458
FXUS10 KWNH 181645
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1245 PM EDT THU JUN 18 2020
VALID JUN 18/1200 UTC THRU JUN 22/0000 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
EASTERN U.S. CLOSED LOW AND COASTAL FRONT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: MODERATE-HIGH
THE CLOSED UPPER LOW CURRENTLY OVER THE CENTRAL APPALACHIANS WILL
GRADUALLY WEAKEN AND REMAIN NEARLY STATIONARY THROUGH SATURDAY
MORNING, AND THEN IS EXPECTED TO SLOWLY EVOLVE INTO AN OPEN WAVE
AND EVENTUALLY BECOME ABSORBED BY THE WESTERLIES BY THE END OF THE
FORECAST PERIOD. THERE IS EXCELLENT AGREEMENT IN THE LATEST MODEL
GUIDANCE WITH THIS EVOLUTION THROUGH SATURDAY EVENING. AFTERWARD,
AS THE OPEN WAVE BEGINS TO BECOME ABSORBED BY THE APPROACHING
TROUGH FROM THE GREAT LAKES REGION, THE GFS AND ITS ENSEMBLE MEAN
BECOME A LITTLE FASTER AS THE WAVE TRACKS TOWARDS THE NORTHEAST.
IT IS STILL CLOSE ENOUGH TO THE MODEL CONSENSUS TO INCLUDE AS PART
OF A GENERAL MODEL BLEND.
CLOSED LOW DEVELOPING OVER NORTHERN HIGH PLAINS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z UKMET/ECMWF/ECENS BLEND
CONFIDENCE: MODERATE
A CLOSED UPPER LOW OVER SASKATCHEWAN AND MANITOBA IS EXPECTED TO
REMAIN NEARLY ANCHORED IN PLACE OVER THE NEXT FEW DAYS AS IT
GRADUALLY DEEPENS WITH ASSOCIATED SHORTWAVE ENERGY CROSSING THE
NORTH-CENTRAL U.S. THIS WEEKEND, SUSTAINING A SLOW MOVING COLD
FRONT WITH MULTIPLE WAVES OF LOW PRESSURE ALONG IT. MODEL
DIFFERENCES BECOME APPARENT BY 12Z SATURDAY WITH THE 12Z GFS MORE
AMPLIFIED WITH THE TROUGH CROSSING THE CENTRAL AND NORTHERN
PLAINS, MAINTAINING CONTINUITY FROM ITS EARLIER RUNS, BUT WITH
LIMITED SUPPORT FROM THE GEFS MEAN. MULTIPLE CMC RUNS HAVE BEEN
WEST OF THE MODEL CONSENSUS REGARDING THE MAIN UPPER LOW OVER
SOUTH-CENTRAL CANADA, AND THE NAM BEING ON THE STRONGER SIDE OF
THE GUIDANCE. A BLEND OF THE UKMET/ECMWF/EC MEAN SHOULD SERVE
WELL AS A STARTING POINT IN THE FORECAST PROCESS.
TROUGH APPROACHING THE PACIFIC NORTHWEST BY FRIDAY NIGHT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GFS/ECMWF BLEND
CONFIDENCE: LIMITED-MODERATE
ANOTHER FAST MOVING SHORTWAVE TROUGH WILL APPROACH THE PACIFIC
NORTHWEST EARLY SATURDAY WHICH IS THEN EXPECTED TO REMAIN IN PLACE
THROUGH THE WEEKEND. THE 12Z GFS IS A LITTLE FASTER WITH THE
INITIAL SURFACE LOW COMING ONSHORE LATE FRIDAY NIGHT AND EARLY
SATURDAY, AND THE UKMET IS CLOSER TO THE CONSENSUS COMPARED TO ITS
SLOWER SOLUTIONS YESTERDAY. GIVEN SOME OF THE TIMING ISSUES, A
BLEND OF THE GFS/ECMWF WOULD LIKELY YIELD A DESIRABLE RESULT AT
THIS TIME.
HAMRICK
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
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