Prognostic Meteorological Discussion
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000
FXUS10 KWNH 270656
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
254 AM EDT THU APR 27 2017

VALID APR 27/0000 UTC THRU APR 30/1200 UTC

...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...

00Z MODEL EVALUATION WITH FINAL MODEL PREFERENCES/CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


...CYCLONE EXITING THE MID-ATLANTIC/SOUTHERN NEW ENGLAND...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE

THE MODELS ARE IN VERY GOOD AGREEMENT WITH THE EXIT OF THIS SYSTEM
AWAY FROM THE MID-ATLANTIC AND SOUTHERN NEW ENGLAND THROUGH THURS.
A GENERAL MODEL BLEND WILL AGAIN BE PREFERRED.


...LARGE UPPER TROUGH/FRONTAL SYSTEM CROSSING THE GREAT
LAKES/UPPER MS VALLEY THROUGH THURS...
...SURFACE FRONT REACHING THE MID-ATLANTIC/NORTHEAST BY FRI
NIGHT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-00Z NAM CONSENSUS
CONFIDENCE: ABOVE AVERAGE

THE 00Z NAM AGAIN IS A TAD SLOWER THAN THE MODEL CONSENSUS WITH
THE UPPER TROUGH LIFTING NORTHEAST ACROSS THE UPPER MS
VALLEY/GREAT LAKES THROUGH THURS. REGARDING THE FRONTAL TIMING
THERE IS MINIMAL SPREAD...SO OVERALL AT THIS POINT...WILL LEAN
TOWARD A NON-NAM CONSENSUS.


...UPPER LOW OVER SOUTHERN ALBERTA MOVING SLOWLY EAST ACROSS
SASKATCHEWAN BY SAT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-00Z NAM CONSENSUS
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE MODELS ARE IN GOOD AGREEMENT WITH THIS SYSTEM UNTIL SAT WHEN
THE 00Z CMC/ECMWF SOLUTIONS BEGIN TO LAG THE PROGRESSION OF THE
00Z NAM/GFS/UKMET SOLUTIONS BY JUST A LITTLE. THE SYSTEM WILL BE
WEAKENING BY SAT WHICH ALL OF THE GUIDANCE AGREES ON...HOWEVER THE
NAM TENDS TO HANG ON TO A SOMEWHAT STRONGER SOLUTION FOR LONGER
AND GRADUALLY BECOMES MORE OF AN OUTLIER. WILL PREFER A NON-NAM
CONSENSUS AT THIS POINT.


...AMPLIFYING TROUGH OVER THE INTERMOUNTAIN WEST THURS/FRI...
...CLOSED LOW EVOLUTION INTO THE CENTRAL/SOUTHERN PLAINS BY SAT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 00Z GFS AND 00Z ECMWF
CONFIDENCE: AVERAGE

MULTIPLE SHORTWAVES EMBEDDED IN A STRONG NORTHWESTERLY JET ACROSS
THE CENTRAL GREAT BASIN WILL DEEPEN A LARGE UPPER TROUGH OVER THE
INTERMOUNTAIN WEST AND PLAINS THURS NIGHT AND FRI...WITH A STRONG
CLOSED MID LEVEL LOW CENTER EJECTING OUT INTO THE CENTRAL/SOUTHERN
PLAINS REGION THROUGH SAT. THIS WILL DRIVE SURFACE LOW PRESSURE
FROM THE SOUTHERN HIGH PLAINS ACROSS THE RED RIVER VALLEY FRI
NIGHT AND SAT...AND NORTHEAST INTO THE MID MS VALLEY BY SUN AS A
TRAILING COLD FRONT SWEEPS ACROSS THE SOUTHERN PLAINS AND LOWER MS
VALLEY. THE MODELS SHOW GENERALLY GOOD MASS FIELD AGREEMENT
THROUGH EARLY SAT AS THE AMPLIFYING UPPER TROUGH CLOSES OFF OVER
THE FOUR CORNERS REGION...ALTHOUGH IT WAS NOTICED THAT THE 00Z
ECMWF AGAIN LOOKS A TAD TOO WEAK IN THE 700/500 MB LAYER. IT WAS
ALSO SEEN THAT THE 00Z UKMET WAS LIKELY A LITTLE TOO FAR NORTH
WITH ITS LOW CENTER OVER WEST TX AND THE DOWNSTREAM WARM FRONT
EXTENDING INTO THE MID MS VALLEY. BY LATER SAT AND SUN...THE 00Z
UKMET TAKES ITS MID LEVEL LOW CENTER A BIT NORTH OF THE MODEL
CONSENSUS WHICH DRIVES ITS SURFACE WAVE FARTHER NORTH. THE 00Z GFS
AND 00Z ECMWF TEND TO CLUSTER TOGETHER THE BEST WITH THE MID LEVEL
LOW CENTER...THE SURFACE LOW EVOLUTION AND THEIR RESPECTIVE
TRAILING FRONTS...ALTHOUGH THE 00Z ECMWF DID SLOW DOWN JUST A TAD
FROM ITS PREVIOUS RUN. OVERALL...THE 00Z CMC REMAINS AS THE
SLOWEST SOLUTION...AND THE 00Z NAM IS THE DEEPEST SOLUTION. THE
LATEST GEFS MEAN AND ECENS MEAN BOTH STILL SUPPORT THE
DETERMINISTIC GFS/ECMWF CLUSTER..AND SO A BLEND OF THE GFS/ECMWF
WILL BE PREFERRED.


...PACIFIC FRONTAL SYSTEM REACHING BRITISH COLUMBIA/PACIFIC
NORTHWEST SAT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z ECMWF
CONFIDENCE: AVERAGE

THE GUIDANCE ALL SUGGESTS AN UPPER TROUGH ADVANCING INTO THE
PACIFIC NORTHWEST BY SAT AND THEN CLIPPING THE NORTHERN ROCKIES BY
SUN. THE 00Z NAM AND 00Z CMC ARE THE SLOWEST SOLUTIONS...WITH THE
00Z UKMET THE FASTEST AND ALSO GENERALLY THE DEEPEST. THE 00Z GFS
AND 00Z ECMWF SPLIT THE DIFFERENCE WITH TIMING...BUT THE 00Z GFS
IS ALSO OVERALL THE WEAKEST SOLUTION. THE 00Z ECMWF TENDS TO
REFLECT A REASONABLE SOLUTION FOR NOW WITH DEPTH AND TIMING OF THE
ENERGY.


WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML... /ALL LOWER CASE/
WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML... /ALL LOWER CASE/

ORRISON

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