFF THIS AM. HOWEVER...STRATUS IN
COWLITZ VALLEY WILL PERSIST INTO THE EARLY AFTERNOON. ANOTHER AREA OF
LOW STRATUS IS IN WILLAMETTE VALLEY FROM KUAO SOUTHWARD...MOSTLY EAST
OF I-5. LIKE THU...THIS STRATUS BREAK UP LATER THIS AFTERNOON. WITH
NOT MUCH CHANGE...IFR FOG AND LOW CLOUDS WILL REFORM IN NEARLY THE
SAME AREAS.

KPDX AND APPROACHES...VFR TODAY INTO THIS EVENING. HOWEVER...AREAS OF
IFR FOG/STRATUS WILL REMAIN OVER OPS AREAS THROUGH 20Z THOUGH VIS 1/4
TO 1/2 MILE UNTIL 18Z. TOPS OF LAYER AROUND 500 TO 600 FEET SO WILL
TAKE UNTIL 20Z FOR FOG TO RETREAT BACK TO NW. ROCKEY.
&&

.MARINE...LITTLE CHANGE. HIGH PRES REMAINS OVER THE REGION INTO
SAT...WITH WINDS 15 KT OR LESS AND SEAS RUNNING 5 TO 6 FT.

WILL SEE PATTERN CHANGE NEXT WEEK...AS A SERIES OF FRONTS PUSH INTO
THE REGION. EACH WILL BE PROGRESSIVELY STRONGER...WITH WINDS 20 TO 25
KT AT TIMES. IF PATTERN HOLDS...GOOD CHANCE OF SOUTHERLY GALES NEXT
THU AND FRI...WITH BUILDING SEAS.    ROCKEY.
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
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.


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