Small Craft Advisory 626, NWS Seattle, WA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
850 PM PST WED JAN 12 2011

.SYNOPSIS...A WET AND MILD WEATHER PATTERN WILL PERSIST THROUGH THE
WEEKEND AS A SERIES OF SYSTEMS MOVES INTO THE AREA FROM THE
SOUTHWEST.

&&

.SHORT TERM...THE STRONG OMEGA BLOCK OVER THE EAST CENTRAL PACIFIC
AND ALASKA HAS COMPLETELY PINCHED OFF AND APPEARS TO BE RETROGRADING
INTO SIBERIA. SHORT TERM MODELS NOW SHOW A SERIES OF MILD AND
MODERATELY STRONG SOUTHERN STREAM SYSTEMS AFFECTING THE AREA TONIGHT
THROUGH AROUND THE FIRST PART OF NEXT WEEK...WITH BRIEF AND
DIFFICULT TO TIME BREAKS BETWEEN SYSTEMS. RIDGING ALONG ABOUT 140W
MAY BECOME ESTABLISHED AGAIN TOWARD THE MIDDLE OF NEXT WEEK...BUT
MODELS ARE SHOWING POOR CONSISTENCY AND CONTINUITY BEYOND ABOUT NEXT
MONDAY. IN THE SHORT TERM...TEMPERATURES WILL AVERAGE WELL ABOVE
NORMAL AND JUST ABOUT EVERY TIME PERIOD WILL SEE SOME PRECIPITATION.

TONIGHT...SATELLITE IMAGERY SHOWS A LOW CENTERED NEAR 47N 132W WITH
A TRIPLE POINT IN THE COASTAL WATERS. PRECIPITATION IS ALREADY
SPREADING INLAND AND PRES GRADIENTS ARE TRENDING OFFSHORE. COLD AIR
IN EASTERN WASHINGTON HAS YET TO COMPLETELY SCOUR OUT WITH
TEMPERATURES AT MOST LOCATIONS IN THE BASIN IN THE TEENS AND 20S.
RATTLESNAKE MOUNTAIN AND THE SKI AREA AT MISSION RIDGE SHOW VERY
THIN LAYERS ABOVE FREEZING AROUND 4000 FEET. IN THE MEAN TIME
STAMPEDE PASS HAS GONE FROM RAIN TO SNOW. THE 18Z MODEL GUIDANCE
SHOWS NEARLY AN INCH OF WATER IN THE CASCADES TONIGHT INTO MIDDAY
THU. SO AS GRADIENTS TURN OFFSHORE EXPECT PRECIPITATION TO
PREDOMINATELY BECOME SNOW...OR A MIXTURE OF SNOW AND FREEZING
RAIN...IN THE PASSES. HENCE A WINTER WEATHER ADVISORY WAS ISSUED
THERE. ONCE THE FRONT PASSES AROUND NOON...EXPECT WESTERLY FLOW TO
TURN PRECIPITATION BELOW ABOUT 5000 FEET BACK TO ALL RAIN.

PRECIPITATION TAPERS OFF THU NIGHT...THEN THE NEXT WARM OCCLUSION
PASSES ACROSS THE AREA ON FRI. BY THIS TIME THE COLD AIR IN EASTERN
WASHINGTON SHOULD BE COMPLETELY SCOURED AND THE PASSES SHOULD BE
RAIN WITH TEMPERATURES ABOVE FREEZING.

ONCE AGAIN...PRECIPITATION TAPERS OFF LATE FRI OR FRI NIGHT ONLY TO
BE FOLLOWED BY YET MORE WARM OCCLUSIONS SAT AND AGAIN SUN.

THE CASCADES WERE UPDATED EARLIER FOR WINTRY PRECIPITATION TONIGHT
INTO MIDDAY THU. THE REMAINDER OF THE FORECASTS LOOK GOOD. ALBRECHT

.LONG TERM...PREVIOUS LONG TERM DISCUSSION FOLLOWS...MOIST ONSHORE
FLOW WILL CONTINUE ACROSS WESTERN WA THROUGH THE WEEKEND AND INTO
EARLY NEXT WEEK...RESULTING IN MORE RAIN AND MILD TEMPERATURES. WE
MAY DRY OUT A BIT BY MIDWEEK AS A STRONG UPPER LEVEL RIDGE BUILDS
OVER THE NE PAC. LOWERED POPS AND DROPPED TEMPS A FEW DEGREES FROM
WEDNESDAY ON. THE GFS AND ECMWF HINT THAT THIS DRYING TREND MAY
STRETCH INTO LATE NEXT WEEK. IF SO WILL CONTINUE TO SLASH AWAY AT
THE POPS. 33

&&

.HYDROLOGY...THE NEXT SEVERAL DAYS WILL BE MILD AND FAIRLY WET AS A
SERIES OF WEATHER SYSTEMS MOVE THROUGH...BRINGING RAIN AT TIMES. THE
ACCUMULATED RAINS FROM THESE WEATHER SYSTEMS ARE EXPECTED TO CAUSE
RISES ON MOST AREA RIVERS OVER THE NEXT COUPLE OF DAYS WITH SOME
RIVERS NEARING BANKFUL BY FRIDAY. AT THIS TIME...NO RIVERS ARE
EXPECTED TO REACH FLOOD STAGE BUT SOME MINOR FLOODING CANNOT BE
COMPLETELY RULED OUT STARTING LATE THIS WEEK AND CONTINUING INTO
NEXT WEEK. FLOODING ON THE GREEN RIVER IS NOT EXPECTED IN THE NEXT
10 DAYS. 33

&&

.AVIATION...STRONG AND MOIST WLY FLOW ALOFT WILL CONTINUE ACROSS THE
REGION. A WMFNT WILL MOVE N ACROSS THE AREA OVERNIGHT THRU THU.
INCREASING LOW LEVEL E OR SE FLOW AHEAD OF THE WMFNT...BECMG ONSHORE
OR SLY BEHIND IT. CIGS ARE ANTICIPATED TO GENERALLY BE IN THE 2-4K
FT RANGE. VSBYS WILL BE RESTRICTED MAINLY IN THE 3-5SM RANGE BY RAIN.
THE CASCADES WILL BE OBSCURED.

KSEA...CIGS WILL GENERALLY IN THE 2-4K FT RANGE...OCCASIONALLY NEAR
1K FT LATE TONIGHT THRU THU MORNING. RAIN WILL REDUCE THE VISIBILITY
INTO MAINLY THE 3-5SM RANGE. THE WMFNT IS EXPECTED TO MOVE ACROSS
THE TERMINAL AROUND 1200 UTC. WINDS SHOULD KICK UP FROM THE S WITH
AND BEHIND THE FRONT.

&&

.MARINE...A WARM FRONT OFF THE OREGON COAST WILL MOVE N ACROSS THE
AREA LATER TONIGHT THROUGH THU. EXPECT ANOTHER FRONTAL SYSTEM TO
FOLLOW LATE THU NIGHT INTO FRI...FOLLOWED BY YET ANOTHER ONE ON
SATURDAY.

&&

.AVALANCHE...AVALANCHE WARNING CONDITIONS CONTINUE THURSDAY.
ADDITIONAL HEAVY SNOWFALL OR RAIN AT FURTHER WARMING TEMPERATURES IS
EXPECTED TO RENEW THE HIGH DANGER OVERNIGHT AND THURSDAY. NATURAL
AVALANCHES CONTINUE TO BE LIKELY. TRAVEL IN AVALANCHE TERRAIN IS NOT
RECOMMENDED. SEE NWAC.US FOR DETAILS. KRAMER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...WINTER WEATHER ADVISORY THROUGH NOON THU FOR THE CASCADE PASSES.
PZ...

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