EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1035 AM EST SUN JAN 22 2017 VALID 12Z WED JAN 25 2017 - 12Z SUN JAN 29 2017 ...GENERAL FLOW PATTERN/MODEL EVALUATION... IN THE WAKE OF A COASTAL STORM LIFTING AWAY FROM MAINE AND A SURFACE CYCLONE TRACKING THROUGH THE GREAT LAKES ON WEDNESDAY...THE PATTERN WILL BECOME FAIRLY QUIET OVER THE LOWER 48 DURING THE LATER HALF OF THE WEEK AND INTO NEXT WEEKEND. A BROAD TROUGH CARVING OUT OVER THE EASTERN HALF OF THE NATION WILL HELP PLUNGE A FRONTAL BOUNDARY WELL SOUTH INTO THE GULF OF MEXICO...WHILE UPPER RIDGING AND SURFACE HIGH PRESSURE ARE EXPECTED TO BUILD IN AND HOLD STRONG OVER THE WESTERN U.S.. THERE REMAINS SOME UNCERTAINTY WITH THE EXACT TIMING OF THE SURFACE LOW CROSSING THE GREAT LAKES ON WEDNESDAY. THE WPC FORECAST STAYED FAIRLY CLOSE TO THE 00Z ECMWF/UKMET/ECMWF ENSEMBLE MEAN...WHICH HAVE BEEN CONSISTENTLY IN THE MIDDLE OF SLOWER CMC SOLUTIONS AND FASTER GFS SOLUTIONS WITH THIS FEATURE...AND THE ECMWF/UKMET/ECMWF ENSEMBLE MEAN ALSO MATCH WELL WITH THE PREVIOUS WPC FORECAST. LATER IN THE FORECAST PERIOD...A BLEND OF THE 00Z GFS/GEFS MEAN AND ECMWF/ECWMF ENSEMBLE MEAN APPEARED TO BEST ACCOUNT FOR THE GOOD AGREEMENT AMONG DETERMINISTIC GUIDANCE WITH THE LONGWAVE PATTERN...EVEN OUT THROUGH DAY 7/NEXT SUNDAY...BUT THE BLEND ALSO SMOOTHED OUT SOME OF THE TIMING/AMPLIFIED DIFFERENCES THAT DEVELOP WITH IMPULSES OF SHORTWAVE ENERGY DIGGING INTO THE NORTH CENTRAL U.S. LATER THIS WEEK AND A POSSIBLE PACIFIC SYSTEM REACHING BRITISH COLUMBIA NEXT WEEKEND. ...WEATHER HIGHLIGHTS/THREATS... SNOW IS EXPECTED WITH BOTH A COASTAL STORM EXITING MAINE AND SURFACE CYCLONE TRACKING ACROSS THE GREAT LAKES ON WEDNESDAY...BUT THEN PRECIPITATION SHOULD BECOME RATHER SPARSE ACROSS THE CONUS TOWARDS THE LATER HALF OF THE WEEK AND THROUGH NEXT WEEKEND. AN EXCEPTION TO THIS WILL BE ACROSS THE GREAT LAKES REGION AND CENTRAL APPALACHIANS...WHERE COOL/DRY NORTHWESTERLY FLOW WILL FOSTER LOCALIZED LAKE EFFECT AND UPSLOPE SNOW SHOWERS. ALSO...PRECIPITATION FROM A SERIES OF PACIFIC SYSTEMS PROGRESSING TOWARDS WESTERN CANADA COULD IMPACT THE EXTREME NORTHWESTERN CORNER OF THE NATION...AND MOISTURE RETURNING NORTH OF A FRONTAL BOUNDARY PLUNGED IN THE GULF OF MEXICO SHOULD INCREASE THE CHANCE OF PRECIPITATION OVER SOUTH TEXAS AND FLORIDA NEXT WEEKEND. INITIALLY MILD CONDITIONS IN THE EAST SHOULD TREND COOLER TOWARDS THE END OF THE WEEK AS A BROAD TROUGH CARVES OUT ALOFT...WHILE TEMPERATURES WILL STAY BELOW AVERAGE IN THE WEST UNDER AN UPPER RIDGE (BUT RATHER STRONG SURFACE HIGH PRESSURE). GERHARDT