461
FXUS10 KWNH 291855
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
254 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: NON-NAM BLEND
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, AND THE
LATEST 12Z GLOBAL MODEL SUITE HAS CLUSTERED IN AGREEMENT ON THAT
AS THE 12Z GFS TRENDED FARTHER SOUTH FROM ITS 00Z RUN. THE UKMET
WHICH HAD BEEN THE ONE NON-NCEP MODEL THAT WAS NORTH OF THE MODEL
CONSENSUS HAS ALSO TRENDED SOUTH WITH ITS 12Z RUN, AND IS NOW WELL
CLUSTERED WITH GLOBAL MODEL SUITE. THE 12Z CMC CAME JUST A TAD
NORTH, AND THE 12Z ECMWF IS VERY CLOSE TO ITS PREVIOUS RUN. THESE
TRENDS ALLOW FOR A WELL-CLUSTERED GLOBAL MODEL CONSENSUS. THE 12Z
NAM DID TREND NOTABLY SOUTH COMPARED TO ITS 00Z RUN, BUT IT MAY BE
A TAD TOO FAR SOUTH, AND ESPECIALLY AFTER 60 HOURS AS THE DEEP
TROUGH/LOW CENTER EDGES OFFSHORE OF THE NORTHEAST. BY THEN THE NAM
ALSO APPEARS TO BE TOO SLOW. SO, AT THIS POINT, WILL SIMPLY
SUGGEST A NON-NAM BLEND IN FAVOR OF THE GLOBAL MODEL CONSENSUS.
..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 12Z 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 12Z UKMET GRADUALLY ENDS UP A TAD
FARTHER SOUTH AND SLOWER 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 12Z
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). THERE
IS A LITTLE BIT OF SUPPORT FROM THE 12Z CMC AND 12Z UKMET AT THE
END OF THE PERIOD FOR A LOW CENTER A TAD FARTHER EAST OF THE
GLOBAL MODEL CONSENSUS (MORE OVER THE OK/TX PANHANDLES), BUT THE
NAM IS STILL LIKELY TOO FAR TO THE SOUTHEAST WITH ITS LOW AND
FRONTAL PLACEMENT. 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/ECMWF AND 12Z 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, AND THE
GUIDANCE IS NOW SHOWING GOOD AGREEMENT WITH ASIDE FROM THE 12Z
UKMET WHICH IS A SLOWER OUTLIER. THE BIGGER DIFFERENCES TEND TO BE
MORE CENTERED ON A POSSIBLE WAVE OF LOW PRESSURE DEVELOPING AND
DEEPENING AROUND THE EAST-SIDE OF THE LARGER SYNOPTIC SCALE LOW
OFFSHORE AS SHORTWAVE ENERGY ROUNDS THE BASE OF THE TROUGH. THE
NAM, GFS AND UKMET ALL FAVOR A REASONABLY WELL-DEVELOPED LOW
CENTER DEVELOPING ALONG THE AFOREMENTIONED FRONT THAT WILL BE
APPROACHING THE WEST COAST. THE CMC AND ECMWF SHOW LESS
DEVELOPMENT. THE ENSEMBLE MEANS ARE A TAD SPLIT WITH THE GEFS
FAVORING THE NAM/GFS/UKMET CAMP, AND THE ECENS MEAN FAVORING THE
CMC/ECMWF CAMP. WILL RECOMMEND A COMPROMISE BETWEEN THE CAMPS WITH
THIS AND CONTINUE TO FAVOR A BLEND OF THE DETERMINISTIC GFS/ECMWF
AND GEFS/ECENS MEANS FOR THE TIME BEING.
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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