FXUS66 KPDT 050932
AFDPDT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
130 AM PST SUN FEB 5 2012

.SHORT TERM...TODAY THROUGH TUESDAY NIGHT...HIGH PRESSURE ALOFT WILL
PERSIST AGAIN TODAY AND MONDAY. IT IS BEGINNING TO BE PINCHED OFF BY
AN AMPLIFIED UPPER TROUGH THAT IS STILL WELL OFF THE COAST.
HOWEVER...THE UPPER RIDGE IS SO ELONGATED THAT A CLOSED UPPER HIGH
IS FORMING FROM IT OVER NORTHERN MONTANA AND SOUTHERN ALBERTA WHILE
THE RIDGE IS BECOMING MORE NARROW OVER THE FORECAST AREA.
NEVERTHELESS THERE IS STILL ABUNDANT STAGNANT AIR OVER THE FORECAST
AREA AS WELL AS AREAS OF FOG AND/OR LOW CLOUDS...MAINLY OVER THE
LOWER COLUMBIA BASIN AND ADJACENT VALLEYS AND FOOTHILLS. THE AREAS
WITH THE THICKEST FOG/LOW STRATUS IS CURRENTLY OVER THE WASHINGTON
AND OREGON BASIN AND THE WASHINGTON BLUE MOUNTAIN FOOTHILLS. THERE
IS ALSO FOG AND/OR STRATUS BEGINNING TO FORM OVER CENTRAL AND NORTH
CENTRAL OREGON AND IN THE EASTERN COLUMBIA RIVER GORGE. ALREADY HAVE
A FREEZING FOG ADVISORY IN EFFECT THIS MORNING FOR THE LOWER
COLUMBIA BASIN AND THE WASHINGTON BLUE MOUNTAIN FOOTHILLS. MAY NEED
ONE SOON FOR CENTRAL OREGON WHERE THE VISIBILITY IS RAPIDLY DROPPING
AT KBDN AND KRDM. WE ALSO HAVE AN AIR STAGNATION ADVISORY IN EFFECT
FOR MUCH OF THE FORECAST AREA THROUGH AT LEAST TUESDAY MORNING. THAT
WILL LIKELY NEED TO BE EXTENDED. ELSEWHERE IN THE FORECAST AREA...
MAINLY IN THE MOUNTAINS...SKIES ARE CLEAR AND THE AIR IS COLD.
EXPECT THIS SCENARIO TO PERSIST ON MONDAY. THEN ON TUESDAY AND
TUESDAY NIGHT A PACIFIC WEATHER SYSTEM WILL MOVE INTO THE UPPER
RIDGE AND WEAKEN IT. HOWEVER IT IS LOOKING MORE AND MORE LIKE THE
RIDGE WILL WIN THE BATTLE AND HOLD ON AND KEEP THE STAGNANT
CONDITIONS LONGER ALONG WITH THE AREAS OF FOG AND/OR LOW CLOUDS. AT
THIS TIME WILL ONLY HAVE A SLIGHT CHANCE OF RAIN/SNOW SHOWERS OVER
THE SOUTHWEST CORNER OF DESCHUTES COUNTY FOR TUESDAY/TUESDAY NIGHT.
THIS ALSO MATCHES WELL WITH THE PRECIP TIMING WITH NEIGHBORING
OFFICE FORECAST AREAS. 88

.LONG TERM...WEDNESDAY THROUGH SATURDAY NIGHT...A RIDGE OF HIGH
PRESSURE WILL REBUILD OVER THE REGION. THIS WILL PUSH PRECIPITATION
NORTHWARD WITH ONLY A SLIGHT CHANCE OF SHOWERS ALONG THE CASCADE
CREST. THE REST OF THE REGION WILL BE DRY WITH THE POSSIBILITY OF
RIVER FOG DURING THE EARLY MORNING HOURS. MODELS TRY TO PUSH THE
RIDGE EAST OUT OF THE AREA BY THE WEEKEND. THE EUROPEAN MODEL TRIES
TO PUSH SEVERAL WEATHER SYSTEM THROUGH STARTING FRIDAY NIGHT WHILE
THE GFS HOLDS ONTO THE RIDGE LONGER. WILL KEEP A SLIGHT CHANCE OF
PRECIPITATION STARTING SATURDAY OVER THE FORECAST AREA DUE TO THE
UNCERTAINTY. MODELS TEND TO TRY AND BREAK DOWN THE RIDGE TOO FAST
AND THEREFORE WILL TREND TOWARD THE DRIER GFS SOLUTION. DMH

&&

.AVIATION...12Z TAFS...FOG WILL REMAIN ALONG THE AREA RIVERS
IMPACTING KALW...KPSC...KDLS...KRDM AND KBDN THIS MORNING. LIFR
CONDITIONS ARE LIKELY IN THESE AREAS THOUGH SOUTHEAST WINDS MAY KEEP
KALW CLEAR FOR A SHORT TIME BEFORE THE FOG RETURNS TO THE TAF SITE.
THIS WILL MAKE FOR A CHALLENGING FORECAST AS CEILINGS AND
VISIBILITIES COULD FLUCTUATE. EXPECT CONDITIONS TO IMPROVE AFTER 18Z
AS THE SUNLIGHT BURNS OFF THE FOG LAYER. VFR CONDITIONS WILL PREVAIL
DURING THE DAY AT ALL TAF SITES. THEN SUNDAY NIGHT...FOG WILL RETURN
TO THE AREA ONCE AGAIN WITH LIFR CONDITIONS POSSIBLE AT ALL TAF
SITES. SURFACE WINDS WILL REMAIN LESS THAN 10 KTS THROUGH THE
PERIOD. DMH


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT 40 23 40 26 / 0 0 0 0
ALW 38 29 39 30 / 0 0 0 0
PSC 41 25 41 28 / 0 0 0 0
YKM 43 23 43 28 / 0 0 0 0
HRI 39 25 40 27 / 0 0 0 0
ELN 40 20 40 25 / 0 0 0 0
RDM 47 21 51 24 / 0 0 0 0
LGD 45 25 46 27 / 0 0 0 0
GCD 47 22 48 25 / 0 0 0 0
DLS 43 27 43 28 / 0 0 0 0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...AIR STAGNATION ADVISORY UNTIL 10 AM PST TUESDAY
ORZ041-042-044-050-505-507-508.

FREEZING FOG ADVISORY UNTIL 11 AM PST THIS MORNING ORZ044.

WA...AIR STAGNATION ADVISORY UNTIL 10 AM PST TUESDAY WAZ024-026>029.

FREEZING FOG ADVISORY UNTIL 11 AM PST THIS MORNING WAZ028-029.

&&

THREAT INDEX
TODAY : YELLOW
MONDAY : GREEN
TUESDAY : GREEN

GREEN: NONE OR LIMITED NEED FOR WATCHES, WARNINGS, OR ADVISORIES.
YELLOW: A FEW WATCHES, WARNINGS, OR ADVISORIES POSSIBLE OR IN EFFECT.
RED: NUMEROUS WATCHES, WARNINGS, OR ADVISORIES POSSIBLE OR IN EFFECT.

FOR ADDITIONAL WEATHER INFORMATION, CHECK OUR WEB SITE AT...
WWW.WEATHER.GOV/PENDLETON

$$

88/84/84


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