Area Forecast Discussion
Issued by NWS Pendleton, OR

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000
FXUS66 KPDT 272341 AAA
AFDPDT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PENDLETON OR
340 PM PST TUE JAN 27 2015

UPDATED AVIATION DISCUSSION

.SHORT TERM...TONIGHT THROUGH FRIDAY...HIGH PRESSURE WILL GRADUALLY
WEAKEN TONIGHT THROUGH WEDNESDAY AS TWO SYSTEMS COLLIDE ACROSS THE
PACIFIC NORTHWEST.  DO NOT ANTICIPATE MUCH IN PRECIPITATION...EXCEPT
A SLIGHT CHANCE ALONG THE EAST SLOPES OF THE CASCADES AND THE
SOUTHERN BLUE MOUNTAINS THIS EVENING.  THE COLD AIR ALOFT WITH THIS
SYSTEM WILL WEAKEN THE INVERSION THAT HAS BEEN IN PLACE ACROSS THE
LOWER ELEVATIONS.  THIS SHOULD HELP LIFT THE FOG INTO A STATUS
DECK...AND MAY EVEN CLEAR OUT SOME AREAS TEMPORARILY.  EXPECT PARTLY
TO MOSTLY CLOUDY SKIES WEDNESDAY WITH SOME CLEARING AND FOG
REDEVELOPMENT WEDNESDAY NIGHT AS HIGH PRESSURE REBUILDS FOR THE
REMAINDER OF THE SHORT TERM.  THE MOST FAVORED AREAS FOR FOG ON
THURSDAY AND FRIDAY LOOK TO BE ALONG THE FOOTHILLS OF THE BLUE
MOUNTAINS...CENTRAL AND NORTH CENTRAL OREGON.  PATCHY FOG IS
EXPECTED FOR THE LOWER ELEVATIONS.  OTHERWISE...MOSTLY DRY
CONDITIONS EXPECTED THURSDAY AND FRIDAY. WEBER

.LONG TERM...FRIDAY NIGHT THROUGH TUESDAY NIGHT...THE LONG TERM
PERIOD STARTS OFF WITH AN UPPER LEVEL RIDGE OVER THE PAC NW...WHICH
WILL ALLOW PATCHY FOG/FREEZING FOG TO FORM IN THE BASINS FRIDAY
NIGHT THROUGH SATURDAY NIGHT/SUNDAY. HEADING INTO THE SUNDAY THROUGH
TUESDAY PERIOD WE ARE EXPECTING A MUCH MORE ACTIVE WEATHER PATTERN
AS THE UPPER LEVEL RIDGE BEGINS TO BREAK DOWN. MODEL GUIDANCE IS IN
GOOD AGREEMENT THAT SEVERAL DISTURBANCES WILL MOVE THROUGH THE
REGION...BRINGING CHANCES OF RAIN AND MOUNTAIN SNOW. AT THIS TIME
SNOW LEVELS ARE GENERALLY FORECAST TO REMAIN BETWEEN 3000 TO 5000
FEET WITH THESE STORM SYSTEMS...PERHAPS LOWERING TO 1500-2500 FEET
TUESDAY NIGHT IN SOME LOCATIONS. SOUTH TO SOUTHWEST WINDS WILL
INCREASE SUNDAY NIGHT INTO MONDAY...UP INTO THE 10-20 MPH RANGE AS A
SURFACE LOW PASSES NEAR OR JUST TO THE NORTH OF OUR CWA. DROPPED
TEMPERATURES BACK SEVERAL DEGREES IN THE MONDAY/TUESDAY TIMEFRAME TO
ACCOUNT FOR THE POTENTIAL OF COLDER AIR ALOFT. THE 27/12Z ECMWF IS
INDICATING 850MB TEMPERATURES DROPPING TO BETWEEN 0 TO -4 DEGREES
CELSIUS DURING THIS TIME. IN GENERAL EXPECT NEAR TO SLIGHTLY ABOVE
AVERAGE TEMPERATURES THROUGH THE LONG TERM PERIOD. 77

&&

.AVIATION...00Z TAFS...A WEAK WEATHER SYSTEM MOVED THROUGH THE AREA
HELPING TO BREAK UP THE LOW CLOUDS AND FOG ACROSS MUCH OF THE
REGION....EXCEPT FOR AT KPSC AND KYKM WHERE IFR CIGS REMAIN. AFTER
28/03Z AND ESPECIALLY AFTER 28/10Z THERE IS THE POTENTIAL FOR MVFR
OR IFR CIGS/VIS IN LOW CLOUDS...FOG AND MIST TO RETURN AT SEVERAL
TAFS SITES. THE AFFECTED TAF SITES INCLUDE KDLS...KYKM...KPSC...KPDT
AND KALW. CONDITIONS SHOULD AGAIN BEGIN TO IMPROVE BACK TO MVFR/VFR
FOR MOST OF THESE AFFECTED TAF SITES AFTER 28/19Z. INTRODUCED VCSH
AT KDLS AND KYKM AFTER 28/12-15Z TO ACCOUNT FOR A WEAK DISTURBANCE
THAT MOVES ALONG THE CASCADES. WINDS WILL REMAIN LIGHT...AOB 10KTS
THROUGH THE PERIOD AT ALL TAF SITES. 77


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  38  46  34  44 /  10  10  10  10
ALW  39  45  35  44 /  10  10  10  10
PSC  37  45  35  44 /  10  10  10  10
YKM  33  42  32  42 /  10  10  10  10
HRI  39  47  35  45 /  10  10  10  10
ELN  33  42  33  43 /  10  10  20  10
RDM  35  56  33  49 /  10  10  10  10
LGD  36  51  32  47 /  10  10  10  10
GCD  36  54  34  52 /  10  10  10  10
DLS  41  49  39  49 /  20  10  10  10

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
&&

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

$$

89/77/77





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