MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 139 AM EDT THU MAR 31 2016 VALID MAR 31/0000 UTC THRU APR 03/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 0Z PRELIMINARY MODEL EVALUATION ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...TROUGH MOVING INTO THE EAST/ASSOCIATED SURFACE LOW MOVING NORTH OF NEW ENGLAND AND EASTWARD PROGRESSING COLD FRONT... GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE MULTIPLE SHORTWAVES WILL EJECT EAST OUT OF THE CENTRAL PLAINS THURSDAY INTO FRIDAY HELPING SUPPRESS THE EAST COAST RIDGE. A LOW PRESSURE SYSTEM WILL TRACK FROM THE GREAT LAKES INTO SOUTHERN CANADA DRAGGING A COLD FRONT INTO THE EAST COAST. AN ADDITIONAL PIECE OF SHORTWAVE ENERGY MAY TRY TO ALLOW FOR A SECONDARY LOW REDEVELOPMENT ACROSS NORTHERN NEW ENGLAND ON FRIDAY...ALTHOUGH GUIDANCE IS SPLIT ON THIS SOLUTION. WITH REGARDS TO THE INITIAL LOW PRESSURE AND COLD FRONTAL PROGRESSION...MOST OF THE DETERMINISTIC GUIDANCE LIES WITHIN THE GENERAL ENSEMBLE SPREAD...WITH NO CLEAR OUTLIERS SEEN. ON FRIDAY THE GFS/GEM REDEVELOP A SURFACE LOW ALONG THE FRONT ACROSS NORTHERN NEW ENGLAND...WHILE THE ECMWF AND UKMET ARE LESS AGGRESSIVE THIS SOLUTION. BUT HONESTLY WHETHER THIS OCCURS OR NOT WILL GENERALLY HAVE LITTLE IMPACT ON SENSIBLE WEATHER...WITH THE FRONT STILL PROGRESSING EAST AT A SIMILAR CLIP IN ALL THE MODELS. THUS WILL PREFER A GENERAL MODEL CONSENSUS SYNOPTICALLY FOR THIS SYSTEM. THERE ARE SOME DIFFERENCES CLOSER TO THE GULF COAST ON FRIDAY...AND WILL DISCUSS THIS MORE IN THE SECTION BELOW TALKING ABOUT THE SOUTEHRN STREAM SHORTWAVE ENERGY THAT WILL INTERACT WITH THIS FRONT. ...MID-LEVEL SHORTWAVE DROPPING SOUTHWARD OVER THE NORTH-CENTRAL U.S. BY THURSDAY... PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE A SHORTWAVE DISTURBANCE DROPPING SOUTHWARD FROM THE NORTHERN STREAM TROUGH OVER CANADA IS FORECAST TO REACH THE DAKOTAS BY THURSDAY MORNING AND PIVOT AROUND THE SOUTHERN PERIPHERY OF THAT TROUGH AND PROGRESS EASTWARD TOWARDS THE OHIO VALLEY AND GREAT LAKES BY THE END OF THE PERIOD. OVERALL...THE MODELS ARE IN RELATIVELY GOOD AGREEMENT WITH THIS FEATURE AND A GENERAL MODEL COMPROMISE WORKS WELL. ...ELONGATED TROUGH HANGING BACK OVER THE SOUTHWEST BY MIDWEEK...EJECTING ACROSS TX INTO THE SOUTHEAST INTO SATURDAY... PREFERENCE: GFS/ECMWF/UKMET BLEND CONFIDENCE: AVERAGE AS THIS SHORTWAVE ENERGY EJECTS EAST ACROSS TX INTO THE SOUTHEAST...IT...ALONG WITH ITS ASSOCIATED SUBTROPICAL JET MAX...WILL INTERACT WITH THE LINGERING FRONTAL BOUNDARY ACROSS THE SOUTHEAST...WHICH SHOULD CAUSE A REGENERATION OF CONVECTION FRIDAY INTO FRIDAY NIGHT ACROSS THE GULF COAST REGION. OVERALL THE MODELS ARE IN GOOD AGREEMENT ON THE SYNOPTIC EVOLUTION OF THIS SETUP. THE 0Z NAM CONTINUES TO APPEAR TOO STRONG WITH THE SHORTWAVE THOUGH...WHICH RESULTS IN EVERYTHING BEGIN SHIFTED A BIT TOO FAR NORTH. OTHERWISE DIFFERENCES IN THE MODELS COME DOWN TO THE EXACT PLACEMENT OF THE FRONT WHEN THIS ADDITIONAL FORCING INTERACTS WITH IT. THIS WILL LIKELY BE CONTROLLED BY TWO FACTORS...ONE BEING THE SYNOPTIC SETUP AND THE OTHER BEING THE ROLE OF CONVECTION ACTING TO SUPPRESS THE EFFECTIVE FRONT SOUTH TOWARDS THE GULF COAST. GIVEN IT IS DIFFICULT TO PREDICT THE EXACT CONVECTIVE EVOLUTION THIS FAR OUT...CONFIDENCE ON THE EXACT FRONTAL LOCATION IS THUS LOW. IN GENERAL A BLEND OF THE ECMWF/GFS/UKMET SEEMED TO BEST REPRESENT A SOLUTION IN THE MIDDLE OF THE GUIDANCE ENVELOPE. ...SHORTWAVE DIVING INTO THE UPPER MIDWEST EARLY SATURDAY...REINFORCING THE NORTHEAST TROUGH THROUGH SATURDAY... PREFERENCE: GENERAL MODEL CONSENSUS CONFIDENCE: AVERAGE A SURFACE LOW AND ARCTIC FRONT ARE FORECAST TO REACH NORTHERN MN AND LAKE SUPERIOR LATE FRIDAY NIGHT. SOME MODEL DIFFERENCES REMAIN WITH REGARDS TO HOW FAR SOUTH THIS SHORTWAVE GOES AND THUS HOW DEEP IT CARVES OUT THE TROUGH OVER THE NORTHEAST. THIS ALSO RESULTS IN DIFFERENCES IN PLACEMENT OF THE SURFACE LOW AS IT INTENSIFIES OFF THE NEW ENGLAND COAST. UNTIL CONSISTENT TRENDS ARE SEEN A GENERAL MODEL CONSENSUS SHOULD HANDLE THIS SYSTEM WELL. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... CHENARD