034  
FXUS02 KWBC 110600  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1259 AM EST THU JAN 11 2018  
 
VALID 12Z SUN JAN 14 2018 - 12Z THU JAN 18 2018  
 
...INCREASINGLY WET/WHITE NEXT WEEK FOR THE PACIFIC NORTHWEST NEXT  
WEEK...  
 
   
..OVERVIEW
 
 
QUIETER PATTERN FOR SUN-MON OVER MOST OF THE LOWER 48 AS A CLIPPER  
SYSTEM DIVES THROUGH THE GREAT LAKES. BY NEXT TUE-WED, THIS MAY  
SPIN UP A DEEPER SYSTEM JUST OFFSHORE NEW ENGLAND BEFORE MOVING  
OUT TO SEA. THE WEST WILL BECOME MUCH MORE ACTIVE AS THE UPPER  
RIDGE YIELDS COMPLETELY TO STRONG FLOW OUT OF THE NORTHEAST  
PACIFIC OCEAN. A COUPLE FRONTS WILL MOVE THROUGH WA/OR AND  
NORTHERN CALIFORNIA NEXT TUE-THU.  
 
   
..GUIDANCE ASSESSMENT/PREFERENCES
 
 
ASIDE FROM THE 12Z UKMET, THE 12Z GFS/ECMWF/CANADIAN (AND 18Z GFS)  
OFFERED GOOD CLUSTERING WITH THE CLIPPER SYSTEM THROUGH THE LAKES  
SUN/MON AND THE EROSION OF THE WESTERN RIDGE. BY TUESDAY, ECMWF  
BECAME SLOWER TO MOVE THE CLIPPER OFF THE EAST COAST BUT JUMPED  
THE FRONT INTO THE ATLANTIC ANYWAY TO CATCH UP TO THE GFS/CANADIAN  
CLUSTER BY WEDNESDAY. ENSEMBLES VARY ON HOW MUCH TO DEEPEN THIS  
SYSTEM BUT ITS TRACK NEAR THE 40/70 BENCHMARK MEANS THERE IS  
FAIRLY LARGE UPSIDE POTENTIAL FOR SNOW OVER E/SE NEW ENGLAND  
DEPENDING ON HOW THINGS PLAY OUT.  
 
FOR THE WEST, THE STRONG 200KT W PAC JET IN THE SHORT TERM WILL  
MIGRATE EASTWARD OVER THE NEXT SEVERAL DAYS AND EVENTUALLY CARRY A  
LEAD COLD FRONT INTO WA/OR/NORCAL LATE MONDAY INTO TUESDAY. THAT  
SHOULD PASS THROUGH THE INTERIOR NW INTO THE ROCKIES AND WEAKEN AS  
THE RIDGE TO ITS EAST WEAKENS AS WELL. NEXT SYSTEM OUT OF THE  
PACIFIC SHOULD TAKE THE MAIN LOW PRESSURE CENTER CLOSER TO  
VANCOUVER ISLAND BY NEXT THURSDAY (ENSEMBLE MEAN CONSENSUS IS  
NEARLY ALIGNED IN LOCATION/DEPTH) BUT THE GFS/ECMWF LIED ON EITHER  
SIDE OF THE MEAN (GFS FARTHER SE AND ECMWF TO THE NW) BUT THE  
CANADIAN WAS WELL REMOVED TO THE SOUTHWEST ALONG 40N (ONLY ONE  
ENSEMBLE MEMBER NEAR THAT LOCATION). BLEND OF THE GFS/ECMWF WITH  
THEIR MEANS SEEMED PRUDENT.  
 
   
..WEATHER HIGHLIGHTS
 
 
CLIPPER SYSTEM WILL BRING LIGHT SNOW TO THE GREAT LAKES (WITH  
LOCAL ENHANCEMENT) AND ANOTHER PUSH OF COLDER AIR (SUB-ZERO HIGHS  
FOR MUCH OF THE DAKOTAS AND MINNESOTA ON MONDAY). TEMPERATURES  
10-25 DEGREES BELOW AVERAGE WILL LINGER IN THE EAST THROUGH THE  
WEEK. DEPENDING ON HOW THE CLIPPER SYSTEMS TURNS THE CORNER NEAR  
THE NORTHEAST WILL DETERMINE HOW MUCH (IF ANY) SNOW WILL FALL OVER  
NEW ENGLAND. FOR NOW, HIGHLIGHTED THE AREA IN THE EXPERIMENTAL DAY  
4-7 WINTER WEATHER OUTLOOK GRAPHICS (ALSO AVAILABLE ON  
WWW.DIGITAL.WEATHER.GOV).  
 
ABOVE AVERAGE TEMPERATURES WILL RULE FOR NEXT WEEK IN THE WEST  
EVEN AFTER THE FIRST FRONT PUSHES THROUGH. PRECIPITATION WILL  
ENTER THE PAC NW STARTING MONDAY AND LIKELY CONTINUE WITH FEW  
BREAKS FOR THE COAST THROUGH THURSDAY. EAST OF THE CASCADES, THERE  
SHOULD BE AT LEAST SOME RESPITE BETWEEN THE FIRST AND SECOND  
FRONT. SECOND SYSTEM APPEARS TO HAVE MORE MOISTURE TO PUSH INTO  
THE REGION AND THIS IS REFLECTED IN THE HIGHER ENSEMBLE  
PROBABILITIES OF AT LEAST AN INCH OF QPF AND HIGH IVT VALUES  
RELATIVE TO CLIMATOLOGY.  
 
FRACASSO  
 

 
 
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