Prognostic Meteorological Discussion
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FXUS10 KWNH 041641
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1140 AM EST WED MAR 04 2015

VALID MAR 04/1200 UTC THRU MAR 08/0000 UTC

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

12Z MODEL EVALUATION...INCLUDING THE NAM AND GFS


...NORTHERN STREAM TROUGH DIGGING THROUGH THE MIDWEST/NORTHEAST...
...COLD FRONT SETTLING THROUGH THE EAST...
...SURFACE WAVE DEVELOPING ALONG THE FRONT AND IMPACTING THE
MID-ATLANTIC...

PREFERENCE: BLEND OF THE 12Z NAM/12Z GFS AND 00Z ECMWF
CONFIDENCE: AVERAGE

THE MODELS CONTINUE TO FORECAST A COLD FRONT ADVANCING
SOUTHEASTWARD OVER THE NEXT DAY OR SO DOWN THROUGH THE
MID-ATLANTIC AND SOUTHEAST AS ARCTIC HIGH PRESSURE NOSES SOUTH
DOWN THROUGH THE PLAINS AND MIDWEST. THE 00Z UKMET AND 00Z GEM ARE
OVERALL STILL A LITTLE SLOWER THAN THE MULTI-MODEL CONSENSUS WITH
THE FRONTAL PROGRESSION. THE 12Z NAM/12Z GFS AND 00Z ECMWF ARE A
TAD FASTER TO DROP THE FRONT DOWN TO THE SOUTH...WHICH IS
SUPPORTED BY THE LATEST GEFS MEAN/SREF MEAN AND ECENS MEAN.
MEANWHILE...A SHORTWAVE TROUGH IS FORECAST TO BE DIGGING SOUTHEAST
ACROSS THE MIDWEST THROUGH THE PERIOD AND SHOULD CROSS THE OH
VALLEY BY LATE THURS AND THEN THE NORTHEAST THURS NIGHT. THIS
ENERGY IS EXPECTED TO DEVELOP A COUPLE OF WEAK AREAS OF LOW
PRESSURE ALONG THE AFOREMENTIONED FRONT WHICH SHOULD TRACK FROM
THE TN VALLEY THROUGH THE SOUTHERN MID-ATLANTIC REGION ON THURS
BEFORE EJECTING RAPIDLY OUT TO SEA. WILL FAVOR THE MORE STRONGLY
CLUSTERED 12Z NAM/12Z GFS AND 00Z ECMWF GIVEN THE STRONGER
ENSEMBLE SUPPORT.


...CLOSED LOW/UPPER TROUGH REDEVELOPING OVER NORTHWEST MEXICO
THURS/FRI...

PREFERENCE: NON-UKMET CONSENSUS
CONFIDENCE: ABOVE AVERAGE

THE MODELS SHOW ENERGY DIGGING BACK INTO PARTS OF THE FAR
SOUTHWEST U.S. AND THE BAJA PENINSULA BY THURS AND FRI. ASIDE FROM
THE 00Z UKMET...WHICH IS FARTHER TO THE WEST AND WEAKER WITH A
CLOSED LOW BY MIDDAY FRIDAY...THE DETERMINISTIC/ENSEMBLE GUIDANCE
SHOWS GOOD AGREEMENT. THEREFORE...A NON-UKMET CONSENSUS WILL BE
PREFERRED.


...NORTHWEST FLOW IMPACTING THE NORTHERN TIER OF THE NATION FRI
AND SAT...
...EMBEDDED SHORTWAVE IMPULSES...

PREFERENCE: BLEND OF THE 12Z GFS AND 00Z ECMWF...THROUGH 60 HOURS
            BLEND OF THE 06Z GEFS MEAN AND 00Z ECENS MEAN...AFTER
60 HOURS
CONFIDENCE: BELOW AVERAGE

THE MODELS ARE FORECASTING A SERIES OF SHORTWAVE IMPULSES THAT
WILL TRACK FROM THE GULF OF ALASKA TO TRACK INTO WESTERN CANADA
AND THEN SOUTHEAST IN A SHEARED FASHION DOWN ACROSS THE MIDWEST
AND INTO THE GREAT LAKES REGION THROUGH SAT. ALL OF THE MODELS
AGREE ON THE LARGER SCALE WITH DOMINANT NORTHERN STREAM FLOW...BUT
THERE ARE DIFFERENCES WITH RESPECT TO TIMING AND DEPTH OF
INDIVIDUAL SHORTWAVE IMPULSES. THE 12Z GFS AND 00Z ECMWF SHOW
REASONABLY GOOD AGREEMENT THROUGH ABOUT 60 HOURS WITH ENERGY THAT
DROPS SOUTHEAST ACROSS BRITISH COLUMBIA AND DOWN TOWARD THE
NORTHERN PLAINS. THE 12Z NAM IS A BIT STRONGER WITH THIS
ENERGY...WITH THE 00Z UKMET AND 00Z GEM A BIT FLATTER/SHEARED.
THEREAFTER...THE 00Z ECMWF SUGGESTS SOME SHORTWAVE AMPLIFICATION
OVER THE GREAT LAKES REGION WHICH IS SUPPORTED BY THE 00Z ECENS
MEAN...HOWEVER...THE REMAINING MODELS ARE FLATTER INCLUDING THE
06Z GEFS MEAN. WILL PREFER A BLEND OF THE 12Z GFS AND 00Z ECMWF
THROUGH 60 HOURS...AND LEAN TOWARD A CONSENSUS OF THE ENSEMBLE
MEANS THEREAFTER. CONFIDENCE IS LIMITED.


...MODEL TREND GRAPHICS 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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