EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 213 AM EDT WED OCT 05 2016 VALID 12Z SAT OCT 08 2016 - 12Z WED OCT 12 2016 OVERVIEW ~~~~~~~~ UPPER PATTERN WILL TRANSITION TO A MOSTLY ZONAL FLOW BY EARLY NEXT WEEK BEFORE PACIFIC TROUGHING INCHES TOWARD THE PAC NW LATER IN THE WEEK. OFF THE SOUTHEAST COAST, HURRICANE MATTHEW IS EXPECTED TO CURVE EASTWARD ON SATURDAY PER THE NATIONAL HURRICANE CENTER BUT ITS TRACK AFTER THAT BECOMES INCREDIBLY UNCERTAIN. GUIDANCE AND UNCERTAINTY ASSESSMENT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ OUT WEST, A VERY STRONG PACIFIC JET STILL LOOKS TO SET UP NEXT WEEK BETWEEN A DEEP LOW IN THE BERING SEA AND SUBTROPICAL RIDGING OVER THE PAPAHANAUMOKUAKEA MARINE NATIONAL MONUMENT. FAST FLOW WOULD NATURALLY DECREASE CONTINUITY OF SYSTEM TIMING BUT THE ENSEMBLES SEEM TO BE TRENDING TOWARD SENDING SHORTWAVES OR CLOSED LOWS EASTWARD IN PIECES AS THE JET EXTENDS EASTWARD IN TIME, THE MAIN ONE COMING MIDWEEK AT THE EXPENSE OF THE LEAD TROUGH THAT SHOULD WEAKEN THROUGH CALIFORNIA ON MONDAY. IN THE CENTRAL STATES, EAST OF THE DIVIDE, LOW AMPLITUDE FLOW WILL SUPPORT A WAVY BOUNDARY THROUGH THE HIGH PLAINS, BUT WHERE THIS SETS UP WILL DETERMINE THE WARMER VS COLDER TEMPERATURES. ENSEMBLE SPREAD IS MAXIMIZED IN THIS AREA FROM MONTANA TO THE DAKOTAS. ENSEMBLE MEANS HELPED FORM A MIDDLE GROUND SOLUTION FOR TEMPERATURES AND PRESSURES SINCE THERE IS UNCERTAINTY IN THE DETAILS. IN THE EAST, IT WOULD BE AN UNDERSTATEMENT TO SAY THAT HURRICANE MATTHEW REPRESENTS A FORECAST CHALLENGE. LATEST ENSEMBLES NUDGED PAST THE TIPPING POINT AND NOW MOSTLY CARRY MATTHEW EASTWARD AWAY FROM THE CAROLINAS RATHER THAN NORTHEASTWARD TOWARD NEW ENGLAND INTO THE APPROACHING (AND NOW WEAKER) FRONT. BY NEXT WEEK, THE SPREAD IS ABOUT AS BIG AS IT GETS AS SOME MEMBERS STILL TAKE IT RAPIDLY NORTHEASTWARD WHILE OTHERS MEANDER IT EASTWARD AND STILL OTHERS CURVE IT BACK TO THE SOUTHEAST OR SOUTH NEAR/PAST 30N. THE VARIOUS ENSEMBLE MEMBER'S SOLUTIONS MAKE FOR ENLIGHTENING FORECAST SCENARIOS -- MANY OF WHICH ARE TRULY BIZARRE. PLEASE CONSULT THE NATIONAL HURRICANE CENTER FOR THE LATEST FORECAST OUT THROUGH DAY 5. USED A MODEL/ENSEMBLE CONSENSUS EARLY BEFORE SWITCHING TO A 50/50 18Z GEFS/12Z ECMWF ENSEMBLE MEAN BLEND FOR NEXT WEEK GIVEN THE UNCERTAINTY IN THE EAST AS WELL AS OUT OF THE PACIFIC. WEATHER HIGHLIGHTS/THREATS ~~~~~~~~~~~~~~~~~~~~~~~~~~ ASIDE FROM THE HEAVY RAIN AROUND MATTHEW'S CIRCULATION OFF THE SE COAST, PRECIPITATION SHOULD GENERALLY BE LIGHT ACROSS THE CONUS. THE EXCEPTION MAY BE OVER THE FOUR CORNERS REGION AS MID-LEVEL ENERGY PUSHES THROUGH THE REGION THIS WEEKEND. BY THE END OF THE PERIOD, THE PAC NW WILL SEE AN INCREASED CHANCE OF PRECIPITATION AS THE UPPER TROUGH APPROACHES, BUT TIMING IS STILL UNCLEAR. FRACASSO