MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1144 PM EST WED JAN 22 2014 VALID JAN 23/0000 UTC THRU JAN 26/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION...INCLUDING THE NAM AND GFS NO SIGNIFICANT INITIALIZATION ERRORS WERE SEEN IMPACTING THE SHORT RANGE FORECAST. ...WEAKENING UPPER TROUGH/SURFACE LOW CROSSING THE GREAT LAKES/OH VALLEY/MID-ATLANTIC AND NORTHEAST U.S. THROUGH FRI... PREFERENCE: NON-NAM CONSENSUS CONFIDENCE: ABOVE AVERAGE ALL OF THE MODELS SHOW THE CURRENT POLAR LOW IMPACTING THE U.P. OF MI WEAKENING ON THURS...AND SHIFTING EAST ACROSS THE OH VLY/MID-ATLANTIC AND NEW ENGLAND BY EARLY FRI AS A PROGRESSIVE TROUGH AXIS. THE 12Z ECMWF TENDS TO HAVE A LITTLE MORE ENERGY IN THE BASE OF THE TROUGH AXIS THAN THE MULTI-MODEL CONSENSUS...AND THEREFORE WAS A LITTLE SLOWER WITH THIS PORTION OF THE TROUGH...BUT THE 12Z ECENS MEAN SUPPORTED THIS AS WELL. REGARDING THE SFC LOW...THE 00Z NAM IS THE QUICKEST TO WEAKEN THE SFC LOW ASSOCIATED AS IT CROSSES OUT OF LWR MI AND EAST ACROSS NRN PA AND NRN NJ. BASED ON THE LATEST MODEL CLUSTERING AND SPREAD...WILL FAVOR A NON-NAM CONSENSUS ATTM. ...POLAR LOW DROPPING DOWN OVER HUDSON/JAMES BAY... ...ARCTIC BOUNDARY DROPPING DOWN ACROSS THE MIDWEST AND EASTERN U.S. PREFERENCE: 12Z ECMWF CONFIDENCE: AVERAGE THE LATEST MODELS SHOW THE CORE OF THE POLAR LOW/VORTEX OVER NRN CANADA SHIFTING SOUTH OVER THE NEXT COUPLE OF DAYS AND INTENSIFYING DOWN OVER HUDSON BAY AND JAMES BAY SAT AND SUN. ENERGY DIGGING SOUTH AROUND THE WRN FLANK OF THE DEEP LOW CENTER WILL HELP ADVANCE ANOTHER ARCTIC COLD FRONT DOWN THROUGH SRN CANADA...AND THEN ACROSS THE MIDWEST THROUGH FRI. THIS SAME FRONT WILL ADVANCE ACROSS THE EASTERN U.S. ON SAT AS LOW PRESSURE INTENSIFIES NEAR THE ST LAWRENCE RIVER VALLEY AND PIVOTS NORTH UP INTO QUEBEC AROUND THE ERN SIDE OF THE AFOREMENTIONED VORTEX CENTER REFOCUSING DOWN OVER HUDSON/JAMES BAY. ALL OF THE MODELS AGREE ON THIS SCENARIO...WITH THE 12Z ECMWF ACTUALLY THE FASTEST WITH THE FRONTAL PROGRESSION...AND THE 12Z UKMET THE SLOWEST. THE 00Z NAM/00Z GFS AND 12Z GEM GLOBAL SPLIT THE DIFF. THERE IS NOT REALLY MUCH SPREAD WITH REGARD TO THE SFC LOW DEVELOPMENT/INTENSIFICATION NEAR THE ST LAWRENCE RIVER VLY...BUT THE SAME TIMING DIFFS APPLY AS NOTED WITH THE ASSOCIATED FRONT. THE 18Z GEFS MEAN AND ESP THE 12Z ECENS MEAN TEND TO FAVOR A MORE PROGRESSIVE SCENARIO WITH THE VORT ENERGY AROUND THE WRN AND SRN FLANKS OF THIS DEEP LOW CENTER...AND WITH SUCH STRONG NWLY MEAN LAYER FLOW...WILL FAVOR THE MORE PROGRESSIVE ECMWF. ...RETROGRADING SHORTWAVE TROUGH CROSSING THE GREAT BASIN/NORTHERN CALIFORNIA... PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: AVERAGE A SHORTWAVE IMPULSE CURRENTLY DIGGING SWD ACROSS THE GREAT BASIN DOWN THE EAST SIDE OF A STRENGTHENING MEAN LAYER RIDGE JUST OFF THE WEST COAST IS EXPECTED TO ACTUALLY UNDERCUT THE RIDGE AXIS LATE THURS AND RETROGRADED BACK WWD ACROSS NRN CA AND OFFSHORE THE WEST COAST. THIS WILL OCCUR AS A PORTION OF THE MEAN RIDGE STRENGTHENS AND CLOSES OFF OVER COASTAL SECTIONS OF SRN BRITISH COLUMBIA. ALL OF THE MODELS AGREE WITH THIS SCENARIO. THE RETROGRADING ENERGY ADVANCING OFFSHORE THE WEST COAST WILL THEN GET CAUGHT UP IN STRONG DEEP LAYER SRLY FLOW AHEAD OF A DEEP TROUGH/CLOSED LOW SOUTH OF THE ALEUTIANS AND EJECTED NORTH INTO THE GULF OF AK. THE MODELS ARE REASONABLY WELL CLUSTERED ON THE LARGER SCALE WITH THE MASS FIELD DETAILS OF THIS RETROGRADING ENERGY. WILL PREFER A GENERAL MODEL COMPROMISE TO RESOLVE THE SMALLER SCALE/FINER DETAILS. www.wpc.ncep.noaa.gov/html/model2.shtml... ORRISON