MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 242 AM EDT THU MAR 26 2015 VALID MAR 26/0000 UTC THRU MAR 29/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... ...AN EVALUATION OF THE 00Z MODEL GUIDANCE ALONG WITH FINAL PREFERENCES/FORECAST CONFIDENCE... THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE 00Z NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS. ...FULL-LATITUDE TROF CROSSING THE EASTERN U.S. BY EARLY IN THE WEEKEND... ...STRONG COLD FRONT/ASSOCIATED SURFACE WAVES... FINAL PREFERENCE: BLEND OF THE 00Z GFS/ECMWF...WEIGHTED 2/3 TOWARD THE 00Z ECMWF FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE THE CURRENT WATER VAPOR IMAGERY SHOWED A PAIR OF STRONG SHORTWAVES AFFECTING THE OZARKS AND SOUTHERN ONTARIO...RESPECTIVELY. THE FORMER HAS HELPED IGNITE A LARGE CLUSTER OF SHOWERS AND THUNDERSTORMS ACROSS OK/AR WHICH HAS BEEN RESPONSIBLE FOR SEVERE WEATHER REPORTS AND FLASH FLOODING. ALL FEATURES MOVING FORWARD SHOULD BECOME MORE PROGRESSIVE IN NATURE AS HEIGHT FALLS PROJECT EASTWARD IN TIME. A COMPLEX ARRAY OF IMPULSES MOVING IN FROM CENTRAL CANADA WILL HELP DRAG THE UPPER TROF EASTWARD WITH THE SYSTEM EVENTUALLY REACHING THE WESTERN ATLANTIC BY LATE IN THE WEEKEND. THE ACCOMPANYING COLD FRONT WILL FEATURE A MULTITUDE OF SURFACE WAVES WITH THE GUIDANCE GENERALLY DIFFERING WITH REGARD TO THE POSITION AND INTENSITY OF EACH OF THESE LOWS. OVERALL...THE 00Z GFS/GEFS MEAN HAVE TENDED TO BE A BIT QUICKER WITH THE SOUTHERN EXTENT OF THE UPPER TROF ON FRIDAY EVENING ACROSS THE SOUTHEASTERN U.S. THIS ULTIMATELY LEADS TO THE GFS SUITE OF SOLUTIONS BEING MORE PROGRESSIVE WITH THE EJECTING SURFACE LOW OVER THE WESTERN ATLANTIC. LATER IN THE PERIOD...THE 00Z CMC/UKMET STAND OUT AS BEING RATHER SLOW WITH THE BACK EDGE OF THE UPPER TROF. IN FACT...THE 12Z/00Z CMC CLOSE OFF A 534-DM UPPER LOW ACROSS THE MID-ATLANTIC BY 29/0000Z. THIS LEADS TO A MORE WRAPPED UP COASTAL SOLUTION WHICH KEEPS PRECIPITATION ACROSS THE MID-ATLANTIC INTO DAY 3. ENSEMBLE LOW PLOTS SUGGEST SUCH A SOLUTION IS A MINORITY AT THIS POINT. AS A WHOLE LIKE THE COMBO OF THE 00Z GFS/ECMWF BUT WILL WEIGHT THE SOLUTION TWO-THIRDS TOWARD THE LATTER GIVEN THE THOUGHT THAT THE GFS IS TOO FAST INTO DAY 3. ...PROGRESSIVE SHORTWAVE REACHING THE PACIFIC NORTHWEST BY LATE FRIDAY... ...WELL-DEVELOPED SURFACE CYCLONE MOVING THROUGH THE NORTHERN TIER THIS WEEKEND... FINAL PREFERENCE: BLEND OF THE 00Z GFS/21Z SREF MEAN FORECAST CONFIDENCE: BELOW AVERAGE A STOUT UPPER RIDGE ANCHORING THE WESTERN U.S. WILL QUICKLY GIVE WAY TO A PROGRESSIVE SHORTWAVE CROSSING THE PACIFIC NORTHWEST BY FRIDAY NIGHT. THE MODELS CONTINUE TO NOT AGREE WITH THE TIMING OF THIS IMPULSE AS IT MOVES TOWARD THE UPPER INTERMOUNTAIN WEST. THE 00Z UKMET DID TREND IN THE FASTER DIRECTION RELATIVE TO THE PREVIOUS SOLUTION WHICH CARRIES A BULK OF ITS ENERGY TOWARD NORTHERN CA. LOOKING TOWARD DAY 3....THE 00Z/12Z ECMWF START TO BECOME SLOWER THAN THE ENSEMBLE MEANS INCLUDING ITS OWN 12Z ECMWF ENSEMBLE MEAN. PREFER TO STAY ON THE MORE PROGRESSIVE SIDE AS SUPPORTED BY THE ENSEMBLE MEANS. LOOKING AT EACH OF THE DETERMINISTIC MODELS COMPARED TO THEIR PREVIOUS CYCLE...THERE CONTINUES TO BE A LOT OF WAFFLING AROUND IN THE SOLUTIONS WHICH SHOWS CONFIDENCE IS BELOW AVERAGE IN THIS SETUP. WILL CONTINUE TO FAVOR A COMBINATION OF THE 00Z GFS WITH THE 21Z SREF MEAN. THE 00Z GFS IS ON THE SOUTHERN END OF THE ENSEMBLE SPREAD REGARDING THE LOW TRACK. SO WILL SPLIT THE DIFFERENCE BETWEEN THE TWO. ...SHORTWAVES CROSSING THE DESERT SOUTHWEST ON SATURDAY... FINAL PREFERENCE: BLEND OF THE 00Z GEFS/12Z ECMWF ENSEMBLE MEANS FORECAST CONFIDENCE: BELOW AVERAGE THIS AREA OF THE COUNTRY IS PLAGUED BY QUITE A BIT OF SPREAD AS THE REGION WILL BE AFFECTED BY A PAIR OF DISTURBANCES. AS MENTIONED EARLIER...SOME OF THE VORTICITY MOVING THROUGH THE PACIFIC NORTHWEST WILL SLIDE SOUTHWARD INTO THE CENTRAL GREAT BASIN. MEANWHILE...LURKING TO THE WEST ACROSS THE EASTERN PACIFIC IS ANOTHER SHORTWAVE EXPECTED TO APPROACH THE AREA LATE IN THE PERIOD. THE 00Z NAM/UKMET ARE MORE EMPHATIC ABOUT CARRYING THIS ENERGY INTO THE MAP DOMAIN WHILE THE 00Z/12Z ECWMF CONTINUE TO SHOW A MORE SHEARED OUT SYSTEM. THE 00Z GFS/CMC SEEMS TO FOLLOW SOMETHING IN BETWEEN THESE SOLUTIONS. GIVEN THE SPREAD IN PLACE AND LACK OF CONTINUITY IN THE MODELS...WILL BLEND THE ENSEMBLE MEANS HERE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... RUBIN-OSTER