Prognostic Meteorological Discussion
Issued by NWS

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5
000
FXUS10 KWNH 090456
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1156 PM EST THU DEC 8 2016

VALID DEC 9/0000 UTC THRU DEC 12/1200 UTC

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

00Z NAM/GFS MODEL EVALUATION ALONG WITH PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
***00Z NAM INITIALIZED 850MB TEMPERATURES 3-4 DEGREES C TOO COLD
OVER PARTS OF THE PACIFIC NORTHWEST***

DEEP UPPER TROUGH SWINGING THROUGH THE NORTHEASTERN U.S.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE LARGE SYNOPTIC SCALE TROUGH OVER THE NORTHEAST U.S. AT THE
BEGINNING OF THE PERIOD IS PROGGED TO MOVE OVER THE CANADIAN
MARITIMES BY FRIDAY.  GOOD OVERALL MODEL AGREEMENT EXISTS TO
SUPPORT A GENERAL MODEL COMPROMISE HERE.


LOW AMPLITUDE SHORTWAVE CROSSING THE GREAT LAKES AND NEW ENGLAND
THROUGH SATURDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~~~~~~~~~

PREFERENCE: 00Z NAM/12Z UKMET/12Z ECMWF COMPROMISE
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

A COUPLE OF WEAK SHORTWAVES CURRENTLY OVER SOUTH-CENTRAL CANADA
SHOULD MIGRATE EASTWARD AND CONSOLIDATE INTO A LOW-AMPLITUDE
LONGWAVE TROUGH WHICH WILL MOVE ACROSS THE GREAT LAKES BY FRIDAY
NIGHT AND INTO SATURDAY.  THE 12Z CMC IS STILL WEAKER AND SLOWER
THAN THE MODEL CONSENSUS, WHILST THE GFS IS MORE AMPLIFIED WITH
THE TROUGH.  THIS TREND CONTINUES INTO SUNDAY AS THE TROUGH MOVES
OVER NEW ENGLAND.


PROGRESSIVE SHORTWAVE AND SURFACE LOW REACHING THE MIDWEST BY
MONDAY MORNING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~~~~

PREFERENCE: BLEND OF THE 12Z ECMWF/12Z UKMET/12Z CMC
CONFIDENCE: SLIGHTLY BELOW AVERAGE

A SURFACE LOW TRACKING FROM THE LEE OF THE ROCKIES SATURDAY
AFTERNOON TO THE OHIO VALLEY BY MONDAY MORNING WILL BE SUPPORTED
BY A BROAD MID-LEVEL TROUGH ORIGINATING FROM THE PACIFIC
NORTHWEST.  BY THE END OF THE FORECAST PERIOD ON MONDAY, THE
CMC/ECMWF/UKMET ARE WELL CLUSTERED OVER INDIANA AND OHIO, AND THE
NAM AND GFS FARTHER TO THE NORTH AND STRONGER WITH THE SURFACE
LOW.  THE NAM IS AN OUTLIER WITH HAVING AN OVER-AMPLIFIED TROUGH
OVER THE MIDWEST, AND THE GFS IS MORE PROGRESSIVE THAN THE MODEL
CONSENSUS.


PACIFIC STORM SYSTEM AFFECTING THE PACIFIC NORTHWEST THIS WEEKEND
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

PREFERENCE: BLEND OF THE 00Z GFS/12Z UKMET/18Z GEFS MEAN
CONFIDENCE: SLIGHTLY BELOW AVERAGE

A STRONG PACIFIC STORM OFF THE PACIFIC NORTHWEST COAST ON FRIDAY
IS PROGGED TO APPROACH THIS REGION ON SATURDAY, WITH THE SURFACE
LOW EXPECTED TO REACH NORTHWESTERN WASHINGTON AROUND 00Z SUNDAY.
THE 12Z ECMWF IS STILL INDICATING TWO SEPARATE LOWS PIVOTING
AROUND EACH OTHER THROUGH THE FIRST 36 HOURS OF THE FORECAST,
WHEREAS THE OTHER MODELS ARE ON BOARD WITH THE IDEA OF ONE MAIN
SURFACE LOW.  LOOKING ALOFT, THE NAM BECOMES MORE AMPLIFIED WITH
THE SHORTWAVE AXIS BY 36 HOURS, AND THE 12Z EC MEAN IS A BIT
SLOWER THAN THE MODEL CONSENSUS.


...MODEL TREND GRAPHICS AT
www.wpc.ncep.noaa.gov/html/model2.shtml...

...500 MB FORECASTS AT
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...


HAMRICK



$$





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.