[ W WA | SW WA and W OR | SE WA and NE OR | NE WA and N ID ]

Western Washington


105 
FXUS66 KSEW 272303
AFDSEW

AREA FORECAST DISCUSSION 
NATIONAL WEATHER SERVICE SEATTLE WA
300 PM PST FRI FEB 27 2015

.SYNOPSIS...SHOWERS WILL END TONIGHT AS DRIER NORTHERLY FLOW ALOFT 
AND LOW LEVEL OFFSHORE FLOW DEVELOPS. THE UPPER RIDGE AND OFFSHORE 
FLOW WILL BRING SUNNY DAYS AND COOL NIGHTS THIS WEEKEND. A WEAK 
SYSTEM WILL MOVE THROUGH SUNDAY NIGHT AND MONDAY...WITH DRY WEATHER 
AGAIN TUESDAY AND WEDNESDAY.

&&

.SHORT TERM...AN UPPER LOW OVER NORTHWEST OREGON WILL SHIFT SOUTH 
TONIGHT. SHOWERS WILL CONTINUE TO DECREASE ACROSS THE AREA THIS 
EVENING AS THE UPPER LOW PULLS AWAY. SHOWERS SHOULD PRETTY MUCH COME 
TO AN END AFTER MIDNIGHT TONIGHT AS DRIER NORTHERLY FLOW ALOFT AND 
LOW LEVEL OFFSHORE FLOW DEVELOP. 

A SURFACE HIGH MOVING INTO SOUTHERN BRITISH COLUMBIA WILL RESULT IN 
LOCALLY BREEZY NORTHERLY WINDS TONIGHT AND SATURDAY. OTHERWISE... 
SATURDAY SHOULD BE A SUNNY DAY AFTER SOME LINGERING EARLY MORNING 
CLOUDS. SUNDAY SHOULD BE ANOTHER SUNNY DAY. 

LOW LEVEL OFFSHORE FLOW WILL WEAKEN AND THE FLOW ALOFT WILL BACK TO 
NORTHWEST ON WEDNESDAY AS A WEATHER SYSTEM APPROACHES FROM THE 
NORTHWEST FOR LESS WIND. THIS WEATHER SYSTEM WILL DROP DOWN FROM THE 
NORTHWEST SUNDAY NIGHT AND MONDAY...BRINGING CLOUDS. THE ECMWF SHOWS 
RAIN ALL AREAS WITH THIS FEATURE BUT THE GFS JUST HAS SPOTTY 
PRECIPITATION AND THE GEM IS DRY. THE FORECAST IS A BLEND OF THESE 
MODELS FOR NOW WHICH MEANS MOSTLY CLOUDY WITH A CHANCE OF RAIN. 
SCHNEIDER 

.LONG TERM...AN UPPER RIDGE WILL BE OVER THE NORTHEAST PACIFIC 
TUESDAY AND WEDNESDAY...GIVING DRY NORTHERLY FLOW ALOFT TO WESTERN 
WASHINGTON. THERE WILL BE SOME BREEZY NORTH WINDS TUESDAY AS A 
SURFACE HIGH MOVES INTO SOUTHERN BRITISH COLUMBIA...THEN LESS WIND 
WEDNESDAY AS THE HIGH SHIFTS SOUTHEAST. 

MODELS SHOW THE UPPER RIDGE WEAKENING A BIT THURSDAY WITH A WARM 
FRONT MOVING OVER THE TOP. THIS WILL BRING SOME CLOUDS TO THE AREA 
AND PERHAPS A CHANCE OF RAIN...WITH THE BEST CHANCES COAST AND FAR 
NORTH. A COLD FRONT WILL APPROACH FROM THE WEST ON FRIDAY. THIS DAY 
COULD WIND UP BEING DRY BUT A CHANCE OF RAIN CANNOT BE COMPLETELY 
RULED OUT FOR NOW. SCHNEIDER 

&&

.HYDROLOGY...FLOODING IS UNLIKELY FOR THE NEXT 7 DAYS.

&&

.AVIATION...A SMALL UPPER LEVEL AND SURFACE LOW NEAR ASTORIA AT 22Z  
WILL MOVE S OVER N CA BY 12Z. DRIER N-NE FLOW SURFACE AND ALOFT WILL 
GRADUALLY PUSH S OVER W WA TONIGHT AS AN UPPER LEVEL RIDGE MOVES 
OVER N B.C. AND A SURFACE RIDGE MOVES OVER S B.C. 

RAIN IS BEGINNING TO DIMINISH OVER THE N INTERIOR THIS AFTERNOON 
WHILE SHOWERS HAVE DEVELOPED OVER THE SW INTERIOR. THIS HAS ALLOWED 
A MIX OF CLOUD LAYERS TO PERSIST OVER W WA. VFR CONDITIONS 
PREDOMINATE OVER THE N INTERIOR BUT A MIX OF VFR AND IFR CIGS IS 
STILL PRESENT OVER PUGET SOUND AND THE SW INTERIOR. LATEST MODELS 
STILL INDICATE DECREASING MOISTURE FROM THE N ACROSS THE AREA 
TONIGHT...BUT PROBABLY A LITTLE SLOWER THAN PREVIOUSLY EXPECTED. THE 
SURFACE RIDGE OVER S B.C. WILL INCREASE N-NE SURFACE WINDS ACROSS W 
WA THROUGH 06Z WITH LOCALLY WINDY CONDITIONS CONTINUING THROUGH 
18Z...PARTICULARLY OVER THE N INTERIOR. WITH AN UPPER LEVEL RIDGE 
OVER B.C. ON SATURDAY AND DRY N-NE FLOW ALOFT...GOOD VFR CONDITIONS 
ARE EXPECTED.

KSEA...CIGS AT KSEA ARE EXPECTED TO REMAIN VFR...GENERALLY 
BKN-OVC050 AND HIGHER THROUGH 09Z...WITH CLOUD LAYERS BECOMING 
SCATTERED AFTER 09Z. N-NE SURFACE WINDS WILL REMAIN 5-10 KT THROUGH 
09Z...INCREASING TO 10-15 AFTER 09Z. THE INCREASE IN SURFACE WINDS 
WILL PROVIDE ENOUGH MIXING TO PRECLUDE FOG FROM FORMING. KAM

&&

.MARINE...A 1006 MB SURFACE LOW NEAR ASTORIA AT 22Z WILL MOVE S OVER 
N CA BY 12Z SATURDAY. MODERATE N-NE SURFACE FLOW WILL DEVELOP THIS 
EVENING AS A SURFACE RIDGE MOVES DOWN OVER SOUTHERN B.C. BEHIND THE 
LOW. SMALL CRAFT ADVISORIES ARE IN EFFECT FOR ALL WATERS FOR THE 
N-NE SURFACE WINDS. MOST AREAS SHOULD REMAIN IN THE 15-25 
RANGE...BUT THE N INLAND WATERS AND THE E ENTRANCE SHOULD BE A 
LITTLE STRONGER. THE CANADIAN MESOSCALE MODEL IS STILL THE ONLY ONE 
THAT SHOWS 30-35 KT GALE WINDS OVER THE N INLAND AND E ENTRANCE FROM 
06Z-12Z...SO I WILL STICK WITH THE CONSENSUS AND KEEP WINDS 30 KT OR 
BELOW.

SURFACE WINDS WILL GRADUALLY DIMINISH SATURDAY AS THE SURFACE RIDGE 
SETTLES OVER W WA. 

MODELS SHOW AN UPPER LEVEL AND SURFACE TROUGH MOVING S ACROSS THE 
AREA SUNDAY NIGHT. THE WRF-GFS INDICATED A BRIEF PERIOD OF NORTHERLY 
SCA WINDS MAINLY OVER THE COASTAL WATERS AND THROUGH PUGET SOUND 
IMMEDIATELY BEHIND THIS FEATURE. ANOTHER SURFACE RIDGE WILL MOVE 
DOWN OVER B.C. MONDAY NIGHT AND TUESDAY FOR ANOTHER PERIOD OF 
MODERATE E-NE FLOW. KAM

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY ALL WATERS.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION AT 
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML










[ W WA | SW WA and W OR | SE WA and NE OR | NE WA and N ID ]

Southwestern Washington and Western Oregon


348 
FXUS66 KPQR 272224
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR 
223 PM PST FRI FEB 27 2015

.SYNOPSIS...SHOWERS WILL CONTINUE THROUGH THIS EVENING AN UPPER LEVEL
TROUGH PUSHES SOUTHWARD ACROSS OREGON...THEN TAPER OFF FROM NORTH TO
SOUTH TONIGHT. SNOW LEVELS ARE NEAR THE CASCADE PASSES... AND A FEW
MORE INCHES ARE POSSIBLE IN THE LANE COUNTY CASCADES BEFORE SNOW
SHOWERS TAPER OFF LATER TONIGHT. HIGH PRESSURE AND INCREASING
OFFSHORE FLOW SHOULD YIELD A MOSTLY SUNNY AND DRY WEEKEND WITH CHILLY
NIGHTS AND MILD DAYS. THE NEXT UPPER LEVEL THROUGH FORECAST TO DIG
DOWN THE BRITISH COLUMBIA COAST WILL BRING ANOTHER SHOT OF RELATIVELY
COOL AIR AND POSSIBLY MORE VALLEY RAIN AND MOUNTAIN SNOW SHOWERS
SUNDAY NIGHT AND MONDAY. STRONG HIGH PRESSURE WILL THEN BUILD BACK
FOR DRIER WEATHER FOR MUCH OF NEXT WEEK.

&&

.SHORT TERM...TONIGHT THROUGH MONDAY...WATER VAPOR AND INFRARED
SATELLITE IMAGERY SHOW AN UPPER LEVEL TROUGH CONTINUING TO PROGRESS
SOUTHWARD INTO OREGON THIS AFTERNOON. SHALLOW INSTABILITY IS CAUSING
NUMEROUS SHOWERS TO PERSIST ACROSS THE FORECAST AREA THIS AFTERNOON.
SOME SUNBREAKS HAVE DEVELOPED AS WELL...AND MAY STILL PROVIDE JUST
ENOUGH INSTABILITY FOR A STRAY THUNDERSTORM OR TWO BEFORE SUNSET.
WITH FREEZING LEVELS IN THE 5000 FT RANGE...ANY HEAVIER SHOWERS WILL
HAVE THE POTENTIAL TO PRODUCE A BRIEF PERIOD OF SMALL HAIL. 

AREA WEBCAMS INDICATE SNOW LEVELS ARE LINGERING IN THE 4000-5000 FT
RANGE THIS AFTERNOON. SNOW IS ONLY BRIEFLY STICKING TO THE ROADS OVER
THE CASCADE PASSES WHEN HEAVIER SNOW SHOWERS PASS THROUGH. SNOW
SHOULD HAVE AN EASIER TIME STICKING AS TEMPERATURES START TO FALL
AFTER 4 PM THIS AFTERNOON. HOWEVER THE NUMBER OF SNOW SHOWERS WILL BE
DECREASING BY THEN FOR THE S WA/N OR CASCADES...SO WE WILL LET THE
SNOW ADVISORY EXPIRE AT 3 PM FOR THOSE ZONES. LANE COUNTY CASCADES
WILL REMAIN IN BETTER OROGRAPHIC FLOW A LITTLE LONGER...AND AS A
RESULT THE LATEST NAM/HRRR RUNS HAVE ABOUT 0.25 INCH OF ADDITIONAL
QPF IN THE 00-06Z PERIOD. THIS SHOULD TRANSLATE TO ANOTHER 2-4 INCHES
OF SNOW ABOVE 5000 FEET...SO WE DECIDED TO EXTEND THE SNOW ADVISORY
UNTIL 10 PM FOR THE LANE COUNTY CASCADES.

MODELS SHOW GOOD AGREEMENT THAT ANY LINGERING SHOWERS WILL TAPER OFF
QUICKLY SATURDAY MORNING AS OUR UPPER TROUGH MOVES INTO NORTHERN CA
AND FLOW TURNS OFFSHORE. HIGH PRESSURE WILL BUILD INTO WASHINGTON
SATURDAY...WITH THE RESULTING DRY N-NE FLOW CLEARING US OUT QUICKLY.
BY MIDDAY EXPECT PLENTY OF SUNSHINE FOR MOST OF THE DISTRICT BUT WITH
SOME BLUSTERY NORTHERLY FLOW AND TEMPS STUCK IN THE LOWER 50S. THE
N-NE FLOW AND DRY AIR MASS MAY MAKE IT DIFFICULT FOR ANY NIGHT AND
MORNING FOG TO FORM THIS WEEKEND EXCEPT IN THE MOST SHELTERED
VALLEYS. NOT MUCH CHANGE EXPECTED FOR SUNDAY...EXCEPT PERHAPS LESS
WIND AWAY FROM THE GORGE AND A FEW MORE HIGH CLOUDS IN ADVANCE OF OUR
NEXT DISTURBANCE.

NORTHWEST FLOW ALOFT WILL GUIDE THE NEXT DISTURBANCE INTO THE PAC NW
SUN NIGHT/EARLY MON. MODELS CONTINUE TO STRUGGLE A BIT WITH THE FINER
DETAILS...BUT THE BROAD CONSENSUS KEEPS TWO DISTINCT SYSTEMS DURING
THIS EVENT. ONE WILL DIG SE ALONG THE SPINE OF THE ROCKIES...
FOLLOWED THE NEXT SURGE OF COLD AIR TO PUSH INTO THE NORTHERN PLAINS
STATES. THE SECOND DISTURBANCE REMAINS WEAKER AND TRACKS DOWN THE BC
COAST. 12Z/18Z GFS/NAM/ECMWF ALL HAVE ENOUGH OVERWATER TRAJECTORY FOR
AT LEAST SOME SHOWERS SUN NIGHT/MON...WHILE THE 12Z GEM KEEPS OUR
SYSTEM TOO WEAK TO PRODUCE MUCH IN THE WAY OF SHOWER ACTIVITY. HELD
POPS GENERALLY IN THE CHANCE CATEGORY LATE SUN NIGHT/EARLY MON. IF WE
DO GET PRECIP...THE CASCADES COULD GET ANOTHER DUSTING OF SNOW BUT IT
PROBABLY WILL NOT BE MUCH.  WEAGLE 

.LONG TERM...TUESDAY THROUGH FRIDAY...THE MEAN UPPER RIDGE POSITION
RETURNS TO WHERE IT HAS BEEN MUCH OF THIS WINTER TUE/WED...OVER THE
NE PACIFIC. THEREFORE EXPECT AT LEAST A COUPLE DAYS OF DRY WEATHER
TUE/WED...PROBABLY LONGER. IT APPEARS THE BULK OF THE COLD AIR BEHIND
THE SUN NIGHT/MON SYSTEM WILL STAY EAST OF THE ROCKIES...WITH ONLY A
SMALL PIECE OF IT PUSHING INTO THE MID-COLUMBIA BASIN. THUS EXPECT
NEAR NORMAL TEMPERATURES AND DRY WEATHER THROUGH MIDWEEK...CLEAR AND
CHILLY NIGHTS WITH SUNNY DAYS AND AFTERNOON TEMPS IN THE 50S FOR THE
LOWLANDS. OFFSHORE FLOW SHOULD LIMIT FOG FORMATION. HELD POPS BELOW
CLIMO TOWARD THE END OF THE WEEK AS MODELS CONTINUE TO SHOW THE MEAN
RIDGE POSITION ANCHORED NEAR THE WEST COAST.  WEAGLE

&&

.AVIATION...SHOWERS WILL DECREASE THIS EVENING FROM THE NORTH TO
THE SOUTH AS THE RESPONSIBLE SURFACE LOW SLIDES SOUTH INTO
SOUTHERN OREGON. A MIX OF MVFR AND VFR WILL CONTINUE THIS
AFTERNOON THROUGH THE EARLY EVENING TO THE NORTH...AND INTO THE
LATE EVENING FOR AREAS IN LANE COUNTY. SATELLITE IMAGERY SHOWS
CLEAR SKIES NORTH OF THE LOW...AND IT IS LOOKING MORE PROMISING
FOR VFR CONDITIONS LATE TONIGHT INTO SATURDAY MORNING. EAST WINDS
ARE DEVELOPING THROUGH THE GORGE...ALL BE IT LIGHT SO FAR...AND
WILL STRENGTHEN OVERNIGHT. THIS WILL HELP WITH MIXING AND INHIBIT
FOG/LOW CLOUDS IN THE NORTHERN INTERIOR VALLEYS. AREAS SOUTH OF
SALEM MAY HOLD ON TO SOME MVFR STRATUS LATE TONIGHT THROUGH
EARLY SATURDAY MORNING. THE EAST WINDS SHOULD MAKE IT TO THE
COAST AND EXPECT MOSTLY VFR CONDITIONS SATURDAY MORNING THERE TOO.
GUSTY N-E WINDS EXPECTED AT MANY OF THE AIRPORTS SATURDAY
AFTERNOON. 

KPDX AND APPROACHES...SHOWERS WILL DECREASE THIS EVENING AND
SATELLITE IMAGERY SUGGESTS THAT THERE WILL BE A DECENT AMOUNT OF
CLEARING TONIGHT. EAST WINDS SHOULD DEVELOP THIS EVENING BUT
REMAIN BELOW 12 KT THROUGH EARLY SATURDAY MORNING. THE EAST
WINDS...AND ANY CLOUD COVER...SHOULD HELP INHIBIT IFR FOG FROM
DEVELOPING LATE TONIGHT THROUGH SATURDAY MORNING. EAST WINDS WILL
INCREASE LATE SATURDAY MORNING.  TJ

&&

.MARINE...THE A LOW IS STILL MAKING ITS WAY ALONG THE CENTRAL
OREGON COAST THIS AFTERNOON. AREAS UNDER THE LOW WILL HAVE A
COUPLE OF HOURS OF CALM WIND...BUT THE WINDS WILL INCREASE BEHIND
THE LOW AS HIGH PRESSURE FILLS IN. STILL EXPECT GUSTS AROUND 25 KT
BEYOND 10 NM LATER THIS EVENING THROUGH SATURDAY MORNING ALTHOUGH
THERE WILL BE A BRIEF REPRIEVE OF THE WINDS LATE THIS AFTERNOON
AND EARLY EVENING AS THE WINDS VEER TO THE NE. WEAK HIGH PRESSURE
WILL PRODUCE BELOW ADVISORY WINDS SATURDAY AFTERNOON THROUGH
SUNDAY AFTERNOON. THERE MAY ANOTHER PERIOD WITH MARGINAL ADVISORY
WINDS SUNDAY NIGHT THROUGH MONDAY MORNING...MAINLY BEYOND 10 NM.

THE SEAS SHOULD BECOME LESS STEEP LATER THIS AFTERNOON AND
EVENING AS THE WAVE PERIODS REMAIN AROUND 9 SECONDS AND THE SWELL
DECREASES TO 7 TO 8 FEET. THESE SEAS ARE STILL RATHER STEEP...BUT
THE STEEPNESS SHOULD DECREASE TONIGHT THROUGH SATURDAY MORNING.
THE W-NW SWELL WILL GRADUALLY DECREASE THROUGH THE WEEKEND AND
FLUCTUATE BETWEEN 3 AND 5 FEET SUNDAY THROUGH AT LEAST THURSDAY. TJ

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...WINTER WEATHER ADVISORY UNTIL 10 PM PST TONIGHT FOR CASCADES
     IN LANE COUNTY.
WA...NONE. 
PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 10 AM PST SATURDAY FOR
     WATERS FROM 10 TO 60.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL MIDNIGHT PST 
     TONIGHT FOR WATERS FROM 10 TO 60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 4 PM PST THIS
     AFTERNOON OUT 10 NM.
&&

$$

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.

[ W WA | SW WA and W OR | SE WA and NE OR | NE WA and N ID ]

Southeastern Washington and Northeastern Oregon


181 
FXUS66 KPDT 272335 AAA
AFDPDT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PENDLETON OR
335 PM PST FRI FEB 27 2015

UPDATED AVIATION DISCUSSION

.SHORT TERM...TONIGHT THROUGH SUNDAY NIGHT...THE LATEST PACIFIC 
SYSTEM WILL CONTINUE TO WEAKEN AND DROP SOUTH-SOUTHEAST ALONG THE 
PACIFIC NORTHWEST COAST THIS EVENING. THIS SYSTEM WILL THEN 
REDEVELOP OVER THE GREAT BASIN LATER TONIGHT. A DEFORMATION PRECIP 
BAND ASSOCIATED WITH THE SYSTEM CURRENTLY EXTENDS FROM SOUTHEAST 
OREGON NORTHWEST TO SOUTH-CENTRAL WASHINGTON. THIS BAND WILL BECOME 
ALIGNED EAST TO WEST ACROSS EAST-CENTRAL AND CENTRAL OREGON TONIGHT 
AS THE SYSTEM STRENGTHENS OVER NEVADA. WITH THE PRECIP BAND OVER 
EAST-CENTRAL AND CENTRAL OREGON OVERNIGHT AND LOW TEMPS FALLING 
BELOW FREEZING, EXPECT SNOW ACCUMULATIONS TO CONTINUE ACROSS THIS 
AREA. AS SUCH WILL CONTINUE THE CURRENT WINTER WEATHER HIGHLIGHTS. 
WILL SEE PRECIP CHANCES DECREASE THROUGH THE NIGHT ACROSS OUR 
WASHINGTON AND NORTHERN OREGON ZONES AS THE PRECIP BAND ADJUSTS IT'S 
POSITION. COOLER AND DRIER AIR WILL MOVE INTO THE REGION LATE 
TONIGHT AND SATURDAY. THUS THE PRECIP OVER EAST-CENTRAL AND CENTRAL 
OREGON WILL WIND DOWN SATURDAY MORNING, AND LARGELY BE DONE BY 
AFTERNOON. NORTHERLY WINDS WILL INCREASE ACROSS THE AREA LATE 
TONIGHT AND PERSIST INTO SATURDAY. THESE WINDS LOOK TO BE STRONGEST 
ACROSS THE LOWER COLUMBIA BASIN, THE YAKIMA VALLEY AND THE SIMCOE 
HIGHLANDS. THESE WINDS MAY APPROACH SUSTAINED 30 MPH AT SOME 
LOCATIONS. FOR NOW WILL HOLD OFF ON ANY WIND ADVISORIES AS WOULD 
LIKE TO SEE HOW THINGS PROGRESS THROUGH THE NIGHT. SUNDAY WILL SEE 
FAIR, DRY AND COOL CONDITIONS. ANOTHER SYSTEM WILL BEGIN TO APPROACH 
THE REGION LATE SUNDAY NIGHT. AT THIS TIME EXPECT INCREASING CLOUDS 
SUNDAY NIGHT WITH A SLIGHT CHANCE OF LIGHT PRECIP REACHING THE 
CASCADE CREST LATE SUNDAY NIGHT. 90 

.LONG TERM...MONDAY THROUGH FRIDAY...A SHORTWAVE WILL MOVE DOWN FROM 
THE NORTH ON MONDAY...BRINGING A CHANCE OF RAIN AND SNOW SHOWERS. AS 
THIS DISTURBANCE MOVES AWAY FROM THE AREA ON TUESDAY...SHOWERS WILL 
TAPER OFF. NORTHERLY FLOW WILL RETURN BEHIND THE COLD FRONT AND 
COOLER TEMPERATURES CAN ALSO BE EXPECTED ON TUESDAY...WITH HIGHS 
ONLY IN THE MID 20S TO LOWER 40S. HIGH PRESSURE WILL THEN BUILD INTO 
THE REGION ON WEDNESDAY AND THE AREA WILL BE MOSTLY DRY THROUGH 
FRIDAY. TEMPERATURES WILL GRADUALLY WARM DURING THIS PERIOD AND 
HIGHS ON FRIDAY WILL BE IN THE 50S. A DEEP TROUGH OF LOW PRESSURE 
WILL BE APPROACHING THE COAST AT THE END OF THE WEEK...BUT ANY LOCAL 
PRECIPITATION SHOULD BE LIMITED TO THE CASCADES. COBB 

&&

.AVIATION...00Z TAFS...IT WILL CONTINUE TO RAIN AT KDLS THROUGH AT 
LEAST 03Z CAUSING MVFR CEILINGS. KALW AND KPSC WILL REMAIN DRY...AND 
SHOWERS ARE NOT LIKELY TO RETURN TO KYKM AND KPDT. RAIN WILL RETURN 
TO KRDM AND KBDN THIS EVENING...AND CHANGE TO SNOW OVER NIGHT. 
PRECIPITATION WILL MOVE OUT OF THE AREA SATURDAY MORNING...AND CLEAR 
SKIES WILL FOLLOW. WINDS WILL BE NORTHERLY AT MOST LOCATIONS 10-20 
KTS. 82 

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  27  42  20  44 /  60  10   0   0 
ALW  30  43  24  44 /  20  10   0   0 
PSC  32  50  19  49 /  10   0   0   0 
YKM  34  49  22  48 /  30   0   0   0 
HRI  30  48  18  48 /  20  10   0   0 
ELN  31  48  20  49 /  20  10   0   0 
RDM  25  37   8  46 /  80  30   0   0 
LGD  30  41  15  42 /  50  20   0   0 
GCD  25  37  10  43 /  80  60   0   0 
DLS  34  52  24  49 /  30  10   0   0 

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...WINTER STORM WARNING UNTIL 7 AM PST SATURDAY ORZ506.

     WINTER WEATHER ADVISORY UNTIL 4 AM PST SATURDAY ORZ511.

     WINTER WEATHER ADVISORY UNTIL 7 AM PST SATURDAY ORZ505.

     WINTER WEATHER ADVISORY UNTIL 4 AM PST SATURDAY ORZ503.

     WINTER WEATHER ADVISORY UNTIL 4 AM PST SATURDAY ORZ509.

WA...NONE.
&&

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

$$

90/82/82




[ W WA | SW WA and W OR | SE WA and NE OR | NE WA and N ID ]

Northeastern Washington and Northern Idaho


120 
FXUS66 KOTX 272329
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
329 PM PST FRI FEB 27 2015

.SYNOPSIS...
Windy conditions will bring cold wind chill temperatures Friday
night and Saturday morning. Dry weather is expected through
Sunday. Another weather system will pass Monday into early
Tuesday with wintry weather possible, especially the Idaho
Panhandle. Much colder air will move into the area behind this
system with temperatures well below average for the middle of next
week. Drier weather, with moderating temperature follows into 
the end of next week.

&&

.DISCUSSION...

WINDY TONIGHT WITH LOW WIND CHILL TEMPERATURES SATURDAY MORNING

Tonight through Sunday night...This period will be dominated by
the arrival of a cold and dry Canadian continental air mass.
Currently an upper level wave bearing a surface low pressure is
moving down the Washington/Oregon coast. The forecast area is
being impacted by the fringe of this system with valley rain and
minor accumulations of mountain snow in and near the Cascades.
All the latest model guidance is in agreement and plausible
against satellite extrapolation in taking this upper level trough
far south into the Great Basin (with a tapering off of lingering
precipitation near the Cascades by dawn tomorrow) over the next 12
to 24 hours...leaving the forecast area high and dry under a flop-
over ridge aloft. The northerly flow under this building ridge
will hustle in a shot of dry...cool and dense continental polar
air. Thus evolves the main forecast issue for the next 24 hours.

The arrival of this new air mass will manifest itself as windy
conditions tonight and tomorrow morning through the northern
mountain gaps and into the Columbia Basin as this dense air is
squeezed through the gaps and then receives a gravity assist as
it flows downhill and pools in the deep basin. Gradient analysis
and previous case histories suggest low end Wind Advisories are
prudent measures for the Purcell Trench and the Okanogan Valley
tonight and into Saturday morning. 

Meanwhile skies will be clearing. The gradient will slacken during
the day Saturday leading to a night of good radiational cooling
with very cool morning lows by dawn Sunday. Adiabatic mixing of
the low level air mass on Saturday...and on Sunday the lack of low
level snow pack...the higher late season sun angle and the dry
air mass efficiently exploiting the available sun will allow high
temperatures to recover to only slightly below normal readings.

Sunday night the next weather system will approach the region from
the west allowing an increase in clouds and then potential for
some light snow to develop overnight in the Cascades and northern
mountains...while the rest of the area remains dry but cloudy and
thus a bit warmer due to less radiational cooling potential.
/Fugazzi

´╗┐Monday through Friday: The next system drops across the Pacific
Northwest early in the week, with snow chances and another shot of
cold air, before milder and drier conditions return.

Between Monday and Tuesday night a mid-level trough, currently
pushing into Bering Sea, dives southeast across western Canada and
the northwest United States. How quickly it moves by and whether
it will carry a precipitation threat throughout the Inland NW or a
threat relegated to just the northern mountains and Idaho is where
models disagree. The wettest model by far has been the ECMWF and
it has some run-to-run consistency. However the drier models, such
as the GFS, have also been consistently drier. So right now they
staunchly disagree with each other.

The official forecast goes somewhere in the middle. A broader
precipitation threat is forecast, but the best threat of more
measurable snow will be in the mountains and ID panhandle. And
within that latter area confidence is highest toward the ID
Panhandle mountains, where some snow impacts are possible in the
passes. Chances rise early Monday. Between Monday afternoon and
evening the threat will be ending near the lee of the Cascades,
but chances will remain higher farther east, again particularly
across Idaho. Overall chances then dissipate over the east
overnight into Tuesday as the drier air and subsidence pushes in
with a rebounding ridge of high pressure, with the main chances
lingering across the Central Panhandle mountains and Camas Prairie
on Tuesday. There is also the potential for some showers lingering
across the northern mountains on Tuesday as some weaker ripples
drop south along the incoming jet and interact with some shallow
instability in that region.

Behind the precipitation threat comes increased winds and that
next push of cold air. As there are disagreements in the
precipitation potential, there are disagreements in the wind
speeds. In general, however, look for increasing northerly winds
between Monday afternoon and Tuesday. The speeds abate through the
Tuesday night. Tuesday afternoon temperatures are expected to be
below normal by 5 to 10 degrees, followed by lows dropping some 10
to 15 degrees below normal Tuesday night in an atmosphere more
conducive to good rational cooling (i.e. dry, with few clouds and
lighter winds). This means lows in the singles digits and teens
Tuesday night/Wednesday morning.

Between Wednesday and Friday the rebounded ridge is eventually
dampened again by another shortwave trough moving in from the
west. The primary wave stays north of the Canadian border, but
some weaker ripples do skim in on an the westerly flow. For the
most part the forecast is dry, but some shower chances will return
to the toward the north Cascades and along the Canadian border
toward the end of the work week. The rebounding ridge is also
accompanied by some milder air, so look for temperatures to
moderate back toward normal and, by Friday, slightly above normal
again. /J. Cote'

&&

.AVIATION...
00Z TAFS: A storm system will pass out of the region to the south
between 00Z and 12Z. There will be some residual snow showers over
and near the Cascades through 12Z. Meanwhile a push of cold
Canadian air will squeeze through mountain gaps and drain into
the Columbia Basin through 00Z Sunday. While skies will clear out
for VFR conditions at all TAF sites...winds will become gusty and
locally strong with a general north to northeast winds of 20 to 30
kts at the KGEG...KSFF...KCOE...KPUW and KMWH TAF sites. KLWS and
KEAT will be somewhat sheltered but still breezy. /MJF



&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        23  40  19  42  24  39 /  10   0   0   0  10  30 
Coeur d'Alene  22  40  18  44  22  40 /  10   0   0   0  10  40 
Pullman        27  40  18  41  23  40 /  10   0   0   0   0  40 
Lewiston       29  45  23  45  28  44 /  10   0   0   0   0  20 
Colville       25  45  20  46  24  43 /  10   0   0   0  10  30 
Sandpoint      22  39  17  40  21  38 /  10   0   0   0  10  60 
Kellogg        22  36  16  41  22  37 /  10   0   0   0   0  70 
Moses Lake     31  48  22  47  26  48 /  10   0   0   0  10  20 
Wenatchee      32  48  27  48  30  48 /  20   0   0   0  10  20 
Omak           30  48  22  48  26  47 /  30   0   0   0  20  20 

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Wind Advisory until 10 AM PST Saturday for Coeur d'Alene Area-
     Northern Panhandle.

WA...Wind Advisory until 10 AM PST Saturday for Okanogan Valley.

&&

$$


[ W WA | SW WA and W OR | SE WA and NE OR | NE WA and N ID ]

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