338
FXUS10 KWNH 270645
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
244 AM EDT SAT JUN 27 2020
VALID JUN 27/0000 UTC THRU JUN 30/1200 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
CLOSED LOW OVER QUEBEC
TROUGH IMPACTING THE NORTHEAST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-NAM BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
THE MODELS ARE IN GOOD AGREEMENT ON THE DETAILS OF THE LARGE
CLOSED LOW OVER QUEBEC AND SOUTHWARD EXTENSION OF THE TROUGH
ACROSS THE NORTHEAST U.S. GOING THROUGH SATURDAY. BY SUNDAY, THE
MODELS SUGGEST A NEW SHORTWAVE TROUGH WILL CROSS THE GREAT LAKES
AND HELP TO AMPLIFY THE SYNOPTIC SCALE TROUGH OVER THE NORTHEAST,
AND THE MODELS SUPPORT THE CLOSED LOW ACTUALLY THEN DROPPING SOUTH
INTO THE INTERIOR OF THE NORTHEAST GOING THROUGH MONDAY AND
TUESDAY. THE 00Z NAM IS STILL A LITTLE MORE ROBUST WITH THIS
SHORTWAVE AND RESULTS IN A SOMEWHAT STRONGER CLOSED LOW THAT IS ON
THE SOUTHWEST SIDE OF THE MODEL CONSENSUS ACROSS THE NORTHEAST BY
THE END OF THE PERIOD. THE GLOBAL MODELS ARE REASONABLY WELL
CLUSTERED AT THIS POINT, SO A NON-NAM BLEND WILL BE PREFERRED.
DEEP UPPER TROUGH/CLOSED LOW DIGGING INTO THE WEST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 00Z GFS/UKMET/ECMWF
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
A DEEP UPPER TROUGH AND ASSOCIATED CLOSED LOW IS FORECAST TO
AMPLIFY ACROSS THE NORTHERN ROCKIES AND INTERMOUNTAIN WEST THIS
WEEKEND AS AN UPPER-LEVEL RIDGE BUILDS ACROSS THE GULF OF ALASKA
AND ALSO ACROSS THE MIDWEST AND GREAT LAKES REGION, SUGGESTING A
POTENTIAL OMEGA-BLOCK PATTERN. THE MODELS ARE IN GOOD AGREEMENT ON
THE EVOLUTION THROUGH SUNDAY EVENING, AFTER WHICH THE 00Z CMC
TAKES THE UPPER LOW FARTHER SOUTH THAN THE OTHER GUIDANCE. THE 00Z
NAM GRADUALLY ENDS UP WITH A STRONGER UPPER LOW IMPACTING THE
NORTHERN ROCKIES FROM SUNDAY NIGHT THROUGH EARLY TUESDAY. WILL
PREFER A BLEND OF THE BETTER CLUSTERED 00Z GFS, 00Z UKMET AND 00Z
ECMWF SOLUTIONS WHICH ALSO AGAIN HAVE GOOD ENSEMBLE SUPPORT.
SHORTWAVES LIFTING NORTHEAST OVER THE PLAINS/MIDWEST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 00Z GEFS MEAN AND 12Z ECENS MEAN
CONFIDENCE: AVERAGE
AHEAD OF THE DEEP WESTERN U.S. TROUGH/CLOSED LOW WILL BE A PAIR OF
SHORTWAVE TROUGHS THAT EJECT NORTHEAST OUT OF THE SOUTHWEST AND
ACROSS THE PLAINS AND MIDWEST. THE 00Z NAM IS A STRONG OUTLIER
WITH THE FIRST SHORTWAVE AS IT RIDES NORTHEAST FROM THE CENTRAL
PLAINS TO THE UPPER MIDWEST GOING THROUGH SUNDAY WITH THE GLOBAL
MODELS LARGELY FLATTER. THE 00Z CMC ALSO AGAIN IS STRONGER THAN
THE MODEL CONSENSUS. THE 00Z GFS FOR ITS PART IS SEEN AS ALSO
TAKING THIS FIRST SHORTWAVE A BIT FARTHER EAST ACROSS AREAS OF THE
MIDWEST VERSUS THE MODEL CONSENSUS. THE SECOND SHORTWAVE HAS SOME
MODEL SPREAD NOTED AS THE 00Z ECMWF AND 12Z ECENS MEAN SUPPORT A
SOMEWHAT STRONGER SOLUTION VERSUS THE REMAINING GUIDANCE WHICH IS
FLATTER. FOR NOW, A BLEND OF THE ENSEMBLE MEANS WILL BE PREFERRED
WITH BOTH SHORTWAVE IMPULSES.
REMNANT ENERGY ACROSS THE LOWER MS VALLEY
WEAKNESS LINGERING OVER TEXAS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
THE MODEL SUPPORT A GRADUAL BUILDING OF THE SUBTROPICAL RIDGE THIS
WEEKEND ACROSS THE FL PENINSULA AND ADJACENT AREAS OF THE GULF
COAST STATES. SOME OF THE WEAK SHORTWAVE ENERGY LINGERING OVER
THE LOWER MISSISSIPPI VALLEY SHOULD SHEAR OUT OVER TOP OF THE
RIDGE THROUGH SATURDAY. HOWEVER, THERE WILL STILL BE A BROAD
MID-LEVEL WEAKNESS/TROUGH LINGERING OVER TEXAS WHICH SHOULD TEND
TO RETROGRADE WESTWARD THROUGH SATURDAY, BEFORE THEN LIFTING NORTH
ACROSS THE SOUTHERN AND CENTRAL PLAINS AHEAD OF THE DEEP WESTERN
U.S. TROUGH/CLOSED LOW. A GENERAL MODEL BLEND WILL AGAIN BE
PREFERRED WITH THE WEAK TROUGH OVER TEXAS.
UPPER TROUGH/LOW OVER MANITOBA/SASKATCHEWAN
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-CMC BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
A SEPARATE CLOSED LOW AND ASSOCIATED TROUGH OVER SOUTHWEST CANADA
WILL DRIVE DEEPENING SURFACE LOW PRESSURE OVER AREAS OF MANITOBA
AND SASKATCHEWAN GOING THROUGH SATURDAY AND SUNDAY. THE 00Z CMC IS
STILL PERHAPS A TAD TOO STRONG WITH THIS ENERGY, BUT THE REMAINDER
OF THE GUIDANCE HAS COME INTO BETTER AGREEMENT WITH THEIR MASS
FIELD SOLUTIONS. SO, A NON-CMC BLEND WILL BE PREFERRED.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
ORRISON
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