EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1100 AM EST THU JAN 11 2018 VALID 12Z SUN JAN 14 2018 - 12Z THU JAN 18 2018 ...STORMS TO THREATEN THE NWRN US AND NERN US NEXT WEEK... ...OVERVIEW... A MORE BENIGN WEATHER PATTERN IS ON TAP SUN-MON OVER MOST OF THE LOWER 48 AS A CLIPPER SYSTEM DIVES THROUGH THE GREAT LAKES. THERE IS A THREAT TO SPIN UP A DEEPENED MID-ATLANTIC TO NEW ENGLAND COASTAL STORM BY TUE/WED WITH THIS AND/OR THE DIGGING OF UPSTREAM NRN STREAM SHORTWAVE ENERGY. THE WEST WILL BE BECOME MUCH MORE ACTIVE AS WELL AS THE UPPER RIDGE YIELDS COMPLETELY TO STRONG FLOW OUT OF THE NERN PACIFIC AND HEIGHT FALLS/FRONTS MOVE THROUGH WA/OR/NRN CA TUE-THU IN AN INCREASINGLY WET AND UNSETTLED PATTERN. ...GUIDANCE ASSESSMENT/PREFERENCES... MODELS AND ENSEMBLES ARE WELL CLUSTERED AND UNCERTAINTY IS BELOW AVERAGE DAYS INTO MONDAY ACROSS MUCH OF THE NATION. A BLEND OF THE 06 UTC GFS AND 00 UTC ECMWF SEEMS TO REPRESENT WELL. FORECAST CLUSTERING AND PREDICTABILITY WANES SOME IN THE TUE-THU TIMEFRAME JUST A SEVERAL POTENTIAL STORMS WORK TOWARD THE NWRN US AND WELL DOWNSTREAM FROM THE GREAT LAKES TO JUST OFFSHORE THE MID-ATLANTIC AND NEW ENGLAND. A BLEND OF THE 06 UTC GEFS AND 00 UTC ECMWF SEEMS TO BEST RESPRESENT THE MORE PREDICTABLE WEATHER FEATURES IN THIS TIME FRAME INCLUDING AN INCREASING THREAT FOR ACTIVE STORMY WEATHER ON BOTH COASTS. ...WEATHER HIGHLIGHTS... A WELL DEVELOPED CLIPPER SYSTEM WILL BRING LIGHT TO MODERATE SNOWS 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 CENTRAL AND ERN US NEXT WEEK AS A SERIES OF COLD HIGH PRESSURE CELLS DIG FAR SOUTHWARD IN THE WAKE OF THE LOWS. UNCERTAINTY ABOUNDS WITH HOW THE CLIPPER SYSTEM TURN THE CORNER NEAR THE NORTHEAST AND THE EXTENT OF MIDWEEK ERN US MID-UPPER LEVEL TROUGH AMPLITUDE AND THREAT OF HEAVY SNOW WITH POTENTIAL MID-ATLANTIC/NEW ENGLAND COASTAL LOWS. ABOVE AVERAGE TEMPERATURES WILL RULE FOR NEXT WEEK IN THE WEST EVEN AFTER THE FIRST FRONT/HEIGHT FALLS WORKS THROUGH. PRECIPITATION RAMPS UP OVER THE PAC NW/NRN CA MONDAY AND CONTINUES WITH FEW BREAKS FOR THE COAST THROUGH THURSDAY. EAST OF THE CASCADES...THERE SHOULD BE AT LEAST SOME RESPITE BETWEEN THE FIRST AND SECOND SYSTEM. A SECOND DEEP SYSTEM APPROACH ALLOWS MORE MOISTURE TO FEED INTO THE REGION AND THIS IS REFLECTED IN THE HIGHER ENSEMBLE PROBABILITIES OF AT LEAST AN INCH OF QPF AND HIGH IVT RELATIVE TO CLIMATOLOGY. FRACASSO