MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 241 PM EDT FRI MAR 31 2017 VALID MAR 31/1200 UTC THRU APR 04/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ CLOSED LOW CROSSING THROUGH THE OH/TN VALLEYS TODAY AND MID-ATLANTIC/COASTAL SOUTHEAST LATE FRI INTO SAT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL BLEND CONFIDENCE: ABOVE AVERAGE AS THE SYSTEM MOVES OFFSHORE...THE NAM IS A LITTLE FASTER IN COMPARISON TO ITS 00Z RUN. THE GFS HAS SHOWN GOOD RUN-TO-RUN CONTINUITY. THROUGH 00Z SUN AS THE SYSTEM STARTS TO MOVE WELL OFF OF THE NORTHERN MID ATLANTIC/NORTHEAST COAST...THE GUIDANCE IS IN GENERALLY GOOD AGREEMENT WITH THE LARGE SCALE FEATURES. VIGOROUS WESTERN CLOSED LOW OVER THE FOUR CORNERS BY FRI/SAT BEFORE STRETCHING/OPENING UP INTO THE HIGH PLAINS EARLY SUN SPURRING SURFACE LOW ACROSS S TEXAS INTO ARKLATEX EARLY MONDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL BLEND CONFIDENCE: AVERAGE THE NAM HAS SHOWN GOOD RUN-TO-RUN CONTINUITY WITH ITS OVERNIGHT RUN. BY 12Z SUN AS THE SYSTEM STARTS TO MOVE ACROSS THE SOUTHERN ROCKIES AND HIGH PLAINS...THE 12Z GFS IS SLOWER THAN ITS 00Z RUN. THIS CONTINUES THROUGH THE REMAINDER OF SUN AND INTO MON AS THE SYSTEM SWINGS ACROSS THE SOUTHERN PLAINS AND INTO THE LOWER MS AND TN VALLEYS. OVERALL...THE 12Z DETERMINISTIC MODELS ARE ALL IN FAIRLY GOOD AGREEMENT WITH THE LARGER SCALE FEATURES. THE UKMET...WHICH HAD BEEN A FAST OUTLIER WITH ITS PREVIOUS RUN...HAS SLOWED WITH ITS 12Z RUN PUTTING IT INTO BETTER AGREEMENT WITH THE OTHER GUIDANCE. LEAD NORTHERN STREAM SHORTWAVE TRACKING ACROSS SW CANADA INTO CENTRAL CANADA AND THE NORTHERN PLAINS/UPPER MIDWEST SAT INTO SUN ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL BLEND (SOUTH OF THE US/CANADA BORDER) CONFIDENCE: AVERAGE BOTH THE NAM/GFS ARE A LITTLE FASTER THAN THEIR 00Z RUNS TO PUSH THE MID-UPPER LEVEL TROUGH ACROSS CENTRAL CANADA ON SUN AND IN TURN A LITTLE FASTER AS WELL WITH THE ASSOCIATED SURFACE FRONT AS IT MOVES ACROSS THE NORTHERN PLAINS/UPPER MIDWEST. DIFFERENCES ACROSS THE NORTHERN PLAINS AND UPPER MIDWEST WITH REGARDS TO THE TIMING OF THE FRONT REMAIN MINOR AND CAN BE ADDRESSED WITH A GENERAL MODEL BLEND. ACROSS CENTRAL CANADA...THE 12Z GUIDANCE HAS SHOWN CONVERGING TRENDS...WITH THE GFS/ECMWF/UKMET/CANADIAN GLOBAL SHOWING FAR LESS SPREAD THAN PREVIOUS RUNS WITH RESPECT TO THE MID-UPPER LEVEL TROUGH AND THE STRENGTHENING SURFACE CYCLONE LIFTING ACROSS SASKATCHEWAN AND MANITOBA ON SUN. NEXT SHORTWAVE ACROSS THE NORTHWEST US SUN PHASING WITH FURTHER UPSTREAM ENERGY AMPLIFYING INTO INTERMOUNTAIN WEST MON ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~ PREFERENCE: GFS/NAM/ECMWF BLEND CONFIDENCE: AVERAGE THE 12Z NAM/GFS/UKMET/ECMWF HAVE ALL TO VARYING DEGREES TRENDED MORE AMPLIFIED/OR AND SLOWER WITH THIS SYSTEM. THE 12Z CANADIAN GLOBAL IS THE DETERMINISTIC MODEL THAT IS FASTER THAN ITS 00Z RUN. OVERALL THE 12Z NAM/GFS/ECMWF ARE IN GOOD AGREEMENT WITH THIS SYSTEM. AS THE TROUGH STARTS TO DIG ACROSS CA 12Z MON...THE 12Z UKMET MOVES TO THE SLOW SIDE OF THE GUIDANCE. IN CONTRAST...AROUND THE SAME TIME...THE 12Z CANADIAN STARTS TO BECOME A FAST OUTLIER. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... PEREIRA