Prognostic Meteorological Discussion
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000
FXUS10 KWNH 250447
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1247 AM EDT SAT MAR 25 2017

VALID MAR 25/0000 UTC THRU MAR 28/1200 UTC

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

00Z MODEL EVALUATION...INCLUDING THE NAM AND GFS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...CLOSED LOW DIVING THROUGH EASTERN CANADA BY SAT MORNING...
...COLD FRONT ADVANCING DOWN ACROSS THE GREAT LAKES/NORTHEAST...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 00Z GFS AND 12Z ECMWF
CONFIDENCE: ABOVE AVERAGE

THERE ARE ONLY MINOR DIFFERENCES ASSOCIATED WITH THE HEIGHT FALLS
PUSHING THROUGH EASTERN CANADA. REGARDING THE COLD FRONT SAGGING
DOWN ACROSS THE NORTHEAST AND INTO THE MID-ATLANTIC REGION...THE
00Z NAM DRIVES THE COLD FRONT THE FARTHEST SOUTH...WITH THE 12Z
UKMET HANGING THE FRONT UP FARTHEST NORTH. THE 00Z GFS/12Z ECMWF
AND 12Z CMC SPLIT THE DIFFERENCE IN THE MIDDLE. WILL LEAN TOWARD A
BLEND OF THE 00Z GFS AND 12Z ECMWF AT THIS TIME WITH THE FRONT. A
GENERAL MODEL COMPROMISE WILL OTHERWISE BE FINE WITH THE CLOSED
LOW EVOLUTION.


...CLOSED LOW EVOLUTION OVER THE CENTRAL PLAINS FRI...
...ENERGY CROSSING THE MID MS/OH VALLEYS THROUGH SAT...
...SYSTEM WEAKENING INTO THE GREAT LAKES/NORTHEAST BY SUN/MON...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE LATEST GUIDANCE TAKES THE CLOSED LOW/UPPER TROUGH APPROACHING
THE LOWER/MID MS VALLEY OFF TO THE NORTHEAST OVER THE NEXT COUPLE
OF DAYS...WITH THE SYSTEM GRADUALLY WEAKENING AS IT CROSSES THE OH
VALLEY AND LIFTS INTO THE GREAT LAKES REGION. BY LATER MON AND
TUES THE SYSTEM WILL BE ENTERING CONFLUENT FLOW ALOFT AS IT MOVES
INTO THE NORTHEAST AND WILL BE GRADUALLY DAMPENING OUT. THERE ARE
ONLY MINOR MASS FIELD DIFFERENCES...SO A GENERAL MODEL COMPROMISE
WILL BE PREFERRED AT THIS POINT.


...WEAKENING TROUGH/COLD FRONT OVER THE NORTHERN PLAINS ON SAT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

ONLY VERY MINOR DIFFERENCES NOTED WITH THIS SYSTEM ARE NOTED...SO
A GENERAL MODEL COMPROMISE WILL BE PREFERRED.


...NORTHERN STREAM TROUGH CROSSING THE PACIFIC NORTHWEST ON SAT...
...EJECTING ACROSS THE NORTHERN PLAINS/UPPER MIDWEST SUN/MON...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

PREFERENCE: NON-GFS CONSENSUS...WEIGHTED TOWARD THE 12Z ECMWF
CONFIDENCE: AVERAGE

THE MODELS ADVERTISE THE NORTHERN STREAM COMPONENT OF A LARGER
SCALE WESTERN U.S. TROUGH CROSSING THE PACIFIC NORTHWEST ON SUN
WITH THE ENERGY THEN PROGRESSIVELY ADVANCING EASTWARD ACROSS THE
NORTHERN PLAINS AND UPPER MIDWEST SUN AND MON. THE 00Z GFS TENDS
TO HANG ON TO A STRONGER AND GRADUALLY SLOWER UPPER TROUGH VERSUS
THE MODEL CONSENSUS. THE REMAINING MODELS ARE MORE PROGRESSIVE AND
A BIT FLATTER...BUT THE 00Z NAM AND 12Z UKMET BY THE END OF THE
PERIOD ARE THE FASTEST...WITH THE 12Z CMC/12Z ECMWF SOLUTIONS A
LITTLE SLOWER. WILL PREFER A NON-GFS CONSENSUS AT THIS
POINT...WITH SOMEWHAT STRONGER WEIGHTING TOWARD THE ECMWF.


...SOUTHERN STREAM UPPER TROUGH OVER THE WEST ON SAT...
...ENERGY EJECTING INTO THE CNTRL/SRN PLAINS SUN NIGHT/MON...
...SYSTEM WEAKENING INTO THE OH VALLEY MON NIGHT/TUES...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE...THROUGH 48 HOURS
            12Z ECMWF...AFTER 48 HOURS
CONFIDENCE: AVERAGE

THE MODELS ARE IN RATHER STRONG AGREEMENT THROUGH ABOUT 48 HOURS
WITH THE EVOLUTION OF THE SOUTHERN STREAM TROUGH/ENERGY CROSSING
THE SOUTHWEST/FOUR CORNERS REGION AND EJECTING OUT INTO THE
CENTRAL/SOUTHERN PLAINS REGION. THEREAFTER...THE 00Z GFS BECOMES
AN OUTLIER IN BECOMING TOO WEAK AND PROGRESSIVE WITH THE HEIGHT
FALL EVOLUTION AND ALSO WITH ITS ATTENDANT WAVE OF LOW PRESSURE
WHICH IT HAS QUICKLY LIFTING UP ACROSS THE OH VALLEY BY LATER
MON/TUES. THE 00Z NAM FOR ITS PART APPEARS TO BE A TAD TOO DEEP
WITH THE ENERGY AS IT ADVANCES EAST OF THE PLAINS AND INTO THE
LOWER MS/TN VALLEYS. THE 12Z CMC IS ONLY A TAD WEAKER THAN THE 00Z
NAM. THE 12Z UKMET AND 12Z ECMWF ARE A BIT WEAKER THAN THE NAM/CMC
SOLUTIONS BY COMPARISON BUT NOT AS WEAK AS THE GFS. WILL PREFER A
GENERAL MODEL COMPROMISE THROUGH 48 HOURS...AND THEN LEAN TOWARD
THE ECMWF THEREAFTER SINCE IT IS VERY CLOSE TO THE MODEL CONSENSUS.


...UPPER TROUGH/COLD FRONT REACHING THE WEST COAST SUN...
...CLOSED LOW EVOLUTION INTO THE SOUTHWEST MON/TUES...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE...THROUGH 48 HOURS
            BLEND OF THE 12Z CMC AND 12Z ECMWF...AFTER 48 HOURS
CONFIDENCE: AVERAGE

THE MODELS TAKE ANOTHER UPPER TROUGH AND ASSOCIATED COLD FRONT
ACROSS THE WEST COAST ON SUN...WITH SPLIT FLOW THEN ALLOWING THE
BULK OF THE ENERGY TO DIG SOUTHEAST INTO THE SOUTHWEST AND FOUR
CORNERS REGION THROUGH MON AND TUES. THE 00Z GFS GRADUALLY BECOMES
SLOWER THAN THE MODEL CONSENSUS WITH THE CLOSED LOW
EVOLUTION...WITH THE 12Z UKMET A BIT FASTER AND TENDING TO DIG THE
UPPER LOW FARTHER SOUTH. THE 00Z NAM IS A BIT DEEPER THAN ANY
OTHER MODEL BY THE END OF THE PERIOD. THE 12Z ECMWF AND 12Z CMC
ARE WELL CLUSTERED AND VERY CLOSE TO THE MODEL CONSENSUS THROUGH
THE PERIOD...AND SO WHILE A GENERAL MODEL COMPROMISE SHOULD WORK
THROUGH ABOUT 48 HOURS...A ECMWF/CMC COMPROMISE WILL BE PREFERRED
THEREAFTER.

www.wpc.ncep.noaa.gov/html/model2.shtml...

www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

ORRISON

$$





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