EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1123 AM EST SAT MAR 12 2016 VALID 12Z TUE MAR 15 2016 - 12Z SAT MAR 19 2016 ...GENERAL FLOW PATTERN... VIGOROUS MID-LEVEL ENERGY DIGGING INTO THE NORTH CENTRAL U.S. ON TUESDAY WILL BE THE MAIN FOCUS OF THE MEDIUM RANGE PERIOD AS IT TRANSITIONS INTO A DEEP VORTEX NEAR THE GREAT LAKES REGION BY WEDNESDAY. THE ACCOMPANYING SURFACE FRONT WILL PROGRESS EASTWARD OUT OF THE MISSISSIPPI VALLEY BEFORE PUSHING OFF THE EASTERN SEABOARD....WITH THE TAIL END OF THE BOUNDARY EXPECTED TO LINGER OVER THE SOUTHEAST AND NORTHERN GULF OF MEXICO LATE NEXT WEEK. UPSTREAM...SHORTWAVE ENERGY STREAKING OUT OF BRITISH COLUMBIA ON THURSDAY COULD POTENTIALLY AMPLIFY WHILE THE ENERGY DIVES INTO THE NORTHERN ROCKIES AND AN UPPER RIDGE GRADUALLY BUILDS INTO THE WESTERN U.S.. ...OVERVIEW AND GUIDANCE EVALUATION... DETERMINISTIC GUIDANCE CONTINUES TO SHOW LARGE FLUCTUATIONS WITH THE EXACT EVOLUTION OF THE DEEP VORTEX CLOSING OFF OVER THE GREAT LAKES AND DISTINCT DIFFERENCES WITH THE UPPER RIDGE BUILDING INTO THE WESTERN U.S.. MODELS HAVE GENERALLY BEEN TRENDING TOWARDS MORE AMPLIFIED FLOW OVER THE GREAT LAKES NEXT WEDNESDAY AND THURSDAY...SUGGESTING THE CORE OF THE UPPER LOW COULD BE FARTHER SOUTH AND SLOWER TO LIFT INTO CANADA THAN THE CURRENT ENSEMBLE MEANS ARE ADVERTISING. WITH REGARDS TO THE RIDGE BUILDING INTO THE WEST...THE ECWMF REMAINS TO BE ON THE SHARPER/MORE AMPLIFIED SIDE OF MODEL SPREAD...WHILE THE GFS CONTINUES TO BE BROADER/MORE SUPPRESSED WITH THE RIDGE. UNCERTAINTY IN THE DETAILS OF THE PATTERN LED TO A FORECAST LARGELY BASED ON ENSEMBLE MEAN GUIDANCE...WITH MORE CREDIT GIVEN TO THE ECMWF ENSEMBLE MEAN SINCE IT BEST REPRESENTS THE OVERALL TREND TOWARDS A MORE AMPLIFIED SOLUTION WITH THE FLOW OVER THE GREAT LAKES WEDNESDAY AND THURSDAY. ...SENSIBLE WEATHER HIGHLIGHTS... THE DEEP VORTEX CLOSING OFF OVER THE GREAT LAKES AND THE ASSOCIATED COLD FRONT PUSHING FROM THE MISSISSIPPI VALLEY TO THE EASTERN SEABOARD WILL BE THE MAIN WEATHER MAKERS NEXT WEEK. AHEAD OF THE FRONT...TEMPERATURES WILL REMAIN ABOVE AVERAGE IN THE EAST. COOLER TEMPERATURES WILL FOLLOW BEHIND THE FRONT BUT MOSTLY BACK TO NEAR CLIMATOLOGICAL AVERAGES FOR MID-MARCH. PRECIPITATION SHOULD BE LIGHT TO MODERATE ALONG AND AHEAD OF THE FRONT...CONCENTRATED INITIALLY NEAR THE SURFACE LOW TRACK WITH SOME WINTRY WEATHER ON THE NORTHWESTERN SIDE. THE TAIL END OF THE BOUNDARY IS EXPECTED TO STALL ACROSS THE SOUTHEAST AND NORTHERN GULF AS IT ALIGNS PARALLEL TO THE UPPER FLOW. LOW LEVEL MOISTURE SHOULD INCREASE FROM THE SOUTH INTO THE GULF STATES AND HELP EXPAND THE PRECIPITATION NORTHWARD THEN EASTWARD. QUESTIONS REMAIN FOR THE CENTRAL STATES LATE NEXT WEEK AS ONE OR MORE SHORTWAVES MAY STREAM OUT FROM A TROUGH AMPLIFYING OVER THE ROCKIES. GERHARDT