677
FXUS10 KWNH 291639
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1238 PM EDT WED APR 29 2020
VALID APR 29/1200 UTC THRU MAY 03/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION INCLUDING LATEST PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..DEEP TROUGH/CLOSED LOW IMPACTING THE EAST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z GFS AND 00Z ECMWF
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
THE MODELS SHOW GOOD AGREEMENT IN TAKING THE DEEP UPPER TROUGH AND
ASSOCIATED CLOSED LOW OVER THE MIDWEST GRADUALLY OFF TO THE EAST
THROUGH TONIGHT, WITH LOW PRESSURE FOCUSING PREDOMINANTLY OVER THE
GREAT LAKES REGION OVER THE NEXT 24 HOURS. HOWEVER, AS ADDITIONAL
SHORTWAVE ENERGY ROUNDS THE BASE OF THE TROUGH OVER THE GULF COAST
STATES, TN VALLEY AND SOUTHERN APPALACHIANS EARLY ON THURSDAY, THE
CLOSED LOW ITSELF SHOULD BEGIN TO RE-CONSOLIDATE DOWN ACROSS THE
OH VALLEY LATER THURSDAY AND THEN OVER THE CENTRAL MID-ATLANTIC
REGION BY FRIDAY. THIS WILL ALLOW A NEW SURFACE LOW TO DEVELOP AND
CONCENTRATE OVER THE VA/NC PIEDMONT AREA BEFORE THEN LIFTING
NORTHEAST TOWARD SOUTHERN NEW ENGLAND ON FRIDAY. ON SATURDAY, THE
SYSTEM SHOULD BEGIN TO EXIT OFFSHORE OF THE NORTHEAST.
MULTI-MODEL TRENDS IN THE GUIDANCE FAVORS THE CLOSED LOW EVOLUTION
OVER THE MID-ATLANTIC REGION TO BE A TAD FARTHER SOUTH. THE 12Z
NAM MADE A NOTABLE TREND SOUTH COMPARED TO ITS 00Z RUN, AND THIS
IS CLOSE IN ALIGNMENT TO THE 00Z CMC WHICH IS SOUTH OF THE MODEL
CONSENSUS. THE 12Z GFS ALSO HAS TRENDED FARTHER SOUTH, AND IS IN
GOOD AGREEMENT WITH THE 00Z ECMWF SOLUTION. THIS CLUSTER IS JUST A
TAD NORTH OF THE NAM/CMC CAMP. THEN WE HAVE THE 00Z UKMET WHICH IS
ON THE NORTH SIDE OF THE MODEL SPREAD. THE GFS/ECMWF CLUSTER VERY
CLOSELY APPROXIMATES THE MODEL CONSENSUS AND HAS GOOD SUPPORT FROM
THE 00Z ECENS MEAN, SO A BLEND OF THE GFS AND ECMWF WILL BE
PREFERRED OR AT LEAST A MULTI-MODEL BLEND WEIGHTED TOWARD THE
GFS/ECMWF CAMP.
..WEAK SHORTWAVE CLIPPING THE PACIFIC NORTHWEST LATER TODAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
A MODEST AND RATHER PROGRESSIVE SHORTWAVE TROUGH WILL COME IN OFF
THE PACIFIC OCEAN AND CLIP AREAS OF THE PACIFIC NORTHWEST AND
SOUTHERN BRITISH COLUMBIA LATER TODAY AND TONIGHT. A WEAK AREA OF
LOW PRESSURE AND ATTENDANT FRONT IS EXPECTED TO ACCOMPANY THIS
ENERGY. MODEL SPREAD IS VERY MODEST WITH THIS FEATURE, AND SO A
GENERAL MODEL BLEND WILL BE PREFERRED.
..SHORTWAVE CROSSING THE NORTHWEST ON THURSDAY
..CLIPPING THE NORTHERN PLAINS ON FRIDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z GFS AND 00Z ECMWF
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
THE MODELS BRING ANOTHER SHORTWAVE TROUGH IN ACROSS THE NORTHWEST
ON THURSDAY AND CLIP THE NORTHERN PLAINS ON FRIDAY AS SURFACE LOW
PRESSURE CROSSES SOUTHERN CANADA AND A TRAILING FRONT EXTENDS
SOUTH ACROSS THE PLAINS. THE 00Z UKMET GRADUALLY ENDS UP A TAD
FARTHER SOUTH WITH ITS ENERGY AND THE FOCUS OF ITS SURFACE LOW
RELATIVE TO THE MODEL CONSENSUS. THE 12Z NAM CAME IN A BIT ON THE
NORTH SIDE OF THE MODEL SPREAD. THE 12Z GFS AND 00Z ECMWF SHOW
GOOD MODEL CLUSTERING AND ARE CLOSE TO THE MODEL CONSENSUS THROUGH
THE PERIOD, SO A BLEND OF THESE TWO SOLUTIONS WILL BE PREFERRED.
..SURFACE LOW OVER THE SOUTHERN PLAINS BY SATURDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND...THROUGH 72 HOURS
NON-NAM BLEND...AFTER 72 HOURS
CONFIDENCE: ABOVE AVERAGE
A SURFACE LOW CENTER IS EXPECTED TO BE FOCUSED ACROSS THE SOUTHERN
HIGH PLAINS BY SATURDAY ALONG THE TAIL END OF A FRONT. THE
GUIDANCE IS IN GOOD AGREEMENT GENERALLY THROUGH ABOUT 72 HOURS
WITH THE PLACEMENT OF THE LOW AND THE FRONT, BUT THEREAFTER, THE
12Z NAM TENDS TO DISPLACE ITS SURFACE LOW AND FRONT A TAD FARTHER
TO THE SOUTHEAST (CLOSER TO NORTHWEST AND NORTH-CENTRAL TX)AND
AWAY FROM THE GLOBAL MODEL CLUSTERING WHICH HAS IT OVER THE HIGH
PLAINS (OK/TX PANHANDLES). SO, A GENERAL MODEL BLEND WILL BE
PREFERRED THROUGH 72 HOURS, AND THEN A NON-NAM BLEND THEREAFTER.
..DEEP TROUGH OFFSHORE THE WEST COAST BY SATURDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/00Z ECMWF AND 06Z GEFS/00Z ECENS MEAN BLEND
CONFIDENCE: AVERAGE
A DEEP TROUGH IS FORECAST TO BE EVOLVING OFFSHORE OF THE WEST
COAST BY SATURDAY ALONG WITH A STRONG SURFACE LOW REFLECTION. MUCH
OF THE ENERGY IS EXPECTED TO BE CONFINED TO THE GULF OF AK, BUT A
PORTION OF THE TROUGH/HEIGHT FALLS WILL PIVOT ACROSS THE WEST
COAST AND IMPACT ESPECIALLY THE PACIFIC NORTHWEST BY LATE
SATURDAY. A COLD FRONT IS EXPECTED TO BE APPROACHING, WITH THE 12Z
NAM/GFS SOLUTIONS FASTER AND THE 00Z NON-NCEP MODELS (ESPECIALLY
THE UKMET) SLOWER. THE ENSEMBLE MEANS ARE A TAD SPLIT WITH THE
GEFS FAVORING THE NAM/GFS CAMP, AND THE ECENS MEAN FAVORING THE
ECMWF. THE CMC OVERALL LOOKS LIKE A WEAK OUTLIER WITH THE OFFSHORE
TROUGH/CLOSED LOW. WILL RECOMMEND A COMPROMISE BETWEEN THE
DETERMINISTIC GFS/ECMWF AND ENSEMBLE MEANS AT THIS POINT.
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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