833  
FXUS10 KWNH 020446  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1245 AM EDT TUE JUN 02 2020  
 
VALID JUN 02/0000 UTC THRU JUN 05/1200 UTC  
 
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
00Z INITIAL MODEL EVALUATION INCLUDING PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
UPPER LEVEL TROUGH EXITING THE NORTHEAST U.S. ON TUESDAY  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: HIGH  
 
A PRONOUNCED UPPER LEVEL TROUGH BY EARLY JUNE STANDARDS WILL BE IN  
PLACE ACROSS THE NORTHEASTERN U.S. ON TUESDAY BEFORE LIFTING OUT  
ACROSS EASTERN CANADA AS THE UPPER LEVEL FLOW PATTERN BECOMES MORE  
ZONAL AND THE AIRMASS WARMS UP SUBSTANTIALLY. ALTHOUGH THERE ARE  
SOME MINOR DIFFERENCES ONCE THE TROUGH REACHES EASTERN CANADA,  
THERE IS EXCELLENT AGREEMENT FOR THE NORTHEAST U.S. THROUGH  
TUESDAY BEFORE THE TROUGH LIFTS OUT, SO A GENERAL MODEL BLEND CAN  
BE RECOMMENDED.  
 
UPPER LEVEL LOW SLOWLY LIFTING ACROSS WEST TEXAS AND INTO OKLAHOMA  
THROUGH TUESDAY  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: MODERATE-HIGH  
 
A BROAD UPPER LOW CURRENTLY CENTERED OVER WESTERN TEXAS WILL  
CONTINUE TO SLOWLY LIFT NORTHEASTWARD ACROSS OKLAHOMA THROUGH  
TUESDAY NIGHT, AND THEN GRADUALLY WEAKEN OVER ARKANSAS AS IT  
BECOMES EMBEDDED IN THE BROAD UPPER LEVEL RIDGE. ALL GLOBAL  
GUIDANCE ARE IN CLOSE ENOUGH AGREEMENT ON THE MAIN FEATURES TO  
MERIT THE USE OF A MULTI-DETERMINISTIC MODEL BLEND.  
 
DEVELOPING CUT-OFF LOW LINGERING SOUTHWEST OF CALIFORNIA THROUGH  
MIDWEEK  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 00Z NAM/12Z ECMWF/12Z UKMET  
CONFIDENCE: MODERATE-HIGH  
 
A BROAD UPPER LOW HAS BECOME PINCHED OFF FROM THE WESTERLIES  
FARTHER NORTH, AND BECAUSE OF THE RIDGE AXIS OVER THE SOUTHERN  
ROCKIES, IT SHOULD REMAIN NEARLY ANCHORED IN PLACE THROUGH  
THURSDAY BEFORE BEGINNING TO EJECT SLOWLY EAST TOWARD SOUTHERN  
CALIFORNIA BY FRIDAY MORNING. SIMILAR TO LAST NIGHT, THE ECMWF  
ENSEMBLE MEMBERS ARE GENERALLY A LITTLE TO THE WEST THAN MOST OF  
THE GEFS ENSEMBLE MEMBERS. BY FRIDAY MORNING, THE GFS AND THE  
GEFS MEAN ARE THE QUICKEST TO PROGRESS THE LOW EASTWARD. THE 12Z  
UKMET LIES NEAR THE MIDDLE OF THE ENSEMBLE SPREAD AND REPRESENTS A  
GOOD CHOICE IN TERMS OF MODEL CHOICES, ALONG WITH SOME OF THE  
ECMWF AND NAM.  
 
ACTIVE FLOW PATTERN ACROSS NORTHERN TIER OF U.S.  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 00Z NAM/12Z UKMET/12Z EC MEAN  
CONFIDENCE: MODERATE  
 
THE WESTERLIES ON THE NORTHERN PERIPHERY OF THE CENTRAL U.S. RIDGE  
ARE EXPECTED TO BE RATHER ACTIVE WITH THREE WELL DEFINED SHORTWAVE  
DISTURBANCES TRACKING EASTWARD NEAR THE U.S./CANADA BORDER THROUGH  
MID-WEEK. THE FIRST SYSTEM IS AN OCCLUDED LOW MOVING ACROSS  
ONTARIO AND QUEBEC THAT WILL GRADUALLY WEAKEN, AND BRING A STRONG  
WARM FRONT SURGING EASTWARD TOWARDS THE EAST COAST BY TUESDAY  
NIGHT AND EARLY WEDNESDAY. THE SECOND DISTURBANCE IS A SHORTWAVE  
OVER MONTANA AND ALBERTA WHICH WILL TRACK ACROSS SOUTH-CENTRAL  
CANADA TO THE HUDSON BAY BY WEDNESDAY MORNING, WHICH WILL LEAVE A  
FRONT NEAR THE CANADIAN BORDER THAT WILL DIRECT THE NEXT AND THIRD  
SYSTEM REACHING THE BRITISH COLUMBIA COAST LATE TUESDAY WHICH WILL  
TRACK JUST NORTH OF THE BORDER AND EVOLVE INTO AN UPPER LOW OVER  
MANITOBA BY THURSDAY. THIS WILL SUPPORT A COLD FRONT ACROSS THE  
NORTHERN GREAT PLAINS WEDNESDAY NIGHT.  
 
GIVEN THE QUASI-ZONAL AND PROGRESSIVE FLOW PATTERN IN PLACE ACROSS  
THE REGION, THIS IS WHERE THE GREATEST MODEL DIFFERENCES CURRENTLY  
EXIST, MAINLY WITH THE SECOND AND THIRD SYSTEMS. BOTH THE 18Z AND  
00Z GFS HAVE BEEN MORE SUPPRESSED WITH THE UPPER LEVEL HEIGHT  
PATTERN ACROSS THE NORTHERN TIER STATES COMPARED TO THE OTHER  
GUIDANCE, AND NEAR THE SOUTHERN EXTENT OF THE ENSEMBLE MEMBER  
SPREAD. BY THURSDAY MORNING, THE ECMWF AND THE CMC BECOME FASTER  
WITH THE UPPER LOW REACHING MANITOBA, AND THE ECMWF IS ALSO AHEAD  
OF ITS ENSEMBLE MEAN.  
 
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
HAMRICK  
 

 
 
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