041
FXUS10 KWNH 080459
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1157 PM EST FRI FEB 07 2020
VALID FEB 08/0000 UTC THRU FEB 11/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION WITH LATEST PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..SHORTWAVE CROSSING THE OH VALLEY/APPALACHIANS ON SATURDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
WEAK SHORTWAVE ENERGY WILL BE QUICKLY CROSSING THE OH VALLEY AND
CENTRAL APPALACHIANS ON SATURDAY. A WEAK AREA OF SURFACE LOW
PRESSURE AND A FRONT WILL BE ASSOCIATED WITH THIS ENERGY. MODEL
SPREAD IS MINIMAL, AND SO A GENERAL MODEL BLEND WILL BE PREFERRED.
..DEEP TROUGH/CYCLONE CROSSING THE PACIFIC NORTHWEST SATURDAY
..DIGGING ENERGY OVER THE GREAT BASIN/SOUTHWEST BY SUNDAY
..DOWNSTREAM TROUGHING OVER THE NORTHERN PLAINS BY SUNDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-NAM BLEND...PACIFIC NORTHWEST TO THE UPPER MIDWEST
12Z CMC/ECMWF AND 18Z GEFS/12Z ECENS BLEND...SOUTHWEST
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
A STRONG COMPACT CLOSED LOW AND ASSOCIATED UPPER TROUGH WILL BE
CROSSING THE PACIFIC NORTHWEST THROUGH EARLY SATURDAY. BY SUNDAY,
A PORTION OF THIS ENERGY WILL QUICKLY EJECT DOWNSTREAM ACROSS THE
NORTHERN ROCKIES, NORTHERN PLAINS AND TOWARD THE UPPER MIDWEST. ON
MONDAY, THE ENERGY SHOULD BE SHEARING ACROSS THE GREAT LAKES AND
NORTHEAST. THE 00Z NAM IS A BIT OF A DEEPER OUTLIER WITH ITS
MID-LEVEL REFLECTION ONCE THE SYSTEM EXITS THE NORTHERN ROCKIES.
AS A RESULT, ITS SURFACE LOW EVOLUTION OVER THE NORTHERN PLAINS
AND UPPER MIDWEST, ALONG WITH ITS CORRESPONDING QPF AXIS, IS JUST
A SHADE NORTH OF THE OTHERWISE WELL-CLUSTERED GLOBAL MODEL
GUIDANCE. THUS, A NON-NAM BLEND IS PREFERRED WITH THIS NORTHERN
STREAM ENERGY EVOLUTION.
MEANWHILE, A SPLIT IN THE UPPER FLOW WILL ALLOW FOR A SUBSTANTIAL
AMOUNT OF ENERGY ASSOCIATED WITH THE ORIGINAL TROUGH TO THEN DIG
SOUTHWARD OVER THE GREAT BASIN AND INTO THE SOUTHWEST AROUND THE
EASTERN SIDE OF A STRONG
DEEP LAYER RIDGE DEVELOPING OFFSHORE THE WEST COAST THIS WEEKEND.
IN FACT, ALL OF THE GUIDANCE SHOWS A WELL-DEFINED AND FAIRLY
ROBUST UPPER LOW DEVELOPING AND DROPPING SOUTH THROUGH CALIFORNIA
GOING THROUGH SUNDAY. ON MONDAY, THE ENERGY IS EXPECTED TO BEGIN
EJECTING EAST. THE 00Z GFS WITH THIS SYSTEM IS A MUCH MORE
PROGRESSIVE OUTLIER BY THE END OF THE PERIOD WITH ITS CLOSED LOW
ADVANCING INTO THE FOUR CORNERS REGION. THE 00Z NAM FOR ITS PART
GRADUALLY BECOMES A SLOWER AND DEEPER OUTLIER, WITH THE 12Z
NON-NCEP MODELS ALL SPLITTING THE DIFFERENCE BETWEEN FASTER AND
SLOWER CAMPS. THE UKMET THOUGH DOES LEAN NOTABLY TOWARD THE FASTER
SIDE OF THE GUIDANCE, BUT NOT QUITE TO THE EXTENT AS THE GFS. THE
CMC/ECMWF SOLUTIONS ARE ACTUALLY IN MUCH BETTER ALIGNMENT WITH THE
ENSEMBLE MEANS, AND ESPECIALLY THE 12Z ECENS MEAN. THUS A 12Z
CMC/ECMWF BLEND ALONG WITH THE 18Z GEFS MEAN AND 12Z ECENS MEAN
WILL BE PREFERRED FOR NOW WITH THE EVOLVING SOUTHERN STREAM ENERGY.
..NORTHERN STREAM TROUGH/FRONT OVER THE MIDWEST BY TUESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-NAM BLEND
CONFIDENCE: ABOVE AVERAGE
THE GUIDANCE INDICATES A NORTHERN STREAM TROUGH AND ATTENDANT COLD
FRONT DROPPING SOUTHEAST FROM CANADA AND CROSSING THE NORTHERN
PLAINS LATE MONDAY AND ARRIVING ACROSS THE MIDWEST ON TUESDAY. THE
00Z NAM IS A MORE PROGRESSIVE OUTLIER SOLUTION BY THE END OF THE
PERIOD WITH ITS HEIGHT FALLS. ALTHOUGH SPREAD WITH THE COLD FRONT
IS ACTUALLY QUITE MODEST. GIVEN GOOD GLOBAL MODEL AGREEMENT WITH
THE HEIGHT FALLS, A NON-NAM BLEND WILL BE PREFERRED.
..QUASI-STATIONARY FRONT OVER THE GULF COAST STATES BY TUESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-GFS BLEND
CONFIDENCE: AVERAGE
THE MODELS ALL AGREE IN PLACING A QUASI-STATIONARY FRONT ACROSS
THE GULF COAST STATES BY TUESDAY, WHICH IS EXPECTED TO PLAY A KEY
ROLE IN WHAT IS LIKELY TO BE THE START OF A MULTI-DAY EXCESSIVE
RAINFALL EVENT (SEE LATEST QPFERD) FOR THE REGION. THE MODEL
SPREAD WITH THE PLACEMENT OF THE FRONT IS MODEST, BUT THE 00Z GFS
IS A TAD FARTHER NORTH WITH ITS FRONTAL PLACEMENT FROM CENTRAL
MS/NORTHERN AL NORTHEAST INTO THE SOUTHERN MID-ATLANTIC REGION.
PERHAPS MORE CONCERNING WITH THE GFS THOUGH IS ITS MASS FIELD
SOLUTION ALOFT, WHICH AT LEAST FOR THE LATE MONDAY/EARLY TUESDAY
TIME FRAME IS MUCH MORE DIFFLUENT COMPARED TO THE REMAINING
GUIDANCE. THIS IS A RESULT OF THE GFS BEING MORE PROGRESSIVE WITH
THE ENERGY UPSTREAM OVER THE SOUTHWEST WHICH HELPS TO BACK THE
MID/UPPER-LEVEL FLOW MORE DOWNSTREAM OVER THE LOWER MS VALLEY.
CONSEQUENTLY, THE GFS HAS A BROADER AND HEAVIER AXIS OF RAIN
IMPACTING AN AREA FROM THE LOWER MS VALLEY TO THE TN VALLEY
THROUGH TUESDAY MORNING. AT LEAST FOR THIS PERIOD, A SOLUTION AWAY
FROM THE GFS IS PREFERRED, AND THUS A NON-GFS BLEND.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
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