MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 130 PM EST SUN MAR 05 2017 VALID MAR 05/1200 UTC THRU MAR 09/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION WITH PREFERENCES/CONFIDENCE INTERVALS ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT RANGE FORECASTS. DEEP CYCLONE MOVING BY CENTRAL US/CAN BORDER MONDAY EVE COLD FRONT MOVING THROUGH THE PLAINS AND EAST ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: AVERAGE WHILE THE GUIDANCE AGREES IN PRINCIPLE ON THE LOW TRACK, DIFFERENCES IN DEPTH APPEAR TO BE CAUSED BY WHAT IS EVOLVING, AND ASSOCIATED DIFFERENCES, ALOFT. THE 12Z GFS APPEARS TO GENERATE A LARGE VERTICAL MOTION BULL'S EYE NEAR THE WIND RIVER RANGE OF WY WHICH RADICALLY STRENGTHENS THE SYSTEM ALOFT AND ENDS UP WITH A STRONGER SURFACE LOW. THE 06Z GEFS MEAN DOUBLES DOWN ON THE 12Z GFS SOLUTION, SHOWING AN EVEN STRONGER 500 HPA LOW. THE 12Z UKMET IS CLOSING IN ON THE GFS' DEPTH ALOFT AND AT THE SURFACE, BUT IS BEGINNING TO LAG THE OTHER GUIDANCE AS THE LOW LIFTS OUT OF ND INTO MANITOBA/ONTARIO. BELIEVE THESE SOLUTIONS ARE TOO STRONG. NO MATTER WHICH SOLUTION YOU CHOOSE, THE CYCLONE COULD REACH A RECORD DEPTH FOR THE MONTH OF MARCH PORTIONS OF THE DAKOTAS AND MINNESOTA -- THE TRACK AND DEPTH ARE MORE REMINISCENT OF AN EARLY AUTUMN CYCLONE. ACROSS THE PLAINS, MIDWEST, AND EAST THERE HAS BEEN SOME NOTABLE ADJUSTMENTS IN THE NON-GFS GUIDANCE TOWARDS A QUICKER FRONTAL PROGRESSION, TOWARDS OLDER GFS RUNS, SO DO NOT WANT TO SUMMARILY THROW THE GFS OUT FOR BEING QUICK WITH ITS FRONTAL PROGRESSION. A COMPROMISE OF THE AVAILABLE GUIDANCE SHOULD DEAL WITH ISSUES ALOFT AND AT THE SURFACE REASONABLY, WHICH IS PREFERRED WITH AVERAGE CONFIDENCE. ZONAL FLOW INTO THE PACIFIC NORTHWEST TUE/WED SURFACE LOW TRACKING REACHING THE PACIFIC NORTHWEST ON TUESDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-UKMET COMPROMISE CONFIDENCE: ABOVE AVERAGE THE 12Z UKMET HANDLES AN UPPER LOW NEAR THE AK/BRITISH COLUMBIA DIFFERENTLY/WEAKER THAN THE OTHER GUIDANCE, WHICH ALLOWS A STRONGER AND MORE PROGRESSIVE SYSTEM MOVING THROUGH THE ZONAL FLOW REGIME ACROSS THE PACIFIC NORTHWEST THAN THE OTHER GUIDANCE. BELIEVE ITS AMPLITUDE SHOULD BE LESS, WHICH SHOULD LEAD TO A LESS PROGRESSIVE SURFACE FRONT. A COMPROMISE OF THE 12Z GFS/12Z NAM/12Z CANADIAN/12Z ECMWF IS PREFERRED WITH ABOVE AVERAGE CONFIDENCE. UPPER LEVEL SYSTEM SHEARING THROUGH THE SOUTHEAST ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ THE GUIDANCE SHOWS GOOD AGREEMENT WITH THIS SYSTEM, SO PREFER A GENERAL MODEL COMPROMISE TO DEAL WITH ANY LINGERING DETAIL ISSUES WITH ABOVE AVERAGE CONFIDENCE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... Roth