640
FXUS10 KWNH 080650
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
145 AM EST SAT FEB 08 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
00Z CMC/UKMET/ECMWF AND 00Z GEFS MEAN 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 00Z
NON-NCEP MODEL SUITE (UKMET, CMC AND ECMWF) ALL NOW NICELY
CLUSTERED IN BETWEEN THE FASTER AND SLOWER CAMPS. THE 00Z GEFS
MEAN SOLUTION IS STRONGLY SUPPORTIVE OF THE NON-NCEP CONSENSUS,
AND THIS GROUPING IS JUST A TAD FASTER THAN YESTERDAY'S 12Z ECENS
MEAN. BASED ON THE LATEST MODEL CLUSTERING AND TRENDS, A BLEND OF
THE NON-NCEP SOLUTIONS ALONG WITH THE LATEST GEFS MEAN WILL BE
PREFERRED.
..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: 00Z UKMET/CMC/ECMWF 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, WITH THE 00Z NAM
NOW APPEARING TO BE A TAD TOO FAR SOUTH WITH ITS SURFACE BOUNDARY.
THIS APPEARS TO BE RELATED TO THE NAM BEING MORE PROGRESSIVE WITH
NORTHERN STREAM HEIGHT FALLS DROPPING DOWN ACROSS THE MIDWEST.
MEANWHILE, THE 00Z GFS WHICH DID APPEAR EARLIER TO BE A LITTLE TOO
FAR NORTH WITH ITS FRONT ACTUALLY NOW HAS RATHER GOOD AGREEMENT
FROM THE NON-NCEP MODELS. HOWEVER, ONE AREA OF CONCERN AGAIN WITH
THE GFS THOUGH IS ITS MASS FIELD SOLUTION ALOFT, WHICH AT LEAST
FOR THE LATE MONDAY/EARLY TUESDAY TIME FRAME IS 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 AXIS OF
HEAVIER RAINFALL IMPACTING AN AREA FROM THE LOWER MS VALLEY TO THE
TN VALLEY THROUGH TUESDAY MORNING. GIVEN THE GOOD CLUSTERING SEEN
UPSTREAM WITH THE ENERGY NEAR THE SOUTHWEST, AND WITH THE
DOWNSTREAM FLOW ALOFT DOWNSTREAM OVER THE GULF COAST STATES
INCLUDING THE SURFACE FRONT PLACEMENT, A BLEND OF THE NON-NCEP
SOLUTIONS WILL BE PREFERRED.
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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